Provided by: dmsetup_1.02.77-6ubuntu2_amd64 bug


       dmsetup - low level logical volume management


       dmsetup clear device_name
       dmsetup create device_name [-u uuid] [--notable|--table <table>|
              table_file] [{--addnodeoncreate|--addnodeonresume}] [--readahead
       dmsetup deps [-o options] [device_name]
       dmsetup help [-c|-C|--columns]
       dmsetup info [device_name]
       dmsetup info -c|-C|--columns [--noheadings] [--separator separator]
              [-o fields] [-O|--sort sort_fields] [device_name]
       dmsetup load device_name [--table <table>|table_file]
       dmsetup ls [--target target_type] [--exec command] [--tree] [-o options]
       dmsetup message device_name sector message
       dmsetup mknodes [device_name]
       dmsetup mangle [device_name]
       dmsetup reload device_name [--table <table>|table_file]
       dmsetup wipe_table device_name
       dmsetup remove [-f|--force] [--retry] device_name
       dmsetup remove_all [-f|--force]
       dmsetup rename device_name new_name
       dmsetup rename device_name --setuuid uuid
       dmsetup resume device_name [{--addnodeoncreate|--addnodeonresume}]
              [--readahead [+]<sectors>|auto|none]
       dmsetup setgeometry device_name cyl head sect start
       dmsetup splitname device_name [subsystem]
       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 udevcookies
       dmsetup udevcreatecookie
       dmsetup udevflags cookie
       dmsetup udevreleasecookie [cookie]
       dmsetup version
       dmsetup wait [--noflush] device_name [event_nr]

       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.


              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.

              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.

       --manglename <mangling_mode>
              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:  none  (no  mangling),  hex
              (always  do  the  mangling)  and  auto (only do the mangling if not mangled yet, do
              nothing if already mangled, error on mixed; this is used  by  default).   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.

       -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 device.

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

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

              Do not synchronise with udev when creating, renaming or removing devices.

              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.

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

       --udevcookie cookie
              Use cookie for udev synchronisation.

              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]
              [{--addnodeoncreate|--addnodeonresume}] [--readahead [+]<sectors>|auto|none]
              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/mapper/<device-name>.  See below for 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 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  [--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.  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.

       wipe_table device_name
              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).

       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.

       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).

       remove [-f|--force] [--retry] 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. 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.

       remove_all [-f|--force]
              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           [{--addnodeoncreate|--addnodeonresume}]          [--readahead
              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.  Default subsystem is LVM.

       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  [--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.  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 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.


       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

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

              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:

              Transparent encryption of block devices using the kernel crypto API.

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

              Creates  a  similar  mapping to the linear target but exhibits unreliable behaviour
              periodically.  Useful for simulating failing devices when testing.

              Mirrors data across two or more devices.

              Mediates access through multiple paths to the same device.

              Offers an interface to the kernel's software raid driver, md.

              Supports snapshots of devices.

       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 option.


       Original version: Joe Thornber (


       Device-mapper resource page: