dmsetup(8) -- Linux man page

NAME

SYNOPSIS

devmap_name major minor
devmap_name major:minor  

DESCRIPTION

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 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]
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.

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

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.

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.

TABLE FORMAT

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

SEE ALSO