libblkid - block device identification library
#include <blkid.h>
cc file.c -lblkid
The
libblkid 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 the extraction of 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
variable
BLKID_FILE.
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 determine
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) man page.
libblkid was written by Andreas Dilger for the ext2 filesystem utilities,
with input from Ted Ts’o. The library was subsequently heavily modified
by Ted Ts’o.
The low-level probing code was rewritten by Karel Zak.
libblkid is available under the terms of the GNU Library General Public
License (LGPL), version 2 (or at your discretion any later version).
blkid(8),
findfs(8)
For bug reports, use the issue tracker at
<
https://github.com/util-linux/util-linux/issues>.
The
libblkid library is part of the util-linux package since version
2.15. It can be downloaded from
Linux Kernel Archive
<
https://www.kernel.org/pub/linux/utils/util-linux/>.