| .\" Copyright 2000 Andreas Dilger (adilger@turbolinux.com) |
| .\" |
| .\" This man page was created for blkid from e2fsprogs-1.25. |
| .\" |
| .\" This file may be copied under the terms of the GNU Public License. |
| .\" |
| .\" Based on uuidgen, Mon Sep 17 10:42:12 2000, Andreas Dilger |
| .TH BLKID 8 "February 2009" "Linux" "MAINTENANCE COMMANDS" |
| .SH NAME |
| blkid \- command\-line utility to locate/print block device attributes |
| .SH SYNOPSIS |
| .B blkid |
| .RB \-L |
| .IR label " | " |
| .RB \-U |
| .IR uuid |
| |
| .B blkid |
| .RB [ \-ghlv ] |
| .RB [ \-c |
| .IR file ] |
| .RB [ \-w |
| .IR file ] |
| .RB [ \-o |
| .IR format ] |
| .in +6 |
| .RB [ \-s |
| .IR tag ] |
| .RB [ \-t |
| .IR NAME=value ] |
| .I device |
| [\fIdevice\fR ...] |
| .in -6 |
| |
| .B blkid |
| .RB -p |
| .RB [ \-O |
| .IR offset ] |
| .RB [ \-S |
| .IR size ] |
| .RB [ \-o |
| .IR format ] |
| .RB [ \-s |
| .IR tag ] |
| .in +9 |
| .RB [ \-u |
| .IR list ] |
| .I device |
| [\fIdevice\fR ...] |
| |
| .SH DESCRIPTION |
| The |
| .B blkid |
| program is the command-line interface to working with |
| .BR libblkid (3) |
| library. It can determine the type of content (e.g. filesystem, swap) |
| a block device holds, and also attributes (tokens, NAME=value pairs) |
| from the content metadata (e.g. LABEL or UUID fields). |
| .PP |
| .B blkid |
| has two main forms of operation: either searching for a device with a |
| specific NAME=value pair, or displaying NAME=value pairs for one or |
| more devices. |
| .SH OPTIONS |
| .TP |
| .BI \-c " cachefile" |
| Read from |
| .I cachefile |
| instead of reading from the default cache file |
| .IR /etc/blkid.tab . |
| If you want to start with a clean cache (i.e. don't report devices previously |
| scanned but not necessarily available at this time), specify |
| .IR /dev/null . |
| .TP |
| .B \-g |
| Perform a garbage collection pass on the blkid cache to remove |
| devices which no longer exist. |
| .TP |
| .B \-h |
| Display a usage message and exit. |
| .TP |
| .B \-l |
| Look up one device that matches the search parameter specified using |
| the |
| .B \-t |
| option. If there are multiple devices that match the specified search |
| parameter, then the device with the highest priority is returned, and/or |
| the first device found at a given priority. Device types in order of |
| decreasing priority are Device Mapper, EVMS, LVM, MD, and finally regular |
| block devices. If this option is not specified, |
| .B blkid |
| will print all of the devices that match the search parameter. |
| .TP |
| .B \-L " label " |
| Look up one device that uses the label (same as: -l -o device -t |
| LABEL=<label>). This look up method is able to reliable use /dev/disk/by-label |
| udev symlinks (depends on setting in /etc/blkid.conf). Avoid to use the |
| symlinks directly. It is not reliable to use the symlinks without verification. |
| The \fB-L\fR option works on systems with and without udev. |
| |
| Unfortunately, the original |
| .B blkid(8) |
| from e2fsprogs use the \fB-L\fR option as a |
| synonym to the \fB-o list\fR option. For better portability use "-l -o device |
| -t LABEL=<label>" and "-o list" in your scripts rather than -L option. |
| .TP |
| .B \-u " list " |
| Restrict probing functions to defined (comma separated) list of "usage" types. |
| Supported usage types are: filesystem, raid, crypto and other. The list can be |
| prefixed with "no" to specify the usage types which should be ignored. For example: |
| .sp |
| blkid -p -u filesystem,other /dev/sda1 |
| .sp |
| probes for all filesystems and others (e.g. swap) formats, and |
| .sp |
| blkid -p -u noraid /dev/sda1 |
| .sp |
| probes for all supported formats exclude RAIDs. This option is useful with |
| \fB-p\fR only. |
| .TP |
| .B \-U " uuid " |
| Look up one device that uses the uuid. For more details see the \fB-L\fR option. |
| .TP |
| .BI \-o " format" |
| Display |
| .BR blkid 's |
| output using the specified format. The |
| .I format |
| parameter may be: |
| .RS |
| .TP |
| .B full |
| print all tags (the default) |
| .TP |
| .B value |
| print the value of the tags |
| .TP |
| .B list |
| print the devices in a user-friendly format, this output format is unsupported |
| for low-level probing (\fB-p\fR) |
| .TP |
| .B device |
| print the device name only, this output format is always enabled for \fB-L\fR |
| and \fB-U\fR options |
| .TP |
| .B udev |
| vol_id compatible mode; usable in udev rules |
| .RE |
| .TP |
| .BI \-O " bytes" |
| Probe at the given offset (only useful with \fB-p\fR). |
| .TP |
| .BI \-p |
| Switch to low-level probing mode (bypass cache) |
| .TP |
| .BI \-s " tag" |
| For each (specified) device, show only the tags that match |
| .IR tag . |
| It is possible to specify multiple |
| .B \-s |
| options. If no tag is specified, then all tokens are shown for all |
| (specified) devices. |
| In order to just refresh the cache without showing any tokens, use |
| .B "-s none" |
| with no other options. |
| .TP |
| .BI \-S " bytes" |
| Overwrite device/file size (only useful with \fB-p\fR). |
| .TP |
| .BI \-t " NAME" = "value" |
| Search for block devices with tokens named |
| .I NAME |
| that have the value |
| .IR value , |
| and display any devices which are found. |
| Common values for |
| .I NAME |
| include |
| .BR TYPE , |
| .BR LABEL , |
| and |
| .BR UUID . |
| If there are no devices specified on the command line, all block devices |
| will be searched; otherwise only the specified devices are searched. |
| .TP |
| .B \-v |
| Display version number and exit. |
| .TP |
| .BI \-w " writecachefile" |
| Write the device cache to |
| .I writecachefile |
| instead of writing it to the default cache file |
| .IR /etc/blkid.tab . |
| If you don't want to save the cache to the default file, specify |
| .IR /dev/null. |
| If not specified it will be the same file as that given by the |
| .B \-c |
| option. |
| .TP |
| .I device |
| Display tokens from only the specified device. It is possible to |
| give multiple |
| .I device |
| options on the command line. If none is given, all devices which |
| appear in |
| .I /proc/partitions |
| are shown, if they are recognized. |
| .SH "RETURN CODE" |
| If the specified token was found, or if any tags were shown from (specified) |
| devices, 0 is returned. If the specified token was not found, or no |
| (specified) devices could be identified, an exit code of 2 is returned. |
| For usage or other errors, an exit code of 4 is returned. |
| .SH AUTHOR |
| .B blkid |
| was written by Andreas Dilger for libblkid and improved by Theodore Ts'o |
| and Karel Zak. |
| .SH AVAILABILITY |
| The blkid command is part of the util-linux-ng package and is available from |
| ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/. |
| .SH "SEE ALSO" |
| .BR libblkid (3) |
| .BR findfs (8) |
| .BR wipefs (8) |