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DMSETUP(8) MAINTENTANCE COMMANDS DMSETUP(8)
NAME
dmsetup - low level logical volume management
SYNOPSIS
dmsetup create device_name [-u uuid] [--notable] [table_file]
dmsetup remove device_name
dmsetup remove_all
dmsetup suspend [--nolockfs] device_name
dmsetup resume device_name
dmsetup load device_name [table_file]
dmsetup clear device_name
dmsetup reload device_name [table_file]
dmsetup rename device_name new_name
dmsetup ls [--target target_type] [--exec command] [--tree [-o
options]]
dmsetup info [device_name]
dmsetup info -c|-C|--columns [--noheadings] [-o name] [device_name]
dmsetup deps [device_name]
dmsetup status [--target target_type] [device_name]
dmsetup table [--target target_type] [device_name]
dmsetup wait device_name [event_nr]
dmsetup mknodes [device_name]
dmsetup targets
dmsetup version
devmap_name major minor
devmap_name major:minor
DESCRIPTION
dmsetup manages logical devices that use the device-mapper driver.
Devices are created by loading a table that specifies a target for
each sector (512 bytes) in the logical device.
The first argument to dmsetup is a command. The second argument is
the logical device name or uuid.
Invoking the command as devmap_name is equivalent to
dmsetup info -c --noheadings -j major -m minor.
OPTIONS
-c|-C|--columns
Display output in columns rather than as Field: Value lines.
-j|--major major
Specify the major number.
-m|--minor minor
Specify the minor number.
-n|--noheadings
Suppress the headings line when using columnar output.
--noopencount
Tell the kernel not to supply the open reference count for the
device.
--notable
When creating a device, don't load any table.
-o|--options
Specify which fields to display. Only -o name is supported.
-r|--readonly
Set the table being loaded read-only.
-u|--uuid
Specify the uuid.
-v|--verbose
Produce additional output.
--version
Display the library and kernel driver version.
COMMANDS
create device_name [-u uuid] [--notable] [table_file]
Creates a device with the given name. If table_file is sup-
plied, the table is loaded and made live. Otherwise a table is
read from standard input unless --notable is used. The
optional uuid can be used in place of device_name in subsequent
dmsetup commands. If successful a device will appear as
/dev/device-mapper/. See below for information on
the table format.
deps [device_name]
Outputs a list of (major, minor) pairs for devices referenced
by the live table for the specified device.
info [device_name]
Outputs some brief information about the device in the form:
State: SUSPENDED|ACTIVE, READ-ONLY
Tables present: LIVE and/or INACTIVE
Open reference count
Last event sequence number (used by wait)
Major and minor device number
Number of targets in the live table
UUID
ls [--target target_type] [--exec command] [--tree [-o options]]
List device names. Optionally only list devices that have at
least one target of the specified type. Optionally execute a
command for each device. The device name is appended to the
supplied command. --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.
load|reload
device_name [table_file]
Loads table_file into the inactive table slot for device_name.
If table_file is not supplied, reads a table from standard
input.
remove device_name
Removes a device. It will no longer be visible to dmsetup and
will be deleted when its open_count is zero.
remove_all
Attempts to remove all device definitions i.e. reset the
driver. Use with care!
rename device_name new_name
Renames a device.
resume device_name
Un-suspends a device. If an inactive table has been loaded, it
becomes live. Postponed I/O then gets re-queued for process-
ing.
status [--target target_type] [device_name]
Outputs status information for each of the device's targets.
With --target, only information relating to the specified tar-
get type is displayed.
suspend
[--nolockfs] device_name
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. If there's a filesystem on the device which sup-
ports the operation, an attempt will be made to sync it first
unless --nolockfs is specified.
table [--target target_type] [device_name]
Outputs the current table for the device in a format that can
be fed back in using the create or load commands. With --tar-
get, only information relating to the specified target type is
displayed.
targets
Displays the names and versions of the currently-loaded tar-
gets.
version
Outputs version information.
wait device_name [event_nr]
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 info to find the last
event number.
TABLE FORMAT
Each line of the table specifies a single target and is of the form:
logical_start_sector num_sectors target_type target_args
There are currently three simple target types available together with
more complex optional ones that implement snapshots and mirrors.
linear destination_device start_sector
The traditional linear mapping.
striped
num_stripes chunk_size [destination start_sector]+
Creates a striped area.
e.g. striped 2 32 /dev/hda1 0 /dev/hdb1 0 will map the first
chunk (16k) as follows:
LV chunk 1 -> hda1, chunk 1
LV chunk 2 -> hdb1, chunk 1
LV chunk 3 -> hda1, chunk 2
LV chunk 4 -> hdb1, chunk 2
etc.
error
Errors any I/O that goes to this area. Useful for testing or
for creating devices with holes in them.
EXAMPLES
# A table to join two disks together
0 1028160 linear /dev/hda 0
1028160 3903762 linear /dev/hdb 0
# A table to stripe across the two disks,
# and add the spare space from
# hdb to the back of the volume
0 2056320 striped 2 32 /dev/hda 0 /dev/hdb 0
2056320 2875602 linear /dev/hdb 1028160
AUTHORS
Original version: Joe Thornber (thornber@sistina.com)
SEE ALSO
Device-mapper resource page: http://sources.redhat.com/dm/
Linux Apr 06 2006 DMSETUP(8)
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