gdbserver - Remote Server for the GNU Debugger
gdbserver comm prog
gdbserver --attach comm pid
gdbserver --multi comm
is a program that allows you to run GDB on a different machine
than the one which is running the program being debugged.
Usage (server (target) side):
First, you need to have a copy of the program you want to debug put onto the
target system. The program can be stripped to save space if needed, as
doesn't care about symbols. All symbol handling is taken care
of by the GDB running on the host system.
To use the server, you log on to the target system, and run the gdbserver
program. You must tell it (a) how to communicate with GDB, (b) the name of
your program, and (c) its arguments. The general syntax is:
target> gdbserver <comm> <program> [<args> ...]
For example, using a serial port, you might say:
target> gdbserver /dev/com1 emacs foo.txt
This tells gdbserver
to debug emacs with an argument of foo.txt, and to
communicate with GDB via /dev/com1
patiently for the host GDB to communicate with it.
To use a TCP connection, you could say:
target> gdbserver host:2345 emacs foo.txt
This says pretty much the same thing as the last example, except that we are
going to communicate with the "host" GDB via TCP. The
"host:2345" argument means that we are expecting to see a TCP
connection from "host" to local TCP port 2345. (Currently, the
"host" part is ignored.) You can choose any number you want for the
port number as long as it does not conflict with any existing TCP ports on the
target system. This same port number must be used in the host GDBs
"target remote" command, which will be described shortly. Note that
if you chose a port number that conflicts with another service,
will print an error message and exit.
can also attach to running programs. This is accomplished via
argument. The syntax is:
target> gdbserver --attach <comm> <pid>
is the process ID of a currently running process. It isn't necessary
to point gdbserver
at a binary for the running process.
To start "gdbserver" without supplying an initial command to run or
process ID to attach, use the --multi
command line option. In such case
you should connect using "target extended-remote" to start the
program you want to debug.
target> gdbserver --multi <comm>
Usage (host side):
You need an unstripped copy of the target program on your host system, since GDB
needs to examine it's symbol tables and such. Start up GDB as you normally
would, with the target program as the first argument. (You may need to use the
option if the serial line is running at anything except 9600
baud.) That is "gdb TARGET-PROG", or "gdb --baud BAUD
TARGET-PROG". After that, the only new command you need to know about is
"target remote" (or "target extended-remote"). Its
argument is either a device name (usually a serial device, like
), or a "HOST:PORT" descriptor. For example:
(gdb) target remote /dev/ttyb
communicates with the server via serial line /dev/ttyb
(gdb) target remote the-target:2345
communicates via a TCP connection to port 2345 on host `the-target', where you
previously started up gdbserver
with the same port number. Note that
for TCP connections, you must start up gdbserver
prior to using the
`target remote' command, otherwise you may get an error that looks something
like `Connection refused'.
can also debug multiple inferiors at once, described in the GDB
manual in node "Inferiors and Programs" -- shell command "info
-f gdb -n 'Inferiors and Programs'". In such case use the
"extended-remote" GDB command variant:
(gdb) target extended-remote the-target:2345
may or may not be used in such case.
There are three different modes for invoking gdbserver
- Debug a specific program specified by its program name:
gdbserver <comm> <prog> [<args>...]
The comm parameter specifies how should the server communicate with
GDB; it is either a device name (to use a serial line), a TCP port number
(":1234"), or "-" or "stdio" to use
stdin/stdout of "gdbserver". Specify the name of the program to
debug in prog. Any remaining arguments will be passed to the
program verbatim. When the program exits, GDB will close the connection,
and "gdbserver" will exit.
- Debug a specific program by specifying the process ID of a
gdbserver --attach <comm> <pid>
The comm parameter is as described above. Supply the process ID of a
running program in pid; GDB will do everything else. Like with the
previous mode, when the process pid exits, GDB will close the
connection, and "gdbserver" will exit.
- Multi-process mode -- debug more than one program/process:
gdbserver --multi <comm>
In this mode, GDB can instruct gdbserver which command(s) to run.
Unlike the other 2 modes, GDB will not close the connection when a process
being debugged exits, so you can debug several processes in the same
In each of the modes you may specify these options:
- List all options, with brief explanations.
- This option causes gdbserver to print its version
number and exit.
- gdbserver will attach to a running program. The
target> gdbserver --attach <comm> <pid>
pid is the process ID of a currently running process. It isn't
necessary to point gdbserver at a binary for the running
- To start "gdbserver" without supplying an initial
command to run or process ID to attach, use this command line option. Then
you can connect using "target extended-remote" and start the
program you want to debug. The syntax is:
target> gdbserver --multi <comm>
- Instruct "gdbserver" to display extra status
information about the debugging process. This option is intended for
"gdbserver" development and for bug reports to the
- Instruct "gdbserver" to display remote protocol
debug output. This option is intended for "gdbserver"
development and for bug reports to the developers.
- Instruct "gdbserver" to include extra information
in each line of debugging output.
- Specify a wrapper to launch programs for debugging. The
option should be followed by the name of the wrapper, then any
command-line arguments to pass to the wrapper, then "--"
indicating the end of the wrapper arguments.
- By default, gdbserver keeps the listening TCP port
open, so that additional connections are possible. However, if you start
"gdbserver" with the --once option, it will stop
listening for any further connection attempts after connecting to the
first GDB session.
The full documentation for GDB is maintained as a Texinfo manual. If the
"info" and "gdb" programs and GDB's Texinfo documentation
are properly installed at your site, the command
should give you access to the complete manual.
Using GDB: A Guide to the GNU Source-Level Debugger
, Richard M. Stallman
and Roland H. Pesch, July 1991.
Copyright (c) 1988-2018 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.3 or any later version
published by the Free Software Foundation; with the Invariant Sections being
"Free Software" and "Free Software Needs Free
Documentation", with the Front-Cover Texts being "A GNU
Manual," and with the Back-Cover Texts as in (a) below.
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