projects / thirdparty / util-linux.git / blame
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1 | .\" Copyright 2001 Andreas Dilger (adilger@turbolinux.com) |
| 2 | .\" | |
| 3 | .\" This man page was created for libblkid.so.1.0 from e2fsprogs-1.24. | |
| 4 | .\" | |
| 5 | .\" This file may be copied under the terms of the GNU Public License. | |
| 6 | .\" | |
| 7 | .\" Created Wed Sep 14 12:02:12 2001, Andreas Dilger | |
| fc7a1669 | 8 | .TH LIBBLKID 3 "February 2009" "Linux" "MAINTENANCE COMMANDS"" |
| a0948ffe KZ |
9 | .SH NAME |
| 10 | libblkid \- block device identification library | |
| 11 | .SH SYNOPSIS | |
| 12 | .B #include <blkid/blkid.h> | |
| 13 | .sp | |
| 14 | .B cc | |
| 15 | .I file.c | |
| 16 | .B \-lblkid | |
| 17 | .SH DESCRIPTION | |
| 18 | The | |
| 19 | .B libblkid | |
| 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. | |
| 25 | .P | |
| 26 | Block device information is normally kept in a cache file | |
| 27 | .I /etc/blkid.tab | |
| 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. | |
| 34 | .P | |
| 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. | |
| 41 | .P | |
| 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 | |
| 46 | .B required | |
| 47 | in this situation. | |
| 48 | .SH AUTHOR | |
| 49 | .B libblkid | |
| 50 | was written by Andreas Dilger for the ext2 filesystem utilties, with input | |
| 51 | from Ted Ts'o. The library was subsequently heavily modified by Ted Ts'o. | |
| 52 | .SH FILES | |
| 53 | .TP | |
| 54 | .I /etc/blkid.tab | |
| 55 | Caches data extracted from each recognized block device. | |
| 56 | .SH AVAILABILITY | |
| 57 | .B libblkid | |
| fc7a1669 KZ |
58 | is part of the util-linux-ng package since version 2.15 and is available from |
| 59 | ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/. | |
| a0948ffe KZ |
60 | .SH COPYING |
| 61 | .B libblkid | |
| 62 | is available under the terms of the GNU Library General Public License (LGPL), | |
| 63 | version 2 (or at your discretion any later version). A copy of the LGPL | |
| 64 | should be included with this library in the file COPYING. If not, write to | |
| 65 | .RS | |
| 66 | Free Software Foundation, Inc. | |
| 67 | .br | |
| 68 | 51 Franklin St | |
| 69 | .br | |
| 70 | Fifth Floor | |
| 71 | .br | |
| 72 | Boston, MA 02110-1301 USA | |
| 73 | .RE | |
| 74 | .PP | |
| 75 | or visit | |
| 76 | .UR http://www.gnu.org/licenses/licenses.html#LGPL | |
| 77 | http://www.gnu.org/licenses/licenses.html#LGPL | |
| 78 | .UE | |
| 79 | .SH "SEE ALSO" | |
| 80 | .BR blkid (8) | |
| fc7a1669 | 81 | .BR findfs (8) |