dmsetup

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 create --concise [concise_device_specification]
       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 op-
                tions]
       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 [--concise] [--target target_type] [--showkeys] [de-
                vice_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.  De-
       vices 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  dis-
       tributed and is supported only for historical 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  includ-
              ing 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 de-
              fault 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 man-
              gled 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_DE-
              FAULT_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 auto-
              matically.  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
              Process only items that match selection criteria.  If  the  com-
              mand  is  producing  report output, adding the "selected" column
              (-o selected) displays all rows and shows 1 if the  row  matches
              the  selection  and  0 otherwise. The selection criteria are de-
              fined 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  selec-
              tion  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  be-
              low 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 opera-
              tions 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 af-
              terwards 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  op-
              tional  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.

       create --concise [concise_device_specification]
              Creates one or more devices from a concise device specification.
              Each  device is specified by a comma-separated list: name, uuid,
              minor number, flags, comma-separated  table  lines.   Flags  de-
              faults to read-write (rw) or may be read-only (ro).  Uuid, minor
              number and flags are optional so those fields may be  empty.   A
              semi-colon separates specifications of different devices.  Use a
              backslash to escape the following character, for example a comma
              or semi-colon in a name or table. See also CONCISE FORMAT below.

       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 de-
              fault), 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 includ-
              ing 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, seg-
              ments, events, uuid.  Attributes are: (L)ive, (I)nactive, (s)us-
              pended, (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  de-
              fault),  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; ac-
              tive, 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 de-
              vice_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.   Af-
              ter 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 de-
              fault 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 encod-
              ing 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  sup-
              ports  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 [--concise] [--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 dis-
              played.  Real encryption keys are suppressed in the table output
              for  crypt and integrity targets unless the --showkeys parameter
              is supplied. Kernel key references prefixed with : are  not  af-
              fected  by  the parameter and get displayed always (crypt target
              only).  With --concise, the output is presented concisely  on  a
              single  line.  Commas then separate the name, uuid, minor device
              number, flags ('ro' or 'rw') and the table (if  present).  Semi-
              colons  separate  devices.  Backslashes escape any commas, semi-
              colons or backslashes.  See CONCISE FORMAT below.

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

       udevcomplete cookie
              Wake any processes that are waiting for udev  to  complete  pro-
              cessing 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 process-
              ing.  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 suit-
              able 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 al-
              ways 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 sta-
              tistics.

       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  dis-
              carded  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 dynam-
              ically  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  un-
              reliable  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  de-
       vice-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

CONCISE FORMAT
       A concise representation of one of more devices.

       - A comma separates the fields of each device.
       - A semi-colon separates devices.

       The representation of a device takes the form:

              <name>,<uuid>,<minor>,<flags>,<table>[,<ta-
              ble>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]

       The fields are:

       name   The name of the device.

       uuid   The UUID of the device (or empty).

       minor  The minor number of the device.  If empty, the kernel assigns  a
              suitable minor number.

       flags  Supported flags are:

              ro Sets the table being loaded for the device read-only
              rw  Sets  the  table being loaded for the device read-write (de-
              fault)

       table  One line of the table. See TABLE FORMAT above.

EXAMPLES
       # A simple linear read-only device
       test-linear-small,,,ro,0 2097152 linear /dev/loop0 0,  2097152  2097152
       linear /dev/loop1 0

       # Two linear devices
       test-linear-small,,,,0    2097152    linear    /dev/loop0   0;test-lin-
       ear-large,,,, 0 2097152 linear /dev/loop1  0,  2097152  2097152  linear
       /dev/loop2 0

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 op-
              tion.

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

AUTHORS
       Original version: Joe Thornber <thornber@redhat.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)
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