NAME | SYNOPSIS | DESCRIPTION | OPTIONS | COMMANDS | TABLE FORMAT | EXAMPLES | ENVIRONMENT VARIABLES | AUTHORS | SEE ALSO | COLOPHON

DMSETUP(8)                  MAINTENANCE COMMANDS                  DMSETUP(8)

NAME         top

       dmsetup — low level logical volume management

SYNOPSIS         top

       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         top

       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 historical reasons) is
       equivalent to dmsetup info -c --noheadings -j major -m minor.

OPTIONS         top

       --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 format.
       --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         top

       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  blkdevname  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  generates  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.
       status [--target target_type] [--noflush] [device_name...]
              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.  Real encryption keys are suppressed in the
              table  output  for  the  crypt  target  unless  the --showkeys
              parameter is supplied. Kernel key references prefixed  with  :
              are not affected by the parameter and get displayed always.
       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. 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.
       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 output  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.
       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.
       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         top

       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         top

       # 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         top

       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         top

       Original version: Joe Thornber <thornber@redhat.com>

SEE ALSO         top

       dmstats(8), udev(7), udevadm(8)
       LVM2 resource page: https://www.sourceware.org/lvm2/
       Device-mapper resource page: http://sources.redhat.com/dm/

COLOPHON         top

       This page is part of the lvm2 (Logical Volume Manager 2) project.
       Information about the project can be found at 
       ⟨http://www.sourceware.org/lvm2/⟩.  If you have a bug report for this
       manual page, send it to linux-lvm@redhat.com.  This page was obtained
       from the project's upstream Git repository 
       ⟨git://sourceware.org/git/lvm2.git⟩ on 2017-07-05.  If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page, or
       you have corrections or improvements to the information in this
       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org
Linux                            Apr 06 2006                      DMSETUP(8)

Pages that refer to this page: pmdadm(1)blkdeactivate(8)blkmapd(8)cryptsetup(8)dmstats(8)fsfreeze(8)lvm(8)