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Linux 2.6 - man page for dmsetup (linux section 8)

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> | table_file]
       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 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  including  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.

       --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 cho-
	      sen 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
       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
		  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, 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 informa-
	      tion 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 nei-
	      ther is supplied, reads a table from standard 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 cur-
	      rently 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.

       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  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 spec-
	      ified target type is displayed.  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 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 explic-
	      itly 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  sema-
	      phore 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 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  sym-
	      bolic   names   assigned	 and   these  ones  are  always  reported  as  DM_SUBSYS-
	      TEM_UDEV_FLAG<flag_position>='1'. There are 16 udev flags altogether.

       udevcomplete
	      cookie
	      Wake any processes that are waiting for udev to complete processing  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 fol-
	      lows:
		  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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