bionic (8) dmsetup.8.gz

Provided by: dmsetup_1.02.145-4.1ubuntu3.18.04.3_amd64 bug

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 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 [--concise] [--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
       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  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
              Process only items that match selection criteria.  If the  command  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 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

       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.

       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
              defaults 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  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 [--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
              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.  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 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

       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

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>[,<table>+][;<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 (default)

       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-linear-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 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 <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/