libblkid(3) — Linux manual page


LIBBLKID(3)                  Programmer's Manual                 LIBBLKID(3)

NAME         top

       libblkid - block device identification library

SYNOPSIS         top

       #include <blkid.h>

       cc file.c -lblkid

DESCRIPTION         top

       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 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


       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.

AUTHORS         top

       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.

COPYING         top

       libblkid is available under the terms of the GNU Library General
       Public License (LGPL), version 2 (or at your discretion any later

SEE ALSO         top

       blkid(8), findfs(8)

AVAILABILITY         top

       libblkid is part of the util-linux package since version 2.15 and is
       available from

COLOPHON         top

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util-linux                        May 2009                       LIBBLKID(3)

Pages that refer to this page: name_to_handle_at(2)open_by_handle_at(2)blkid(8)mount(8)