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

       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.

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

       This page is part of the util-linux (a random collection of Linux
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util-linux                      May 2009                     LIBBLKID(3)

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