libblkid

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



NAME
       libblkid - block device identification library

SYNOPSIS
       #include <blkid.h>

       cc file.c -lblkid

DESCRIPTION
       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.

CONFIGURATION FILE
       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.

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

SEE ALSO
       blkid(8), findfs(8)

AVAILABILITY
       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/.



util-linux                         May 2009                        LIBBLKID(3)