1DMSETUP(8)                   MAINTENANCE COMMANDS                   DMSETUP(8)
2
3
4

NAME

6       dmsetup — low level logical volume management
7

SYNOPSIS

9       dmsetup clear device_name
10       dmsetup create device_name [-u|--uuid uuid]
11                [--addnodeoncreate|--addnodeonresume] [-n|--notable|--table
12                table|table_file] [--readahead [+]sectors|auto|none]
13       dmsetup create --concise [concise_device_specification]
14       dmsetup deps [-o options] [device_name...]
15       dmsetup help [-c|-C|--columns]
16       dmsetup info [device_name...]
17       dmsetup info -c|-C|--columns [--count count] [--interval seconds]
18                [--nameprefixes] [--noheadings] [-o fields] [-O|--sort
19                sort_fields] [--separator separator] [device_name]
20       dmsetup load device_name [--table table|table_file]
21       dmsetup ls [--target target_type] [--exec command] [--tree] [-o
22                options]
23       dmsetup mangle [device_name...]
24       dmsetup message device_name sector message
25       dmsetup mknodes [device_name...]
26       dmsetup reload device_name [--table table|table_file]
27       dmsetup remove [-f|--force] [--retry] [--deferred] device_name...
28       dmsetup remove_all [-f|--force] [--deferred]
29       dmsetup rename device_name new_name
30       dmsetup rename device_name --setuuid uuid
31       dmsetup resume device_name...  [--addnodeoncreate|--addnodeonresume]
32                [--noflush] [--nolockfs] [--readahead [+]sectors|auto|none]
33       dmsetup setgeometry device_name cyl head sect start
34       dmsetup splitname device_name [subsystem]
35       dmsetup stats command [options]
36       dmsetup status [--target target_type] [--noflush] [device_name...]
37       dmsetup suspend [--nolockfs] [--noflush] device_name...
38       dmsetup table [--concise] [--target target_type] [--showkeys]
39                [device_name...]
40       dmsetup targets
41       dmsetup udevcomplete cookie
42       dmsetup udevcomplete_all [age_in_minutes]
43       dmsetup udevcookie
44       dmsetup udevcreatecookie
45       dmsetup udevflags cookie
46       dmsetup udevreleasecookie [cookie]
47       dmsetup version
48       dmsetup wait [--noflush] device_name [event_nr]
49       dmsetup wipe_table device_name...  [-f|--force] [--noflush]
50                [--nolockfs]
51
52       devmap_name major minor
53       devmap_name major:minor
54

DESCRIPTION

56       dmsetup  manages  logical  devices  that  use the device-mapper driver.
57       Devices are created by loading a table that specifies a target for each
58       sector (512 bytes) in the logical device.
59
60       The first argument to dmsetup is a command.  The second argument is the
61       logical device name or uuid.
62
63       Invoking the dmsetup tool as devmap_name (which is  not  normally  dis‐
64       tributed and is supported only for historical reasons) is equivalent to
65       dmsetup info -c --noheadings -j major -m minor.
66

OPTIONS

68       --addnodeoncreate
69              Ensure /dev/mapper node exists after dmsetup create.
70
71       --addnodeonresume
72              Ensure /dev/mapper node exists  after  dmsetup  resume  (default
73              with udev).
74
75       --checks
76              Perform additional checks on the operations requested and report
77              potential problems.  Useful when  debugging  scripts.   In  some
78              cases these checks may slow down operations noticeably.
79
80       -c|-C|--columns
81              Display output in columns rather than as Field: Value lines.
82
83       --count count
84              Specify the number of times to repeat a report. Set this to zero
85              continue until interrupted.  The default interval is one second.
86
87       -f|--force
88              Try harder to complete operation.
89
90       -h|--help
91              Outputs a summary of the commands available, optionally  includ‐
92              ing the list of report fields (synonym with help command).
93
94       --inactive
95              When  returning  any table information from the kernel report on
96              the inactive table instead of the live table.   Requires  kernel
97              driver version 4.16.0 or above.
98
99       --interval seconds
100              Specify  the  interval  in seconds between successive iterations
101              for repeating reports. If --interval is specified but --count is
102              not,  reports  will  continue  to repeat until interrupted.  The
103              default interval is one second.
104
105       --manglename auto|hex|none
106              Mangle any character not on a whitelist using mangling_mode when
107              processing  device-mapper  device names and UUIDs. The names and
108              UUIDs are mangled on input and unmangled  on  output  where  the
109              mangling  mode is one of: auto (only do the mangling if not man‐
110              gled yet, do nothing if already mangled, error  on  mixed),  hex
111              (always  do  the mangling) and none (no mangling).  Default mode
112              is auto.  Character whitelist: 0-9,  A-Z,  a-z,  #+-.:=@_.  This
113              whitelist  is  also  supported  by  udev. Any character not on a
114              whitelist is replaced with its hex value (two  digits)  prefixed
115              by    \x.    Mangling   mode   could   be   also   set   through
116              DM_DEFAULT_NAME_MANGLING_MODE environment variable.
117
118       -j|--major major
119              Specify the major number.
120
121       -m|--minor minor
122              Specify the minor number.
123
124       -n|--notable
125              When creating a device, don't load any table.
126
127       --nameprefixes
128              Add a "DM_" prefix plus the field name to  the  output.   Useful
129              with  --noheadings  to  produce a list of field=value pairs that
130              can be used  to  set  environment  variables  (for  example,  in
131              udev(7) rules).
132
133       --noheadings Suppress the headings line when using columnar output.
134
135       --noflush  Do  not flush outstading I/O when suspending a device, or do
136              not commit thin-pool metadata when obtaining thin-pool status.
137
138       --nolockfs
139              Do not attempt to synchronize filesystem eg, when  suspending  a
140              device.
141
142       --noopencount
143              Tell  the  kernel not to supply the open reference count for the
144              device.
145
146       --noudevrules
147              Do not allow udev to manage nodes for devices  in  device-mapper
148              directory.
149
150       --noudevsync
151              Do not synchronise with udev when creating, renaming or removing
152              devices.
153
154       -o|--options options
155              Specify which fields to display.
156
157       --readahead [+]sectors|auto|none
158              Specify read ahead size in units of sectors.  The default  value
159              is auto which allows the kernel to choose a suitable value auto‐
160              matically.  The + prefix lets you specify a minimum value  which
161              will  not  be used if it is smaller than the value chosen by the
162              kernel.  The value none is equivalent to specifying zero.
163
164       -r|--readonly
165              Set the table being loaded read-only.
166
167       -S|--select selection
168              Process only items that match selection criteria.  If  the  com‐
169              mand  is  producing  report output, adding the "selected" column
170              (-o selected) displays all rows and shows 1 if the  row  matches
171              the  selection  and  0  otherwise.  The  selection  criteria are
172              defined by specifying column names and their valid values  while
173              making  use  of  supported comparison operators. As a quick help
174              and to see full list of column names that can be used in  selec‐
175              tion  and  the  set  of supported selection operators, check the
176              output of dmsetup info -c -S help command.
177
178       --table table
179              Specify a one-line table directly  on  the  command  line.   See
180              below for more information on the table format.
181
182       --udevcookie cookie
183              Use  cookie  for udev synchronisation.  Note: Same cookie should
184              be used for same type of operations i.e.  creation  of  multiple
185              different  devices. It's not adviced to combine different opera‐
186              tions on the single device.
187
188       -u|--uuid
189              Specify the uuid.
190
191       -y|--yes
192              Answer yes to all prompts automatically.
193
194       -v|--verbose [-v|--verbose]
195              Produce additional output.
196
197       --verifyudev
198              If udev synchronisation is enabled, verify that udev  operations
199              get  performed  correctly  and  try  to  fix up the device nodes
200              afterwards if not.
201
202       --version
203              Display the library and kernel driver version.
204

COMMANDS

206       clear device_name
207              Destroys the table in the inactive table slot for device_name.
208
209       create device_name [-u|--uuid uuid]
210              [--addnodeoncreate|--addnodeonresume] [-n|--notable|--table
211              table|table_file] [--readahead [+]sectors|auto|none]
212              Creates a device with the given name.  If table or table_file is
213              supplied,  the table is loaded and made live.  Otherwise a table
214              is read from standard  input  unless  --notable  is  used.   The
215              optional  uuid can be used in place of device_name in subsequent
216              dmsetup commands.  If successful the device will appear in table
217              and for live device the node /dev/mapper/device_name is created.
218              See below for more information on the table format.
219
220       create --concise [concise_device_specification]
221              Creates one or more devices from a concise device specification.
222              Each  device is specified by a comma-separated list: name, uuid,
223              minor  number,  flags,  comma-separated  table   lines.    Flags
224              defaults  to  read-write  (rw)  or may be read-only (ro).  Uuid,
225              minor number and flags are  optional  so  those  fields  may  be
226              empty.   A  semi-colon  separates  specifications  of  different
227              devices.  Use a backslash to escape the following character, for
228              example  a comma or semi-colon in a name or table. See also CON‐
229              CISE FORMAT below.
230
231       deps [-o options] [device_name...]
232              Outputs a list of devices referenced by the live table  for  the
233              specified  device.  Device  names on output can be customised by
234              following  options:  devno  (major  and  minor  pair,  used   by
235              default),  blkdevname (block device name), devname (map name for
236              device-mapper devices, equal to blkdevname otherwise).
237
238       help [-c|-C|--columns]
239              Outputs a summary of the commands available, optionally  includ‐
240              ing the list of report fields.
241
242       info [device_name...]
243              Outputs some brief information about the device in the form:
244                      State: SUSPENDED|ACTIVE, READ-ONLY
245                      Tables present: LIVE and/or INACTIVE
246                      Open reference count
247                      Last event sequence number (used by wait)
248                      Major and minor device number
249                      Number of targets in the live table
250                      UUID
251
252       info -c|-C|--columns [--count count] [--interval seconds]
253              [--nameprefixes] [--noheadings] [-o fields] [-O|--sort
254              sort_fields] [--separator separator] [device_name]
255              Output you can customise.  Fields are comma-separated and chosen
256              from the following list: name, major, minor,  attr,  open,  seg‐
257              ments,   events,  uuid.   Attributes  are:  (L)ive,  (I)nactive,
258              (s)uspended, (r)ead-only, read-(w)rite.  Precede the  list  with
259              '+'  to  append  to  the default selection of columns instead of
260              replacing it.  Precede any sort field with  '-'  for  a  reverse
261              sort on that column.
262
263       ls [--target target_type] [--exec command] [--tree] [-o options]
264              List  device  names.   Optionally only list devices that have at
265              least one target of the specified type.   Optionally  execute  a
266              command  for  each  device.   The device name is appended to the
267              supplied command.  Device names on output can be  customised  by
268              following   options:  devno  (major  and  minor  pair,  used  by
269              default), blkdevname (block device name), devname (map name  for
270              device-mapper  devices,  equal to blkdevname otherwise).  --tree
271              displays dependencies between devices as a tree.  It  accepts  a
272              comma-separate  list  of  options.  Some specify the information
273              displayed  against  each  node:   device/nodevice;   blkdevname;
274              active,  open,  rw,  uuid.   Others specify how the tree is dis‐
275              played: ascii, utf, vt100; compact, inverted, notrunc.
276
277       load|reload device_name [--table table|table_file]
278              Loads table or table_file  into  the  inactive  table  slot  for
279              device_name.   If  neither is supplied, reads a table from stan‐
280              dard input.
281
282       mangle [device_name...]
283              Ensure existing device-mapper device_name and  UUID  is  in  the
284              correct  mangled  form  containing  only  whitelisted characters
285              (supported by udev) and do a rename if necessary. Any  character
286              not  on  the whitelist will be mangled based on the --manglename
287              setting. Automatic rename works only for device  names  and  not
288              for  device UUIDs because the kernel does not allow changing the
289              UUID of active devices. Any incorrect UUIDs  are  reported  only
290              and  they  must be manually corrected by deactivating the device
291              first and then reactivating it with proper  mangling  mode  used
292              (see also --manglename).
293
294       message device_name sector message
295              Send message to target. If sector not needed use 0.
296
297       mknodes [device_name...]
298              Ensure  that the node in /dev/mapper for device_name is correct.
299              If  no  device_name  is  supplied,  ensure  that  all  nodes  in
300              /dev/mapper correspond to mapped devices currently loaded by the
301              device-mapper kernel driver, adding, changing or removing  nodes
302              as necessary.
303
304       remove [-f|--force] [--retry] [--deferred] device_name...
305              Removes  a  device.   It  will  no longer be visible to dmsetup.
306              Open devices cannot be removed, but adding --force will  replace
307              the  table  with one that fails all I/O.  --deferred will enable
308              deferred removal of open devices - the device  will  be  removed
309              when  the  last  user closes it. The deferred removal feature is
310              supported since  version  4.27.0  of  the  device-mapper  driver
311              available in upstream kernel version 3.13.  (Use dmsetup version
312              to check this.)  If an attempt to remove a device fails, perhaps
313              because  a process run from a quick udev rule temporarily opened
314              the device, the --retry option will cause the  operation  to  be
315              retried  for  a  few  seconds  before  failing.   Do NOT combine
316              --force and --udevcookie, as udev  may  start  to  process  udev
317              rules  in  the  middle of error target replacement and result in
318              nondeterministic result.
319
320       remove_all [-f|--force] [--deferred]
321              Attempts to remove all device definitions i.e. reset the driver.
322              This also runs mknodes afterwards.  Use with care!  Open devices
323              cannot be removed, but adding --force  will  replace  the  table
324              with  one  that  fails all I/O.  --deferred will enable deferred
325              removal of open devices - the device will be  removed  when  the
326              last  user closes it.  The deferred removal feature is supported
327              since version 4.27.0 of the device-mapper  driver  available  in
328              upstream kernel version 3.13.
329
330       rename device_name new_name
331              Renames a device.
332
333       rename device_name --setuuid uuid
334              Sets  the  uuid  of  a  device  that was created without a uuid.
335              After a uuid has been set it cannot be changed.
336
337       resume device_name...  [--addnodeoncreate|--addnodeonresume]
338              [--noflush] [--nolockfs] [--readahead [+]sectors|auto|none]
339              Un-suspends  a device.  If an inactive table has been loaded, it
340              becomes live.  Postponed I/O then gets re-queued for processing.
341
342       setgeometry device_name cyl head sect start
343              Sets the device geometry to C/H/S.
344
345       splitname device_name [subsystem]
346              Splits given  device  name  into  subsystem  constituents.   The
347              default  subsystem is LVM.  LVM currently generates device names
348              by concatenating the names of the Volume Group,  Logical  Volume
349              and  any internal Layer with a hyphen as separator.  Any hyphens
350              within the names are doubled to escape them.  The precise encod‐
351              ing  might  change  without  notice in any future release, so we
352              recommend you always decode using the current  version  of  this
353              command.
354
355       stats command [options]
356              Manages  IO  statistics regions for devices.  See dmstats(8) for
357              more details.
358
359       status [--target target_type] [--noflush] [device_name...]
360              Outputs status information for each  of  the  device's  targets.
361              With --target, only information relating to the specified target
362              type any is displayed.  With --noflush, the  thin  target  (from
363              version  1.3.0)  doesn't  commit any outstanding changes to disk
364              before reporting its statistics.
365
366
367       suspend [--nolockfs] [--noflush] device_name...
368              Suspends a device.  Any I/O that has already been mapped by  the
369              device  but  has not yet completed will be flushed.  Any further
370              I/O to that device will be postponed for as long as  the  device
371              is  suspended.  If there's a filesystem on the device which sup‐
372              ports the operation, an attempt will be made to  sync  it  first
373              unless  --nolockfs  is  specified.   Some targets such as recent
374              (October 2006) versions of multipath may support  the  --noflush
375              option.   This lets outstanding I/O that has not yet reached the
376              device to remain unflushed.
377
378       table [--concise] [--target target_type] [--showkeys] [device_name...]
379              Outputs the current table for the device in a format that can be
380              fed  back  in using the create or load commands.  With --target,
381              only information relating to the specified target type  is  dis‐
382              played.  Real encryption keys are suppressed in the table output
383              for crypt and integrity targets unless the --showkeys  parameter
384              is  supplied.  Kernel  key  references  prefixed  with : are not
385              affected by the parameter and get displayed always (crypt target
386              only).   With  --concise, the output is presented concisely on a
387              single line.  Commas then separate the name, uuid, minor  device
388              number,  flags  ('ro' or 'rw') and the table (if present). Semi-
389              colons separate devices. Backslashes escape  any  commas,  semi-
390              colons or backslashes.  See CONCISE FORMAT below.
391
392       targets
393              Displays the names and versions of the currently-loaded targets.
394
395       udevcomplete cookie
396              Wake  any  processes  that are waiting for udev to complete pro‐
397              cessing the specified cookie.
398
399       udevcomplete_all [age_in_minutes]
400              Remove all cookies older than the specified number  of  minutes.
401              Any process waiting on a cookie will be resumed immediately.
402
403       udevcookie
404              List  all  existing  cookies. Cookies are system-wide semaphores
405              with keys prefixed by two predefined bytes (0x0D4D).
406
407       udevcreatecookie
408              Creates a new cookie to synchronize actions with  udev  process‐
409              ing.   The  output  is a cookie value. Normally we don't need to
410              create cookies since dmsetup creates and destroys them for  each
411              action automatically. However, we can generate one explicitly to
412              group several actions together and use only one cookie  instead.
413              We can define a cookie to use for each relevant command by using
414              --udevcookie option. Alternatively, we  can  export  this  value
415              into  the  environment  of the dmsetup process as DM_UDEV_COOKIE
416              variable and it will be used automatically with  all  subsequent
417              commands  until  it is unset.  Invoking this command will create
418              system-wide semaphore that needs to be cleaned up explicitly  by
419              calling udevreleasecookie command.
420
421       udevflags cookie
422              Parses  given  cookie  value and extracts any udev control flags
423              encoded.  The output is in environment key format that is  suit‐
424              able  for  use  in udev rules. If the flag has its symbolic name
425              assigned then the  output  is  DM_UDEV_FLAG_<flag_name>  =  '1',
426              DM_UDEV_FLAG<flag_position>  =  '1'  otherwise.   Subsystem udev
427              flags don't have symbolic names  assigned  and  these  ones  are
428              always  reported as DM_SUBSYSTEM_UDEV_FLAG<flag_position> = '1'.
429              There are 16 udev flags altogether.
430
431       udevreleasecookie [cookie]
432              Waits for all pending udev  processing  bound  to  given  cookie
433              value  and clean up the cookie with underlying semaphore. If the
434              cookie is not given directly, the command  will  try  to  use  a
435              value defined by DM_UDEV_COOKIE environment variable.
436
437       version
438              Outputs version information.
439
440       wait [--noflush] device_name [event_nr]
441              Sleeps until the event counter for device_name exceeds event_nr.
442              Use -v to see the event number returned.  To wait until the next
443              event  is  triggered,  use  info  to find the last event number.
444              With --noflush, the thin target  (from  version  1.3.0)  doesn't
445              commit any outstanding changes to disk before reporting its sta‐
446              tistics.
447
448       wipe_table device_name...  [-f|--force] [--noflush] [--nolockfs]
449              Wait for any I/O in-flight through the device to complete,  then
450              replace  the  table with a new table that fails any new I/O sent
451              to the device.  If successful, this should release  any  devices
452              held open by the device's table(s).
453

TABLE FORMAT

455       Each line of the table specifies a single target and is of the form:
456
457       logical_start_sector num_sectors target_type target_args
458
459       Simple target types and target args include:
460
461       linear destination_device start_sector
462              The traditional linear mapping.
463
464       striped num_stripes chunk_size [destination start_sector]...
465              Creates a striped area.
466              e.g.  striped  2  32  /dev/hda1 0 /dev/hdb1 0 will map the first
467              chunk (16k) as follows:
468                      LV chunk 1-> hda1, chunk 1
469                      LV chunk 2-> hdb1, chunk 1
470                      LV chunk 3-> hda1, chunk 2
471                      LV chunk 4-> hdb1, chunk 2
472                      etc.
473
474       error  Errors any I/O that goes to this area.  Useful  for  testing  or
475              for creating devices with holes in them.
476
477       zero   Returns  blocks  of  zeroes  on reads.  Any data written is dis‐
478              carded silently.  This  is  a  block-device  equivalent  of  the
479              /dev/zero character-device data sink described in null(4).
480
481       More complex targets include:
482
483       cache  Improves performance of a block device (eg, a spindle) by dynam‐
484              ically migrating some of its data to  a  faster  smaller  device
485              (eg, an SSD).
486
487       crypt  Transparent  encryption of block devices using the kernel crypto
488              API.
489
490       delay  Delays reads and/or writes to  different  devices.   Useful  for
491              testing.
492
493       flakey Creates  a  similar  mapping  to  the linear target but exhibits
494              unreliable behaviour periodically.  Useful for simulating  fail‐
495              ing devices when testing.
496
497       mirror Mirrors data across two or more devices.
498
499       multipath
500              Mediates access through multiple paths to the same device.
501
502       raid   Offers an interface to the kernel's software raid driver, md.
503
504       snapshot
505              Supports snapshots of devices.
506
507       thin, thin-pool
508              Supports thin provisioning of devices and also provides a better
509              snapshot support.
510
511       To find out more about the various targets and their table formats  and
512       status  lines, please read the files in the Documentation/device-mapper
513       directory in the kernel source tree.  (Your distribution might  include
514       a  copy  of  this  information  in  the documentation directory for the
515       device-mapper package.)
516

EXAMPLES

518       # A table to join two disks together
519       0 1028160 linear /dev/hda 0
520       1028160 3903762 linear /dev/hdb 0
521       # A table to stripe across the two disks,
522       # and add the spare space from
523       # hdb to the back of the volume
524       0 2056320 striped 2 32 /dev/hda 0 /dev/hdb 0
525       2056320 2875602 linear /dev/hdb 1028160
526

CONCISE FORMAT

528       A concise representation of one of more devices.
529
530       - A comma separates the fields of each device.
531       - A semi-colon separates devices.
532
533       The representation of a device takes the form:
534
535              <name>,<uuid>,<minor>,<flags>,<table>[,<ta‐
536              ble>+][;<dev_name>,<uuid>,<minor>,<flags>,<table>[,<table>+]]
537
538       The fields are:
539
540       name   The name of the device.
541
542       uuid   The UUID of the device (or empty).
543
544       minor  The  minor number of the device.  If empty, the kernel assigns a
545              suitable minor number.
546
547       flags  Supported flags are:
548
549              ro Sets the table being loaded for the device read-only
550              rw Sets  the  table  being  loaded  for  the  device  read-write
551              (default)
552
553       table  One line of the table. See TABLE FORMAT above.
554

EXAMPLES

556       # A simple linear read-only device
557       test-linear-small,,,ro,0  2097152  linear /dev/loop0 0, 2097152 2097152
558       linear /dev/loop1 0
559
560       # Two linear devices
561       test-linear-small,,,,0   2097152    linear    /dev/loop0    0;test-lin‐
562       ear-large,,,,  0  2097152  linear  /dev/loop1 0, 2097152 2097152 linear
563       /dev/loop2 0
564

ENVIRONMENT VARIABLES

566       DM_DEV_DIR
567              The device directory name.  Defaults to "/dev" and  must  be  an
568              absolute path.
569
570       DM_UDEV_COOKIE
571              A  cookie  to  use for all relevant commands to synchronize with
572              udev processing.  It is an  alternative  to  using  --udevcookie
573              option.
574
575       DM_DEFAULT_NAME_MANGLING_MODE
576              A  default mangling mode. Defaults to "auto" and it is an alter‐
577              native to using --manglename option.
578

AUTHORS

580       Original version: Joe Thornber <thornber@redhat.com>
581

SEE ALSO

583       dmstats(8), udev(7), udevadm(8)
584
585       LVM2 resource page: https://www.sourceware.org/lvm2/
586       Device-mapper resource page: http://sources.redhat.com/dm/
587
588
589
590Linux                             Apr 06 2006                       DMSETUP(8)
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