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 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
       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]
       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]

       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  dis-
       tributed 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  includ-
              ing 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 man-
              gled 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.

              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

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

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

              Do not synchronise with udev when creating, renaming or removing

       -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 auto-
              matically.  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  com-
              mand  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  selec-
              tion  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 opera-
              tions 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
              afterwards 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 [+]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.

       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 CON-
              CISE 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
              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  includ-
              ing 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

       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,  seg-
              ments,   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 dis-
              played: 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 stan-
              dard 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 encod-
              ing  might  change  without  notice in any future release, so we
              recommend you always decode using the current  version  of  this

       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 sup-
              ports 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 [--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  dis-
              played.  Real encryption keys are suppressed in the table output
              for the crypt target unless the  --showkeys  parameter  is  sup-
              plied. 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 pro-
              cessing 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  process-
              ing.   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  suit-
              able  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 sta-

       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 dis-
              carded 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 dynam-
              ically migrating some of its data to  a  faster  smaller  device
              (eg, an SSD).

       crypt  Transparent  encryption of block devices using the kernel crypto

       delay  Delays reads and/or writes to  different  devices.   Useful  for

       flakey Creates  a  similar  mapping  to  the linear target but exhibits
              unreliable behaviour periodically.  Useful for simulating  fail-
              ing 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-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

       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

       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-lin-
       ear-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

              A  default mangling mode. Defaults to "auto" and it is an alter-
              native 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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