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/.