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DMSETUP(8)                   MAINTENANCE COMMANDS                   DMSETUP(8)



NAME
       dmsetup -- low level logical volume management

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


       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 dmsetup tool as devmap_name (which is not normally distributed and is supported only for histori-
       cal reasons) is equivalent to dmsetup info -c --noheadings -j major -m minor

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

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

       --checks
              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.

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

       --count count
              Specify  the  number  of  times  to  repeat  a report. Set this to zero continue until interrupted.  The
              default interval is one second.

       -f|--force
              Try harder to complete operation.

       -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.

       --interval seconds
              Specify the interval in seconds between successive iterations for repeating reports.  If  --interval  is
              specified  but  --count is not, reports will continue to repeat until interrupted.  The default interval
              is one second.

       --manglename {auto|hex|none}
              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: auto (only do the mangling if not mangled yet, do nothing if already mangled, error  on  mixed),
              hex  (always  do the mangling) and none (no mangling).  Default mode is auto.  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.  Mangling mode could be also set through
              DM_DEFAULT_NAME_MANGLING_MODE environment variable.

       -j|--major major
              Specify the major number.

       -m|--minor minor
              Specify the minor number.

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

       --nameprefixes
              Add a "DM_" prefix plus the field name to the output.  Useful with --noheadings to  produce  a  list  of
              field=value pairs that can be used to set environment variables (for example, in udev(7) rules).

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

       --noflush  Do  not  flush  outstading  I/O  when  suspending a device, or do not commit thin-pool metadata when
              obtaining thin-pool status.

       --nolockfs
              Do not attempt to synchronize filesystem eg, when suspending a device.

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

       --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 options
              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.

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

       -S|--select selection
              Display  only  rows that match selection criteria. All rows are displayed with the additional "selected"
              column (-o selected) showing 1 if the row matches the selection and 0 otherwise. The selection  criteria
              are  defined  by specifying column names and their valid values while making use of supported comparison
              operators. As a quick help and to see full list of column names that can be used in  selection  and  the
              set of supported selection operators, check the output of dmsetup info -c -S help command.

       --table table
              Specify a one-line table directly on the command line.  See below for more information on the table for-
              mat.

       --udevcookie cookie
              Use cookie for udev synchronisation.  Note: Same cookie should be used for same type of operations  i.e.
              creation  of  multiple different devices. It's not adviced to combine different operations on the single
              device.

       -u|--uuid
              Specify the uuid.

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

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

       --verifyudev
              If udev synchronisation is enabled, verify that udev operations get performed correctly and try  to  fix
              up the device nodes afterwards if not.

       --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 uuid] [--addnodeoncreate|--addnodeonresume] [-n|--notable|--table
              {table|table_file}] [--readahead {[+]sectors|auto|none}]
              Creates a device with the given name.  If table or table_file 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 the device  will  appear  in
              table  and  for live device the node /dev/mapper/device_name is created.  See below for more 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
                      UUID

       info -c|-C|--columns [--count count] [--interval seconds] [--nameprefixes] [--noheadings] [-o fields]
              [-O|--sort sort_fields] [--separator separator] [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 blkdev-
              name 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.

       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).

       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] [--retry] [--deferred] device_name
              Removes  a device.  It will no longer be visible to dmsetup.  Open devices cannot be removed, but adding
              --force will replace the table with one that fails all I/O.  --deferred will enable deferred removal  of
              open  devices - the device will be removed when the last user closes it. The deferred removal feature is
              supported since version 4.27.0 of the device-mapper driver available in upstream  kernel  version  3.13.
              (Use  dmsetup version to check this.)  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.  Do NOT combine --force and --udevcookie, as udev may start
              to process udev rules in the middle of error target replacement and result in nondeterministic result.

       remove_all [-f|--force] [--deferred]
              Attempts to remove all device definitions i.e. reset the driver.  This  also  runs  mknodes  afterwards.
              Use  with care!  Open devices cannot be removed, but adding --force will replace the table with one that
              fails all I/O.  --deferred will enable deferred removal of open devices - the  device  will  be  removed
              when  the  last  user  closes it.  The deferred removal feature is supported since version 4.27.0 of the
              device-mapper driver available in upstream kernel version 3.13.

       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] [--noflush] [--nolockfs] [--readahead
              {[+]sectors|auto|none}]
              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.  The default subsystem is LVM.  LVM currently gen-
              erates device names by concatenating the names of the Volume Group,  Logical  Volume  and  any  internal
              Layer with a hyphen as separator.  Any hyphens within the names are doubled to escape them.  The precise
              encoding might change without notice in any future release, so we recommend you always decode using  the
              current version of this command.

       stats command [options]
              Manages IO statistics regions for devices.  See dmstats(8) for more details.

       stats command [options]
              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.  Encryp-
              tion 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.

       udevcomplete cookie
              Wake any processes that are waiting for udev to complete processing the specified cookie.

       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.

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

       udevcreatecookie
              Creates  a  new  cookie to synchronize actions with udev processing.  The output is a cookie value. Nor-
              mally we don't need to create cookies since dmsetup creates and destroys them for each action  automati-
              cally. 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.  Alterna-
              tively,  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.

       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 out-
              put 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_SUBSYS-
              TEM_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  underly-
              ing  semaphore.  If  the  cookie  is  not given directly, the command will try to use a value defined by
              DM_UDEV_COOKIE environment variable.

       version
              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.

       wipe_table device_name [-f|--force] [--noflush] [--nolockfs]
              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).

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

       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 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.

       zero   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:

       cache  Improves performance of a block device (eg, a spindle) by dynamically migrating some of its  data  to  a
              faster smaller device (eg, an SSD).

       crypt  Transparent encryption of block devices using the kernel crypto API.

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

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

       mirror Mirrors data across two or more devices.

       multipath
              Mediates access through multiple paths to the same device.

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

       snapshot
              Supports snapshots of devices.

       thin, thin-pool
              Supports thin provisioning of devices and also provides a better snapshot support.

       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.)

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.

       DM_DEFAULT_NAME_MANGLING_MODE
              A default mangling mode. Defaults to "auto" and it is an alternative to using --manglename option.

AUTHORS
       Original version: Joe Thornber <thornberATredhat.com>

SEE ALSO
       dmstats(8), udev(7), udevadm(8)

       LVM2 resource page: https://www.sourceware.org/lvm2/
       Device-mapper resource page: http://sources.redhat.com/dm/



Linux                             Apr 06 2006                       DMSETUP(8)