libblkid(3)

1LIBBLKID(3)                Library Functions Manual                LIBBLKID(3)
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NAME

6       libblkid - block device identification library
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SYNOPSIS

9       #include <blkid/blkid.h>
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11       cc file.c -lblkid
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DESCRIPTION

14       The  libblkid  library  is used to identify block devices (disks) as to
15       their content (e.g.  filesystem type) as well as extracting  additional
16       information  such  as  filesystem  labels/volume  names, unique identi‐
17       fiers/serial numbers, etc.  A common use is to allow use of LABEL=  and
18       UUID= tags instead of hard-coding specific block device names into con‐
19       figuration files.
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21       Block  device  information  is  normally   kept   in   a   cache   file
22       /etc/blkid/blkid.tab  and  is  verified  to still be valid before being
23       returned to the user (if the user has read permission on the raw  block
24       device,  otherwise not).  The cache file also allows unprivileged users
25       (normally anyone other than root, or those not in the "disk" group)  to
26       locate devices by label/id.
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28       In  situations  where  one  is getting information about a single known
29       device, it does not impact performance whether the cache is used or not
30       (unless  you  are  not able to read the block device directly).  If you
31       are dealing with multiple devices use of the  cache  is  highly  recom‐
32       mended (even if empty) as devices will be scanned at most one time, and
33       the on-disk cache will be updated if possible.  There is rarely a  rea‐
34       son not to use the cache.
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36       In  some  cases  (modular  kernels), block devices are not even visible
37       until after they are accessed the first time, so it  is  critical  that
38       there is some way to locate these devices without enumerating only vis‐
39       ible devices, so the use of the cache file is required in  this  situa‐
40       tion.
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AUTHOR

43       libblkid  was  written  by Andreas Dilger for the ext2 filesystem util‐
44       ties, with input from Ted Ts'o.  The library was  subsequently  heavily
45       modified by Ted Ts'o.
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FILES

48       /etc/blkid/blkid.tab
49              Caches data extracted from each recognized block device.
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AVAILABILITY

52       libblkid  is  part  of  the e2fsprogs package since version 1.33 and is
53       available from http://e2fsprogs.sourceforge.net.
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COPYING

56       libblkid is available under the terms of the GNU Library General Public
57       License (LGPL), version 2 (or at your discretion any later version).  A
58       copy of the LGPL should be included with this library in the file COPY‐
59       ING.  If not, write to
60              Free Software Foundation, Inc.
61              59 Temple Place
62              Suite 330
63              Boston, MA  02111-1307  USA
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65       or         visit         http://www.gnu.org/licenses/licenses.html#LGPL
66       ⟨http://www.gnu.org/licenses/licenses.html#LGPL⟩
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