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DMSETUP(8)                             MAINTENANCE COMMANDS                            DMSETUP(8)

       dmsetup — low level logical volume management

       dmsetup clear device_name
       dmsetup create device_name [-u uuid] [-n|--notable|--table <table>|
              table_file] [{--addnodeoncreate|--addnodeonresume}] [--readahead [+]<sec‐
       dmsetup deps [-o options] [device_name]
       dmsetup help [-c|-C|--columns]
       dmsetup info [device_name]
       dmsetup info -c|-C|--columns [--noheadings] [--separator separator]
              [-o fields] [-O|--sort sort_fields] [-S|--select Selection] [device_name]
       dmsetup load device_name [--table <table>|table_file]
       dmsetup ls [--target target_type] [--exec command] [--tree]
              [-o options]
       dmsetup message device_name sector message
       dmsetup mknodes [device_name]
       dmsetup mangle [device_name]
       dmsetup reload device_name [--table <table>|table_file]
       dmsetup wipe_table device_name
       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}]
              [--readahead [+]<sectors>|auto|none]
       dmsetup setgeometry device_name cyl head sect start
       dmsetup splitname device_name [subsystem]
       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 udevcookies
       dmsetup udevcreatecookie
       dmsetup udevflags cookie
       dmsetup udevreleasecookie [cookie]
       dmsetup version
       dmsetup wait [--noflush] device_name [event_nr]

       devmap_name major minor
       devmap_name major:minor

       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.

              Ensure /dev/mapper node exists after dmsetup create.

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

              Perform additional checks on the operations requested and  report  potential  prob‐
              lems.   Useful  when  debugging  scripts.  In some cases these checks may slow down
              operations noticeably.

              Display output in columns rather than as Field: Value lines.

              Outputs a summary of the commands  available,  optionally  including  the  list  of
              report fields (synonym with help command).

              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.

       --manglename {none|hex|auto}
              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 unman‐
              gled on output where the mangling mode is one of: none (no mangling),  hex  (always
              do  the  mangling) and auto (only do the mangling if not mangled yet, do nothing if
              already mangled, error on mixed) 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.

              When creating a device, don't load any table.

              Suppress the headings line when using columnar output.

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

              Do not allow udev to manage nodes for devices in device-mapper directory.

              Do not synchronise with udev when creating, renaming or removing devices.

              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 cho‐
              sen by the kernel.  The value none is equivalent to specifying zero.

              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 Selec‐
              tion 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.

       --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.

              Specify the uuid.

              Answer yes to all prompts automatically.

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

              If udev synchronisation is enabled, verify that udev operations get performed  cor‐
              rectly and try to fix up the device nodes afterwards if not.

              Display the library and kernel driver version.

       clear  device_name
              Destroys the table in the inactive table slot for device_name.

       create device_name  [-u  uuid] [-n|--notable|--table <table>|table_file] [{--addnodeoncre‐
              ate|--addnodeonresume}] [--readahead [+]<sectors>|auto|none]
              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/map‐
              per/<device-name>.  See below for 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

       info   -c|-C|--columns  [--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.  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 oth‐
              erwise).  --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 nei‐
              ther is supplied, reads a table from standard input.

       wipe_table device_name
              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).

       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.

       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  nec‐
              essary.  Any  character not on the whitelist will be mangled based on the --mangle‐
              name 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 incor‐
              rect 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

       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  ver‐
              sion  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 nonde‐
              terministic 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}]    [--readahead     [+]<sec‐
              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.

       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 spec‐
              ified target type is displayed.  Encryption keys are suppressed in the table output
              for the crypt target unless the --showkeys parameter is supplied.

              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

       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.

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

              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  explic‐
              itly  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 sema‐
              phore 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 sym‐
              bolic  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 underlying semaphore. If the cookie is not given directly, the  command
              will try to use a value defined by DM_UDEV_COOKIE environment variable.

              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.

       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  fol‐
                      LV chunk 1 -> hda1, chunk 1
                      LV chunk 2 -> hdb1, chunk 1
                      LV chunk 3 -> hda1, chunk 2
                      LV chunk 4 -> hdb1, chunk 2

              Errors  any I/O that goes to this area.  Useful for testing or for creating devices
              with holes in them.

              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:

              Transparent encryption of block devices using the kernel crypto API.

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

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

              Mirrors data across two or more devices.

              Mediates access through multiple paths to the same device.

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

              Supports snapshots of devices.

       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.)

       # 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

              The device directory name.  Defaults to "/dev" and must be an absolute path.

              A cookie to use for all relevant commands to synchronize with udev processing.   It
              is an alternative to using --udevcookie option.

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

       Original version: Joe Thornber (thornber AT redhat.com)

       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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