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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> | 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] [device_name]
       dmsetup wait device_name [event_nr]
       dmsetup mknodes [device_name]
       dmsetup targets
       dmsetup version
       dmsetup setgeometry device_name cyl head sect start

       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.

       -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.

       -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.

       -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   [--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
	      processess 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.

       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] [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.

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

       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.

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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