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.TH DMSETUP 8 "Apr 06 2006" "Linux" "MAINTENTANCE COMMANDS"
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.SH NAME
dmsetup \- low level logical volume management
.SH SYNOPSIS
.ad l
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.B dmsetup create
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.I device_name [-u uuid] [--notable | --table <table> | table_file]
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.br
.B dmsetup remove
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.I [-f|--force] device_name
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.br
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.B dmsetup remove_all
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.I [-f|--force]
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.br
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.B dmsetup suspend
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.I [--nolockfs] device_name
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.B dmsetup resume
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.I device_name
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.B dmsetup load
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.I device_name [--table <table> | table_file]
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.B dmsetup clear
.I device_name
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.B dmsetup reload
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.I device_name [--table <table> | table_file]
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.br
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.B dmsetup rename
.I device_name new_name
.br
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.B dmsetup ls [--target target_type] [--exec command] [--tree [-o options]]
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.br
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.B dmsetup info
.I [device_name]
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.B dmsetup info -c|-C|--columns [--noheadings] [-o name]
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.I [device_name]
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.B dmsetup deps
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.I [device_name]
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.br
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.B dmsetup status [--target target_type]
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.I [device_name]
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.br
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.B dmsetup table [--target target_type]
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.I [device_name]
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.B dmsetup wait
.I device_name
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.I [event_nr]
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.B dmsetup mknodes
.I [device_name]
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.B dmsetup targets
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.B dmsetup version
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.B devmap_name
.I major minor
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.B devmap_name
.I major:minor
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.ad b
.SH DESCRIPTION
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dmsetup manages logical devices that use the device-mapper driver.
Devices are created by loading a table that specifies a target for
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each sector (512 bytes) in the logical device.
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The first argument to dmsetup is a command.
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The second argument is the logical device name or uuid.
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Invoking the command as \fB devmap_name\fP is equivalent to
.br
\fB dmsetup info -c --noheadings -j \fI major\fB -m \fI minor\fP .
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.SH OPTIONS
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.IP \fB -c|-C|--columns
.br
Display output in columns rather than as Field: Value lines.
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.IP \fB -j|--major\ \fI major
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Specify the major number.
.IP \fB -m|--minor\ \fI minor
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Specify the minor number.
.IP \fB -n|--noheadings
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Suppress the headings line when using columnar output.
.IP \fB --noopencount
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.br
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Tell the kernel not to supply the open reference count for the device.
.IP \fB --notable
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When creating a device, don't load any table.
.IP \fB -o|--options
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Specify which fields to display. Only \fB -o\ name\fP is supported.
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.IP \fB -r|--readonly
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Set the table being loaded read-only.
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.IP \fB --table\ <table>
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Specify a one-line table directly on the command line.
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.IP \fB -u|--uuid
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Specify the uuid.
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.IP \fB -v|--verbose\ [-v|--verbose]
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Produce additional output.
.IP \fB --version
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Display the library and kernel driver version.
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.SH COMMANDS
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.IP \fB create
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.I device_name [-u uuid] [--notable | --table <table> | table_file]
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.br
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Creates a device with the given name.
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If table_file or <table> is supplied, the table is loaded and made live.
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Otherwise a table is read from standard input unless --notable is used.
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The optional uuid can be used in place of
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device_name in subsequent dmsetup commands.
If successful a device will appear as
/dev/device-mapper/<device-name>.
See below for information on the table format.
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.IP \fB deps
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.I [device_name]
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Outputs a list of (major, minor) pairs for devices referenced by the
live table for the specified device.
.IP \fB info
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.I [device_name]
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Outputs some brief information about the device in the form:
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State: SUSPENDED|ACTIVE, READ-ONLY
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Tables present: LIVE and/or INACTIVE
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Open reference count
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Last event sequence number (used by \fB wait\fP )
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Major and minor device number
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Number of targets in the live table
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UUID
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.IP \fB ls
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.I [--target target_type]
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.I [--exec command]
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.I [--tree [-o options]]
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.br
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List device names. Optionally only list devices that have at least
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one target of the specified type. Optionally execute a command for
each device. The device name is appended to the supplied command.
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--tree displays dependencies between devices as a tree.
It accepts a comma-separate list of options.
Some specify the information displayed against each node:
device/nodevice; active, open, rw, uuid.
Others specify how the tree is displayed:
ascii, utf, vt100; compact, inverted, notrunc.
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.IP \fB load|reload
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.I device_name [--table <table> | table_file]
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.br
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Loads <table> or table_file into the inactive table slot for device_name.
If neither is supplied, reads a table from standard input.
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.IP \fB mknodes
.I [device_name]
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Ensure that the node in /dev/mapper for device_name is correct.
If no device_name is supplied, ensure that all nodes in /dev/mapper
correspond to mapped devices currently loaded by the device-mapper kernel
driver, adding, changing or removing nodes as necessary.
.IP \fB remove
.I [-f|--force] device_name
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Removes a device. It will no longer be visible to dmsetup.
Open devices cannot be removed except with older kernels
that contain a version of device-mapper prior to 4.8.0.
In this case the device will be deleted when its open_count
drops to zero. From version 4.8.0 onwards, if a device can't
be removed because an uninterruptible process is waiting for
I/O to return from it, adding --force will replace the table
with one that fails all I/O, which might allow the
process to be killed.
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.IP \fB remove_all
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.I [-f|--force]
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Attempts to remove all device definitions i.e. reset the driver.
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Use with care! From version 4.8.0 onwards, if devices can't
be removed because uninterruptible processess are waiting for
I/O to return from them, adding --force will replace the table
with one that fails all I/O, which might allow the
process to be killed. This also runs \fB mknodes\fP afterwards.
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.IP \fB rename
.I device_name new_name
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Renames a device.
.IP \fB resume
.I device_name
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Un-suspends a device.
If an inactive table has been loaded, it becomes live.
Postponed I/O then gets re-queued for processing.
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.IP \fB status
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.I [--target target_type]
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.I [device_name]
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Outputs status information for each of the device's targets.
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With --target, only information relating to the specified target type
is displayed.
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.IP \fB suspend
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.I [--nolockfs]
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.I device_name
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Suspends a device. Any I/O that has already been mapped by the device
but has not yet completed will be flushed. Any further I/O to that
device will be postponed for as long as the device is suspended.
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If there's a filesystem on the device which supports the operation,
an attempt will be made to sync it first unless --nolockfs is specified.
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.IP \fB table
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.I [--target target_type]
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.I [device_name]
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.br
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Outputs the current table for the device in a format that can be fed
back in using the create or load commands.
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With --target, only information relating to the specified target type
is displayed.
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.IP \fB targets
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Displays the names and versions of the currently-loaded targets.
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.IP \fB version
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Outputs version information.
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.IP \fB wait
.I device_name
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.I [event_nr]
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.br
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Sleeps until the event counter for device_name exceeds event_nr.
Use -v to see the event number returned.
To wait until the next event is triggered, use \fB info\fP to find
the last event number.
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.SH TABLE FORMAT
Each line of the table specifies a single target and is of the form:
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logical_start_sector num_sectors target_type target_args
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There are currently three simple target types available together
with more complex optional ones that implement snapshots and mirrors.
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.IP \fB linear
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.I destination_device start_sector
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The traditional linear mapping.
.IP \fB striped
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.I num_stripes chunk_size [destination start_sector]+
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Creates a striped area.
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e.g. striped 2 32 /dev/hda1 0 /dev/hdb1 0
will map the first chunk (16k) as follows:
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LV chunk 1 -> hda1, chunk 1
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LV chunk 2 -> hdb1, chunk 1
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LV chunk 3 -> hda1, chunk 2
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LV chunk 4 -> hdb1, chunk 2
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etc.
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.IP \fB error
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Errors any I/O that goes to this area. Useful for testing or
for creating devices with holes in them.
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.SH EXAMPLES
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# A table to join two disks together
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0 1028160 linear /dev/hda 0
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1028160 3903762 linear /dev/hdb 0
# A table to stripe across the two disks,
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# and add the spare space from
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# hdb to the back of the volume
0 2056320 striped 2 32 /dev/hda 0 /dev/hdb 0
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2056320 2875602 linear /dev/hdb 1028160
.SH AUTHORS
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Original version: Joe Thornber (thornber@sistina.com)
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.SH SEE ALSO
Device-mapper resource page: http://sources.redhat.com/dm/