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