dmsetup - low level logical volume management

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

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.

-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.

create device_name [-u uuid] [--notable] [table_file]

Creates a device with the given name. If table_file is supplied, 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/<device-name>. 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 processing.

status [--target target_type] [device_name]

Outputs status information for each of the device's targets. With --target, only information relating to the specified target 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 supports 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 --target, only information relating to the specified target type is displayed.

targets

Displays the names and versions of the currently-loaded targets.

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.

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.

# 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

Original version: Joe Thornber (thornber@sistina.com)

Device-mapper resource page: http://sources.redhat.com/dm/