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dmsetup(8) [bsd man page]


       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
       dmsetup create --concise [concise_device_specification]
       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 [--concise] [--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.

	      Ensure /dev/mapper node exists after dmsetup create.

	      Ensure /dev/mapper node exists after dmsetup resume (default with udev).

	      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.

	      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.

	      Try harder to complete operation.

	      Outputs a summary of the commands available, optionally including the list of report fields (synonym with help command).

	      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.  Charac-
	      ter  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  vari-

       -j|--major major
	      Specify the major number.

       -m|--minor minor
	      Specify the minor number.

	      When creating a device, don't load any table.

	      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.

	      Do not attempt to synchronize filesystem eg, when suspending a device.

	      Tell the kernel not to supply the open reference count for the device.

	      Do not allow udev to manage nodes for devices in device-mapper directory.

	      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 automati-
	      cally.   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.

	      Set the table being loaded read-only.

       -S|--select selection
	      Process only items that match selection criteria.  If the command is producing report  output,  adding  the  "selected"  column  (-o
	      selected)  displays  all	rows  and  shows 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 differ-
	      ent devices. It's not adviced to combine different operations on the single device.

	      Specify the uuid.

	      Answer yes to all prompts automatically.

       -v|--verbose [-v|--verbose]
	      Produce additional output.

	      If  udev	synchronisation  is enabled, verify that udev operations get performed correctly and try to fix up the device nodes after-
	      wards if not.

	      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
	      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 com-
	      mands.   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.

       create --concise [concise_device_specification]
	      Creates one or more devices from a concise device specification.	Each device is specified by a comma-separated  list:  name,  uuid,
	      minor  number,  flags, comma-separated table lines.  Flags defaults to read-write (rw) or may be read-only (ro).	Uuid, minor number
	      and flags are optional so those fields may be empty.  A semi-colon separates specifications of different devices.  Use  a  backslash
	      to escape the following character, for example a comma or semi-colon in a name or table. See also CONCISE FORMAT below.

       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 follow-
	      ing 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:
		      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

       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.  Auto-
	      matic  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 reacti-
	      vating 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 ta-
	      ble 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 con-
	      catenating 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) ver-
	      sions  of  multipath  may  support  the  --noflush  option.  This lets outstanding I/O that has not yet reached the device to remain

       table [--concise] [--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.  With --concise, the output is presented concisely on a single line.  Commas then separate the name, uuid,
	      minor device number, flags ('ro' or 'rw') and the table (if present). Semi-colons separate devices. Backslashes escape  any  commas,
	      semi-colons or backslashes.  See CONCISE FORMAT below.

	      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.

	      List all existing cookies. Cookies are system-wide semaphores with keys prefixed by two predefined bytes (0x0D4D).

	      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 sev-
	      eral 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.

	      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

       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

       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.

	      Mediates access through multiple paths to the same device.

       raid   Offers an interface to the kernel's software raid driver, md.

	      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-map-
       per  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

       A concise representation of one of more devices.

       - A comma separates the fields of each device.
       - A semi-colon separates devices.

       The representation of a device takes the form:


       The fields are:

       name   The name of the device.

       uuid   The UUID of the device (or empty).

       minor  The minor number of the device.  If empty, the kernel assigns a suitable minor number.

       flags  Supported flags are:

	      ro Sets the table being loaded for the device read-only
	      rw Sets the table being loaded for the device read-write (default)

       table  One line of the table. See TABLE FORMAT above.

       # A simple linear read-only device
       test-linear-small,,,ro,0 2097152 linear /dev/loop0 0, 2097152 2097152 linear /dev/loop1 0

       # Two linear devices
       test-linear-small,,,,0 2097152 linear /dev/loop0 0;test-linear-large,,,, 0 2097152 linear /dev/loop1 0, 2097152 2097152 linear /dev/loop2 0

	      The device directory name.  Defaults to "/dev" and must be an absolute path.

	      A cookie to use for all relevant commands to synchronize with udev processing.  It is an alternative to using --udevcookie option.

	      A default mangling mode. Defaults to "auto" and it is an alternative to using --manglename option.

       Original version: Joe Thornber <>

       dmstats(8), udev(7), udevadm(8)

       LVM2 resource page:
       Device-mapper resource page:

Linux								    Apr 06 2006 							DMSETUP(8)
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