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DMSETUP(8)		     MAINTENANCE COMMANDS		    DMSETUP(8)

NAME
       dmsetup - low level logical volume management

SYNOPSIS
       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
       options]]
       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
       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

DESCRIPTION
       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.

OPTIONS
       -c|-C|--columns
	      Display output in columns rather than as Field: Value lines.

       -h|--help
	      Outputs  a summary of the commands available, optionally includ-
	      ing the list of report fields (synonym with help command).

       --inactive
	      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.

       -n|--noheadings
	      Suppress the headings line when using columnar output.

       --noopencount
	      Tell the kernel not to supply the open reference count  for  the
	      device.

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

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

       --addnodeoncreate
	      Ensure /dev/mapper node exists after dmsetup create.

       --udevcookie cookie
	      Use cookie for udev synchronisation.

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

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

       -o|--options
	      Specify which fields to display.

       -r|--readonly
	      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.

       -u|--uuid
	      Specify the uuid.

       -y|--yes
	      Answer yes to all prompts automatically.

       -v|--verbose [-v|--verbose]
	      Produce additional output.

       --version
	      Display the library and kernel driver version.

COMMANDS
       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
		  UUID

       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,
	      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.

       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] 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.

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

       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.

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

       udevcreatecookie
	      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.

       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.

       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   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.

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

       udevcomplete_all
	      Remove all cookies. Any process waiting  on  a  cookie  will  be
	      resumed immediately.

       udevcookies
	      List  all	 existing  cookies. Cookies are system-wide semaphores
	      with keys prefixed by two predefined bytes (0x0D4D).

       version
	      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.

TABLE FORMAT
       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.

       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
		  etc.

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

EXAMPLES
       # 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

ENVIRONMENT VARIABLES
       DM_DEV_DIR
	      The  device  directory  name.  Defaults to "/dev" and must be an
	      absolute path.

       DM_UDEV_COOKIE
	      A cookie to use for all relevant commands	 to  synchronize  with
	      udev  processing.	  It  is  an alternative to using --udevcookie
	      option.

AUTHORS
       Original version: Joe Thornber (thornber@sistina.com)

SEE ALSO
       Device-mapper resource page: http://sources.redhat.com/dm/

Linux				  Apr 06 2006			    DMSETUP(8)


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