dmsetup



DMSETUP(8)                   MAINTENTANCE COMMANDS                  DMSETUP(8)




NAME

       dmsetup - low level logical volume management


SYNOPSIS

       dmsetup create device_name [-u uuid] [--notable] [table_file]
       dmsetup remove device_name
       dmsetup remove_all
       dmsetup suspend device_name
       dmsetup resume device_name
       dmsetup load device_name [table_file]
       dmsetup clear device_name
       dmsetup reload device_name [table_file]
       dmsetup rename device_name new_name
       dmsetup ls [--target target_type] [--exec command]
       dmsetup info [device_name]
       dmsetup info -c|-C|--columns [--noheadings] [-o name] [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

       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.  Only -o name is supported.

       -r|--readonly
              Set the table being loaded read-only.

       -u|--uuid
              Specify the uuid.

       -v|--verbose
              Produce additional output.

       --version
              Display the library and kernel driver version.


COMMANDS

       create device_name [-u uuid] [--notable] [table_file]
              Creates  a  device  with  the given name.  If table_file is sup-
              plied, 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.

       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

       ls     [--target target_type] [--exec command]
              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.

       load|reload
              device_name [table_file]
              Loads  table_file  into the inactive table slot for device_name.
              If table_file is not  supplied,  reads  a  table  from  standard
              input.

       remove device_name
              Removes  a  device.  It will no longer be visible to dmsetup and
              will be deleted when its open_count is zero.

       remove_all
              Attempts to remove all device definitions i.e. reset the driver.
              Use with care!

       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.

       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
              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.

       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  dis-
              played.

       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 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



AUTHORS

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



SEE ALSO

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



Linux                             Sep 17 2003                       DMSETUP(8)

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