Provided by: dmsetup_1.02.167-1ubuntu1_amd64 bug


       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]
       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.  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

       -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 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.

              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 different 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 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
              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 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

       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 [--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  crypt  and integrity targets unless the --showkeys parameter is
              supplied. Kernel key references prefixed with : are not affected by  the  parameter
              and  get  displayed  always  (crypt  target  only).   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

       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  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

       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
                      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 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.

              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

       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: