libblkid - block device identification library
cc file.c -lblkid
library is used to identify block devices (disks) as to
their content (e.g. filesystem type) as well as extracting additional
information such as filesystem labels/volume names, unique identifiers/serial
numbers. A common use is to allow use of LABEL= and UUID= tags instead of
hard-coding specific block device names into configuration files.
The low-level part of the library also allows to extract information about
partitions and block device topology.
The high-level part of the library keeps information about block devices in a
cache file and is verified to still be valid before being returned to the user
(if the user has read permission on the raw block device, otherwise not). The
cache file also allows unprivileged users (normally anyone other than root, or
those not in the "disk" group) to locate devices by label/id. The
standard location of the cache file can be overridden by the environment
In situations where one is getting information about a single known device, it
does not impact performance whether the cache is used or not (unless you are
not able to read the block device directly).
The high-level part of the library supports two methods to evaluate LABEL/UUID.
It reads information directly from a block device or read information from
/dev/disk/by-* udev symlinks. The udev is preferred method by default.
If you are dealing with multiple devices, use of the cache is highly recommended
(even if empty) as devices will be scanned at most one time and the on-disk
cache will be updated if possible.
In some cases (modular kernels), block devices are not even visible until after
they are accessed the first time, so it is critical that there is some way to
locate these devices without enumerating only visible devices, so the use of
the cache file is required
in this situation.
The standard location of the /etc/blkid.conf
config file can be
overridden by the environment variable BLKID_CONF. For more details about the
config file see blkid(8)
was written by Andreas Dilger for the ext2 filesystem utilities,
with input from Ted Ts'o. The library was subsequently heavily modified by Ted
The low-level probing code was rewritten by Karel Zak.
is available under the terms of the GNU Library General Public
License (LGPL), version 2 (or at your discretion any later version).
libblkid is part of the util-linux package since version 2.15 and is available