Provided by: libblkid-dev_2.20.1-1ubuntu3_i386 bug

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  infomation
       about partitions and block device topology.

       The  high-level  part  of  the  library  keeps  information about block
       devices in a cache file /etc/blkid.tab 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.   The  following
       options control the libblkid library:

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

       CACHE_FILE=<path>
              Overrides the standard location of the cache file. This  setting
              can  be  overridden  by  the  environment  variable  BLKID_FILE.
              Default is /etc/blkid.tab.

       EVALUATE=<methods>
              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.

AUTHOR

       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.

FILES

       /etc/blkid.tab    caches  data  extracted  from  each  recognized block
                         device

       /etc/blkid.conf   configuration file

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/.

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)