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
       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  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
              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  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.

       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.

       stats command [options]
              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 [--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.  Encryption keys are suppressed in the table output  for
              the crypt target unless the --showkeys parameter is supplied.

              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

              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)
Man Pages Copyright Respective Owners. Site Copyright (C) 1994 - 2021 Hurricane Electric. All Rights Reserved.