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       libblkid - block device identification library


       #include <blkid/blkid.h>

       cc file.c -lblkid


       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, etc.  A common  use  is  to  allow  use  of
       LABEL=  and  UUID=  tags  instead  of hard-coding specific block device
       names into configuration files.

       Block  device  information  is  normally   kept   in   a   cache   file
       /etc/  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).   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.  There is rarely a
       reason not to use the cache.

       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.   The following
       options control the libblkid library:

              Sends uevent when /dev/disk/by-{label,uuid}/  symlink  does  not
              match with LABEL or UUID on the device. Default is "yes".

              Overrides  the standard location of the cache file. This setting
              can  be  overridden  by  the  environment  variable  BLKID_FILE.
              Default is /etc/

              Defines  LABEL  and  UUID  evaluation  method(s). Currently, the
              libblkid library supports "udev" and "scan" methods.  More  than
              one  methods may be specified in a comma separated list. Default
              is "udev,scan".  The  "udev"  method  uses  udev  /dev/disk/by-*
              symlinks  and the "scan" method scans all block devices from the
              /proc/partitions file.


       libblkid  was  written  by  Andreas  Dilger  for  the  ext2  filesystem
       utilties,  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.


       /etc/    caches data  extracted  from  each  recognized  block

       /etc/blkid.conf   configuration file


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


       libblkid is available under the terms of the GNU Library General Public
       License (LGPL), version 2 (or at your discretion any later version).  A
       copy of the LGPL should be included  with  this  library  in  the  file
       COPYING.  If not, write to
              Free Software Foundation, Inc.
              51 Franklin St
              Fifth Floor
              Boston, MA  02110-1301  USA

       or visit


       blkid(8) findfs(8)