| .\" Copyright 2001 Andreas Dilger (adilger@turbolinux.com) |
| .\" |
| .\" This man page was created for libblkid.so.1.0 from e2fsprogs-1.24. |
| .\" |
| .\" This file may be copied under the terms of the GNU Public License. |
| .\" |
| .\" Created Wed Sep 14 12:02:12 2001, Andreas Dilger |
| .TH LIBBLKID 3 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@" |
| .SH NAME |
| libblkid \- block device identification library |
| .SH SYNOPSIS |
| .B #include <blkid/blkid.h> |
| .sp |
| .B cc |
| .I file.c |
| .B \-lblkid |
| .SH DESCRIPTION |
| The |
| .B 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. |
| .P |
| Block device information is normally kept in a cache file |
| .I /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. |
| .P |
| 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. |
| .P |
| 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 |
| .B required |
| in this situation. |
| .SH AUTHOR |
| .B 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. |
| .SH FILES |
| .TP |
| .I /etc/blkid.tab |
| Caches data extracted from each recognized block device. |
| .SH AVAILABILITY |
| .B libblkid |
| is part of the e2fsprogs package since version 1.33 and is available from |
| http://e2fsprogs.sourceforge.net. |
| .SH COPYING |
| .B 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 |
| .RS |
| Free Software Foundation, Inc. |
| .br |
| 59 Temple Place |
| .br |
| Suite 330 |
| .br |
| Boston, MA 02111-1307 USA |
| .RE |
| .PP |
| or visit |
| .UR http://www.gnu.org/licenses/licenses.html#LGPL |
| http://www.gnu.org/licenses/licenses.html#LGPL |
| .UE |
| .SH "SEE ALSO" |
| .BR blkid_get_cache (3), |
| .BR blkid_put_cache (3), |
| .BR blkid_get_dev (3), |
| .BR blkid_probe_all (3), |
| .BR blkid_get_devname (3), |
| .BR blkid_get_tag_value (3), |
| .BR blkid.tab (7) |
