DMSETUP(8)                   MAINTENANCE COMMANDS                   DMSETUP(8)
       dmsetup - low level logical volume management

       dmsetup help [-c|-C|--columns]
       dmsetup create device_name [-u uuid] [--notable | --table <table> | ta-
       ble_file] [{ --addnodeonresume | --addnodeoncreate }]
       dmsetup remove [-f|--force] device_name
       dmsetup remove_all [-f|--force]
       dmsetup suspend [--nolockfs] [--noflush] device_name
       dmsetup resume device_name
       dmsetup load device_name [--table <table> | table_file]
       dmsetup clear device_name
       dmsetup reload device_name [--table <table> | table_file]
       dmsetup rename device_name new_name
       dmsetup rename device_name --setuuid uuid
       dmsetup message device_name sector message
       dmsetup ls [--target target_type] [--exec command] [--tree [-o
       dmsetup info [device_name]
       dmsetup info -c|-C|--columns [--noheadings] [--separator separator] [-o
       fields] [-O|--sort sort_fields] [device_name]
       dmsetup deps [device_name]
       dmsetup status [--target target_type] [device_name]
       dmsetup table [--target target_type] [--showkeys] [device_name]
       dmsetup wait device_name [event_nr]
       dmsetup mknodes [device_name]
       dmsetup udevcreatecookie
       dmsetup udevreleasecookie [cookie]
       dmsetup udevflags cookie
       dmsetup udevcomplete cookie
       dmsetup udevcomplete_all [age_in_minutes]
       dmsetup udevcookies
       dmsetup targets
       dmsetup version
       dmsetup setgeometry device_name cyl head sect start
       dmsetup splitname device_name [subsystem]

       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 command as devmap_name is equivalent to
       dmsetup info -c --noheadings -j major -m minor.

              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.

              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.

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

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

              Suppress the headings line when using columnar output.

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

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

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

              Ensure /dev/mapper node exists after dmsetup create.

       --udevcookie cookie
              Use cookie for udev synchronisation.

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

              Do not synchronise with udev when creating, renaming or removing

              Specify which fields to display.

              Set the table being loaded read-only.

       --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.  "None" is equivalent to specifying zero.

       --table <table>
              Specify a one-line table directly on the command line.

              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] [--notable | --table <table> | table_file]
              Creates  a device with the given name.  If table_file or <table>
              is supplied, the table is loaded and made live.  Otherwise a ta-
              ble  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  a  device  will  appear  as
              /dev/device-mapper/<device-name>.  See below for information  on
              the table format.

       deps   [device_name]
              Outputs a list of (major, minor) pairs for devices referenced by
              the live table for the specified device.

       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   [--noheadings]   [--separator  separator]  [-o
              fields] [-O|--sort sort_fields] [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.  --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; active, open, rw, uuid.  Others specify how the
              tree   is  displayed:  ascii,  utf,  vt100;  compact,  inverted,

              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.

              device_name sector message
              Send message to target. If sector not needed use 0.

              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] device_name
              Removes a device.  It will no  longer  be  visible  to  dmsetup.
              Open  devices  cannot  be removed except with older kernels that
              contain a version of device-mapper prior to 4.8.0.  In this case
              the  device  will  be deleted when its open_count drops to zero.
              From version 4.8.0 onwards, if a device can't be removed because
              an uninterruptible process is waiting for I/O to return from it,
              adding --force will replace the table with one  that  fails  all
              I/O, which might allow the process to be killed.

              Attempts to remove all device definitions i.e. reset the driver.
              Use with care!  From version 4.8.0 onwards, if devices can't  be
              removed because uninterruptible processes are waiting for I/O to
              return from them, adding --force will replace the table with one
              that  fails all I/O, which might allow the process to be killed.
              This also runs mknodes afterwards.

       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
              Un-suspends  a device.  If an inactive table has been loaded, it
              becomes live.  Postponed I/O then gets re-queued for processing.

              device_name cyl head sect start
              Sets the device geometry to C/H/S.

              device_name [subsystem]
              Splits  given  device name into subsystem constituents.  Default
              subsystem is LVM.

       status [--target target_type] [device_name]
              Outputs status information for each  of  the  device's  targets.
              With --target, only information relating to the specified target
              type is displayed.

              [--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.

              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.

              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.

              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.

              Wake any processes that are waiting for udev  to  complete  pro-
              cessing the specified cookie.

              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).

              Outputs version information.

       wait   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.

       Each line of the table specifies a single target and is of the form:
           logical_start_sector num_sectors target_type target_args

       There  are  currently three simple target types available together with
       more complex optional ones that implement snapshots and mirrors.

       linear destination_device start_sector
              The traditional linear mapping.

              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

              Errors  any  I/O  that goes to this area.  Useful for testing or
              for creating devices with holes in them.

       # 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

       Original version: Joe Thornber (

       Device-mapper resource page:

Linux                             Apr 06 2006                       DMSETUP(8)