1 .\" Copyright 2001 Andreas Dilger (adilger@turbolinux.com)
3 .\" This man page was created for libblkid.so.1.0 from e2fsprogs-1.24.
5 .\" This file may be copied under the terms of the GNU Public License.
7 .\" Created Wed Sep 14 12:02:12 2001, Andreas Dilger
8 .TH LIBBLKID 3 "May 2009" "util-linux-ng"
10 libblkid \- block device identification library
12 .B #include <blkid/blkid.h>
20 library is used to identify block devices (disks) as to their content (e.g.
21 filesystem type) as well as extracting additional information such as
22 filesystem labels/volume names, unique identifiers/serial numbers, etc.
23 A common use is to allow use of LABEL= and UUID= tags instead of hard-coding
24 specific block device names into configuration files.
26 Block device information is normally kept in a cache file
28 and is verified to still be valid before being returned to the user
29 (if the user has read permission on the raw block device, otherwise not).
30 The cache file also allows unprivileged users (normally anyone other
31 than root, or those not in the "disk" group) to locate devices by label/id.
32 The standard location of the cache file can be overridden by the
33 environment variable BLKID_FILE.
35 In situations where one is getting information about a single known device,
36 it does not impact performance whether the cache is used or not (unless you
37 are not able to read the block device directly). If you are dealing with
38 multiple devices, use of the cache is highly recommended (even if empty) as
39 devices will be scanned at most one time and the on-disk cache will be
40 updated if possible. There is rarely a reason not to use the cache.
42 In some cases (modular kernels), block devices are not even visible until
43 after they are accessed the first time, so it is critical that there is
44 some way to locate these devices without enumerating only visible devices,
45 so the use of the cache file is
48 .SH CONFIGURATION FILE
49 The standard location of the
51 config file can be overridden by the environment variable BLKID_CONF.
52 The following options control the libblkid library:
54 .I SEND_UEVENT=<yes|not>
56 .I /dev/disk/by-{label,uuid}/
57 symlink does not match with LABEL or UUID on the device. Default is "yes".
60 Overrides the standard location of the cache file. This setting can be
61 overridden by the environment variable BLKID_FILE. Default is
65 Defines LABEL and UUID evaluation method(s). Currently, the libblkid library
66 supports "udev" and "scan" methods. More than one methods may be specified in
67 a comma separated list. Default is "udev,scan". The "udev" method uses udev
69 symlinks and the "scan" method scans all block devices from the
74 was written by Andreas Dilger for the ext2 filesystem utilties, with input
75 from Ted Ts'o. The library was subsequently heavily modified by Ted Ts'o.
77 The low-level probing code was rewritten by Karel Zak.
81 caches data extracted from each recognized block device
87 is part of the util-linux-ng package since version 2.15 and is available from
88 ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
91 is available under the terms of the GNU Library General Public License (LGPL),
92 version 2 (or at your discretion any later version). A copy of the LGPL
93 should be included with this library in the file COPYING. If not, write to
95 Free Software Foundation, Inc.
101 Boston, MA 02110-1301 USA
105 .UR http://www.gnu.org/licenses/licenses.html#LGPL
106 http://www.gnu.org/licenses/licenses.html#LGPL