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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COMMANDS | TABLE FORMAT | EXAMPLES | ENVIRONMENT VARIABLES | AUTHORS | SEE ALSO | COLOPHON |
DMSETUP(8) MAINTENANCE COMMANDS DMSETUP(8)
dmsetup — low level logical volume management
dmsetup clear device_name
dmsetup create device_name [-u|--uuid uuid]
[--addnodeoncreate|--addnodeonresume] [-n|--notable|--table
table|table_file] [--readahead [+]sectors|auto|none]
dmsetup deps [-o options] [device_name...]
dmsetup help [-c|-C|--columns]
dmsetup info [device_name...]
dmsetup info -c|-C|--columns [--count count] [--interval seconds]
[--nameprefixes] [--noheadings] [-o fields] [-O|--sort
sort_fields] [--separator separator] [device_name]
dmsetup load device_name [--table table|table_file]
dmsetup ls [--target target_type] [--exec command] [--tree] [-o
options]
dmsetup mangle [device_name...]
dmsetup message device_name sector message
dmsetup mknodes [device_name...]
dmsetup reload device_name [--table table|table_file]
dmsetup remove [-f|--force] [--retry] [--deferred] device_name...
dmsetup remove_all [-f|--force] [--deferred]
dmsetup rename device_name new_name
dmsetup rename device_name --setuuid uuid
dmsetup resume device_name... [--addnodeoncreate|--addnodeonresume]
[--noflush] [--nolockfs] [--readahead [+]sectors|auto|none]
dmsetup setgeometry device_name cyl head sect start
dmsetup splitname device_name [subsystem]
dmsetup stats command [options]
dmsetup status [--target target_type] [--noflush] [device_name...]
dmsetup suspend [--nolockfs] [--noflush] device_name...
dmsetup table [--target target_type] [--showkeys] [device_name...]
dmsetup targets
dmsetup udevcomplete cookie
dmsetup udevcomplete_all [age_in_minutes]
dmsetup udevcookie
dmsetup udevcreatecookie
dmsetup udevflags cookie
dmsetup udevreleasecookie [cookie]
dmsetup version
dmsetup wait [--noflush] device_name [event_nr]
dmsetup wipe_table device_name... [-f|--force] [--noflush]
[--nolockfs]
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 dmsetup tool as devmap_name (which is not normally
distributed and is supported only for historical reasons) is
equivalent to dmsetup info -c --noheadings -j major -m minor.
--addnodeoncreate
Ensure /dev/mapper node exists after dmsetup create.
--addnodeonresume
Ensure /dev/mapper node exists after dmsetup resume (default
with udev).
--checks
Perform additional checks on the operations requested and
report potential problems. Useful when debugging scripts. In
some cases these checks may slow down operations noticeably.
-c|-C|--columns
Display output in columns rather than as Field: Value lines.
--count count
Specify the number of times to repeat a report. Set this to
zero continue until interrupted. The default interval is one
second.
-f|--force
Try harder to complete operation.
-h|--help
Outputs a summary of the commands available, optionally
including the list of report fields (synonym with help
command).
--inactive
When returning any table information from the kernel report on
the inactive table instead of the live table. Requires kernel
driver version 4.16.0 or above.
--interval seconds
Specify the interval in seconds between successive iterations
for repeating reports. If --interval is specified but --count
is not, reports will continue to repeat until interrupted.
The default interval is one second.
--manglename auto|hex|none
Mangle any character not on a whitelist using mangling_mode
when processing device-mapper device names and UUIDs. The
names and UUIDs are mangled on input and unmangled on output
where the mangling mode is one of: auto (only do the mangling
if not mangled yet, do nothing if already mangled, error on
mixed), hex (always do the mangling) and none (no mangling).
Default mode is auto. Character whitelist: 0-9, A-Z, a-z,
#+-.:=@_. This whitelist is also supported by udev. Any
character not on a whitelist is replaced with its hex value
(two digits) prefixed by \x. Mangling mode could be also set
through DM_DEFAULT_NAME_MANGLING_MODE environment variable.
-j|--major major
Specify the major number.
-m|--minor minor
Specify the minor number.
-n|--notable
When creating a device, don't load any table.
--nameprefixes
Add a "DM_" prefix plus the field name to the output. Useful
with --noheadings to produce a list of field=value pairs that
can be used to set environment variables (for example, in
udev(7) rules).
--noheadings Suppress the headings line when using columnar output.
--noflush Do not flush outstading I/O when suspending a device, or do
not commit thin-pool metadata when obtaining thin-pool status.
--nolockfs
Do not attempt to synchronize filesystem eg, when suspending a
device.
--noopencount
Tell the kernel not to supply the open reference count for the
device.
--noudevrules
Do not allow udev to manage nodes for devices in device-mapper
directory.
--noudevsync
Do not synchronise with udev when creating, renaming or
removing devices.
-o|--options options
Specify which fields to display.
--readahead [+]sectors|auto|none
Specify read ahead size in units of sectors. The default
value is auto which allows the kernel to choose a suitable
value automatically. The + prefix lets you specify a minimum
value which will not be used if it is smaller than the value
chosen by the kernel. The value none is equivalent to
specifying zero.
-r|--readonly
Set the table being loaded read-only.
-S|--select selection
Display only rows that match selection criteria. All rows are
displayed with the additional "selected" column (-o selected)
showing 1 if the row matches the selection and 0 otherwise.
The selection criteria are defined by specifying column names
and their valid values while making use of supported
comparison operators. As a quick help and to see full list of
column names that can be used in selection and the set of
supported selection operators, check the output of
dmsetup info -c -S help command.
--table table
Specify a one-line table directly on the command line. See
below for more information on the table format.
--udevcookie cookie
Use cookie for udev synchronisation. Note: Same cookie should
be used for same type of operations i.e. creation of multiple
different devices. It's not adviced to combine different
operations on the single device.
-u|--uuid
Specify the uuid.
-y|--yes
Answer yes to all prompts automatically.
-v|--verbose [-v|--verbose]
Produce additional output.
--verifyudev
If udev synchronisation is enabled, verify that udev
operations get performed correctly and try to fix up the
device nodes afterwards if not.
--version
Display the library and kernel driver version.
clear device_name
Destroys the table in the inactive table slot for device_name.
create device_name [-u|--uuid uuid]
[--addnodeoncreate|--addnodeonresume] [-n|--notable|--table
table|table_file] [--readahead [+]sectors|auto|none]
Creates a device with the given name. If table or 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 the device will
appear in table and for live device the node
/dev/mapper/device_name is created. See below for more
information on the table format.
deps [-o options] [device_name...]
Outputs a list of devices referenced by the live table for the
specified device. Device names on output can be customised by
following options: devno (major and minor pair, used by
default), blkdevname (block device name), devname (map name
for device-mapper devices, equal to blkdevname otherwise).
help [-c|-C|--columns]
Outputs a summary of the commands available, optionally
including the list of report fields.
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
info -c|-C|--columns [--count count] [--interval seconds]
[--nameprefixes] [--noheadings] [-o fields] [-O|--sort
sort_fields] [--separator separator] [device_name]
Output you can customise. Fields are comma-separated and
chosen from the following list: name, major, minor, attr,
open, segments, events, uuid. Attributes are: (L)ive,
(I)nactive, (s)uspended, (r)ead-only, read-(w)rite. Precede
the list with '+' to append to the default selection of
columns instead of replacing it. Precede any sort field with
'-' for a reverse sort on that column.
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. Device names on output can be customised by
following options: devno (major and minor pair, used by
default), blkdevname (block device name), devname (map name
for device-mapper devices, equal to blkdevname otherwise).
--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;
blkdevname; active, open, rw, uuid. Others specify how the
tree is displayed: ascii, utf, vt100; compact, inverted,
notrunc.
load|reload device_name [--table table|table_file]
Loads table or table_file into the inactive table slot for
device_name. If neither is supplied, reads a table from
standard input.
mangle [device_name...]
Ensure existing device-mapper device_name and UUID is in the
correct mangled form containing only whitelisted characters
(supported by udev) and do a rename if necessary. Any
character not on the whitelist will be mangled based on the
--manglename setting. Automatic rename works only for device
names and not for device UUIDs because the kernel does not
allow changing the UUID of active devices. Any incorrect UUIDs
are reported only and they must be manually corrected by
deactivating the device first and then reactivating it with
proper mangling mode used (see also --manglename).
message device_name sector message
Send message to target. If sector not needed use 0.
mknodes [device_name...]
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.
remove [-f|--force] [--retry] [--deferred] device_name...
Removes a device. It will no longer be visible to dmsetup.
Open devices cannot be removed, but adding --force will
replace the table with one that fails all I/O. --deferred
will enable deferred removal of open devices - the device will
be removed when the last user closes it. The deferred removal
feature is supported since version 4.27.0 of the device-mapper
driver available in upstream kernel version 3.13. (Use
dmsetup version to check this.) If an attempt to remove a
device fails, perhaps because a process run from a quick udev
rule temporarily opened the device, the --retry option will
cause the operation to be retried for a few seconds before
failing. Do NOT combine --force and --udevcookie, as udev may
start to process udev rules in the middle of error target
replacement and result in nondeterministic result.
remove_all [-f|--force] [--deferred]
Attempts to remove all device definitions i.e. reset the
driver. This also runs mknodes afterwards. Use with care!
Open devices cannot be removed, but adding --force will
replace the table with one that fails all I/O. --deferred
will enable deferred removal of open devices - the device will
be removed when the last user closes it. The deferred removal
feature is supported since version 4.27.0 of the device-mapper
driver available in upstream kernel version 3.13.
rename device_name new_name
Renames a device.
rename device_name --setuuid uuid
Sets the uuid of a device that was created without a uuid.
After a uuid has been set it cannot be changed.
resume device_name... [--addnodeoncreate|--addnodeonresume]
[--noflush] [--nolockfs] [--readahead [+]sectors|auto|none]
Un-suspends a device. If an inactive table has been loaded,
it becomes live. Postponed I/O then gets re-queued for
processing.
setgeometry device_name cyl head sect start
Sets the device geometry to C/H/S.
splitname device_name [subsystem]
Splits given device name into subsystem constituents. The
default subsystem is LVM. LVM currently generates device
names by concatenating the names of the Volume Group, Logical
Volume and any internal Layer with a hyphen as separator. Any
hyphens within the names are doubled to escape them. The
precise encoding might change without notice in any future
release, so we recommend you always decode using the current
version of this command.
stats command [options]
Manages IO statistics regions for devices. See dmstats(8) for
more details.
status [--target target_type] [--noflush] [device_name...]
Outputs status information for each of the device's targets.
With --target, only information relating to the specified
target type any is displayed. With --noflush, the thin target
(from version 1.3.0) doesn't commit any outstanding changes to
disk before reporting its statistics.
suspend [--nolockfs] [--noflush] 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. Some targets
such as recent (October 2006) versions of multipath may
support the --noflush option. This lets outstanding I/O that
has not yet reached the device to remain unflushed.
table [--target target_type] [--showkeys] [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. Real encryption keys are suppressed in the
table output for the crypt target unless the --showkeys
parameter is supplied. Kernel key references prefixed with :
are not affected by the parameter and get displayed always.
targets
Displays the names and versions of the currently-loaded
targets.
udevcomplete cookie
Wake any processes that are waiting for udev to complete
processing the specified cookie.
udevcomplete_all [age_in_minutes]
Remove all cookies older than the specified number of minutes.
Any process waiting on a cookie will be resumed immediately.
udevcookie
List all existing cookies. Cookies are system-wide semaphores
with keys prefixed by two predefined bytes (0x0D4D).
udevcreatecookie
Creates a new cookie to synchronize actions with udev
processing. The output is a cookie value. Normally we don't
need to create cookies since dmsetup creates and destroys them
for each action automatically. However, we can generate one
explicitly to group several actions together and use only one
cookie instead. We can define a cookie to use for each
relevant command by using --udevcookie option. Alternatively,
we can export this value into the environment of the dmsetup
process as DM_UDEV_COOKIE variable and it will be used
automatically with all subsequent commands until it is unset.
Invoking this command will create system-wide semaphore that
needs to be cleaned up explicitly by calling udevreleasecookie
command.
udevflags cookie
Parses given cookie value and extracts any udev control flags
encoded. The output is in environment key format that is
suitable for use in udev rules. If the flag has its symbolic
name assigned then the output is DM_UDEV_FLAG_<flag_name> =
'1', DM_UDEV_FLAG<flag_position> = '1' otherwise. Subsystem
udev flags don't have symbolic names assigned and these ones
are always reported as DM_SUBSYSTEM_UDEV_FLAG<flag_position> =
'1'. There are 16 udev flags altogether.
udevreleasecookie [cookie]
Waits for all pending udev processing bound to given cookie
value and clean up the cookie with underlying semaphore. If
the cookie is not given directly, the command will try to use
a value defined by DM_UDEV_COOKIE environment variable.
version
Outputs version information.
wait [--noflush] 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. With --noflush, the thin target (from version
1.3.0) doesn't commit any outstanding changes to disk before
reporting its statistics.
wipe_table device_name... [-f|--force] [--noflush] [--nolockfs]
Wait for any I/O in-flight through the device to complete,
then replace the table with a new table that fails any new I/O
sent to the device. If successful, this should release any
devices held open by the device's table(s).
Each line of the table specifies a single target and is of the form:
logical_start_sector num_sectors target_type target_args
Simple target types and target args include:
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.
zero Returns blocks of zeroes on reads. Any data written is
discarded silently. This is a block-device equivalent of the
/dev/zero character-device data sink described in null(4).
More complex targets include:
cache Improves performance of a block device (eg, a spindle) by
dynamically migrating some of its data to a faster smaller
device (eg, an SSD).
crypt Transparent encryption of block devices using the kernel
crypto API.
delay Delays reads and/or writes to different devices. Useful for
testing.
flakey Creates a similar mapping to the linear target but exhibits
unreliable behaviour periodically. Useful for simulating
failing devices when testing.
mirror Mirrors data across two or more devices.
multipath
Mediates access through multiple paths to the same device.
raid Offers an interface to the kernel's software raid driver, md.
snapshot
Supports snapshots of devices.
thin, thin-pool
Supports thin provisioning of devices and also provides a
better snapshot support.
To find out more about the various targets and their table formats
and status lines, please read the files in the Documentation/device-
mapper directory in the kernel source tree. (Your distribution might
include a copy of this information in the documentation directory for
the device-mapper package.)
# 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
DM_DEV_DIR
The device directory name. Defaults to "/dev" and must be an
absolute path.
DM_UDEV_COOKIE
A cookie to use for all relevant commands to synchronize with
udev processing. It is an alternative to using --udevcookie
option.
DM_DEFAULT_NAME_MANGLING_MODE
A default mangling mode. Defaults to "auto" and it is an
alternative to using --manglename option.
Original version: Joe Thornber <thornber@redhat.com>
dmstats(8), udev(7), udevadm(8)
LVM2 resource page: https://www.sourceware.org/lvm2/
Device-mapper resource page: http://sources.redhat.com/dm/
This page is part of the lvm2 (Logical Volume Manager 2) project.
Information about the project can be found at
⟨http://www.sourceware.org/lvm2/⟩. If you have a bug report for this
manual page, send it to linux-lvm@redhat.com. This page was obtained
from the project's upstream Git repository
⟨git://sourceware.org/git/lvm2.git⟩ on 2017-07-05. If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org
Linux Apr 06 2006 DMSETUP(8)
Pages that refer to this page: pmdadm(1), blkdeactivate(8), blkmapd(8), cryptsetup(8), dmstats(8), fsfreeze(8), lvm(8)