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NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION FILE | AUTHOR | COPYING | SEE ALSO | AVAILABILITY | COLOPHON |
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LIBBLKID(3) Programmer's Manual LIBBLKID(3)
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 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
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 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) 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)
libblkid is part of the util-linux package since version 2.15 and is
available from https://www.kernel.org/pub/linux/utils/util-linux/.
This page is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
util-linux@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
2018-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2018-02-01.) If you discover any
rendering problems in this HTML version of the page, or you believe
there is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
util-linux May 2009 LIBBLKID(3)
Pages that refer to this page: open_by_handle_at(2), blkid(8), mount(8)
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