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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 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.



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