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       dmsetup - low level logical volume management


       dmsetup help [-c|-C|--columns]
       dmsetup create device_name [-u uuid] [--notable | --table <table> |
       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 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] [device_name]
       dmsetup wait device_name [event_nr]
       dmsetup mknodes [device_name]
       dmsetup udevflags cookie
       dmsetup udevcomplete cookie
       dmsetup udevcomplete_all
       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.


              Display output in columns rather than as Field: Value lines.

       -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.

              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.

              Display the library and kernel driver version.


       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
              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  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
              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   [--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,
              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.  --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
              standard 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.

       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
              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  [--target target_type] [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

              Displays the names and versions of the currently-loaded targets.

              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 ouput 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
              processing the specified cookie.

              Remove all cookies. 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.


       Original version: Joe Thornber (


       Device-mapper resource page: