qemu-doc - QEMU version 2.11.1 User Documentation
qemu-system-i386 [
options] [
disk_image]
The QEMU PC System emulator simulates the following peripherals:
- -
- i440FX host PCI bridge and PIIX3 PCI to ISA bridge
- -
- Cirrus CLGD 5446 PCI VGA card or dummy VGA card with Bochs
VESA extensions (hardware level, including all non standard modes).
- -
- PS/2 mouse and keyboard
- -
- 2 PCI IDE interfaces with hard disk and CD-ROM support
- -
- Floppy disk
- -
- PCI and ISA network adapters
- -
- Serial ports
- -
- IPMI BMC, either and internal or external one
- -
- Creative SoundBlaster 16 sound card
- -
- ENSONIQ AudioPCI ES1370 sound card
- -
- Intel 82801AA AC97 Audio compatible sound card
- -
- Intel HD Audio Controller and HDA codec
- -
- Adlib (OPL2) - Yamaha YM3812 compatible chip
- -
- Gravis Ultrasound GF1 sound card
- -
- CS4231A compatible sound card
- -
- PCI UHCI, OHCI, EHCI or XHCI USB controller and a virtual
USB-1.1 hub.
SMP is supported with up to 255 CPUs.
QEMU uses the PC BIOS from the Seabios project and the Plex86/Bochs LGPL VGA
BIOS.
QEMU uses YM3812 emulation by Tatsuyuki Satoh.
QEMU uses GUS emulation (GUSEMU32 <
http://www.deinmeister.de/gusemu/>) by Tibor "TS"
Schütz.
Note that, by default, GUS shares
IRQ(7) with parallel ports and so QEMU
must be told to not have parallel ports to have working GUS.
qemu-system-i386 dos.img -soundhw gus -parallel none
Alternatively:
qemu-system-i386 dos.img -device gus,irq=5
Or some other unclaimed IRQ.
CS4231A is the chip used in Windows Sound System and GUSMAX products
disk_image is a raw hard disk image for IDE hard disk 0. Some targets do
not need a disk image.
Standard options
- -h
- Display help and exit
- -version
- Display version information and exit
- -machine
[type=]name[,prop=value [,...]]
- Select the emulated machine by name. Use
"-machine help" to list available machines.
For architectures which aim to support live migration compatibility across
releases, each release will introduce a new versioned machine type. For
example, the 2.8.0 release introduced machine types
"pc-i440fx-2.8" and "pc-q35-2.8" for the x86_64/i686
architectures.
To allow live migration of guests from QEMU version 2.8.0, to QEMU version
2.9.0, the 2.9.0 version must support the "pc-i440fx-2.8" and
"pc-q35-2.8" machines too. To allow users live migrating VMs to
skip multiple intermediate releases when upgrading, new releases of QEMU
will support machine types from many previous versions.
Supported machine properties are:
- accel=accels1[:accels2[:...]]
- This is used to enable an accelerator. Depending on the
target architecture, kvm, xen, hax or tcg can be available. By default,
tcg is used. If there is more than one accelerator specified, the next one
is used if the previous one fails to initialize.
- kernel_irqchip=on|off
- Controls in-kernel irqchip support for the chosen
accelerator when available.
- gfx_passthru=on|off
- Enables IGD GFX passthrough support for the chosen machine
when available.
- vmport=on|off|auto
- Enables emulation of VMWare IO port, for vmmouse etc. auto
says to select the value based on accel. For accel=xen the default is off
otherwise the default is on.
- kvm_shadow_mem=size
- Defines the size of the KVM shadow MMU.
- dump-guest-core=on|off
- Include guest memory in a core dump. The default is
on.
- mem-merge=on|off
- Enables or disables memory merge support. This feature,
when supported by the host, de-duplicates identical memory pages among VMs
instances (enabled by default).
- aes-key-wrap=on|off
- Enables or disables AES key wrapping support on s390-ccw
hosts. This feature controls whether AES wrapping keys will be created to
allow execution of AES cryptographic functions. The default is on.
- dea-key-wrap=on|off
- Enables or disables DEA key wrapping support on s390-ccw
hosts. This feature controls whether DEA wrapping keys will be created to
allow execution of DEA cryptographic functions. The default is on.
- nvdimm=on|off
- Enables or disables NVDIMM support. The default is
off.
- s390-squash-mcss=on|off
- Enables or disables squashing subchannels into the default
css. The default is off.
- enforce-config-section=on|off
- If enforce-config-section is set to on, force
migration code to send configuration section even if the machine-type sets
the migration.send-configuration property to off. NOTE: this
parameter is deprecated. Please use -global
migration.send-configuration= on|off instead.
- -cpu model
- Select CPU model ("-cpu help" for list and
additional feature selection)
- -accel
name[,prop=value[,...]]
- This is used to enable an accelerator. Depending on the
target architecture, kvm, xen, hax or tcg can be available. By default,
tcg is used. If there is more than one accelerator specified, the next one
is used if the previous one fails to initialize.
- thread=single|multi
- Controls number of TCG threads. When the TCG is
multi-threaded there will be one thread per vCPU therefor taking advantage
of additional host cores. The default is to enable multi-threading where
both the back-end and front-ends support it and no incompatible TCG
features have been enabled (e.g. icount/replay).
- -smp
[cpus=]n[,cores=cores][,threads=
threads
][,sockets=sockets][,maxcpus=maxcpus
]
- Simulate an SMP system with n CPUs. On the PC
target, up to 255 CPUs are supported. On Sparc32 target, Linux limits the
number of usable CPUs to 4. For the PC target, the number of cores
per socket, the number of threads per cores and the total number of
sockets can be specified. Missing values will be computed. If any
on the three values is given, the total number of CPUs n can be
omitted. maxcpus specifies the maximum number of hotpluggable
CPUs.
- -numa
node[,mem=size][,cpus=firstcpu
[-lastcpu ]][,nodeid=node]
- -numa
node[,memdev=id][,cpus=firstcpu
[-lastcpu ]][,nodeid=node]
- -numa
dist,src=source,dst=destination
,val=distance
- -numa
cpu,node-id=node[,socket-id=x
][,core-id=y ][,thread-id=z]
- Define a NUMA node and assign RAM and VCPUs to it. Set the
NUMA distance from a source node to a destination node.
Legacy VCPU assignment uses cpus option where firstcpu and
lastcpu are CPU indexes. Each cpus option represent a
contiguous range of CPU indexes (or a single VCPU if lastcpu is
omitted). A non-contiguous set of VCPUs can be represented by providing
multiple cpus options. If cpus is omitted on all nodes,
VCPUs are automatically split between them.
For example, the following option assigns VCPUs 0, 1, 2 and 5 to a NUMA
node:
-numa node,cpus=0-2,cpus=5
cpu option is a new alternative to cpus option which uses
socket-id|core-id|thread-id properties to assign CPU objects to a
node using topology layout properties of CPU. The set of properties
is machine specific, and depends on used machine type/ smp options.
It could be queried with hotpluggable-cpus monitor command.
node-id property specifies node to which CPU object will be
assigned, it's required for node to be declared with node
option before it's used with cpu option.
For example:
-M pc \
-smp 1,sockets=2,maxcpus=2 \
-numa node,nodeid=0 -numa node,nodeid=1 \
-numa cpu,node-id=0,socket-id=0 -numa cpu,node-id=1,socket-id=1
mem assigns a given RAM amount to a node. memdev assigns RAM
from a given memory backend device to a node. If mem and
memdev are omitted in all nodes, RAM is split equally between them.
mem and memdev are mutually exclusive. Furthermore, if one
node uses memdev, all of them have to use it.
source and destination are NUMA node IDs. distance is
the NUMA distance from source to destination. The distance
from a node to itself is always 10. If any pair of nodes is given a
distance, then all pairs must be given distances. Although, when distances
are only given in one direction for each pair of nodes, then the distances
in the opposite directions are assumed to be the same. If, however, an
asymmetrical pair of distances is given for even one node pair, then all
node pairs must be provided distance values for both directions, even when
they are symmetrical. When a node is unreachable from another node, set
the pair's distance to 255.
Note that the - numa option doesn't allocate any of the specified
resources, it just assigns existing resources to NUMA nodes. This means
that one still has to use the -m, -smp options to allocate
RAM and VCPUs respectively.
- -add-fd
fd=fd,set=set[,opaque=
opaque]
- Add a file descriptor to an fd set. Valid options are:
- fd=fd
- This option defines the file descriptor of which a
duplicate is added to fd set. The file descriptor cannot be stdin, stdout,
or stderr.
- set=set
- This option defines the ID of the fd set to add the file
descriptor to.
- opaque=opaque
- This option defines a free-form string that can be used to
describe fd.
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
- -set
group.id.arg=value
- Set parameter arg for item id of type
group
- -global
driver.prop=value
- -global
driver=driver,property=property
,value=value
- Set default value of driver's property prop
to value, e.g.:
qemu-system-i386 -global ide-hd.physical_block_size=4096 disk-image.img
In particular, you can use this to set driver properties for devices which
are created automatically by the machine model. To create a device which
is not created automatically and set properties on it, use -
device.
-global driver.prop=value is shorthand for -global
driver= driver,property=prop,value=value. The
longhand syntax works even when driver contains a dot.
- -boot
[order=drives][,once=drives
][,menu=on|off][,splash=
sp_name][,splash-time=sp_time
][,reboot-timeout=rb_timeout][,strict=on|off]
- Specify boot order drives as a string of drive
letters. Valid drive letters depend on the target architecture. The x86 PC
uses: a, b (floppy 1 and 2), c (first hard disk), d (first CD-ROM), n-p
(Etherboot from network adapter 1-4), hard disk boot is the default. To
apply a particular boot order only on the first startup, specify it via
once. Note that the order or once parameter should
not be used together with the bootindex property of devices, since
the firmware implementations normally do not support both at the same
time.
Interactive boot menus/prompts can be enabled via menu=on as far as
firmware/BIOS supports them. The default is non-interactive boot.
A splash picture could be passed to bios, enabling user to show it as logo,
when option splash= sp_name is given and menu=on, If firmware/BIOS
supports them. Currently Seabios for X86 system support it. limitation:
The splash file could be a jpeg file or a BMP file in 24 BPP format(true
color). The resolution should be supported by the SVGA mode, so the
recommended is 320x240, 640x480, 800x640.
A timeout could be passed to bios, guest will pause for rb_timeout ms
when boot failed, then reboot. If rb_timeout is '-1', guest will
not reboot, qemu passes '-1' to bios by default. Currently Seabios for X86
system support it.
Do strict boot via strict=on as far as firmware/BIOS supports it.
This only effects when boot priority is changed by bootindex options. The
default is non-strict boot.
# try to boot from network first, then from hard disk
qemu-system-i386 -boot order=nc
# boot from CD-ROM first, switch back to default order after reboot
qemu-system-i386 -boot once=d
# boot with a splash picture for 5 seconds.
qemu-system-i386 -boot menu=on,splash=/root/boot.bmp,splash-time=5000
Note: The legacy format '-boot drives' is still supported but its use
is discouraged as it may be removed from future versions.
- -m
[size=]megs[,slots=n,maxmem=size]
- Sets guest startup RAM size to megs megabytes.
Default is 128 MiB. Optionally, a suffix of "M" or "G"
can be used to signify a value in megabytes or gigabytes respectively.
Optional pair slots, maxmem could be used to set amount of
hotpluggable memory slots and maximum amount of memory. Note that
maxmem must be aligned to the page size.
For example, the following command-line sets the guest startup RAM size to
1GB, creates 3 slots to hotplug additional memory and sets the maximum
memory the guest can reach to 4GB:
qemu-system-x86_64 -m 1G,slots=3,maxmem=4G
If slots and maxmem are not specified, memory hotplug won't be
enabled and the guest startup RAM will never increase.
- -mem-path path
- Allocate guest RAM from a temporarily created file in
path.
- -mem-prealloc
- Preallocate memory when using -mem-path.
- -k language
- Use keyboard layout language (for example
"fr" for French). This option is only needed where it is not
easy to get raw PC keycodes (e.g. on Macs, with some X11 servers or with a
VNC or curses display). You don't normally need to use it on PC/Linux or
PC/Windows hosts.
The available layouts are:
ar de-ch es fo fr-ca hu ja mk no pt-br sv
da en-gb et fr fr-ch is lt nl pl ru th
de en-us fi fr-be hr it lv nl-be pt sl tr
The default is "en-us".
- -audio-help
- Will show the audio subsystem help: list of drivers,
tunable parameters.
- -soundhw card1[,card2,...]
or -soundhw all
- Enable audio and selected sound hardware. Use 'help' to
print all available sound hardware.
qemu-system-i386 -soundhw sb16,adlib disk.img
qemu-system-i386 -soundhw es1370 disk.img
qemu-system-i386 -soundhw ac97 disk.img
qemu-system-i386 -soundhw hda disk.img
qemu-system-i386 -soundhw all disk.img
qemu-system-i386 -soundhw help
Note that Linux's i810_audio OSS kernel (for AC97) module might require
manually specifying clocking.
modprobe i810_audio clocking=48000
- -balloon none
- Disable balloon device.
- -balloon virtio[,addr=addr]
- Enable virtio balloon device (default), optionally with PCI
address addr.
- -device
driver[,prop[=value][,...]]
- Add device driver. prop=value sets
driver properties. Valid properties depend on the driver. To get help on
possible drivers and properties, use "-device help" and
"-device driver,help".
Some drivers are:
- -device
ipmi-bmc-sim,id=id[,slave_addr=
val][,sdrfile=
file][,furareasize=val][,furdatafile=
file ]
- Add an IPMI BMC. This is a simulation of a hardware
management interface processor that normally sits on a system. It provides
a watchdog and the ability to reset and power control the system. You need
to connect this to an IPMI interface to make it useful
The IPMI slave address to use for the BMC. The default is 0x20. This address
is the BMC's address on the I2C network of management controllers. If you
don't know what this means, it is safe to ignore it.
- bmc=id
- The BMC to connect to, one of ipmi-bmc-sim or
ipmi-bmc-extern above.
- slave_addr=val
- Define slave address to use for the BMC. The default is
0x20.
- sdrfile=file
- file containing raw Sensor Data Records (SDR) data. The
default is none.
- fruareasize=val
- size of a Field Replaceable Unit (FRU) area. The default is
1024.
- frudatafile=file
- file containing raw Field Replaceable Unit (FRU) inventory
data. The default is none.
- -device
ipmi-bmc-extern,id=id,chardev=id[,slave_addr=val]
- Add a connection to an external IPMI BMC simulator. Instead
of locally emulating the BMC like the above item, instead connect to an
external entity that provides the IPMI services.
A connection is made to an external BMC simulator. If you do this, it is
strongly recommended that you use the "reconnect=" chardev
option to reconnect to the simulator if the connection is lost. Note that
if this is not used carefully, it can be a security issue, as the
interface has the ability to send resets, NMIs, and power off the VM. It's
best if QEMU makes a connection to an external simulator running on a
secure port on localhost, so neither the simulator nor QEMU is exposed to
any outside network.
See the "lanserv/README.vm" file in the OpenIPMI library for more
details on the external interface.
- -device
isa-ipmi-kcs,bmc=id[,ioport=val][,irq=val]
- Add a KCS IPMI interafce on the ISA bus. This also adds a
corresponding ACPI and SMBIOS entries, if appropriate.
- bmc=id
- The BMC to connect to, one of ipmi-bmc-sim or
ipmi-bmc-extern above.
- ioport=val
- Define the I/O address of the interface. The default is
0xca0 for KCS.
- irq=val
- Define the interrupt to use. The default is 5. To disable
interrupts, set this to 0.
- -device
isa-ipmi-bt,bmc=id[,ioport=val
][,irq=val ]
- Like the KCS interface, but defines a BT interface. The
default port is 0xe4 and the default interrupt is 5.
- -name name
- Sets the name of the guest. This name will be
displayed in the SDL window caption. The name will also be used for
the VNC server. Also optionally set the top visible process name in Linux.
Naming of individual threads can also be enabled on Linux to aid
debugging.
- -uuid uuid
- Set system UUID.
Block device options
- -fda file
- -fdb file
- Use file as floppy disk 0/1 image.
- -hda file
- -hdb file
- -hdc file
- -hdd file
- Use file as hard disk 0, 1, 2 or 3 image.
- -cdrom file
- Use file as CD-ROM image (you cannot use -hdc
and -cdrom at the same time). You can use the host CD-ROM by using
/dev/cdrom as filename.
- -blockdev
option[,option[,
option[,...]]]
- Define a new block driver node. Some of the options apply
to all block drivers, other options are only accepted for a specific block
driver. See below for a list of generic options and options for the most
common block drivers.
Options that expect a reference to another node (e.g. "file") can
be given in two ways. Either you specify the node name of an already
existing node (file= node-name), or you define a new node inline,
adding options for the referenced node after a dot (file.filename=
path,file.aio=native).
A block driver node created with -blockdev can be used for a guest
device by specifying its node name for the "drive" property in a
-device argument that defines a block device.
- Valid options for any block driver node:
- "driver"
- Specifies the block driver to use for the given node.
- "node-name"
- This defines the name of the block driver node by which it
will be referenced later. The name must be unique, i.e. it must not match
the name of a different block driver node, or (if you use -drive as
well) the ID of a drive.
If no node name is specified, it is automatically generated. The generated
node name is not intended to be predictable and changes between QEMU
invocations. For the top level, an explicit node name must be
specified.
- "read-only"
- Open the node read-only. Guest write attempts will
fail.
- "cache.direct"
- The host page cache can be avoided with
cache.direct=on. This will attempt to do disk IO directly to the
guest's memory. QEMU may still perform an internal copy of the data.
- "cache.no-flush"
- In case you don't care about data integrity over host
failures, you can use cache.no-flush=on. This option tells QEMU
that it never needs to write any data to the disk but can instead keep
things in cache. If anything goes wrong, like your host losing power, the
disk storage getting disconnected accidentally, etc. your image will most
probably be rendered unusable.
- "discard=discard"
- discard is one of "ignore" (or
"off") or "unmap" (or "on") and controls
whether "discard" (also known as "trim" or
"unmap") requests are ignored or passed to the filesystem. Some
machine types may not support discard requests.
- "detect-zeroes=detect-zeroes"
- detect-zeroes is "off", "on" or
"unmap" and enables the automatic conversion of plain zero
writes by the OS to driver specific optimized zero write commands. You may
even choose "unmap" if discard is set to
"unmap" to allow a zero write to be converted to an
"unmap" operation.
- Driver-specific options for
"file"
- This is the protocol-level block driver for accessing
regular files.
- "filename"
- The path to the image file in the local filesystem
- "aio"
- Specifies the AIO backend (threads/native, default:
threads)
- "locking"
- Specifies whether the image file is protected with Linux
OFD / POSIX locks. The default is to use the Linux Open File Descriptor
API if available, otherwise no lock is applied. (auto/on/off, default:
auto)
Example:
-blockdev driver=file,node-name=disk,filename=disk.img
- Driver-specific options for
"raw"
- This is the image format block driver for raw images. It is
usually stacked on top of a protocol level block driver such as
"file".
- "file"
- Reference to or definition of the data source block driver
node (e.g. a "file" driver node)
Example 1:
-blockdev driver=file,node-name=disk_file,filename=disk.img
-blockdev driver=raw,node-name=disk,file=disk_file
Example 2:
-blockdev driver=raw,node-name=disk,file.driver=file,file.filename=disk.img
- Driver-specific options for
"qcow2"
- This is the image format block driver for qcow2 images. It
is usually stacked on top of a protocol level block driver such as
"file".
- "file"
- Reference to or definition of the data source block driver
node (e.g. a "file" driver node)
- "backing"
- Reference to or definition of the backing file block device
(default is taken from the image file). It is allowed to pass an empty
string here in order to disable the default backing file.
- "lazy-refcounts"
- Whether to enable the lazy refcounts feature (on/off;
default is taken from the image file)
- "cache-size"
- The maximum total size of the L2 table and refcount block
caches in bytes (default: 1048576 bytes or 8 clusters, whichever is
larger)
- "l2-cache-size"
- The maximum size of the L2 table cache in bytes (default:
4/5 of the total cache size)
- "refcount-cache-size"
- The maximum size of the refcount block cache in bytes
(default: 1/5 of the total cache size)
- "cache-clean-interval"
- Clean unused entries in the L2 and refcount caches. The
interval is in seconds. The default value is 0 and it disables this
feature.
- "pass-discard-request"
- Whether discard requests to the qcow2 device should be
forwarded to the data source (on/off; default: on if discard=unmap is
specified, off otherwise)
- "pass-discard-snapshot"
- Whether discard requests for the data source should be
issued when a snapshot operation (e.g. deleting a snapshot) frees clusters
in the qcow2 file (on/off; default: on)
- "pass-discard-other"
- Whether discard requests for the data source should be
issued on other occasions where a cluster gets freed (on/off; default:
off)
- "overlap-check"
- Which overlap checks to perform for writes to the image
(none/constant/cached/all; default: cached). For details or finer
granularity control refer to the QAPI documentation of
"blockdev-add".
Example 1:
-blockdev driver=file,node-name=my_file,filename=/tmp/disk.qcow2
-blockdev driver=qcow2,node-name=hda,file=my_file,overlap-check=none,cache-size=16777216
Example 2:
-blockdev driver=qcow2,node-name=disk,file.driver=http,file.filename=http://example.com/image.qcow2
- Driver-specific options for other drivers
- Please refer to the QAPI documentation of the
"blockdev-add" QMP command.
- -drive
option[,option[,option[,...]]]
- Define a new drive. This includes creating a block driver
node (the backend) as well as a guest device, and is mostly a shortcut for
defining the corresponding -blockdev and -device options.
-drive accepts all options that are accepted by -blockdev. In
addition, it knows the following options:
- file=file
- This option defines which disk image to use with this
drive. If the filename contains comma, you must double it (for instance,
"file=my,,file" to use file "my,file").
Special files such as iSCSI devices can be specified using protocol specific
URLs. See the section for "Device URL Syntax" for more
information.
- if=interface
- This option defines on which type on interface the drive is
connected. Available types are: ide, scsi, sd, mtd, floppy, pflash,
virtio, none.
- bus=bus,unit=unit
- These options define where is connected the drive by
defining the bus number and the unit id.
- index=index
- This option defines where is connected the drive by using
an index in the list of available connectors of a given interface
type.
- media=media
- This option defines the type of the media: disk or
cdrom.
- cyls=c,heads=h,secs=s[,trans=t]
- These options have the same definition as they have in
-hdachs. These parameters are deprecated, use the corresponding
parameters of "-device" instead.
- snapshot=snapshot
- snapshot is "on" or "off" and
controls snapshot mode for the given drive (see -snapshot).
- cache=cache
- cache is "none", "writeback",
"unsafe", "directsync" or "writethrough" and
controls how the host cache is used to access block data. This is a
shortcut that sets the cache.direct and cache.no-flush
options (as in -blockdev), and additionally cache.writeback,
which provides a default for the write-cache option of block guest
devices (as in -device). The modes correspond to the following
settings:
│ cache.writeback cache.direct cache.no-flush
─────────────┼─────────────────────────────────────────────────
writeback │ on off off
none │ on on off
writethrough │ off off off
directsync │ off on off
unsafe │ on off on
The default mode is cache=writeback.
- aio=aio
- aio is "threads", or "native"
and selects between pthread based disk I/O and native Linux AIO.
- format=format
- Specify which disk format will be used rather than
detecting the format. Can be used to specify format=raw to avoid
interpreting an untrusted format header.
- serial=serial
- This option specifies the serial number to assign to the
device. This parameter is deprecated, use the corresponding parameter of
"-device" instead.
- addr=addr
- Specify the controller's PCI address (if=virtio only). This
parameter is deprecated, use the corresponding parameter of
"-device" instead.
- werror=action,rerror=action
- Specify which action to take on write and read
errors. Valid actions are: "ignore" (ignore the error and try to
continue), "stop" (pause QEMU), "report" (report the
error to the guest), "enospc" (pause QEMU only if the host disk
is full; report the error to the guest otherwise). The default setting is
werror=enospc and rerror=report.
- copy-on-read=copy-on-read
- copy-on-read is "on" or "off"
and enables whether to copy read backing file sectors into the image
file.
- bps=b,bps_rd=r,bps_wr=w
- Specify bandwidth throttling limits in bytes per second,
either for all request types or for reads or writes only. Small values can
lead to timeouts or hangs inside the guest. A safe minimum for disks is 2
MB/s.
- bps_max=bm,bps_rd_max=rm,bps_wr_max=wm
- Specify bursts in bytes per second, either for all request
types or for reads or writes only. Bursts allow the guest I/O to spike
above the limit temporarily.
- iops=i,iops_rd=r,iops_wr=w
- Specify request rate limits in requests per second, either
for all request types or for reads or writes only.
- iops_max=bm,iops_rd_max=rm,iops_wr_max=wm
- Specify bursts in requests per second, either for all
request types or for reads or writes only. Bursts allow the guest I/O to
spike above the limit temporarily.
- iops_size=is
- Let every is bytes of a request count as a new
request for iops throttling purposes. Use this option to prevent guests
from circumventing iops limits by sending fewer but larger requests.
- group=g
- Join a throttling quota group with given name g. All
drives that are members of the same group are accounted for together. Use
this option to prevent guests from circumventing throttling limits by
using many small disks instead of a single larger disk.
By default, the
cache.writeback=on mode is used. It will report data
writes as completed as soon as the data is present in the host page cache.
This is safe as long as your guest OS makes sure to correctly flush disk
caches where needed. If your guest OS does not handle volatile disk write
caches correctly and your host crashes or loses power, then the guest may
experience data corruption.
For such guests, you should consider using
cache.writeback=off. This
means that the host page cache will be used to read and write data, but write
notification will be sent to the guest only after QEMU has made sure to flush
each write to the disk. Be aware that this has a major impact on performance.
When using the
-snapshot option, unsafe caching is always used.
Copy-on-read avoids accessing the same backing file sectors repeatedly and is
useful when the backing file is over a slow network. By default copy-on-read
is off.
Instead of
-cdrom you can use:
qemu-system-i386 -drive file=file,index=2,media=cdrom
Instead of
-hda,
-hdb,
-hdc,
-hdd, you can use:
qemu-system-i386 -drive file=file,index=0,media=disk
qemu-system-i386 -drive file=file,index=1,media=disk
qemu-system-i386 -drive file=file,index=2,media=disk
qemu-system-i386 -drive file=file,index=3,media=disk
You can open an image using pre-opened file descriptors from an fd set:
qemu-system-i386
-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
You can connect a CDROM to the slave of ide0:
qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom
If you don't specify the "file=" argument, you define an empty drive:
qemu-system-i386 -drive if=ide,index=1,media=cdrom
Instead of
-fda,
-fdb, you can use:
qemu-system-i386 -drive file=file,index=0,if=floppy
qemu-system-i386 -drive file=file,index=1,if=floppy
By default,
interface is "ide" and
index is
automatically incremented:
qemu-system-i386 -drive file=a -drive file=b"
is interpreted like:
qemu-system-i386 -hda a -hdb b
- -mtdblock file
- Use file as on-board Flash memory image.
- -sd file
- Use file as SecureDigital card image.
- -pflash file
- Use file as a parallel flash image.
- -snapshot
- Write to temporary files instead of disk image files. In
this case, the raw disk image you use is not written back. You can however
force the write back by pressing C-a s.
- -hdachs
c,h,s,[, t]
- Force hard disk 0 physical geometry (1 <= c <=
16383, 1 <= h <= 16, 1 <= s <= 63) and
optionally force the BIOS translation mode ( t=none, lba or auto).
Usually QEMU can guess all those parameters. This option is deprecated,
please use "-device ide-hd,cyls=c,heads=h,secs=s,..."
instead.
- -fsdev
fsdriver,id=id,path=
path,[security_model=
security_model][,writeout=writeout][,readonly][,socket=socket|sock_fd=sock_fd][,fmode=fmode][,dmode=dmode]
- Define a new file system device. Valid options are:
- fsdriver
- This option specifies the fs driver backend to use.
Currently "local", "handle" and "proxy" file
system drivers are supported.
- id=id
- Specifies identifier for this device
- path=path
- Specifies the export path for the file system device. Files
under this path will be available to the 9p client on the guest.
- security_model=security_model
- Specifies the security model to be used for this export
path. Supported security models are "passthrough",
"mapped-xattr", "mapped-file" and "none". In
"passthrough" security model, files are stored using the same
credentials as they are created on the guest. This requires QEMU to run as
root. In "mapped-xattr" security model, some of the file
attributes like uid, gid, mode bits and link target are stored as file
attributes. For "mapped-file" these attributes are stored in the
hidden .virtfs_metadata directory. Directories exported by this security
model cannot interact with other unix tools. "none" security
model is same as passthrough except the sever won't report failures if it
fails to set file attributes like ownership. Security model is mandatory
only for local fsdriver. Other fsdrivers (like handle, proxy) don't take
security model as a parameter.
- writeout=writeout
- This is an optional argument. The only supported value is
"immediate". This means that host page cache will be used to
read and write data but write notification will be sent to the guest only
when the data has been reported as written by the storage subsystem.
- readonly
- Enables exporting 9p share as a readonly mount for guests.
By default read-write access is given.
- socket=socket
- Enables proxy filesystem driver to use passed socket file
for communicating with virtfs-proxy-helper
- sock_fd=sock_fd
- Enables proxy filesystem driver to use passed socket
descriptor for communicating with virtfs-proxy-helper. Usually a helper
like libvirt will create socketpair and pass one of the fds as
sock_fd
- fmode=fmode
- Specifies the default mode for newly created files on the
host. Works only with security models "mapped-xattr" and
"mapped-file".
- dmode=dmode
- Specifies the default mode for newly created directories on
the host. Works only with security models "mapped-xattr" and
"mapped-file".
-fsdev option is used along with -device driver "virtio-9p-pci".
- -device
virtio-9p-pci,fsdev=id,mount_tag= mount_tag
- Options for virtio-9p-pci driver are:
- fsdev=id
- Specifies the id value specified along with -fsdev
option
- mount_tag=mount_tag
- Specifies the tag name to be used by the guest to mount
this export point
- -virtfs
fsdriver[,path=path],mount_tag=
mount_tag[,security_model=security_model][,writeout=writeout][,readonly][,socket=socket|sock_fd=sock_fd][,fmode=fmode][,dmode=dmode]
- The general form of a Virtual File system pass-through
options are:
- fsdriver
- This option specifies the fs driver backend to use.
Currently "local", "handle" and "proxy" file
system drivers are supported.
- id=id
- Specifies identifier for this device
- path=path
- Specifies the export path for the file system device. Files
under this path will be available to the 9p client on the guest.
- security_model=security_model
- Specifies the security model to be used for this export
path. Supported security models are "passthrough",
"mapped-xattr", "mapped-file" and "none". In
"passthrough" security model, files are stored using the same
credentials as they are created on the guest. This requires QEMU to run as
root. In "mapped-xattr" security model, some of the file
attributes like uid, gid, mode bits and link target are stored as file
attributes. For "mapped-file" these attributes are stored in the
hidden .virtfs_metadata directory. Directories exported by this security
model cannot interact with other unix tools. "none" security
model is same as passthrough except the sever won't report failures if it
fails to set file attributes like ownership. Security model is mandatory
only for local fsdriver. Other fsdrivers (like handle, proxy) don't take
security model as a parameter.
- writeout=writeout
- This is an optional argument. The only supported value is
"immediate". This means that host page cache will be used to
read and write data but write notification will be sent to the guest only
when the data has been reported as written by the storage subsystem.
- readonly
- Enables exporting 9p share as a readonly mount for guests.
By default read-write access is given.
- socket=socket
- Enables proxy filesystem driver to use passed socket file
for communicating with virtfs-proxy-helper. Usually a helper like libvirt
will create socketpair and pass one of the fds as sock_fd
- sock_fd
- Enables proxy filesystem driver to use passed 'sock_fd' as
the socket descriptor for interfacing with virtfs-proxy-helper
- fmode=fmode
- Specifies the default mode for newly created files on the
host. Works only with security models "mapped-xattr" and
"mapped-file".
- dmode=dmode
- Specifies the default mode for newly created directories on
the host. Works only with security models "mapped-xattr" and
"mapped-file".
- -virtfs_synth
- Create synthetic file system image
USB options
- -usb
- Enable the USB driver (if it is not used by default
yet).
- -usbdevice devname
- Add the USB device devname. Note that this option is
deprecated, please use "-device usb-..." instead.
- mouse
- Virtual Mouse. This will override the PS/2 mouse emulation
when activated.
- tablet
- Pointer device that uses absolute coordinates (like a
touchscreen). This means QEMU is able to report the mouse position without
having to grab the mouse. Also overrides the PS/2 mouse emulation when
activated.
- disk:[format=format]:file
- Mass storage device based on file. The optional
format argument will be used rather than detecting the format. Can
be used to specify "format=raw" to avoid interpreting an
untrusted format header.
- host:bus.addr
- Pass through the host device identified by
bus.addr (Linux only).
- host:vendor_id:product_id
- Pass through the host device identified by
vendor_id: product_id (Linux only).
- serial:[vendorid=vendor_id][,productid=product_id]:dev
- Serial converter to host character device dev, see
"-serial" for the available devices.
- braille
- Braille device. This will use BrlAPI to display the braille
output on a real or fake device.
- net:options
- Network adapter that supports CDC ethernet and RNDIS
protocols.
Display options
- -display type
- Select type of display to use. This option is a replacement
for the old style -sdl/-curses/... options. Valid values for type
are
- sdl
- Display video output via SDL (usually in a separate
graphics window; see the SDL documentation for other possibilities).
- curses
- Display video output via curses. For graphics device models
which support a text mode, QEMU can display this output using a
curses/ncurses interface. Nothing is displayed when the graphics device is
in graphical mode or if the graphics device does not support a text mode.
Generally only the VGA device models support text mode.
- none
- Do not display video output. The guest will still see an
emulated graphics card, but its output will not be displayed to the QEMU
user. This option differs from the -nographic option in that it only
affects what is done with video output; -nographic also changes the
destination of the serial and parallel port data.
- gtk
- Display video output in a GTK window. This interface
provides drop-down menus and other UI elements to configure and control
the VM during runtime.
- vnc
- Start a VNC server on display <arg>
- -nographic
- Normally, if QEMU is compiled with graphical window
support, it displays output such as guest graphics, guest console, and the
QEMU monitor in a window. With this option, you can totally disable
graphical output so that QEMU is a simple command line application. The
emulated serial port is redirected on the console and muxed with the
monitor (unless redirected elsewhere explicitly). Therefore, you can still
use QEMU to debug a Linux kernel with a serial console. Use C-a h
for help on switching between the console and monitor.
- -curses
- Normally, if QEMU is compiled with graphical window
support, it displays output such as guest graphics, guest console, and the
QEMU monitor in a window. With this option, QEMU can display the VGA
output when in text mode using a curses/ncurses interface. Nothing is
displayed in graphical mode.
- -no-frame
- Do not use decorations for SDL windows and start them using
the whole available screen space. This makes the using QEMU in a dedicated
desktop workspace more convenient.
- -alt-grab
- Use Ctrl-Alt-Shift to grab mouse (instead of Ctrl-Alt).
Note that this also affects the special keys (for fullscreen, monitor-mode
switching, etc).
- -ctrl-grab
- Use Right-Ctrl to grab mouse (instead of Ctrl-Alt). Note
that this also affects the special keys (for fullscreen, monitor-mode
switching, etc).
- -no-quit
- Disable SDL window close capability.
- -sdl
- Enable SDL.
- -spice
option[,option[,...]]
- Enable the spice remote desktop protocol. Valid options
are
- port=<nr>
- Set the TCP port spice is listening on for plaintext
channels.
- addr=<addr>
- Set the IP address spice is listening on. Default is any
address.
- ipv4
- ipv6
- unix
- Force using the specified IP version.
- password=<secret>
- Set the password you need to authenticate.
- sasl
- Require that the client use SASL to authenticate with the
spice. The exact choice of authentication method used is controlled from
the system / user's SASL configuration file for the 'qemu' service. This
is typically found in /etc/sasl2/qemu.conf. If running QEMU as an
unprivileged user, an environment variable SASL_CONF_PATH can be used to
make it search alternate locations for the service config. While some SASL
auth methods can also provide data encryption (eg GSSAPI), it is
recommended that SASL always be combined with the 'tls' and 'x509'
settings to enable use of SSL and server certificates. This ensures a data
encryption preventing compromise of authentication credentials.
- disable-ticketing
- Allow client connects without authentication.
- disable-copy-paste
- Disable copy paste between the client and the guest.
- disable-agent-file-xfer
- Disable spice-vdagent based file-xfer between the client
and the guest.
- tls-port=<nr>
- Set the TCP port spice is listening on for encrypted
channels.
- x509-dir=<dir>
- Set the x509 file directory. Expects same filenames as -vnc
$display,x509=$dir
- x509-key-file=<file>
- x509-key-password=<file>
- x509-cert-file=<file>
- x509-cacert-file=<file>
- x509-dh-key-file=<file>
- The x509 file names can also be configured
individually.
- tls-ciphers=<list>
- Specify which ciphers to use.
- tls-channel=[main|display|cursor|inputs|record|playback]
- plaintext-channel=[main|display|cursor|inputs|record|playback]
- Force specific channel to be used with or without TLS
encryption. The options can be specified multiple times to configure
multiple channels. The special name "default" can be used to set
the default mode. For channels which are not explicitly forced into one
mode the spice client is allowed to pick tls/plaintext as he pleases.
- image-compression=[auto_glz|auto_lz|quic|glz|lz|off]
- Configure image compression (lossless). Default is
auto_glz.
- jpeg-wan-compression=[auto|never|always]
- zlib-glz-wan-compression=[auto|never|always]
- Configure wan image compression (lossy for slow links).
Default is auto.
- streaming-video=[off|all|filter]
- Configure video stream detection. Default is off.
- agent-mouse=[on|off]
- Enable/disable passing mouse events via vdagent. Default is
on.
- playback-compression=[on|off]
- Enable/disable audio stream compression (using celt 0.5.1).
Default is on.
- seamless-migration=[on|off]
- Enable/disable spice seamless migration. Default is
off.
- gl=[on|off]
- Enable/disable OpenGL context. Default is off.
- rendernode=<file>
- DRM render node for OpenGL rendering. If not specified, it
will pick the first available. (Since 2.9)
- -portrait
- Rotate graphical output 90 deg left (only PXA LCD).
- -rotate deg
- Rotate graphical output some deg left (only PXA LCD).
- -vga type
- Select type of VGA card to emulate. Valid values for
type are
- cirrus
- Cirrus Logic GD5446 Video card. All Windows versions
starting from Windows 95 should recognize and use this graphic card. For
optimal performances, use 16 bit color depth in the guest and the host OS.
(This card was the default before QEMU 2.2)
- std
- Standard VGA card with Bochs VBE extensions. If your guest
OS supports the VESA 2.0 VBE extensions (e.g. Windows XP) and if you want
to use high resolution modes (>= 1280x1024x16) then you should use this
option. (This card is the default since QEMU 2.2)
- vmware
- VMWare SVGA-II compatible adapter. Use it if you have
sufficiently recent XFree86/XOrg server or Windows guest with a driver for
this card.
- qxl
- QXL paravirtual graphic card. It is VGA compatible
(including VESA 2.0 VBE support). Works best with qxl guest drivers
installed though. Recommended choice when using the spice protocol.
- tcx
- (sun4m only) Sun TCX framebuffer. This is the default
framebuffer for sun4m machines and offers both 8-bit and 24-bit colour
depths at a fixed resolution of 1024x768.
- cg3
- (sun4m only) Sun cgthree framebuffer. This is a simple
8-bit framebuffer for sun4m machines available in both 1024x768 (OpenBIOS)
and 1152x900 (OBP) resolutions aimed at people wishing to run older
Solaris versions.
- virtio
- Virtio VGA card.
- none
- Disable VGA card.
- -full-screen
- Start in full screen.
- -g
widthxheight[xdepth ]
- Set the initial graphical resolution and depth (PPC, SPARC
only).
- -vnc
display[,option[,option[,...]]]
- Normally, if QEMU is compiled with graphical window
support, it displays output such as guest graphics, guest console, and the
QEMU monitor in a window. With this option, you can have QEMU listen on
VNC display display and redirect the VGA display over the VNC
session. It is very useful to enable the usb tablet device when using this
option (option -device usb-tablet). When using the VNC display, you
must use the -k parameter to set the keyboard layout if you are not
using en-us. Valid syntax for the display is
- to=L
- With this option, QEMU will try next available VNC
displays, until the number L, if the origianlly defined
"-vnc display" is not available, e.g. port 5900+
display is already used by another application. By default,
to=0.
- host:d
- TCP connections will only be allowed from host on
display d. By convention the TCP port is 5900+ d.
Optionally, host can be omitted in which case the server will
accept connections from any host.
- unix:path
- Connections will be allowed over UNIX domain sockets where
path is the location of a unix socket to listen for connections
on.
- none
- VNC is initialized but not started. The monitor
"change" command can be used to later start the VNC server.
Following the
display value there may be one or more
option flags
separated by commas. Valid options are
- reverse
- Connect to a listening VNC client via a "reverse"
connection. The client is specified by the display. For reverse
network connections ( host:d,"reverse"), the
d argument is a TCP port number, not a display number.
- websocket
- Opens an additional TCP listening port dedicated to VNC
Websocket connections. If a bare websocket option is given, the
Websocket port is 5700+ display. An alternative port can be
specified with the syntax "websocket"= port.
If host is specified connections will only be allowed from this host.
It is possible to control the websocket listen address independently,
using the syntax "websocket"= host:port.
If no TLS credentials are provided, the websocket connection runs in
unencrypted mode. If TLS credentials are provided, the websocket
connection requires encrypted client connections.
- password
- Require that password based authentication is used for
client connections.
The password must be set separately using the "set_password"
command in the pcsys_monitor. The syntax to change your password
is: "set_password <protocol> <password>" where
<protocol> could be either "vnc" or "spice".
If you would like to change <protocol> password expiration, you should
use "expire_password <protocol> <expiration-time>"
where expiration time could be one of the following options: now, never,
+seconds or UNIX time of expiration, e.g. +60 to make password expire in
60 seconds, or 1335196800 to make password expire on "Mon Apr 23
12:00:00 EDT 2012" (UNIX time for this date and time).
You can also use keywords "now" or "never" for the
expiration time to allow <protocol> password to expire immediately
or never expire.
- tls-creds=ID
- Provides the ID of a set of TLS credentials to use to
secure the VNC server. They will apply to both the normal VNC server
socket and the websocket socket (if enabled). Setting TLS credentials will
cause the VNC server socket to enable the VeNCrypt auth mechanism. The
credentials should have been previously created using the -object
tls-creds argument.
The tls-creds parameter obsoletes the tls, x509, and
x509verify options, and as such it is not permitted to set both new
and old type options at the same time.
- tls
- Require that client use TLS when communicating with the VNC
server. This uses anonymous TLS credentials so is susceptible to a
man-in-the-middle attack. It is recommended that this option be combined
with either the x509 or x509verify options.
This option is now deprecated in favor of using the tls-creds
argument.
- x509=/path/to/certificate/dir
- Valid if tls is specified. Require that x509
credentials are used for negotiating the TLS session. The server will send
its x509 certificate to the client. It is recommended that a password be
set on the VNC server to provide authentication of the client when this is
used. The path following this option specifies where the x509 certificates
are to be loaded from. See the vnc_security section for details on
generating certificates.
This option is now deprecated in favour of using the tls-creds
argument.
- x509verify=/path/to/certificate/dir
- Valid if tls is specified. Require that x509
credentials are used for negotiating the TLS session. The server will send
its x509 certificate to the client, and request that the client send its
own x509 certificate. The server will validate the client's certificate
against the CA certificate, and reject clients when validation fails. If
the certificate authority is trusted, this is a sufficient authentication
mechanism. You may still wish to set a password on the VNC server as a
second authentication layer. The path following this option specifies
where the x509 certificates are to be loaded from. See the
vnc_security section for details on generating certificates.
This option is now deprecated in favour of using the tls-creds
argument.
- sasl
- Require that the client use SASL to authenticate with the
VNC server. The exact choice of authentication method used is controlled
from the system / user's SASL configuration file for the 'qemu' service.
This is typically found in /etc/sasl2/qemu.conf. If running QEMU as an
unprivileged user, an environment variable SASL_CONF_PATH can be used to
make it search alternate locations for the service config. While some SASL
auth methods can also provide data encryption (eg GSSAPI), it is
recommended that SASL always be combined with the 'tls' and 'x509'
settings to enable use of SSL and server certificates. This ensures a data
encryption preventing compromise of authentication credentials. See the
vnc_security section for details on using SASL authentication.
- acl
- Turn on access control lists for checking of the x509
client certificate and SASL party. For x509 certs, the ACL check is made
against the certificate's distinguished name. This is something that looks
like "C=GB,O=ACME,L=Boston,CN=bob". For SASL party, the ACL
check is made against the username, which depending on the SASL plugin,
may include a realm component, eg "bob" or
"bob@EXAMPLE.COM". When the acl flag is set, the initial
access list will be empty, with a "deny" policy. Thus no one
will be allowed to use the VNC server until the ACLs have been loaded.
This can be achieved using the "acl" monitor command.
- lossy
- Enable lossy compression methods (gradient, JPEG, ...). If
this option is set, VNC client may receive lossy framebuffer updates
depending on its encoding settings. Enabling this option can save a lot of
bandwidth at the expense of quality.
- non-adaptive
- Disable adaptive encodings. Adaptive encodings are enabled
by default. An adaptive encoding will try to detect frequently updated
screen regions, and send updates in these regions using a lossy encoding
(like JPEG). This can be really helpful to save bandwidth when playing
videos. Disabling adaptive encodings restores the original static behavior
of encodings like Tight.
- share=[allow-exclusive|force-shared|ignore]
- Set display sharing policy. 'allow-exclusive' allows
clients to ask for exclusive access. As suggested by the rfb spec this is
implemented by dropping other connections. Connecting multiple clients in
parallel requires all clients asking for a shared session (vncviewer:
-shared switch). This is the default. 'force-shared' disables exclusive
client access. Useful for shared desktop sessions, where you don't want
someone forgetting specify -shared disconnect everybody else. 'ignore'
completely ignores the shared flag and allows everybody connect
unconditionally. Doesn't conform to the rfb spec but is traditional QEMU
behavior.
- key-delay-ms
- Set keyboard delay, for key down and key up events, in
milliseconds. Default is 10. Keyboards are low-bandwidth devices, so this
slowdown can help the device and guest to keep up and not lose events in
case events are arriving in bulk. Possible causes for the latter are flaky
network connections, or scripts for automated testing.
i386 target only
- -win2k-hack
- Use it when installing Windows 2000 to avoid a disk full
bug. After Windows 2000 is installed, you no longer need this option (this
option slows down the IDE transfers).
- -no-fd-bootchk
- Disable boot signature checking for floppy disks in BIOS.
May be needed to boot from old floppy disks.
- -no-acpi
- Disable ACPI (Advanced Configuration and Power Interface)
support. Use it if your guest OS complains about ACPI problems (PC target
machine only).
- -no-hpet
- Disable HPET support.
- -acpitable
[sig=str][,rev=n][,oem_id=
str][,oem_table_id= str][,oem_rev=n]
[,asl_compiler_id=
str][,asl_compiler_rev=n][,data=
file1[: file2]...]
- Add ACPI table with specified header fields and context
from specified files. For file=, take whole ACPI table from the specified
files, including all ACPI headers (possible overridden by other options).
For data=, only data portion of the table is used, all header information
is specified in the command line. If a SLIC table is supplied to QEMU,
then the SLIC's oem_id and oem_table_id fields will override the same in
the RSDT and the FADT (a.k.a. FACP), in order to ensure the field matches
required by the Microsoft SLIC spec and the ACPI spec.
- -smbios file=binary
- Load SMBIOS entry from binary file.
- -smbios
type=0[,vendor=str][,version=str][,date=str][,release=%d.%d][,uefi=on|off]
- Specify SMBIOS type 0 fields
- -smbios
type=1[,manufacturer=str][,product=
str][,version=
str][,serial=str][,uuid=
uuid][,sku= str][,family=str]
- Specify SMBIOS type 1 fields
- -smbios
type=2[,manufacturer=str][,product=
str][,version=
str][,serial=str][,asset=
str][,location=
str][,family=str]
- Specify SMBIOS type 2 fields
- -smbios
type=3[,manufacturer=str][,version=
str][,serial=
str][,asset=str][,sku= str]
- Specify SMBIOS type 3 fields
- -smbios
type=4[,sock_pfx=str][,manufacturer=
str][,version=
str][,serial=str][,asset=
str][,part= str]
- Specify SMBIOS type 4 fields
- -smbios
type=17[,loc_pfx=str][,bank=str][,manufacturer=str][,serial=str][,asset=str][,part=str][,speed=%d]
- Specify SMBIOS type 17 fields
Network options
- -net
nic[,vlan=n][,macaddr=mac][,model=type]
[,name=
name][,addr=addr][,vectors=v]
- Create a new Network Interface Card and connect it to VLAN
n (n = 0 is the default). The NIC is an e1000 by default on
the PC target. Optionally, the MAC address can be changed to mac,
the device address set to addr (PCI cards only), and a name
can be assigned for use in monitor commands. Optionally, for PCI cards,
you can specify the number v of MSI-X vectors that the card should
have; this option currently only affects virtio cards; set v = 0 to
disable MSI-X. If no -net option is specified, a single NIC is
created. QEMU can emulate several different models of network card. Valid
values for type are "virtio", "i82551",
"i82557b", "i82559er", "ne2k_pci",
"ne2k_isa", "pcnet", "rtl8139",
"e1000", "smc91c111", "lance" and
"mcf_fec". Not all devices are supported on all targets. Use
"-net nic,model=help" for a list of available devices for your
target.
- -netdev
user,id=id[,option][,
option][,...]
- -net
user[,option][,option][,...]
- Use the user mode network stack which requires no
administrator privilege to run. Valid options are:
- vlan=n
- Connect user mode stack to VLAN n (n = 0 is
the default).
- id=id
- name=name
- Assign symbolic name for use in monitor commands.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be
enabled. If neither is specified both protocols are enabled.
- net=addr[/mask]
- Set IP network address the guest will see. Optionally
specify the netmask, either in the form a.b.c.d or as number of valid
top-most bits. Default is 10.0.2.0/24.
- host=addr
- Specify the guest-visible address of the host. Default is
the 2nd IP in the guest network, i.e. x.x.x.2.
- ipv6-net=addr[/int]
- Set IPv6 network address the guest will see (default is
fec0::/64). The network prefix is given in the usual hexadecimal IPv6
address notation. The prefix size is optional, and is given as the number
of valid top-most bits (default is 64).
- ipv6-host=addr
- Specify the guest-visible IPv6 address of the host. Default
is the 2nd IPv6 in the guest network, i.e. xxxx::2.
- restrict=on|off
- If this option is enabled, the guest will be isolated, i.e.
it will not be able to contact the host and no guest IP packets will be
routed over the host to the outside. This option does not affect any
explicitly set forwarding rules.
- hostname=name
- Specifies the client hostname reported by the built-in DHCP
server.
- dhcpstart=addr
- Specify the first of the 16 IPs the built-in DHCP server
can assign. Default is the 15th to 31st IP in the guest network, i.e.
x.x.x.15 to x.x.x.31.
- dns=addr
- Specify the guest-visible address of the virtual
nameserver. The address must be different from the host address. Default
is the 3rd IP in the guest network, i.e. x.x.x.3.
- ipv6-dns=addr
- Specify the guest-visible address of the IPv6 virtual
nameserver. The address must be different from the host address. Default
is the 3rd IP in the guest network, i.e. xxxx::3.
- dnssearch=domain
- Provides an entry for the domain-search list sent by the
built-in DHCP server. More than one domain suffix can be transmitted by
specifying this option multiple times. If supported, this will cause the
guest to automatically try to append the given domain suffix(es) in case a
domain name can not be resolved.
Example:
qemu -net user,dnssearch=mgmt.example.org,dnssearch=example.org [...]
- tftp=dir
- When using the user mode network stack, activate a built-in
TFTP server. The files in dir will be exposed as the root of a TFTP
server. The TFTP client on the guest must be configured in binary mode
(use the command "bin" of the Unix TFTP client).
- bootfile=file
- When using the user mode network stack, broadcast
file as the BOOTP filename. In conjunction with tftp, this
can be used to network boot a guest from a local directory.
Example (using pxelinux):
qemu-system-i386 -hda linux.img -boot n -net user,tftp=/path/to/tftp/files,bootfile=/pxelinux.0
- smb=dir[,smbserver=addr]
- When using the user mode network stack, activate a built-in
SMB server so that Windows OSes can access to the host files in
dir transparently. The IP address of the SMB server
can be set to addr. By default the 4th IP in the guest network is
used, i.e. x.x.x.4.
In the guest Windows OS, the line:
10.0.2.4 smbserver
must be added in the file C:\WINDOWS\LMHOSTS (for windows 9x/Me) or
C:\WINNT\SYSTEM32\DRIVERS\ETC\LMHOSTS (Windows NT/2000).
Then dir can be accessed in \\smbserver\qemu.
Note that a SAMBA server must be installed on the host OS. QEMU was tested
successfully with smbd versions from Red Hat 9, Fedora Core 3 and OpenSUSE
11.x.
- hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport
- Redirect incoming TCP or UDP connections to the host port
hostport to the guest IP address guestaddr on guest port
guestport. If guestaddr is not specified, its value is
x.x.x.15 (default first address given by the built-in DHCP server). By
specifying hostaddr, the rule can be bound to a specific host
interface. If no connection type is set, TCP is used. This option can be
given multiple times.
For example, to redirect host X11 connection from screen 1 to guest screen
0, use the following:
# on the host
qemu-system-i386 -net user,hostfwd=tcp:127.0.0.1:6001-:6000 [...]
# this host xterm should open in the guest X11 server
xterm -display :1
To redirect telnet connections from host port 5555 to telnet port on the
guest, use the following:
# on the host
qemu-system-i386 -net user,hostfwd=tcp::5555-:23 [...]
telnet localhost 5555
Then when you use on the host "telnet localhost 5555", you connect
to the guest telnet server.
- guestfwd=[tcp]:server:port-dev
- guestfwd=[tcp]:server:port-cmd:command
- Forward guest TCP connections to the IP address
server on port port to the character device dev or to
a program executed by cmd:command which gets spawned for each
connection. This option can be given multiple times.
You can either use a chardev directly and have that one used throughout
QEMU's lifetime, like in the following example:
# open 10.10.1.1:4321 on bootup, connect 10.0.2.100:1234 to it whenever
# the guest accesses it
qemu -net user,guestfwd=tcp:10.0.2.100:1234-tcp:10.10.1.1:4321 [...]
Or you can execute a command on every TCP connection established by the
guest, so that QEMU behaves similar to an inetd process for that virtual
server:
# call "netcat 10.10.1.1 4321" on every TCP connection to 10.0.2.100:1234
# and connect the TCP stream to its stdin/stdout
qemu -net 'user,guestfwd=tcp:10.0.2.100:1234-cmd:netcat 10.10.1.1 4321'
Note: Legacy stand-alone options -tftp, -bootp, -smb and -redir are still
processed and applied to -net user. Mixing them with the new configuration
syntax gives undefined results. Their use for new applications is discouraged
as they will be removed from future versions.
- -netdev
tap,id=id[,fd=h][,ifname=
name][,script=
file][,downscript=dfile][,br=
bridge][,helper= helper]
- -net
tap[,vlan=n][,name=name][,fd=
h][,ifname=
name][,script=file][,downscript=
dfile][,br=
bridge][,helper=helper]
- Connect the host TAP network interface name to VLAN
n.
Use the network script file to configure it and the network script
dfile to deconfigure it. If name is not provided, the OS
automatically provides one. The default network configure script is
/etc/qemu-ifup and the default network deconfigure script is
/etc/qemu-ifdown. Use script=no or downscript=no to
disable script execution.
If running QEMU as an unprivileged user, use the network helper
helper to configure the TAP interface and attach it to the bridge.
The default network helper executable is
/path/to/qemu-bridge-helper and the default bridge device is
br0.
fd=h can be used to specify the handle of an already opened
host TAP interface.
Examples:
#launch a QEMU instance with the default network script
qemu-system-i386 linux.img -net nic -net tap
#launch a QEMU instance with two NICs, each one connected
#to a TAP device
qemu-system-i386 linux.img \
-net nic,vlan=0 -net tap,vlan=0,ifname=tap0 \
-net nic,vlan=1 -net tap,vlan=1,ifname=tap1
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-i386 linux.img \
-net nic -net tap,"helper=/path/to/qemu-bridge-helper"
- -netdev
bridge,id=id[,br=bridge][,helper=helper]
- -net
bridge[,vlan=n][,name=name][,br=bridge][,helper=helper]
- Connect a host TAP network interface to a host bridge
device.
Use the network helper helper to configure the TAP interface and
attach it to the bridge. The default network helper executable is
/path/to/qemu-bridge-helper and the default bridge device is
br0.
Examples:
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge br0
qemu-system-i386 linux.img -net bridge -net nic,model=virtio
#launch a QEMU instance with the default network helper to
#connect a TAP device to bridge qemubr0
qemu-system-i386 linux.img -net bridge,br=qemubr0 -net nic,model=virtio
- -netdev
socket,id=id[,fd=h][,listen=[
host]:
port][,connect=host:port ]
- -net
socket[,vlan=n][,name=name][,fd=h]
[,listen=[
host]:port][,connect=host:port]
- Connect the VLAN n to a remote VLAN in another QEMU
virtual machine using a TCP socket connection. If listen is
specified, QEMU waits for incoming connections on port (
host is optional). connect is used to connect to another
QEMU instance using the listen option. fd=h specifies
an already opened TCP socket.
Example:
# launch a first QEMU instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,listen=:1234
# connect the VLAN 0 of this instance to the VLAN 0
# of the first instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:57 \
-net socket,connect=127.0.0.1:1234
- -netdev
socket,id=id[,fd=h][,mcast=
maddr: port[,localaddr=addr]]
- -net
socket[,vlan=n][,name=name][,fd=h][,mcast=maddr:port[,localaddr=addr]]
- Create a VLAN n shared with another QEMU virtual
machines using a UDP multicast socket, effectively making a bus for every
QEMU with same multicast address maddr and port. NOTES:
- 1.
- Several QEMU can be running on different hosts and share
same bus (assuming correct multicast setup for these hosts).
- 2.
- mcast support is compatible with User Mode Linux (argument
ethN=mcast), see <
http://user-mode-linux.sf.net>.
- 3.
- Use fd=h to specify an already opened UDP multicast
socket.
Example:
# launch one QEMU instance
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=230.0.0.1:1234
# launch another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:57 \
-net socket,mcast=230.0.0.1:1234
# launch yet another QEMU instance on same "bus"
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:58 \
-net socket,mcast=230.0.0.1:1234
Example (User Mode Linux compat.):
# launch QEMU instance (note mcast address selected
# is UML's default)
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=239.192.168.1:1102
# launch UML
/path/to/linux ubd0=/path/to/root_fs eth0=mcast
Example (send packets from host's 1.2.3.4):
qemu-system-i386 linux.img \
-net nic,macaddr=52:54:00:12:34:56 \
-net socket,mcast=239.192.168.1:1102,localaddr=1.2.3.4
- -netdev
l2tpv3,id=id,src=srcaddr
,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6][,udp][,cookie64][,counter][,pincounter][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset]
- -net
l2tpv3[,vlan=n][,name=name],src=srcaddr,dst=dstaddr[,srcport=srcport][,dstport=dstport],txsession=txsession[,rxsession=rxsession][,ipv6][,udp][,cookie64][,counter][,pincounter][,txcookie=txcookie][,rxcookie=rxcookie][,offset=offset]
- Connect VLAN n to L2TPv3 pseudowire. L2TPv3
(RFC3391) is a popular protocol to transport Ethernet (and other Layer 2)
data frames between two systems. It is present in routers, firewalls and
the Linux kernel (from version 3.3 onwards).
This transport allows a VM to communicate to another VM, router or firewall
directly.
- src=srcaddr
- source address (mandatory)
- dst=dstaddr
- destination address (mandatory)
- udp
- select udp encapsulation (default is ip).
- srcport=srcport
- source udp port.
- dstport=dstport
- destination udp port.
- ipv6
- force v6, otherwise defaults to v4.
- rxcookie=rxcookie
- txcookie=txcookie
- Cookies are a weak form of security in the l2tpv3
specification. Their function is mostly to prevent misconfiguration. By
default they are 32 bit.
- cookie64
- Set cookie size to 64 bit instead of the default 32
- counter=off
- Force a 'cut-down' L2TPv3 with no counter as in
draft-mkonstan-l2tpext-keyed-ipv6-tunnel-00
- pincounter=on
- Work around broken counter handling in peer. This may also
help on networks which have packet reorder.
- offset=offset
- Add an extra offset between header and data
For example, to attach a VM running on host 4.3.2.1 via L2TPv3 to the bridge
br-lan on the remote Linux host 1.2.3.4:
# Setup tunnel on linux host using raw ip as encapsulation
# on 1.2.3.4
ip l2tp add tunnel remote 4.3.2.1 local 1.2.3.4 tunnel_id 1 peer_tunnel_id 1 \
encap udp udp_sport 16384 udp_dport 16384
ip l2tp add session tunnel_id 1 name vmtunnel0 session_id \
0xFFFFFFFF peer_session_id 0xFFFFFFFF
ifconfig vmtunnel0 mtu 1500
ifconfig vmtunnel0 up
brctl addif br-lan vmtunnel0
# on 4.3.2.1
# launch QEMU instance - if your network has reorder or is very lossy add ,pincounter
qemu-system-i386 linux.img -net nic -net l2tpv3,src=4.2.3.1,dst=1.2.3.4,udp,srcport=16384,dstport=16384,rxsession=0xffffffff,txsession=0xffffffff,counter
- -netdev
vde,id=id[,sock=socketpath
][,port=n][,group=groupname][,mode=octalmode]
- -net
vde[,vlan=n][,name=name][,sock=
socketpath ]
[,port=n][,group=groupname][,mode=octalmode]
- Connect VLAN n to PORT n of a vde switch
running on host and listening for incoming connections on
socketpath. Use GROUP groupname and MODE octalmode to
change default ownership and permissions for communication port. This
option is only available if QEMU has been compiled with vde support
enabled.
Example:
# launch vde switch
vde_switch -F -sock /tmp/myswitch
# launch QEMU instance
qemu-system-i386 linux.img -net nic -net vde,sock=/tmp/myswitch
- -netdev
hubport,id=id,hubid=hubid
- Create a hub port on QEMU "vlan" hubid.
The hubport netdev lets you connect a NIC to a QEMU "vlan" instead
of a single netdev. "-net" and "-device" with
parameter vlan create the required hub automatically.
- -netdev
vhost-user,chardev=id[,vhostforce=on|off][,queues=n]
- Establish a vhost-user netdev, backed by a chardev
id. The chardev should be a unix domain socket backed one. The
vhost-user uses a specifically defined protocol to pass vhost ioctl
replacement messages to an application on the other end of the socket. On
non-MSIX guests, the feature can be forced with vhostforce. Use
'queues= n' to specify the number of queues to be created for
multiqueue vhost-user.
Example:
qemu -m 512 -object memory-backend-file,id=mem,size=512M,mem-path=/hugetlbfs,share=on \
-numa node,memdev=mem \
-chardev socket,id=chr0,path=/path/to/socket \
-netdev type=vhost-user,id=net0,chardev=chr0 \
-device virtio-net-pci,netdev=net0
- -net
dump[,vlan=n][,file=file][,len=len]
- Dump network traffic on VLAN n to file file
(qemu-vlan0.pcap by default). At most len bytes (64k by
default) per packet are stored. The file format is libpcap, so it can be
analyzed with tools such as tcpdump or Wireshark. Note: For devices
created with '-netdev', use '-object filter-dump,...' instead.
- -net none
- Indicate that no network devices should be configured. It
is used to override the default configuration ( -net nic -net user)
which is activated if no -net options are provided.
Character device options
The general form of a character device option is:
- -chardev backend ,id=id
[,mux=on|off] [, options]
- Backend is one of: null, socket, udp,
msmouse, vc, ringbuf, file, pipe,
console, serial, pty, stdio, braille,
tty, parallel, parport, spicevmc.
spiceport. The specific backend will determine the applicable
options.
Use "-chardev help" to print all available chardev backend types.
All devices must have an id, which can be any string up to 127 characters
long. It is used to uniquely identify this device in other command line
directives.
A character device may be used in multiplexing mode by multiple front-ends.
Specify mux=on to enable this mode. A multiplexer is a
"1:N" device, and here the "1" end is your specified
chardev backend, and the "N" end is the various parts of QEMU
that can talk to a chardev. If you create a chardev with id=myid
and mux=on, QEMU will create a multiplexer with your specified ID,
and you can then configure multiple front ends to use that chardev ID for
their input/output. Up to four different front ends can be connected to a
single multiplexed chardev. (Without multiplexing enabled, a chardev can
only be used by a single front end.) For instance you could use this to
allow a single stdio chardev to be used by two serial ports and the QEMU
monitor:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-serial chardev:char0 \
-serial chardev:char0
You can have more than one multiplexer in a system configuration; for
instance you could have a TCP port multiplexed between UART 0 and UART 1,
and stdio multiplexed between the QEMU monitor and a parallel port:
-chardev stdio,mux=on,id=char0 \
-mon chardev=char0,mode=readline \
-parallel chardev:char0 \
-chardev tcp,...,mux=on,id=char1 \
-serial chardev:char1 \
-serial chardev:char1
When you're using a multiplexed character device, some escape sequences are
interpreted in the input.
Note that some other command line options may implicitly create multiplexed
character backends; for instance -serial mon:stdio creates a
multiplexed stdio backend connected to the serial port and the QEMU
monitor, and -nographic also multiplexes the console and the
monitor to stdio.
There is currently no support for multiplexing in the other direction (where
a single QEMU front end takes input and output from multiple chardevs).
Every backend supports the logfile option, which supplies the path to
a file to record all data transmitted via the backend. The
logappend option controls whether the log file will be truncated or
appended to when opened.
Further options to each backend are described below.
- -chardev null ,id=id
- A void device. This device will not emit any data, and will
drop any data it receives. The null backend does not take any
options.
- -chardev socket ,id=id [TCP
options or unix options] [,server] [,nowait] [,telnet]
[,reconnect= seconds] [,tls-creds=id]
- Create a two-way stream socket, which can be either a TCP
or a unix socket. A unix socket will be created if path is
specified. Behaviour is undefined if TCP options are specified for a unix
socket.
server specifies that the socket shall be a listening socket.
nowait specifies that QEMU should not block waiting for a client to
connect to a listening socket.
telnet specifies that traffic on the socket should interpret telnet
escape sequences.
reconnect sets the timeout for reconnecting on non-server sockets
when the remote end goes away. qemu will delay this many seconds and then
attempt to reconnect. Zero disables reconnecting, and is the default.
tls-creds requests enablement of the TLS protocol for encryption,
and specifies the id of the TLS credentials to use for the handshake. The
credentials must be previously created with the -object tls-creds
argument.
TCP and unix socket options are given below:
- TCP options: port=port
[,host=host ] [,to=to] [,ipv4] [,ipv6]
[,nodelay]
- host for a listening socket specifies the local
address to be bound. For a connecting socket species the remote host to
connect to. host is optional for listening sockets. If not
specified it defaults to 0.0.0.0.
port for a listening socket specifies the local port to be bound.
For a connecting socket specifies the port on the remote host to connect
to. port can be given as either a port number or a service name.
port is required.
to is only relevant to listening sockets. If it is specified, and
port cannot be bound, QEMU will attempt to bind to subsequent ports
up to and including to until it succeeds. to must be
specified as a port number.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used.
If neither is specified the socket may use either protocol.
nodelay disables the Nagle algorithm.
- unix options: path=path
- path specifies the local path of the unix socket.
path is required.
- -chardev udp ,id=id
[,host=host] ,port=port
[,localaddr=localaddr ]
[,localport=localport] [,ipv4] [,ipv6]
- Sends all traffic from the guest to a remote host over UDP.
host specifies the remote host to connect to. If not specified it
defaults to "localhost".
port specifies the port on the remote host to connect to.
port is required.
localaddr specifies the local address to bind to. If not specified
it defaults to 0.0.0.0.
localport specifies the local port to bind to. If not specified any
available local port will be used.
ipv4 and ipv6 specify that either IPv4 or IPv6 must be used.
If neither is specified the device may use either protocol.
- -chardev msmouse ,id=id
- Forward QEMU's emulated msmouse events to the guest.
msmouse does not take any options.
- -chardev vc ,id=id
[[,width=width ] [,height=height]]
[[,cols= cols] [,rows=rows]]
- Connect to a QEMU text console. vc may optionally be
given a specific size.
width and height specify the width and height respectively of
the console, in pixels.
cols and rows specify that the console be sized to fit a text
console with the given dimensions.
- -chardev ringbuf ,id=id
[,size=size ]
- Create a ring buffer with fixed size size.
size must be a power of two and defaults to "64K".
- -chardev file ,id=id
,path=path
- Log all traffic received from the guest to a file.
path specifies the path of the file to be opened. This file will be
created if it does not already exist, and overwritten if it does.
path is required.
- -chardev pipe ,id=id
,path=path
- Create a two-way connection to the guest. The behaviour
differs slightly between Windows hosts and other hosts:
On Windows, a single duplex pipe will be created at
\\.pipe\path .
On other hosts, 2 pipes will be created called
path.in and
path.out. Data written to
path .in will be received by the guest. Data
written by the guest can be read from
path.out. QEMU will not create these fifos,
and requires them to be present.
path forms part of the pipe path as described above. path is
required.
- -chardev console ,id=id
- Send traffic from the guest to QEMU's standard output.
console does not take any options.
console is only available on Windows hosts.
- -chardev serial ,id=id
,path=path
- Send traffic from the guest to a serial device on the host.
On Unix hosts serial will actually accept any tty device, not only serial
lines.
path specifies the name of the serial device to open.
- -chardev pty ,id=id
- Create a new pseudo-terminal on the host and connect to it.
pty does not take any options.
pty is not available on Windows hosts.
- -chardev stdio ,id=id
[,signal=on|off]
- Connect to standard input and standard output of the QEMU
process.
signal controls if signals are enabled on the terminal, that
includes exiting QEMU with the key sequence Control-c. This option
is enabled by default, use signal=off to disable it.
- -chardev braille ,id=id
- Connect to a local BrlAPI server. braille does not
take any options.
- -chardev tty ,id=id
,path=path
- tty is only available on Linux, Sun, FreeBSD,
NetBSD, OpenBSD and DragonFlyBSD hosts. It is an alias for serial.
path specifies the path to the tty. path is required.
- -chardev parallel ,id=id
,path=path
- -chardev parport ,id=id
,path=path
- parallel is only available on Linux, FreeBSD and
DragonFlyBSD hosts.
Connect to a local parallel port.
path specifies the path to the parallel port device. path is
required.
- -chardev spicevmc ,id=id
,debug=debug , name=name
- spicevmc is only available when spice support is
built in.
debug debug level for spicevmc
name name of spice channel to connect to
Connect to a spice virtual machine channel, such as vdiport.
- -chardev spiceport ,id=id
,debug=debug , name=name
- spiceport is only available when spice support is
built in.
debug debug level for spicevmc
name name of spice port to connect to
Connect to a spice port, allowing a Spice client to handle the traffic
identified by a name (preferably a fqdn).
Device URL Syntax
In addition to using normal file images for the emulated storage devices, QEMU
can also use networked resources such as iSCSI devices. These are specified
using a special URL syntax.
- iSCSI
- iSCSI support allows QEMU to access iSCSI resources
directly and use as images for the guest storage. Both disk and cdrom
images are supported.
Syntax for specifying iSCSI LUNs is
"iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>"
By default qemu will use the iSCSI initiator-name
'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from
the command line or a configuration file.
Since version Qemu 2.4 it is possible to specify a iSCSI request timeout to
detect stalled requests and force a reestablishment of the session. The
timeout is specified in seconds. The default is 0 which means no timeout.
Libiscsi 1.15.0 or greater is required for this feature.
Example (without authentication):
qemu-system-i386 -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
-cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
-drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via URL):
qemu-system-i386 -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1
Example (CHAP username/password via environment variables):
LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
qemu-system-i386 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
iSCSI support is an optional feature of QEMU and only available when
compiled and linked against libiscsi.
iSCSI parameters such as username and password can also be specified via a
configuration file. See qemu-doc for more information and examples.
- NBD
- QEMU supports NBD (Network Block Devices) both using TCP
protocol as well as Unix Domain Sockets.
Syntax for specifying a NBD device using TCP
"nbd:<server-ip>:<port>[:exportname=<export>]"
Syntax for specifying a NBD device using Unix Domain Sockets
"nbd:unix:<domain-socket>[:exportname=<export>]"
Example for TCP
qemu-system-i386 --drive file=nbd:192.0.2.1:30000
Example for Unix Domain Sockets
qemu-system-i386 --drive file=nbd:unix:/tmp/nbd-socket
- SSH
- QEMU supports SSH (Secure Shell) access to remote disks.
Examples:
qemu-system-i386 -drive file=ssh://user@host/path/to/disk.img
qemu-system-i386 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
Currently authentication must be done using ssh-agent. Other authentication
methods may be supported in future.
- Sheepdog
- Sheepdog is a distributed storage system for QEMU. QEMU
supports using either local sheepdog devices or remote networked devices.
Syntax for specifying a sheepdog device
sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]
Example
qemu-system-i386 --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine
See also < https://sheepdog.github.io/sheepdog/>.
- GlusterFS
- GlusterFS is a user space distributed file system. QEMU
supports the use of GlusterFS volumes for hosting VM disk images using
TCP, Unix Domain Sockets and RDMA transport protocols.
Syntax for specifying a VM disk image on GlusterFS volume is
URI:
gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]
JSON:
'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
"server":[{"type":"tcp","host":"...","port":"..."},
{"type":"unix","socket":"..."}]}}'
Example
URI:
qemu-system-x86_64 --drive file=gluster://192.0.2.1/testvol/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log
JSON:
qemu-system-x86_64 'json:{"driver":"qcow2",
"file":{"driver":"gluster",
"volume":"testvol","path":"a.img",
"debug":9,"logfile":"/var/log/qemu-gluster.log",
"server":[{"type":"tcp","host":"1.2.3.4","port":24007},
{"type":"unix","socket":"/var/run/glusterd.socket"}]}}'
qemu-system-x86_64 -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
file.debug=9,file.logfile=/var/log/qemu-gluster.log,
file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket
See also < http://www.gluster.org>.
- HTTP/HTTPS/FTP/FTPS
- QEMU supports read-only access to files accessed over
http(s) and ftp(s).
Syntax using a single filename:
<protocol>://[<username>[:<password>]@]<host>/<path>
where:
- protocol
- 'http', 'https', 'ftp', or 'ftps'.
- username
- Optional username for authentication to the remote
server.
- password
- Optional password for authentication to the remote
server.
- host
- Address of the remote server.
- path
- Path on the remote server, including any query string.
The following options are also supported:
- url
- The full URL when passing options to the driver
explicitly.
- readahead
- The amount of data to read ahead with each range request to
the remote server. This value may optionally have the suffix 'T', 'G',
'M', 'K', 'k' or 'b'. If it does not have a suffix, it will be assumed to
be in bytes. The value must be a multiple of 512 bytes. It defaults to
256k.
- sslverify
- Whether to verify the remote server's certificate when
connecting over SSL. It can have the value 'on' or 'off'. It defaults to
'on'.
- cookie
- Send this cookie (it can also be a list of cookies
separated by ';') with each outgoing request. Only supported when using
protocols such as HTTP which support cookies, otherwise ignored.
- timeout
- Set the timeout in seconds of the CURL connection. This
timeout is the time that CURL waits for a response from the remote server
to get the size of the image to be downloaded. If not set, the default
timeout of 5 seconds is used.
Note that when passing options to qemu explicitly,
driver is the value of
<protocol>.
Example: boot from a remote Fedora 20 live ISO image
qemu-system-x86_64 --drive media=cdrom,file=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
qemu-system-x86_64 --drive media=cdrom,file.driver=http,file.url=http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
Example: boot from a remote Fedora 20 cloud image using a local overlay for
writes, copy-on-read, and a readahead of 64k
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"http",, "file.url":"https://dl.fedoraproject.org/pub/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2
qemu-system-x86_64 -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on
Example: boot from an image stored on a VMware vSphere server with a self-signed
certificate using a local overlay for writes, a readahead of 64k and a timeout
of 10 seconds.
qemu-img create -f qcow2 -o backing_file='json:{"file.driver":"https",, "file.url":"https://user:password@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10}' /tmp/test.qcow2
qemu-system-x86_64 -drive file=/tmp/test.qcow2
Bluetooth(R) options
- -bt hci[...]
- Defines the function of the corresponding Bluetooth HCI.
-bt options are matched with the HCIs present in the chosen machine type.
For example when emulating a machine with only one HCI built into it, only
the first "-bt hci[...]" option is valid and defines the HCI's
logic. The Transport Layer is decided by the machine type. Currently the
machines "n800" and "n810" have one HCI and all other
machines have none.
The following three types are recognized:
- -bt hci,null
- (default) The corresponding Bluetooth HCI assumes no
internal logic and will not respond to any HCI commands or emit
events.
- -bt hci,host[:id]
- ("bluez" only) The corresponding HCI passes
commands / events to / from the physical HCI identified by the name
id (default: "hci0") on the computer running QEMU. Only
available on "bluez" capable systems like Linux.
- -bt hci[,vlan=n]
- Add a virtual, standard HCI that will participate in the
Bluetooth scatternet n (default 0). Similarly to -net VLANs,
devices inside a bluetooth network n can only communicate with
other devices in the same network (scatternet).
- -bt vhci[,vlan=n]
- (Linux-host only) Create a HCI in scatternet n
(default 0) attached to the host bluetooth stack instead of to the
emulated target. This allows the host and target machines to participate
in a common scatternet and communicate. Requires the Linux
"vhci" driver installed. Can be used as following:
qemu-system-i386 [...OPTIONS...] -bt hci,vlan=5 -bt vhci,vlan=5
- -bt
device:dev[,vlan=n]
- Emulate a bluetooth device dev and place it in
network n (default 0). QEMU can only emulate one type of bluetooth
devices currently:
- keyboard
- Virtual wireless keyboard implementing the HIDP bluetooth
profile.
TPM device options
The general form of a TPM device option is:
- -tpmdev backend ,id=id
[, options]
- Backend type must be either one of the following:
passthrough, emulator.
The specific backend type will determine the applicable options. The
"-tpmdev" option creates the TPM backend and requires a
"-device" option that specifies the TPM frontend interface
model.
Options to each backend are described below.
Use 'help' to print all available TPM backend types.
qemu -tpmdev help
- -tpmdev passthrough, id=id,
path=path , cancel-path=cancel-path
- (Linux-host only) Enable access to the host's TPM using the
passthrough driver.
path specifies the path to the host's TPM device, i.e., on a Linux
host this would be "/dev/tpm0". path is optional and by
default "/dev/tpm0" is used.
cancel-path specifies the path to the host TPM device's sysfs entry
allowing for cancellation of an ongoing TPM command. cancel-path is
optional and by default QEMU will search for the sysfs entry to use.
Some notes about using the host's TPM with the passthrough driver:
The TPM device accessed by the passthrough driver must not be used by any
other application on the host.
Since the host's firmware (BIOS/UEFI) has already initialized the TPM, the
VM's firmware (BIOS/UEFI) will not be able to initialize the TPM again and
may therefore not show a TPM-specific menu that would otherwise allow the
user to configure the TPM, e.g., allow the user to enable/disable or
activate/deactivate the TPM. Further, if TPM ownership is released from
within a VM then the host's TPM will get disabled and deactivated. To
enable and activate the TPM again afterwards, the host has to be rebooted
and the user is required to enter the firmware's menu to enable and
activate the TPM. If the TPM is left disabled and/or deactivated most TPM
commands will fail.
To create a passthrough TPM use the following two options:
-tpmdev passthrough,id=tpm0 -device tpm-tis,tpmdev=tpm0
Note that the "-tpmdev" id is "tpm0" and is referenced
by "tpmdev=tpm0" in the device option.
- -tpmdev emulator, id=id,
chardev=dev
- (Linux-host only) Enable access to a TPM emulator using
Unix domain socket based chardev backend.
chardev specifies the unique ID of a character device backend that
provides connection to the software TPM server.
To create a TPM emulator backend device with chardev socket backend:
-chardev socket,id=chrtpm,path=/tmp/swtpm-sock -tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0
Linux/Multiboot boot specific
When using these options, you can use a given Linux or Multiboot kernel without
installing it in the disk image. It can be useful for easier testing of
various kernels.
- -kernel bzImage
- Use bzImage as kernel image. The kernel can be
either a Linux kernel or in multiboot format.
- -append cmdline
- Use cmdline as kernel command line
- -initrd file
- Use file as initial ram disk.
- -initrd "file1
arg=foo,file2 "
- This syntax is only available with multiboot.
Use file1 and file2 as modules and pass arg=foo as parameter
to the first module.
- -dtb file
- Use file as a device tree binary (dtb) image and
pass it to the kernel on boot.
Debug/Expert options
- -fw_cfg
[name=]name,file=file
- Add named fw_cfg entry with contents from file
file.
- -fw_cfg
[name=]name,string=str
- Add named fw_cfg entry with contents from string
str.
The terminating NUL character of the contents of str will not be
included as part of the fw_cfg item data. To insert contents with embedded
NUL characters, you have to use the file parameter.
The fw_cfg entries are passed by QEMU through to the guest.
Example:
-fw_cfg name=opt/com.mycompany/blob,file=./my_blob.bin
creates an fw_cfg entry named opt/com.mycompany/blob with contents from
./my_blob.bin.
- -serial dev
- Redirect the virtual serial port to host character device
dev. The default device is "vc" in graphical mode and
"stdio" in non graphical mode.
This option can be used several times to simulate up to 4 serial ports.
Use "-serial none" to disable all serial ports.
Available character devices are:
- vc[:WxH]
- Virtual console. Optionally, a width and height can be
given in pixel with
vc:800x600
It is also possible to specify width or height in characters:
vc:80Cx24C
- pty
- [Linux only] Pseudo TTY (a new PTY is automatically
allocated)
- none
- No device is allocated.
- null
- void device
- chardev:id
- Use a named character device defined with the
"-chardev" option.
- /dev/XXX
- [Linux only] Use host tty, e.g. /dev/ttyS0. The host
serial port parameters are set according to the emulated ones.
- /dev/parportN
- [Linux only, parallel port only] Use host parallel port
N. Currently SPP and EPP parallel port features can be used.
- file:filename
- Write output to filename. No character can be
read.
- stdio
- [Unix only] standard input/output
- pipe:filename
- name pipe filename
- COMn
- [Windows only] Use host serial port n
- udp:[remote_host]:remote_port[@[src_ip]:src_port]
- This implements UDP Net Console. When remote_host or
src_ip are not specified they default to 0.0.0.0. When not using a
specified src_port a random port is automatically chosen.
If you just want a simple readonly console you can use "netcat" or
"nc", by starting QEMU with: "-serial udp::4555" and
nc as: "nc -u -l -p 4555". Any time QEMU writes something to
that port it will appear in the netconsole session.
If you plan to send characters back via netconsole or you want to stop and
start QEMU a lot of times, you should have QEMU use the same source port
each time by using something like "-serial udp::4555@4556" to
QEMU. Another approach is to use a patched version of netcat which can
listen to a TCP port and send and receive characters via udp. If you have
a patched version of netcat which activates telnet remote echo and single
char transfer, then you can use the following options to set up a netcat
redirector to allow telnet on port 5555 to access the QEMU port.
- "QEMU Options:"
- -serial udp::4555@4556
- "netcat options:"
- -u -P 4555 -L 0.0.0.0:4556 -t -p 5555 -I -T
- "telnet options:"
- localhost 5555
- tcp:[host]:port[,server][,nowait][,nodelay][,reconnect=seconds]
- The TCP Net Console has two modes of operation. It can send
the serial I/O to a location or wait for a connection from a location. By
default the TCP Net Console is sent to host at the port. If
you use the server option QEMU will wait for a client socket
application to connect to the port before continuing, unless the
"nowait" option was specified. The "nodelay" option
disables the Nagle buffering algorithm. The "reconnect" option
only applies if noserver is set, if the connection goes down it
will attempt to reconnect at the given interval. If host is
omitted, 0.0.0.0 is assumed. Only one TCP connection at a time is
accepted. You can use "telnet" to connect to the corresponding
character device.
- "Example to send tcp console to 192.168.0.2 port
4444"
- -serial tcp:192.168.0.2:4444
- "Example to listen and wait on port 4444 for
connection"
- -serial tcp::4444,server
- "Example to not wait and listen on ip 192.168.0.100
port 4444"
- -serial tcp:192.168.0.100:4444,server,nowait
- telnet:host:port[,server][,nowait][,nodelay]
- The telnet protocol is used instead of raw tcp sockets. The
options work the same as if you had specified "-serial tcp". The
difference is that the port acts like a telnet server or client using
telnet option negotiation. This will also allow you to send the
MAGIC_SYSRQ sequence if you use a telnet that supports sending the break
sequence. Typically in unix telnet you do it with Control-] and then type
"send break" followed by pressing the enter key.
- unix:path[,server][,nowait][,reconnect=seconds]
- A unix domain socket is used instead of a tcp socket. The
option works the same as if you had specified "-serial tcp"
except the unix domain socket path is used for connections.
- mon:dev_string
- This is a special option to allow the monitor to be
multiplexed onto another serial port. The monitor is accessed with key
sequence of Control-a and then pressing c. dev_string
should be any one of the serial devices specified above. An example to
multiplex the monitor onto a telnet server listening on port 4444 would
be:
- "-serial mon:telnet::4444,server,nowait"
When the monitor is multiplexed to stdio in this way, Ctrl+C will not terminate
QEMU any more but will be passed to the guest instead.
- braille
- Braille device. This will use BrlAPI to display the braille
output on a real or fake device.
- msmouse
- Three button serial mouse. Configure the guest to use
Microsoft protocol.
- -parallel dev
- Redirect the virtual parallel port to host device
dev (same devices as the serial port). On Linux hosts,
/dev/parportN can be used to use hardware devices connected on the
corresponding host parallel port.
This option can be used several times to simulate up to 3 parallel ports.
Use "-parallel none" to disable all parallel ports.
- -monitor dev
- Redirect the monitor to host device dev (same
devices as the serial port). The default device is "vc" in
graphical mode and "stdio" in non graphical mode. Use
"-monitor none" to disable the default monitor.
- -qmp dev
- Like -monitor but opens in 'control' mode.
- -qmp-pretty dev
- Like -qmp but uses pretty JSON formatting.
- -mon [chardev=]name[,mode=readline|control]
- Setup monitor on chardev name.
- -debugcon dev
- Redirect the debug console to host device dev (same
devices as the serial port). The debug console is an I/O port which is
typically port 0xe9; writing to that I/O port sends output to this device.
The default device is "vc" in graphical mode and
"stdio" in non graphical mode.
- -pidfile file
- Store the QEMU process PID in file. It is useful if
you launch QEMU from a script.
- -singlestep
- Run the emulation in single step mode.
- -S
- Do not start CPU at startup (you must type 'c' in the
monitor).
- -realtime mlock=on|off
- Run qemu with realtime features. mlocking qemu and guest
memory can be enabled via mlock=on (enabled by default).
- -gdb dev
- Wait for gdb connection on device dev. Typical
connections will likely be TCP-based, but also UDP, pseudo TTY, or even
stdio are reasonable use case. The latter is allowing to start QEMU from
within gdb and establish the connection via a pipe:
(gdb) target remote | exec qemu-system-i386 -gdb stdio ...
- -s
- Shorthand for -gdb tcp::1234, i.e. open a gdbserver on TCP
port 1234.
- -d item1[,...]
- Enable logging of specified items. Use '-d help' for a list
of log items.
- -D logfile
- Output log in logfile instead of to stderr
- -dfilter range1[,...]
- Filter debug output to that relevant to a range of target
addresses. The filter spec can be either start+size,
start- size or start..end where start
end and size are the addresses and sizes required. For
example:
-dfilter 0x8000..0x8fff,0xffffffc000080000+0x200,0xffffffc000060000-0x1000
Will dump output for any code in the 0x1000 sized block starting at 0x8000
and the 0x200 sized block starting at 0xffffffc000080000 and another
0x1000 sized block starting at 0xffffffc00005f000.
- -L path
- Set the directory for the BIOS, VGA BIOS and keymaps.
To list all the data directories, use "-L help".
- -bios file
- Set the filename for the BIOS.
- -enable-kvm
- Enable KVM full virtualization support. This option is only
available if KVM support is enabled when compiling.
- -enable-hax
- Enable HAX (Hardware-based Acceleration eXecution) support.
This option is only available if HAX support is enabled when compiling.
HAX is only applicable to MAC and Windows platform, and thus does not
conflict with KVM.
- -xen-domid id
- Specify xen guest domain id (XEN only).
- -xen-create
- Create domain using xen hypercalls, bypassing xend.
Warning: should not be used when xend is in use (XEN only).
- -xen-attach
- Attach to existing xen domain. xend will use this when
starting QEMU (XEN only). Restrict set of available xen operations to
specified domain id (XEN only).
- -no-reboot
- Exit instead of rebooting.
- -no-shutdown
- Don't exit QEMU on guest shutdown, but instead only stop
the emulation. This allows for instance switching to monitor to commit
changes to the disk image.
- -loadvm file
- Start right away with a saved state ("loadvm" in
monitor)
- -daemonize
- Daemonize the QEMU process after initialization. QEMU will
not detach from standard IO until it is ready to receive connections on
any of its devices. This option is a useful way for external programs to
launch QEMU without having to cope with initialization race
conditions.
- -option-rom file
- Load the contents of file as an option ROM. This
option is useful to load things like EtherBoot.
- -rtc
[base=utc|localtime|date][,clock=host|vm][,driftfix=none|slew]
- Specify base as "utc" or
"localtime" to let the RTC start at the current UTC or local
time, respectively. "localtime" is required for correct date in
MS-DOS or Windows. To start at a specific point in time, provide
date in the format "2006-06-17T16:01:21" or
"2006-06-17". The default base is UTC.
By default the RTC is driven by the host system time. This allows using of
the RTC as accurate reference clock inside the guest, specifically if the
host time is smoothly following an accurate external reference clock, e.g.
via NTP. If you want to isolate the guest time from the host, you can set
clock to "rt" instead. To even prevent it from
progressing during suspension, you can set it to "vm".
Enable driftfix (i386 targets only) if you experience time drift
problems, specifically with Windows' ACPI HAL. This option will try to
figure out how many timer interrupts were not processed by the Windows
guest and will re-inject them.
- -icount
[shift=N|auto][,rr=record|replay,rrfile=
filename,rrsnapshot=snapshot]
- Enable virtual instruction counter. The virtual cpu will
execute one instruction every 2^ N ns of virtual time. If
"auto" is specified then the virtual cpu speed will be
automatically adjusted to keep virtual time within a few seconds of real
time.
When the virtual cpu is sleeping, the virtual time will advance at default
speed unless sleep=on|off is specified. With sleep=on|off,
the virtual time will jump to the next timer deadline instantly whenever
the virtual cpu goes to sleep mode and will not advance if no timer is
enabled. This behavior give deterministic execution times from the guest
point of view.
Note that while this option can give deterministic behavior, it does not
provide cycle accurate emulation. Modern CPUs contain superscalar out of
order cores with complex cache hierarchies. The number of instructions
executed often has little or no correlation with actual performance.
align=on will activate the delay algorithm which will try to
synchronise the host clock and the virtual clock. The goal is to have a
guest running at the real frequency imposed by the shift option. Whenever
the guest clock is behind the host clock and if align=on is
specified then we print a message to the user to inform about the delay.
Currently this option does not work when shift is "auto".
Note: The sync algorithm will work for those shift values for which the
guest clock runs ahead of the host clock. Typically this happens when the
shift value is high (how high depends on the host machine).
When rr option is specified deterministic record/replay is enabled.
Replay log is written into filename file in record mode and read
from this file in replay mode.
Option rrsnapshot is used to create new vm snapshot named snapshot at
the start of execution recording. In replay mode this option is used to
load the initial VM state.
- -watchdog model
- Create a virtual hardware watchdog device. Once enabled (by
a guest action), the watchdog must be periodically polled by an agent
inside the guest or else the guest will be restarted. Choose a model for
which your guest has drivers.
The model is the model of hardware watchdog to emulate. Use
"-watchdog help" to list available hardware models. Only one
watchdog can be enabled for a guest.
The following models may be available:
- ib700
- iBASE 700 is a very simple ISA watchdog with a single
timer.
- i6300esb
- Intel 6300ESB I/O controller hub is a much more featureful
PCI-based dual-timer watchdog.
- diag288
- A virtual watchdog for s390x backed by the diagnose 288
hypercall (currently KVM only).
- -watchdog-action action
- The action controls what QEMU will do when the
watchdog timer expires. The default is "reset" (forcefully reset
the guest). Other possible actions are: "shutdown" (attempt to
gracefully shutdown the guest), "poweroff" (forcefully poweroff
the guest), "pause" (pause the guest), "debug" (print
a debug message and continue), or "none" (do nothing).
Note that the "shutdown" action requires that the guest responds
to ACPI signals, which it may not be able to do in the sort of situations
where the watchdog would have expired, and thus "-watchdog-action
shutdown" is not recommended for production use.
Examples:
- "-watchdog i6300esb -watchdog-action pause"
- "-watchdog ib700"
- -echr numeric_ascii_value
- Change the escape character used for switching to the
monitor when using monitor and serial sharing. The default is 0x01 when
using the "-nographic" option. 0x01 is equal to pressing
"Control-a". You can select a different character from the ascii
control keys where 1 through 26 map to Control-a through Control-z. For
instance you could use the either of the following to change the escape
character to Control-t.
- -virtioconsole c
- Set virtio console.
This option is maintained for backward compatibility.
Please use "-device virtconsole" for the new way of
invocation.
- -show-cursor
- Show cursor.
- -tb-size n
- Set TB size.
- -incoming
tcp:[host]:port[,to=
maxport][,ipv4][,ipv6]
- -incoming
rdma:host:port[,ipv4][,ipv6]
- Prepare for incoming migration, listen on a given tcp
port.
- -incoming unix:socketpath
- Prepare for incoming migration, listen on a given unix
socket.
- -incoming fd:fd
- Accept incoming migration from a given filedescriptor.
- -incoming exec:cmdline
- Accept incoming migration as an output from specified
external command.
- -incoming defer
- Wait for the URI to be specified via migrate_incoming. The
monitor can be used to change settings (such as migration parameters)
prior to issuing the migrate_incoming to allow the migration to
begin.
- -only-migratable
- Only allow migratable devices. Devices will not be allowed
to enter an unmigratable state.
- -nodefaults
- Don't create default devices. Normally, QEMU sets the
default devices like serial port, parallel port, virtual console, monitor
device, VGA adapter, floppy and CD-ROM drive and others. The
"-nodefaults" option will disable all those default
devices.
- -chroot dir
- Immediately before starting guest execution, chroot to the
specified directory. Especially useful in combination with -runas.
- -runas user
- Immediately before starting guest execution, drop root
privileges, switching to the specified user.
- -prom-env variable=value
- Set OpenBIOS nvram variable to given value
(PPC, SPARC only).
- -semihosting
- Enable semihosting mode (ARM, M68K, Xtensa, MIPS
only).
- -semihosting-config
[enable=on|off][,target=native|gdb|auto][,arg=str[,...]]
- Enable and configure semihosting (ARM, M68K, Xtensa, MIPS
only).
- target="native|gdb|auto"
- Defines where the semihosting calls will be addressed, to
QEMU ("native") or to GDB ("gdb"). The default is
"auto", which means "gdb" during debug sessions and
"native" otherwise.
- arg=str1,arg=str2,...
- Allows the user to pass input arguments, and can be used
multiple times to build up a list. The old-style
"-kernel"/"-append" method of passing a command line
is still supported for backward compatibility. If both the
"--semihosting-config arg" and the
"-kernel"/"-append" are specified, the former is
passed to semihosting as it always takes precedence.
- -old-param
- Old param mode (ARM only).
- -sandbox
arg[,obsolete=string][,elevateprivileges=string][,spawn=string][,resourcecontrol=string]
- Enable Seccomp mode 2 system call filter. 'on' will enable
syscall filtering and 'off' will disable it. The default is 'off'.
- obsolete=string
- Enable Obsolete system calls
- elevateprivileges=string
- Disable set*uid|gid system calls
- spawn=string
- Disable *fork and execve
- resourcecontrol=string
- Disable process affinity and schedular priority
- -readconfig file
- Read device configuration from file. This approach
is useful when you want to spawn QEMU process with many command line
options but you don't want to exceed the command line character
limit.
- -writeconfig file
- Write device configuration to file. The file
can be either filename to save command line and device configuration into
file or dash "-") character to print the output to stdout. This
can be later used as input file for "-readconfig" option.
- -no-user-config
- The "-no-user-config" option makes QEMU not load
any of the user-provided config files on sysconfdir.
- -trace
[[enable=]pattern][,events=file
][,file=file ]
- Specify tracing options.
- [enable=]pattern
- Immediately enable events matching pattern. The file
must contain one event name (as listed in the trace-events-all
file) per line; globbing patterns are accepted too. This option is only
available if QEMU has been compiled with the simple, log or
ftrace tracing backend. To specify multiple events or patterns,
specify the -trace option multiple times.
Use "-trace help" to print a list of names of trace points.
- events=file
- Immediately enable events listed in file. The file
must contain one event name (as listed in the trace-events-all
file) per line; globbing patterns are accepted too. This option is only
available if QEMU has been compiled with the simple, log or
ftrace tracing backend.
- file=file
- Log output traces to file. This option is only
available if QEMU has been compiled with the simple tracing
backend.
- -enable-fips
- Enable FIPS 140-2 compliance mode.
- -msg timestamp[=on|off]
- prepend a timestamp to each log message.(default:on)
- -dump-vmstate file
- Dump json-encoded vmstate information for current machine
type to file in file
Generic object creation
- -object
typename[,prop1=value1,...]
- Create a new object of type typename setting
properties in the order they are specified. Note that the 'id' property
must be set. These objects are placed in the '/objects' path.
- -object
memory-backend-file,id=id,size=
size,mem-path=
dir,share=on|off,discard-data=
on|off
- Creates a memory file backend object, which can be used to
back the guest RAM with huge pages. The id parameter is a unique ID
that will be used to reference this memory region when configuring the
-numa argument. The size option provides the size of the
memory region, and accepts common suffixes, eg 500M. The
mem-path provides the path to either a shared memory or huge page
filesystem mount. The share boolean option determines whether the
memory region is marked as private to QEMU, or shared. The latter allows a
co-operating external process to access the QEMU memory region. Setting
the discard-data boolean option to on indicates that file
contents can be destroyed when QEMU exits, to avoid unnecessarily flushing
data to the backing file. Note that discard-data is only an
optimization, and QEMU might not discard file contents if it aborts
unexpectedly or is terminated using SIGKILL.
- -object
rng-random,id=id,filename=/dev/random
- Creates a random number generator backend which obtains
entropy from a device on the host. The id parameter is a unique ID
that will be used to reference this entropy backend from the
virtio-rng device. The filename parameter specifies which
file to obtain entropy from and if omitted defaults to
/dev/random.
- -object
rng-egd,id=id,chardev=chardevid
- Creates a random number generator backend which obtains
entropy from an external daemon running on the host. The id
parameter is a unique ID that will be used to reference this entropy
backend from the virtio-rng device. The chardev parameter is
the unique ID of a character device backend that provides the connection
to the RNG daemon.
- -object
tls-creds-anon,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off
- Creates a TLS anonymous credentials object, which can be
used to provide TLS support on network backends. The id parameter
is a unique ID which network backends will use to access the credentials.
The endpoint is either server or client depending on
whether the QEMU network backend that uses the credentials will be acting
as a client or as a server. If verify-peer is enabled (the default)
then once the handshake is completed, the peer credentials will be
verified, though this is a no-op for anonymous credentials.
The dir parameter tells QEMU where to find the credential files. For
server endpoints, this directory may contain a file dh-params.pem
providing diffie-hellman parameters to use for the TLS server. If the file
is missing, QEMU will generate a set of DH parameters at startup. This is
a computationally expensive operation that consumes random pool entropy,
so it is recommended that a persistent set of parameters be generated
upfront and saved.
- -object
tls-creds-x509,id=id,endpoint=endpoint,dir=/path/to/cred/dir,verify-peer=on|off,passwordid=id
- Creates a TLS anonymous credentials object, which can be
used to provide TLS support on network backends. The id parameter
is a unique ID which network backends will use to access the credentials.
The endpoint is either server or client depending on
whether the QEMU network backend that uses the credentials will be acting
as a client or as a server. If verify-peer is enabled (the default)
then once the handshake is completed, the peer credentials will be
verified. With x509 certificates, this implies that the clients must be
provided with valid client certificates too.
The dir parameter tells QEMU where to find the credential files. For
server endpoints, this directory may contain a file dh-params.pem
providing diffie-hellman parameters to use for the TLS server. If the file
is missing, QEMU will generate a set of DH parameters at startup. This is
a computationally expensive operation that consumes random pool entropy,
so it is recommended that a persistent set of parameters be generated
upfront and saved.
For x509 certificate credentials the directory will contain further files
providing the x509 certificates. The certificates must be stored in PEM
format, in filenames ca-cert.pem, ca-crl.pem (optional),
server-cert.pem (only servers), server-key.pem (only
servers), client-cert.pem (only clients), and client-key.pem
(only clients).
For the server-key.pem and client-key.pem files which contain
sensitive private keys, it is possible to use an encrypted version by
providing the passwordid parameter. This provides the ID of a
previously created "secret" object containing the password for
decryption.
- -object
filter-buffer,id=id,netdev=netdevid
,interval=
t[,queue=all|rx|tx][,status=on|off]
- Interval t can't be 0, this filter batches the
packet delivery: all packets arriving in a given interval on netdev
netdevid are delayed until the end of the interval. Interval is in
microseconds. status is optional that indicate whether the
netfilter is on (enabled) or off (disabled), the default status for
netfilter will be 'on'.
queue all|rx|tx is an option that can be applied to any netfilter.
all: the filter is attached both to the receive and the transmit
queue of the netdev (default).
rx: the filter is attached to the receive queue of the netdev, where
it will receive packets sent to the netdev.
tx: the filter is attached to the transmit queue of the netdev,
where it will receive packets sent by the netdev.
- -object
filter-mirror,id=id,netdev=netdevid
,outdev=chardevid,queue=all|rx|tx[,vnet_hdr_support]
- filter-mirror on netdev netdevid,mirror net packet
to chardev chardevid, if it has the vnet_hdr_support flag,
filter-mirror will mirror packet with vnet_hdr_len.
- -object
filter-redirector,id=id,netdev=
netdevid,indev=
chardevid,outdev=chardevid
,queue=all|rx|tx [,vnet_hdr_support]
- filter-redirector on netdev netdevid,redirect
filter's net packet to chardev chardevid,and redirect indev's
packet to filter.if it has the vnet_hdr_support flag, filter-redirector
will redirect packet with vnet_hdr_len. Create a filter-redirector we need
to differ outdev id from indev id, id can not be the same. we can just use
indev or outdev, but at least one of indev or outdev need to be
specified.
- -object
filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_support]
- Filter-rewriter is a part of COLO project.It will rewrite
tcp packet to secondary from primary to keep secondary tcp connection,and
rewrite tcp packet to primary from secondary make tcp packet can be
handled by client.if it has the vnet_hdr_support flag, we can parse packet
with vnet header.
usage: colo secondary: -object
filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 -object
filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 -object
filter-rewriter,id=rew0,netdev=hn0,queue=all
- -object
filter-dump,id=id,netdev=dev
[,file=filename ][,maxlen=len]
- Dump the network traffic on netdev dev to the file
specified by filename. At most len bytes (64k by default)
per packet are stored. The file format is libpcap, so it can be analyzed
with tools such as tcpdump or Wireshark.
- -object
colo-compare,id=id,primary_in=chardevid,secondary_in=chardevid,outdev=chardevid[,vnet_hdr_support]
- Colo-compare gets packet from primary_inchardevid
and secondary_in chardevid, than compare primary packet with
secondary packet. If the packets are same, we will output primary packet
to outdev chardevid, else we will notify colo-frame do checkpoint
and send primary packet to outdev chardevid. if it has the
vnet_hdr_support flag, colo compare will send/recv packet with
vnet_hdr_len.
we must use it with the help of filter-mirror and filter-redirector.
primary:
-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown
-device e1000,id=e0,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=mirror0,host=3.3.3.3,port=9003,server,nowait
-chardev socket,id=compare1,host=3.3.3.3,port=9004,server,nowait
-chardev socket,id=compare0,host=3.3.3.3,port=9001,server,nowait
-chardev socket,id=compare0-0,host=3.3.3.3,port=9001
-chardev socket,id=compare_out,host=3.3.3.3,port=9005,server,nowait
-chardev socket,id=compare_out0,host=3.3.3.3,port=9005
-object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0
-object filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out
-object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
-object colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0
secondary:
-netdev tap,id=hn0,vhost=off,script=/etc/qemu-ifup,down script=/etc/qemu-ifdown
-device e1000,netdev=hn0,mac=52:a4:00:12:78:66
-chardev socket,id=red0,host=3.3.3.3,port=9003
-chardev socket,id=red1,host=3.3.3.3,port=9004
-object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0
-object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
If you want to know the detail of above command line, you can read the
colo-compare git log.
- -object
cryptodev-backend-builtin,id=id[,queues=
queues]
- Creates a cryptodev backend which executes crypto opreation
from the QEMU cipher APIS. The id parameter is a unique ID that
will be used to reference this cryptodev backend from the
virtio-crypto device. The queues parameter is optional,
which specify the queue number of cryptodev backend, the default of
queues is 1.
# qemu-system-x86_64 \
[...] \
-object cryptodev-backend-builtin,id=cryptodev0 \
-device virtio-crypto-pci,id=crypto0,cryptodev=cryptodev0 \
[...]
- -object
secret,id=id,data=string
,format=raw|base64
[,keyid=secretid,iv=string]
- -object
secret,id=id,file=filename
,format=raw|base64
[,keyid=secretid,iv=string]
- Defines a secret to store a password, encryption key, or
some other sensitive data. The sensitive data can either be passed
directly via the data parameter, or indirectly via the file
parameter. Using the data parameter is insecure unless the
sensitive data is encrypted.
The sensitive data can be provided in raw format (the default), or base64.
When encoded as JSON, the raw format only supports valid UTF-8 characters,
so base64 is recommended for sending binary data. QEMU will convert from
which ever format is provided to the format it needs internally. eg, an
RBD password can be provided in raw format, even though it will be base64
encoded when passed onto the RBD sever.
For added protection, it is possible to encrypt the data associated with a
secret using the AES-256-CBC cipher. Use of encryption is indicated by
providing the keyid and iv parameters. The keyid
parameter provides the ID of a previously defined secret that contains the
AES-256 decryption key. This key should be 32-bytes long and be base64
encoded. The iv parameter provides the random initialization vector
used for encryption of this particular secret and should be a base64
encrypted string of the 16-byte IV.
The simplest (insecure) usage is to provide the secret inline
# $QEMU -object secret,id=sec0,data=letmein,format=raw
The simplest secure usage is to provide the secret via a file
# printf "letmein" > mypasswd.txt # $QEMU -object
secret,id=sec0,file=mypasswd.txt,format=raw
For greater security, AES-256-CBC should be used. To illustrate usage,
consider the openssl command line tool which can encrypt the data. Note
that when encrypting, the plaintext must be padded to the cipher block
size (32 bytes) using the standard PKCS#5/6 compatible padding algorithm.
First a master key needs to be created in base64 encoding:
# openssl rand -base64 32 > key.b64
# KEY=$(base64 -d key.b64 | hexdump -v -e '/1 "%02X"')
Each secret to be encrypted needs to have a random initialization vector
generated. These do not need to be kept secret
# openssl rand -base64 16 > iv.b64
# IV=$(base64 -d iv.b64 | hexdump -v -e '/1 "%02X"')
The secret to be defined can now be encrypted, in this case we're telling
openssl to base64 encode the result, but it could be left as raw bytes if
desired.
# SECRET=$(printf "letmein" |
openssl enc -aes-256-cbc -a -K $KEY -iv $IV)
When launching QEMU, create a master secret pointing to "key.b64"
and specify that to be used to decrypt the user password. Pass the
contents of "iv.b64" to the second secret
# $QEMU \
-object secret,id=secmaster0,format=base64,file=key.b64 \
-object secret,id=sec0,keyid=secmaster0,format=base64,\
data=$SECRET,iv=$(<iv.b64)
During the graphical emulation, you can use special key combinations to change
modes. The default key mappings are shown below, but if you use
"-alt-grab" then the modifier is Ctrl-Alt-Shift (instead of
Ctrl-Alt) and if you use "-ctrl-grab" then the modifier is the right
Ctrl key (instead of Ctrl-Alt):
- Ctrl-Alt-f
- Toggle full screen
- Ctrl-Alt-+
- Enlarge the screen
- Ctrl-Alt--
- Shrink the screen
- Ctrl-Alt-u
- Restore the screen's un-scaled dimensions
- Ctrl-Alt-n
- Switch to virtual console 'n'. Standard console mappings
are:
- 1
- Target system display
- 2
- Monitor
- 3
- Serial port
- Ctrl-Alt
- Toggle mouse and keyboard grab.
In the virtual consoles, you can use
Ctrl-Up,
Ctrl-Down,
Ctrl-PageUp and
Ctrl-PageDown to move in the back log.
During emulation, if you are using a character backend multiplexer (which is the
default if you are using
-nographic) then several commands are
available via an escape sequence. These key sequences all start with an escape
character, which is
Ctrl-a by default, but can be changed with
-echr. The list below assumes you're using the default.
- Ctrl-a h
- Print this help
- Ctrl-a x
- Exit emulator
- Ctrl-a s
- Save disk data back to file (if -snapshot)
- Ctrl-a t
- Toggle console timestamps
- Ctrl-a b
- Send break (magic sysrq in Linux)
- Ctrl-a c
- Rotate between the frontends connected to the multiplexer
(usually this switches between the monitor and the console)
- Ctrl-a Ctrl-a
- Send the escape character to the frontend
The following options are specific to the PowerPC emulation:
- -g
WxH[xDEPTH]
- Set the initial VGA graphic mode. The default is
800x600x32.
- -prom-env string
- Set OpenBIOS variables in NVRAM, for example:
qemu-system-ppc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=hd:2,\yaboot' \
-prom-env 'boot-args=conf=hd:2,\yaboot.conf'
These variables are not used by Open Hack'Ware.
The following options are specific to the Sparc32 emulation:
- -g
WxHx[xDEPTH]
- Set the initial graphics mode. For TCX, the default is
1024x768x8 with the option of 1024x768x24. For cgthree, the default is
1024x768x8 with the option of 1152x900x8 for people who wish to use
OBP.
- -prom-env string
- Set OpenBIOS variables in NVRAM, for example:
qemu-system-sparc -prom-env 'auto-boot?=false' \
-prom-env 'boot-device=sd(0,2,0):d' -prom-env 'boot-args=linux single'
- -M
[SS-4|SS-5|SS-10|SS-20|SS-600MP|LX|Voyager|SPARCClassic]
[|SPARCbook]
- Set the emulated machine type. Default is SS-5.
The following options are specific to the Sparc64 emulation:
- -prom-env string
- Set OpenBIOS variables in NVRAM, for example:
qemu-system-sparc64 -prom-env 'auto-boot?=false'
- -M [sun4u|sun4v|niagara]
- Set the emulated machine type. The default is sun4u.
The following options are specific to the ARM emulation:
- -semihosting
- Enable semihosting syscall emulation.
On ARM this implements the "Angel" interface.
Note that this allows guest direct access to the host filesystem, so should
only be used with trusted guest OS.
The following options are specific to the ColdFire emulation:
- -semihosting
- Enable semihosting syscall emulation.
On M68K this implements the "ColdFire GDB" interface used by
libgloss.
Note that this allows guest direct access to the host filesystem, so should
only be used with trusted guest OS.
The following options are specific to the Xtensa emulation:
- -semihosting
- Enable semihosting syscall emulation.
Xtensa semihosting provides basic file IO calls, such as
open/read/write/seek/select. Tensilica baremetal libc for ISS and linux
platform "sim" use this interface.
Note that this allows guest direct access to the host filesystem, so should
only be used with trusted guest OS.
The HTML documentation of QEMU for more precise information and Linux user mode
emulator invocation.
Fabrice Bellard