dmsetup − low level logical volume management
dmsetup
create device_name [-u uuid] [--notable]
[table_file]
dmsetup remove device_name
dmsetup remove_all
dmsetup suspend 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
dmsetup info [device_name]
dmsetup deps [device_name]
dmsetup status [device_name]
dmsetup table [device_name]
dmsetup wait device_name [event_nr]
dmsetup mknodes [device_name]
dmsetup targets
dmsetup version
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.
-j|--major major
Specify the major number to use on creation.
-j|--minor minor
Specify the minor number to use on creation.
-r|--readonly
Set the table being loaded read-only.
-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 |
List device names. |
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 |
[device_name] |
Outputs status information for each of the device’s targets.
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 |
[device_name] |
Outputs the current table for the device in a format that can be fed back in using the create or load commands.
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 [AT] sistina.com)
Device-mapper resource page: http://sources.redhat.com/dm/