2 .\" Copyright Neil Brown and others.
3 .\" This program is free software; you can redistribute it and/or modify
4 .\" it under the terms of the GNU General Public License as published by
5 .\" the Free Software Foundation; either version 2 of the License, or
6 .\" (at your option) any later version.
7 .\" See file COPYING in distribution for details.
10 mdadm \- manage MD devices
16 .BI mdadm " [mode] <raiddevice> [options] <component-devices>"
19 RAID devices are virtual devices created from two or more
20 real block devices. This allows multiple devices (typically disk
21 drives or partitions thereof) to be combined into a single device to
22 hold (for example) a single filesystem.
23 Some RAID levels include redundancy and so can survive some degree of
26 Linux Software RAID devices are implemented through the md (Multiple
27 Devices) device driver.
29 Currently, Linux supports
46 is not a Software RAID mechanism, but does involve
48 each device is a path to one common physical storage device.
49 New installations should not use md/multipath as it is not well
50 supported and has no ongoing development. Use the Device Mapper based
51 multipath-tools instead.
54 is also not true RAID, and it only involves one device. It
55 provides a layer over a true device that can be used to inject faults.
60 is a collection of devices that are
61 managed as a set. This is similar to the set of devices connected to
62 a hardware RAID controller. The set of devices may contain a number
63 of different RAID arrays each utilising some (or all) of the blocks from a
64 number of the devices in the set. For example, two devices in a 5-device set
65 might form a RAID1 using the whole devices. The remaining three might
66 have a RAID5 over the first half of each device, and a RAID0 over the
71 there is one set of metadata that describes all of
72 the arrays in the container. So when
76 device, the device just represents the metadata. Other normal arrays (RAID1
77 etc) can be created inside the container.
80 mdadm has several major modes of operation:
83 Assemble the components of a previously created
84 array into an active array. Components can be explicitly given
85 or can be searched for.
87 checks that the components
88 do form a bona fide array, and can, on request, fiddle superblock
89 information so as to assemble a faulty array.
93 Build an array that doesn't have per-device metadata (superblocks). For these
96 cannot differentiate between initial creation and subsequent assembly
97 of an array. It also cannot perform any checks that appropriate
98 components have been requested. Because of this, the
100 mode should only be used together with a complete understanding of
105 Create a new array with per-device metadata (superblocks).
106 Appropriate metadata is written to each device, and then the array
107 comprising those devices is activated. A 'resync' process is started
108 to make sure that the array is consistent (e.g. both sides of a mirror
109 contain the same data) but the content of the device is left otherwise
111 The array can be used as soon as it has been created. There is no
112 need to wait for the initial resync to finish.
115 .B "Follow or Monitor"
116 Monitor one or more md devices and act on any state changes. This is
117 only meaningful for RAID1, 4, 5, 6, 10 or multipath arrays, as
118 only these have interesting state. RAID0 or Linear never have
119 missing, spare, or failed drives, so there is nothing to monitor.
123 Grow (or shrink) an array, or otherwise reshape it in some way.
124 Currently supported growth options including changing the active size
125 of component devices and changing the number of active devices in
126 Linear and RAID levels 0/1/4/5/6,
127 changing the RAID level between 0, 1, 5, and 6, and between 0 and 10,
128 changing the chunk size and layout for RAID 0,4,5,6,10 as well as adding or
129 removing a write-intent bitmap.
132 .B "Incremental Assembly"
133 Add a single device to an appropriate array. If the addition of the
134 device makes the array runnable, the array will be started.
135 This provides a convenient interface to a
137 system. As each device is detected,
139 has a chance to include it in some array as appropriate.
142 flag is passed in we will remove the device from any active array
143 instead of adding it.
149 in this mode, then any arrays within that container will be assembled
154 This is for doing things to specific components of an array such as
155 adding new spares and removing faulty devices.
159 This is an 'everything else' mode that supports operations on active
160 arrays, operations on component devices such as erasing old superblocks, and
161 information gathering operations.
162 .\"This mode allows operations on independent devices such as examine MD
163 .\"superblocks, erasing old superblocks and stopping active arrays.
167 This mode does not act on a specific device or array, but rather it
168 requests the Linux Kernel to activate any auto-detected arrays.
171 .SH Options for selecting a mode are:
174 .BR \-A ", " \-\-assemble
175 Assemble a pre-existing array.
178 .BR \-B ", " \-\-build
179 Build a legacy array without superblocks.
182 .BR \-C ", " \-\-create
186 .BR \-F ", " \-\-follow ", " \-\-monitor
192 .BR \-G ", " \-\-grow
193 Change the size or shape of an active array.
196 .BR \-I ", " \-\-incremental
197 Add/remove a single device to/from an appropriate array, and possibly start the array.
201 Request that the kernel starts any auto-detected arrays. This can only
204 is compiled into the kernel \(em not if it is a module.
205 Arrays can be auto-detected by the kernel if all the components are in
206 primary MS-DOS partitions with partition type
208 and all use v0.90 metadata.
209 In-kernel autodetect is not recommended for new installations. Using
211 to detect and assemble arrays \(em possibly in an
213 \(em is substantially more flexible and should be preferred.
216 If a device is given before any options, or if the first option is
225 then the MANAGE mode is assumed.
226 Anything other than these will cause the
230 .SH Options that are not mode-specific are:
233 .BR \-h ", " \-\-help
234 Display general help message or, after one of the above options, a
235 mode-specific help message.
239 Display more detailed help about command line parsing and some commonly
243 .BR \-V ", " \-\-version
244 Print version information for mdadm.
247 .BR \-v ", " \-\-verbose
248 Be more verbose about what is happening. This can be used twice to be
250 The extra verbosity currently only affects
251 .B \-\-detail \-\-scan
253 .BR "\-\-examine \-\-scan" .
256 .BR \-q ", " \-\-quiet
257 Avoid printing purely informative messages. With this,
259 will be silent unless there is something really important to report.
263 .BR \-f ", " \-\-force
264 Be more forceful about certain operations. See the various modes for
265 the exact meaning of this option in different contexts.
268 .BR \-c ", " \-\-config=
269 Specify the config file or directory. Default is to use
272 .BR /etc/mdadm.conf.d ,
273 or if those are missing then
274 .B /etc/mdadm/mdadm.conf
276 .BR /etc/mdadm/mdadm.conf.d .
277 If the config file given is
279 then nothing will be read, but
281 will act as though the config file contained exactly
283 .B " DEVICE partitions containers"
287 to find a list of devices to scan, and
289 to find a list of containers to examine.
292 is given for the config file, then
294 will act as though the config file were empty.
296 If the name given is of a directory, then
298 will collect all the files contained in the directory with a name ending
301 sort them lexically, and process all of those files as config files.
304 .BR \-s ", " \-\-scan
307 for missing information.
308 In general, this option gives
310 permission to get any missing information (like component devices,
311 array devices, array identities, and alert destination) from the
312 configuration file (see previous option);
313 one exception is MISC mode when using
319 says to get a list of array devices from
323 .BR \-e ", " \-\-metadata=
324 Declare the style of RAID metadata (superblock) to be used. The
325 default is {DEFAULT_METADATA} for
327 and to guess for other operations.
328 The default can be overridden by setting the
337 .ie '{DEFAULT_METADATA}'0.90'
338 .IP "0, 0.90, default"
341 Use the original 0.90 format superblock. This format limits arrays to
342 28 component devices and limits component devices of levels 1 and
343 greater to 2 terabytes. It is also possible for there to be confusion
344 about whether the superblock applies to a whole device or just the
345 last partition, if that partition starts on a 64K boundary.
346 .ie '{DEFAULT_METADATA}'0.90'
347 .IP "1, 1.0, 1.1, 1.2"
349 .IP "1, 1.0, 1.1, 1.2 default"
350 Use the new version-1 format superblock. This has fewer restrictions.
351 It can easily be moved between hosts with different endian-ness, and a
352 recovery operation can be checkpointed and restarted. The different
353 sub-versions store the superblock at different locations on the
354 device, either at the end (for 1.0), at the start (for 1.1) or 4K from
355 the start (for 1.2). "1" is equivalent to "1.2" (the commonly
356 preferred 1.x format).
357 'if '{DEFAULT_METADATA}'1.2' "default" is equivalent to "1.2".
359 Use the "Industry Standard" DDF (Disk Data Format) format defined by
361 When creating a DDF array a
363 will be created, and normal arrays can be created in that container.
365 Use the Intel(R) Matrix Storage Manager metadata format. This creates a
367 which is managed in a similar manner to DDF, and is supported by an
368 option-rom on some platforms:
370 .B http://www.intel.com/design/chipsets/matrixstorage_sb.htm
376 This will override any
378 setting in the config file and provides the identity of the host which
379 should be considered the home for any arrays.
381 When creating an array, the
383 will be recorded in the metadata. For version-1 superblocks, it will
384 be prefixed to the array name. For version-0.90 superblocks, part of
385 the SHA1 hash of the hostname will be stored in the later half of the
388 When reporting information about an array, any array which is tagged
389 for the given homehost will be reported as such.
391 When using Auto-Assemble, only arrays tagged for the given homehost
392 will be allowed to use 'local' names (i.e. not ending in '_' followed
393 by a digit string). See below under
394 .BR "Auto Assembly" .
396 The special name "\fBany\fP" can be used as a wild card. If an array
399 then the name "\fBany\fP" will be stored in the array and it can be
400 assembled in the same way on any host. If an array is assembled with
401 this option, then the homehost recorded on the array will be ignored.
407 needs to print the name for a device it normally finds the name in
409 which refers to the device and is shortest. When a path component is
413 will prefer a longer name if it contains that component. For example
414 .B \-\-prefer=by-uuid
415 will prefer a name in a subdirectory of
420 This functionality is currently only provided by
426 .B \-\-home\-cluster=
427 specifies the cluster name for the md device. The md device can be assembled
428 only on the cluster which matches the name specified. If this option is not
429 provided, mdadm tries to detect the cluster name automatically.
431 .SH For create, build, or grow:
434 .BR \-n ", " \-\-raid\-devices=
435 Specify the number of active devices in the array. This, plus the
436 number of spare devices (see below) must equal the number of
438 (including "\fBmissing\fP" devices)
439 that are listed on the command line for
441 Setting a value of 1 is probably
442 a mistake and so requires that
444 be specified first. A value of 1 will then be allowed for linear,
445 multipath, RAID0 and RAID1. It is never allowed for RAID4, RAID5 or RAID6.
447 This number can only be changed using
449 for RAID1, RAID4, RAID5 and RAID6 arrays, and only on kernels which provide
450 the necessary support.
453 .BR \-x ", " \-\-spare\-devices=
454 Specify the number of spare (eXtra) devices in the initial array.
455 Spares can also be added
456 and removed later. The number of component devices listed
457 on the command line must equal the number of RAID devices plus the
458 number of spare devices.
461 .BR \-z ", " \-\-size=
462 Amount (in Kilobytes) of space to use from each drive in RAID levels 1/4/5/6.
463 This must be a multiple of the chunk size, and must leave about 128Kb
464 of space at the end of the drive for the RAID superblock.
465 If this is not specified
466 (as it normally is not) the smallest drive (or partition) sets the
467 size, though if there is a variance among the drives of greater than 1%, a warning is
470 A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
471 Gigabytes respectively.
473 Sometimes a replacement drive can be a little smaller than the
474 original drives though this should be minimised by IDEMA standards.
475 Such a replacement drive will be rejected by
477 To guard against this it can be useful to set the initial size
478 slightly smaller than the smaller device with the aim that it will
479 still be larger than any replacement.
481 This value can be set with
483 for RAID level 1/4/5/6 though
485 based arrays such as those with IMSM metadata may not be able to
487 If the array was created with a size smaller than the currently
488 active drives, the extra space can be accessed using
490 The size can be given as
492 which means to choose the largest size that fits on all current drives.
494 Before reducing the size of the array (with
495 .BR "\-\-grow \-\-size=" )
496 you should make sure that space isn't needed. If the device holds a
497 filesystem, you would need to resize the filesystem to use less space.
499 After reducing the array size you should check that the data stored in
500 the device is still available. If the device holds a filesystem, then
501 an 'fsck' of the filesystem is a minimum requirement. If there are
502 problems the array can be made bigger again with no loss with another
503 .B "\-\-grow \-\-size="
506 This value cannot be used when creating a
508 such as with DDF and IMSM metadata, though it perfectly valid when
509 creating an array inside a container.
512 .BR \-Z ", " \-\-array\-size=
513 This is only meaningful with
515 and its effect is not persistent: when the array is stopped and
516 restarted the default array size will be restored.
518 Setting the array-size causes the array to appear smaller to programs
519 that access the data. This is particularly needed before reshaping an
520 array so that it will be smaller. As the reshape is not reversible,
521 but setting the size with
523 is, it is required that the array size is reduced as appropriate
524 before the number of devices in the array is reduced.
526 Before reducing the size of the array you should make sure that space
527 isn't needed. If the device holds a filesystem, you would need to
528 resize the filesystem to use less space.
530 After reducing the array size you should check that the data stored in
531 the device is still available. If the device holds a filesystem, then
532 an 'fsck' of the filesystem is a minimum requirement. If there are
533 problems the array can be made bigger again with no loss with another
534 .B "\-\-grow \-\-array\-size="
537 A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
538 Gigabytes respectively.
541 restores the apparent size of the array to be whatever the real
542 amount of available space is.
545 .BR \-c ", " \-\-chunk=
546 Specify chunk size of kilobytes. The default when creating an
547 array is 512KB. To ensure compatibility with earlier versions, the
548 default when building an array with no persistent metadata is 64KB.
549 This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
551 RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a power
552 of 2. In any case it must be a multiple of 4KB.
554 A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
555 Gigabytes respectively.
559 Specify rounding factor for a Linear array. The size of each
560 component will be rounded down to a multiple of this size.
561 This is a synonym for
563 but highlights the different meaning for Linear as compared to other
564 RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in
565 use, and is 0K (i.e. no rounding) in later kernels.
568 .BR \-l ", " \-\-level=
569 Set RAID level. When used with
571 options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
572 raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
573 Obviously some of these are synonymous.
577 metadata type is requested, only the
579 level is permitted, and it does not need to be explicitly given.
583 only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
587 to change the RAID level in some cases. See LEVEL CHANGES below.
590 .BR \-p ", " \-\-layout=
591 This option configures the fine details of data layout for RAID5, RAID6,
592 and RAID10 arrays, and controls the failure modes for
595 The layout of the RAID5 parity block can be one of
596 .BR left\-asymmetric ,
597 .BR left\-symmetric ,
598 .BR right\-asymmetric ,
599 .BR right\-symmetric ,
600 .BR la ", " ra ", " ls ", " rs .
602 .BR left\-symmetric .
604 It is also possible to cause RAID5 to use a RAID4-like layout by
610 Finally for RAID5 there are DDF\-compatible layouts,
611 .BR ddf\-zero\-restart ,
612 .BR ddf\-N\-restart ,
614 .BR ddf\-N\-continue .
616 These same layouts are available for RAID6. There are also 4 layouts
617 that will provide an intermediate stage for converting between RAID5
618 and RAID6. These provide a layout which is identical to the
619 corresponding RAID5 layout on the first N\-1 devices, and has the 'Q'
620 syndrome (the second 'parity' block used by RAID6) on the last device.
622 .BR left\-symmetric\-6 ,
623 .BR right\-symmetric\-6 ,
624 .BR left\-asymmetric\-6 ,
625 .BR right\-asymmetric\-6 ,
627 .BR parity\-first\-6 .
629 When setting the failure mode for level
632 .BR write\-transient ", " wt ,
633 .BR read\-transient ", " rt ,
634 .BR write\-persistent ", " wp ,
635 .BR read\-persistent ", " rp ,
637 .BR read\-fixable ", " rf ,
638 .BR clear ", " flush ", " none .
640 Each failure mode can be followed by a number, which is used as a period
641 between fault generation. Without a number, the fault is generated
642 once on the first relevant request. With a number, the fault will be
643 generated after that many requests, and will continue to be generated
644 every time the period elapses.
646 Multiple failure modes can be current simultaneously by using the
648 option to set subsequent failure modes.
650 "clear" or "none" will remove any pending or periodic failure modes,
651 and "flush" will clear any persistent faults.
653 Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
654 by a small number. The default is 'n2'. The supported options are:
657 signals 'near' copies. Multiple copies of one data block are at
658 similar offsets in different devices.
661 signals 'offset' copies. Rather than the chunks being duplicated
662 within a stripe, whole stripes are duplicated but are rotated by one
663 device so duplicate blocks are on different devices. Thus subsequent
664 copies of a block are in the next drive, and are one chunk further
669 (multiple copies have very different offsets).
670 See md(4) for more detail about 'near', 'offset', and 'far'.
672 The number is the number of copies of each datablock. 2 is normal, 3
673 can be useful. This number can be at most equal to the number of
674 devices in the array. It does not need to divide evenly into that
675 number (e.g. it is perfectly legal to have an 'n2' layout for an array
676 with an odd number of devices).
678 When an array is converted between RAID5 and RAID6 an intermediate
679 RAID6 layout is used in which the second parity block (Q) is always on
680 the last device. To convert a RAID5 to RAID6 and leave it in this new
681 layout (which does not require re-striping) use
682 .BR \-\-layout=preserve .
683 This will try to avoid any restriping.
685 The converse of this is
686 .B \-\-layout=normalise
687 which will change a non-standard RAID6 layout into a more standard
694 (thus explaining the p of
698 .BR \-b ", " \-\-bitmap=
699 Specify a file to store a write-intent bitmap in. The file should not
702 is also given. The same file should be provided
703 when assembling the array. If the word
705 is given, then the bitmap is stored with the metadata on the array,
706 and so is replicated on all devices. If the word
710 mode, then any bitmap that is present is removed. If the word
712 is given, the array is created for a clustered environment. One bitmap
713 is created for each node as defined by the
715 parameter and are stored internally.
717 To help catch typing errors, the filename must contain at least one
718 slash ('/') if it is a real file (not 'internal' or 'none').
720 Note: external bitmaps are only known to work on ext2 and ext3.
721 Storing bitmap files on other filesystems may result in serious problems.
723 When creating an array on devices which are 100G or larger,
725 automatically adds an internal bitmap as it will usually be
726 beneficial. This can be suppressed with
727 .B "\-\-bitmap=none".
730 .BR \-\-bitmap\-chunk=
731 Set the chunksize of the bitmap. Each bit corresponds to that many
732 Kilobytes of storage.
733 When using a file based bitmap, the default is to use the smallest
734 size that is at-least 4 and requires no more than 2^21 chunks.
737 bitmap, the chunksize defaults to 64Meg, or larger if necessary to
738 fit the bitmap into the available space.
740 A suffix of 'K', 'M' or 'G' can be given to indicate Kilobytes, Megabytes or
741 Gigabytes respectively.
744 .BR \-W ", " \-\-write\-mostly
745 subsequent devices listed in a
750 command will be flagged as 'write\-mostly'. This is valid for RAID1
751 only and means that the 'md' driver will avoid reading from these
752 devices if at all possible. This can be useful if mirroring over a
756 .BR \-\-write\-behind=
757 Specify that write-behind mode should be enabled (valid for RAID1
758 only). If an argument is specified, it will set the maximum number
759 of outstanding writes allowed. The default value is 256.
760 A write-intent bitmap is required in order to use write-behind
761 mode, and write-behind is only attempted on drives marked as
766 subsequent devices listed in a
770 command will be flagged as 'failfast'. This is valid for RAID1 and
771 RAID10 only. IO requests to these devices will be encouraged to fail
772 quickly rather than cause long delays due to error handling. Also no
773 attempt is made to repair a read error on these devices.
775 If an array becomes degraded so that the 'failfast' device is the only
776 usable device, the 'failfast' flag will then be ignored and extended
777 delays will be preferred to complete failure.
779 The 'failfast' flag is appropriate for storage arrays which have a
780 low probability of true failure, but which may sometimes
781 cause unacceptable delays due to internal maintenance functions.
784 .BR \-\-assume\-clean
787 that the array pre-existed and is known to be clean. It can be useful
788 when trying to recover from a major failure as you can be sure that no
789 data will be affected unless you actually write to the array. It can
790 also be used when creating a RAID1 or RAID10 if you want to avoid the
791 initial resync, however this practice \(em while normally safe \(em is not
792 recommended. Use this only if you really know what you are doing.
794 When the devices that will be part of a new array were filled
795 with zeros before creation the operator knows the array is
796 actually clean. If that is the case, such as after running
797 badblocks, this argument can be used to tell mdadm the
798 facts the operator knows.
800 When an array is resized to a larger size with
801 .B "\-\-grow \-\-size="
802 the new space is normally resynced in that same way that the whole
803 array is resynced at creation. From Linux version 3.0,
805 can be used with that command to avoid the automatic resync.
808 .BR \-\-backup\-file=
811 is used to increase the number of raid-devices in a RAID5 or RAID6 if
812 there are no spare devices available, or to shrink, change RAID level
813 or layout. See the GROW MODE section below on RAID\-DEVICES CHANGES.
814 The file must be stored on a separate device, not on the RAID array
819 Arrays with 1.x metadata can leave a gap between the start of the
820 device and the start of array data. This gap can be used for various
821 metadata. The start of data is known as the
823 Normally an appropriate data offset is computed automatically.
824 However it can be useful to set it explicitly such as when re-creating
825 an array which was originally created using a different version of
827 which computed a different offset.
829 Setting the offset explicitly over-rides the default. The value given
830 is in Kilobytes unless a suffix of 'K', 'M' or 'G' is used to explicitly
831 indicate Kilobytes, Megabytes or Gigabytes respectively.
835 can also be used with
837 for some RAID levels (initially on RAID10). This allows the
838 data\-offset to be changed as part of the reshape process. When the
839 data offset is changed, no backup file is required as the difference
840 in offsets is used to provide the same functionality.
842 When the new offset is earlier than the old offset, the number of
843 devices in the array cannot shrink. When it is after the old offset,
844 the number of devices in the array cannot increase.
846 When creating an array,
850 In the case each member device is expected to have a offset appended
851 to the name, separated by a colon. This makes it possible to recreate
852 exactly an array which has varying data offsets (as can happen when
853 different versions of
855 are used to add different devices).
859 This option is complementary to the
860 .B \-\-freeze-reshape
861 option for assembly. It is needed when
863 operation is interrupted and it is not restarted automatically due to
864 .B \-\-freeze-reshape
865 usage during array assembly. This option is used together with
869 ) command and device for a pending reshape to be continued.
870 All parameters required for reshape continuation will be read from array metadata.
874 .BR \-\-backup\-file=
875 option to be set, continuation option will require to have exactly the same
876 backup file given as well.
878 Any other parameter passed together with
880 option will be ignored.
883 .BR \-N ", " \-\-name=
886 for the array. This is currently only effective when creating an
887 array with a version-1 superblock, or an array in a DDF container.
888 The name is a simple textual string that can be used to identify array
889 components when assembling. If name is needed but not specified, it
890 is taken from the basename of the device that is being created.
902 run the array, even if some of the components
903 appear to be active in another array or filesystem. Normally
905 will ask for confirmation before including such components in an
906 array. This option causes that question to be suppressed.
909 .BR \-f ", " \-\-force
912 accept the geometry and layout specified without question. Normally
914 will not allow creation of an array with only one device, and will try
915 to create a RAID5 array with one missing drive (as this makes the
916 initial resync work faster). With
919 will not try to be so clever.
922 .BR \-o ", " \-\-readonly
925 rather than read-write as normal. No writes will be allowed to the
926 array, and no resync, recovery, or reshape will be started.
929 .BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
930 Instruct mdadm how to create the device file if needed, possibly allocating
931 an unused minor number. "md" causes a non-partitionable array
932 to be used (though since Linux 2.6.28, these array devices are in fact
933 partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
934 later) to be used. "yes" requires the named md device to have
935 a 'standard' format, and the type and minor number will be determined
936 from this. With mdadm 3.0, device creation is normally left up to
938 so this option is unlikely to be needed.
939 See DEVICE NAMES below.
941 The argument can also come immediately after
946 is not given on the command line or in the config file, then
952 is also given, then any
954 entries in the config file will override the
956 instruction given on the command line.
958 For partitionable arrays,
960 will create the device file for the whole array and for the first 4
961 partitions. A different number of partitions can be specified at the
962 end of this option (e.g.
964 If the device name ends with a digit, the partition names add a 'p',
966 .IR /dev/md/home1p3 .
967 If there is no trailing digit, then the partition names just have a
969 .IR /dev/md/scratch3 .
971 If the md device name is in a 'standard' format as described in DEVICE
972 NAMES, then it will be created, if necessary, with the appropriate
973 device number based on that name. If the device name is not in one of these
974 formats, then a unused device number will be allocated. The device
975 number will be considered unused if there is no active array for that
976 number, and there is no entry in /dev for that number and with a
977 non-standard name. Names that are not in 'standard' format are only
978 allowed in "/dev/md/".
980 This is meaningful with
986 .BR \-a ", " "\-\-add"
987 This option can be used in Grow mode in two cases.
989 If the target array is a Linear array, then
991 can be used to add one or more devices to the array. They
992 are simply catenated on to the end of the array. Once added, the
993 devices cannot be removed.
997 option is being used to increase the number of devices in an array,
1000 can be used to add some extra devices to be included in the array.
1001 In most cases this is not needed as the extra devices can be added as
1002 spares first, and then the number of raid-disks can be changed.
1003 However for RAID0, it is not possible to add spares. So to increase
1004 the number of devices in a RAID0, it is necessary to set the new
1005 number of devices, and to add the new devices, in the same command.
1009 Only works when the array is for clustered environment. It specifies
1010 the maximum number of nodes in the cluster that will use this device
1011 simultaneously. If not specified, this defaults to 4.
1014 .BR \-\-write-journal
1015 Specify journal device for the RAID-4/5/6 array. The journal device
1016 should be a SSD with reasonable lifetime.
1020 Auto creation of symlinks in /dev to /dev/md, option --symlinks must
1021 be 'no' or 'yes' and work with --create and --build.
1027 .BR \-u ", " \-\-uuid=
1028 uuid of array to assemble. Devices which don't have this uuid are
1032 .BR \-m ", " \-\-super\-minor=
1033 Minor number of device that array was created for. Devices which
1034 don't have this minor number are excluded. If you create an array as
1035 /dev/md1, then all superblocks will contain the minor number 1, even if
1036 the array is later assembled as /dev/md2.
1038 Giving the literal word "dev" for
1042 to use the minor number of the md device that is being assembled.
1043 e.g. when assembling
1045 .B \-\-super\-minor=dev
1046 will look for super blocks with a minor number of 0.
1049 is only relevant for v0.90 metadata, and should not normally be used.
1055 .BR \-N ", " \-\-name=
1056 Specify the name of the array to assemble. This must be the name
1057 that was specified when creating the array. It must either match
1058 the name stored in the superblock exactly, or it must match
1061 prefixed to the start of the given name.
1064 .BR \-f ", " \-\-force
1065 Assemble the array even if the metadata on some devices appears to be
1068 cannot find enough working devices to start the array, but can find
1069 some devices that are recorded as having failed, then it will mark
1070 those devices as working so that the array can be started.
1071 An array which requires
1073 to be started may contain data corruption. Use it carefully.
1076 .BR \-R ", " \-\-run
1077 Attempt to start the array even if fewer drives were given than were
1078 present last time the array was active. Normally if not all the
1079 expected drives are found and
1081 is not used, then the array will be assembled but not started.
1084 an attempt will be made to start it anyway.
1088 This is the reverse of
1090 in that it inhibits the startup of array unless all expected drives
1091 are present. This is only needed with
1093 and can be used if the physical connections to devices are
1094 not as reliable as you would like.
1097 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
1098 See this option under Create and Build options.
1101 .BR \-b ", " \-\-bitmap=
1102 Specify the bitmap file that was given when the array was created. If
1105 bitmap, there is no need to specify this when assembling the array.
1108 .BR \-\-backup\-file=
1111 was used while reshaping an array (e.g. changing number of devices or
1112 chunk size) and the system crashed during the critical section, then the same
1114 must be presented to
1116 to allow possibly corrupted data to be restored, and the reshape
1120 .BR \-\-invalid\-backup
1121 If the file needed for the above option is not available for any
1122 reason an empty file can be given together with this option to
1123 indicate that the backup file is invalid. In this case the data that
1124 was being rearranged at the time of the crash could be irrecoverably
1125 lost, but the rest of the array may still be recoverable. This option
1126 should only be used as a last resort if there is no way to recover the
1131 .BR \-U ", " \-\-update=
1132 Update the superblock on each device while assembling the array. The
1133 argument given to this flag can be one of
1153 option will adjust the superblock of an array what was created on a Sparc
1154 machine running a patched 2.2 Linux kernel. This kernel got the
1155 alignment of part of the superblock wrong. You can use the
1156 .B "\-\-examine \-\-sparc2.2"
1159 to see what effect this would have.
1163 option will update the
1164 .B "preferred minor"
1165 field on each superblock to match the minor number of the array being
1167 This can be useful if
1169 reports a different "Preferred Minor" to
1171 In some cases this update will be performed automatically
1172 by the kernel driver. In particular the update happens automatically
1173 at the first write to an array with redundancy (RAID level 1 or
1174 greater) on a 2.6 (or later) kernel.
1178 option will change the uuid of the array. If a UUID is given with the
1180 option that UUID will be used as a new UUID and will
1182 be used to help identify the devices in the array.
1185 is given, a random UUID is chosen.
1189 option will change the
1191 of the array as stored in the superblock. This is only supported for
1192 version-1 superblocks.
1196 option will change the
1198 of the array as stored in the bitmap superblock. This option only
1199 works for a clustered environment.
1203 option will change the
1205 as recorded in the superblock. For version-0 superblocks, this is the
1206 same as updating the UUID.
1207 For version-1 superblocks, this involves updating the name.
1211 option will change the cluster name as recorded in the superblock and
1212 bitmap. This option only works for clustered environment.
1216 option will cause the array to be marked
1218 meaning that any redundancy in the array (e.g. parity for RAID5,
1219 copies for RAID1) may be incorrect. This will cause the RAID system
1220 to perform a "resync" pass to make sure that all redundant information
1225 option allows arrays to be moved between machines with different
1227 When assembling such an array for the first time after a move, giving
1228 .B "\-\-update=byteorder"
1231 to expect superblocks to have their byteorder reversed, and will
1232 correct that order before assembling the array. This is only valid
1233 with original (Version 0.90) superblocks.
1237 option will correct the summaries in the superblock. That is the
1238 counts of total, working, active, failed, and spare devices.
1242 option will rarely be of use. It applies to version 1.1 and 1.2 metadata
1243 only (where the metadata is at the start of the device) and is only
1244 useful when the component device has changed size (typically become
1245 larger). The version 1 metadata records the amount of the device that
1246 can be used to store data, so if a device in a version 1.1 or 1.2
1247 array becomes larger, the metadata will still be visible, but the
1248 extra space will not. In this case it might be useful to assemble the
1250 .BR \-\-update=devicesize .
1253 to determine the maximum usable amount of space on each device and
1254 update the relevant field in the metadata.
1258 option only works on v0.90 metadata arrays and will convert them to
1259 v1.0 metadata. The array must not be dirty (i.e. it must not need a
1260 sync) and it must not have a write-intent bitmap.
1262 The old metadata will remain on the devices, but will appear older
1263 than the new metadata and so will usually be ignored. The old metadata
1264 (or indeed the new metadata) can be removed by giving the appropriate
1267 .BR \-\-zero\-superblock .
1271 option can be used when an array has an internal bitmap which is
1272 corrupt in some way so that assembling the array normally fails. It
1273 will cause any internal bitmap to be ignored.
1277 option will reserve space in each device for a bad block list. This
1278 will be 4K in size and positioned near the end of any free space
1279 between the superblock and the data.
1283 option will cause any reservation of space for a bad block list to be
1284 removed. If the bad block list contains entries, this will fail, as
1285 removing the list could cause data corruption.
1288 .BR \-\-freeze\-reshape
1289 Option is intended to be used in start-up scripts during initrd boot phase.
1290 When array under reshape is assembled during initrd phase, this option
1291 stops reshape after reshape critical section is being restored. This happens
1292 before file system pivot operation and avoids loss of file system context.
1293 Losing file system context would cause reshape to be broken.
1295 Reshape can be continued later using the
1297 option for the grow command.
1301 See this option under Create and Build options.
1303 .SH For Manage mode:
1306 .BR \-t ", " \-\-test
1307 Unless a more serious error occurred,
1309 will exit with a status of 2 if no changes were made to the array and
1310 0 if at least one change was made.
1311 This can be useful when an indirect specifier such as
1316 is used in requesting an operation on the array.
1318 will report failure if these specifiers didn't find any match.
1321 .BR \-a ", " \-\-add
1322 hot-add listed devices.
1323 If a device appears to have recently been part of the array
1324 (possibly it failed or was removed) the device is re\-added as described
1326 If that fails or the device was never part of the array, the device is
1327 added as a hot-spare.
1328 If the array is degraded, it will immediately start to rebuild data
1331 Note that this and the following options are only meaningful on array
1332 with redundancy. They don't apply to RAID0 or Linear.
1336 re\-add a device that was previously removed from an array.
1337 If the metadata on the device reports that it is a member of the
1338 array, and the slot that it used is still vacant, then the device will
1339 be added back to the array in the same position. This will normally
1340 cause the data for that device to be recovered. However based on the
1341 event count on the device, the recovery may only require sections that
1342 are flagged a write-intent bitmap to be recovered or may not require
1343 any recovery at all.
1345 When used on an array that has no metadata (i.e. it was built with
1347 it will be assumed that bitmap-based recovery is enough to make the
1348 device fully consistent with the array.
1350 When used with v1.x metadata,
1352 can be accompanied by
1353 .BR \-\-update=devicesize ,
1354 .BR \-\-update=bbl ", or"
1355 .BR \-\-update=no\-bbl .
1356 See the description of these option when used in Assemble mode for an
1357 explanation of their use.
1359 If the device name given is
1363 will try to find any device that looks like it should be
1364 part of the array but isn't and will try to re\-add all such devices.
1366 If the device name given is
1370 will find all devices in the array that are marked
1372 remove them and attempt to immediately re\-add them. This can be
1373 useful if you are certain that the reason for failure has been
1378 Add a device as a spare. This is similar to
1380 except that it does not attempt
1382 first. The device will be added as a spare even if it looks like it
1383 could be an recent member of the array.
1386 .BR \-r ", " \-\-remove
1387 remove listed devices. They must not be active. i.e. they should
1388 be failed or spare devices.
1390 As well as the name of a device file
1400 The first causes all failed device to be removed. The second causes
1401 any device which is no longer connected to the system (i.e an 'open'
1405 The third will remove a set as describe below under
1409 .BR \-f ", " \-\-fail
1410 Mark listed devices as faulty.
1411 As well as the name of a device file, the word
1415 can be given. The former will cause any device that has been detached from
1416 the system to be marked as failed. It can then be removed.
1418 For RAID10 arrays where the number of copies evenly divides the number
1419 of devices, the devices can be conceptually divided into sets where
1420 each set contains a single complete copy of the data on the array.
1421 Sometimes a RAID10 array will be configured so that these sets are on
1422 separate controllers. In this case all the devices in one set can be
1423 failed by giving a name like
1429 The appropriate set names are reported by
1439 Mark listed devices as requiring replacement. As soon as a spare is
1440 available, it will be rebuilt and will replace the marked device.
1441 This is similar to marking a device as faulty, but the device remains
1442 in service during the recovery process to increase resilience against
1443 multiple failures. When the replacement process finishes, the
1444 replaced device will be marked as faulty.
1448 This can follow a list of
1450 devices. The devices listed after
1452 will be preferentially used to replace the devices listed after
1454 These device must already be spare devices in the array.
1457 .BR \-\-write\-mostly
1458 Subsequent devices that are added or re\-added will have the 'write-mostly'
1459 flag set. This is only valid for RAID1 and means that the 'md' driver
1460 will avoid reading from these devices if possible.
1463 Subsequent devices that are added or re\-added will have the 'write-mostly'
1466 .BR \-\-cluster\-confirm
1467 Confirm the existence of the device. This is issued in response to an \-\-add
1468 request by a node in a cluster. When a node adds a device it sends a message
1469 to all nodes in the cluster to look for a device with a UUID. This translates
1470 to a udev notification with the UUID of the device to be added and the slot
1471 number. The receiving node must acknowledge this message
1472 with \-\-cluster\-confirm. Valid arguments are <slot>:<devicename> in case
1473 the device is found or <slot>:missing in case the device is not found.
1477 Recreate journal for RAID-4/5/6 array that lost a journal device. In the
1478 current implementation, this command cannot add a journal to an array
1479 that had a failed journal. To avoid interrupting on-going write opertions,
1481 only works for array in Read-Only state.
1485 Subsequent devices that are added or re\-added will have
1486 the 'failfast' flag set. This is only valid for RAID1 and RAID10 and
1487 means that the 'md' driver will avoid long timeouts on error handling
1491 Subsequent devices that are re\-added will be re\-added without
1492 the 'failfast' flag set.
1495 Each of these options requires that the first device listed is the array
1496 to be acted upon, and the remainder are component devices to be added,
1497 removed, marked as faulty, etc. Several different operations can be
1498 specified for different devices, e.g.
1500 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1502 Each operation applies to all devices listed until the next
1505 If an array is using a write-intent bitmap, then devices which have
1506 been removed can be re\-added in a way that avoids a full
1507 reconstruction but instead just updates the blocks that have changed
1508 since the device was removed. For arrays with persistent metadata
1509 (superblocks) this is done automatically. For arrays created with
1511 mdadm needs to be told that this device we removed recently with
1514 Devices can only be removed from an array if they are not in active
1515 use, i.e. that must be spares or failed devices. To remove an active
1516 device, it must first be marked as
1522 .BR \-Q ", " \-\-query
1523 Examine a device to see
1524 (1) if it is an md device and (2) if it is a component of an md
1526 Information about what is discovered is presented.
1529 .BR \-D ", " \-\-detail
1530 Print details of one or more md devices.
1533 .BR \-\-detail\-platform
1534 Print details of the platform's RAID capabilities (firmware / hardware
1535 topology) for a given metadata format. If used without argument, mdadm
1536 will scan all controllers looking for their capabilities. Otherwise, mdadm
1537 will only look at the controller specified by the argument in form of an
1538 absolute filepath or a link, e.g.
1539 .IR /sys/devices/pci0000:00/0000:00:1f.2 .
1542 .BR \-Y ", " \-\-export
1545 .BR \-\-detail-platform ,
1549 output will be formatted as
1551 pairs for easy import into the environment.
1557 indicates whether an array was started
1559 or not, which may include a reason
1560 .RB ( unsafe ", " nothing ", " no ).
1563 indicates if the array is expected on this host
1565 or seems to be from elsewhere
1569 .BR \-E ", " \-\-examine
1570 Print contents of the metadata stored on the named device(s).
1571 Note the contrast between
1576 applies to devices which are components of an array, while
1578 applies to a whole array which is currently active.
1581 If an array was created on a SPARC machine with a 2.2 Linux kernel
1582 patched with RAID support, the superblock will have been created
1583 incorrectly, or at least incompatibly with 2.4 and later kernels.
1588 will fix the superblock before displaying it. If this appears to do
1589 the right thing, then the array can be successfully assembled using
1590 .BR "\-\-assemble \-\-update=sparc2.2" .
1593 .BR \-X ", " \-\-examine\-bitmap
1594 Report information about a bitmap file.
1595 The argument is either an external bitmap file or an array component
1596 in case of an internal bitmap. Note that running this on an array
1599 does not report the bitmap for that array.
1602 .B \-\-examine\-badblocks
1603 List the bad-blocks recorded for the device, if a bad-blocks list has
1604 been configured. Currently only
1606 metadata supports bad-blocks lists.
1609 .BI \-\-dump= directory
1611 .BI \-\-restore= directory
1612 Save metadata from lists devices, or restore metadata to listed devices.
1615 .BR \-R ", " \-\-run
1616 start a partially assembled array. If
1618 did not find enough devices to fully start the array, it might leaving
1619 it partially assembled. If you wish, you can then use
1621 to start the array in degraded mode.
1624 .BR \-S ", " \-\-stop
1625 deactivate array, releasing all resources.
1628 .BR \-o ", " \-\-readonly
1629 mark array as readonly.
1632 .BR \-w ", " \-\-readwrite
1633 mark array as readwrite.
1636 .B \-\-zero\-superblock
1637 If the device contains a valid md superblock, the block is
1638 overwritten with zeros. With
1640 the block where the superblock would be is overwritten even if it
1641 doesn't appear to be valid.
1644 .B \-\-kill\-subarray=
1645 If the device is a container and the argument to \-\-kill\-subarray
1646 specifies an inactive subarray in the container, then the subarray is
1647 deleted. Deleting all subarrays will leave an 'empty-container' or
1648 spare superblock on the drives. See
1649 .B \-\-zero\-superblock
1651 removing a superblock. Note that some formats depend on the subarray
1652 index for generating a UUID, this command will fail if it would change
1653 the UUID of an active subarray.
1656 .B \-\-update\-subarray=
1657 If the device is a container and the argument to \-\-update\-subarray
1658 specifies a subarray in the container, then attempt to update the given
1659 superblock field in the subarray. See below in
1664 .BR \-t ", " \-\-test
1669 is set to reflect the status of the device. See below in
1674 .BR \-W ", " \-\-wait
1675 For each md device given, wait for any resync, recovery, or reshape
1676 activity to finish before returning.
1678 will return with success if it actually waited for every device
1679 listed, otherwise it will return failure.
1683 For each md device given, or each device in /proc/mdstat if
1685 is given, arrange for the array to be marked clean as soon as possible.
1687 will return with success if the array uses external metadata and we
1688 successfully waited. For native arrays this returns immediately as the
1689 kernel handles dirty-clean transitions at shutdown. No action is taken
1690 if safe-mode handling is disabled.
1694 Set the "sync_action" for all md devices given to one of
1701 will abort any currently running action though some actions will
1702 automatically restart.
1705 will abort any current action and ensure no other action starts
1715 .BR "SCRUBBING AND MISMATCHES" .
1717 .SH For Incremental Assembly mode:
1719 .BR \-\-rebuild\-map ", " \-r
1720 Rebuild the map file
1724 uses to help track which arrays are currently being assembled.
1727 .BR \-\-run ", " \-R
1728 Run any array assembled as soon as a minimal number of devices are
1729 available, rather than waiting until all expected devices are present.
1732 .BR \-\-scan ", " \-s
1733 Only meaningful with
1737 file for arrays that are being incrementally assembled and will try to
1738 start any that are not already started. If any such array is listed
1741 as requiring an external bitmap, that bitmap will be attached first.
1744 .BR \-\-fail ", " \-f
1745 This allows the hot-plug system to remove devices that have fully disappeared
1746 from the kernel. It will first fail and then remove the device from any
1747 array it belongs to.
1748 The device name given should be a kernel device name such as "sda",
1754 Only used with \-\-fail. The 'path' given will be recorded so that if
1755 a new device appears at the same location it can be automatically
1756 added to the same array. This allows the failed device to be
1757 automatically replaced by a new device without metadata if it appears
1758 at specified path. This option is normally only set by a
1762 .SH For Monitor mode:
1764 .BR \-m ", " \-\-mail
1765 Give a mail address to send alerts to.
1768 .BR \-p ", " \-\-program ", " \-\-alert
1769 Give a program to be run whenever an event is detected.
1772 .BR \-y ", " \-\-syslog
1773 Cause all events to be reported through 'syslog'. The messages have
1774 facility of 'daemon' and varying priorities.
1777 .BR \-d ", " \-\-delay
1778 Give a delay in seconds.
1780 polls the md arrays and then waits this many seconds before polling
1781 again. The default is 60 seconds. Since 2.6.16, there is no need to
1782 reduce this as the kernel alerts
1784 immediately when there is any change.
1787 .BR \-r ", " \-\-increment
1788 Give a percentage increment.
1790 will generate RebuildNN events with the given percentage increment.
1793 .BR \-f ", " \-\-daemonise
1796 to run as a background daemon if it decides to monitor anything. This
1797 causes it to fork and run in the child, and to disconnect from the
1798 terminal. The process id of the child is written to stdout.
1801 which will only continue monitoring if a mail address or alert program
1802 is found in the config file.
1805 .BR \-i ", " \-\-pid\-file
1808 is running in daemon mode, write the pid of the daemon process to
1809 the specified file, instead of printing it on standard output.
1812 .BR \-1 ", " \-\-oneshot
1813 Check arrays only once. This will generate
1815 events and more significantly
1821 .B " mdadm \-\-monitor \-\-scan \-1"
1823 from a cron script will ensure regular notification of any degraded arrays.
1826 .BR \-t ", " \-\-test
1829 alert for every array found at startup. This alert gets mailed and
1830 passed to the alert program. This can be used for testing that alert
1831 message do get through successfully.
1835 This inhibits the functionality for moving spares between arrays.
1836 Only one monitoring process started with
1838 but without this flag is allowed, otherwise the two could interfere
1845 .B mdadm \-\-assemble
1846 .I md-device options-and-component-devices...
1849 .B mdadm \-\-assemble \-\-scan
1850 .I md-devices-and-options...
1853 .B mdadm \-\-assemble \-\-scan
1857 This usage assembles one or more RAID arrays from pre-existing components.
1858 For each array, mdadm needs to know the md device, the identity of the
1859 array, and a number of component-devices. These can be found in a number of ways.
1861 In the first usage example (without the
1863 the first device given is the md device.
1864 In the second usage example, all devices listed are treated as md
1865 devices and assembly is attempted.
1866 In the third (where no devices are listed) all md devices that are
1867 listed in the configuration file are assembled. If no arrays are
1868 described by the configuration file, then any arrays that
1869 can be found on unused devices will be assembled.
1871 If precisely one device is listed, but
1877 was given and identity information is extracted from the configuration file.
1879 The identity can be given with the
1885 option, will be taken from the md-device record in the config file, or
1886 will be taken from the super block of the first component-device
1887 listed on the command line.
1889 Devices can be given on the
1891 command line or in the config file. Only devices which have an md
1892 superblock which contains the right identity will be considered for
1895 The config file is only used if explicitly named with
1897 or requested with (a possibly implicit)
1902 .B /etc/mdadm/mdadm.conf
1907 is not given, then the config file will only be used to find the
1908 identity of md arrays.
1910 Normally the array will be started after it is assembled. However if
1912 is not given and not all expected drives were listed, then the array
1913 is not started (to guard against usage errors). To insist that the
1914 array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1923 does not create any entries in
1927 It does record information in
1931 to choose the correct name.
1935 detects that udev is not configured, it will create the devices in
1939 In Linux kernels prior to version 2.6.28 there were two distinctly
1940 different types of md devices that could be created: one that could be
1941 partitioned using standard partitioning tools and one that could not.
1942 Since 2.6.28 that distinction is no longer relevant as both type of
1943 devices can be partitioned.
1945 will normally create the type that originally could not be partitioned
1946 as it has a well defined major number (9).
1948 Prior to 2.6.28, it is important that mdadm chooses the correct type
1949 of array device to use. This can be controlled with the
1951 option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1952 to use a partitionable device rather than the default.
1954 In the no-udev case, the value given to
1956 can be suffixed by a number. This tells
1958 to create that number of partition devices rather than the default of 4.
1962 can also be given in the configuration file as a word starting
1964 on the ARRAY line for the relevant array.
1971 and no devices are listed,
1973 will first attempt to assemble all the arrays listed in the config
1976 If no arrays are listed in the config (other than those marked
1978 it will look through the available devices for possible arrays and
1979 will try to assemble anything that it finds. Arrays which are tagged
1980 as belonging to the given homehost will be assembled and started
1981 normally. Arrays which do not obviously belong to this host are given
1982 names that are expected not to conflict with anything local, and are
1983 started "read-auto" so that nothing is written to any device until the
1984 array is written to. i.e. automatic resync etc is delayed.
1988 finds a consistent set of devices that look like they should comprise
1989 an array, and if the superblock is tagged as belonging to the given
1990 home host, it will automatically choose a device name and try to
1991 assemble the array. If the array uses version-0.90 metadata, then the
1993 number as recorded in the superblock is used to create a name in
1997 If the array uses version-1 metadata, then the
1999 from the superblock is used to similarly create a name in
2001 (the name will have any 'host' prefix stripped first).
2003 This behaviour can be modified by the
2007 configuration file. This line can indicate that specific metadata
2008 type should, or should not, be automatically assembled. If an array
2009 is found which is not listed in
2011 and has a metadata format that is denied by the
2013 line, then it will not be assembled.
2016 line can also request that all arrays identified as being for this
2017 homehost should be assembled regardless of their metadata type.
2020 for further details.
2022 Note: Auto assembly cannot be used for assembling and activating some
2023 arrays which are undergoing reshape. In particular as the
2025 cannot be given, any reshape which requires a backup-file to continue
2026 cannot be started by auto assembly. An array which is growing to more
2027 devices and has passed the critical section can be assembled using
2038 .BI \-\-raid\-devices= Z
2042 This usage is similar to
2044 The difference is that it creates an array without a superblock. With
2045 these arrays there is no difference between initially creating the array and
2046 subsequently assembling the array, except that hopefully there is useful
2047 data there in the second case.
2049 The level may raid0, linear, raid1, raid10, multipath, or faulty, or
2050 one of their synonyms. All devices must be listed and the array will
2051 be started once complete. It will often be appropriate to use
2052 .B \-\-assume\-clean
2053 with levels raid1 or raid10.
2064 .BI \-\-raid\-devices= Z
2068 This usage will initialise a new md array, associate some devices with
2069 it, and activate the array.
2071 The named device will normally not exist when
2072 .I "mdadm \-\-create"
2073 is run, but will be created by
2075 once the array becomes active.
2077 As devices are added, they are checked to see if they contain RAID
2078 superblocks or filesystems. They are also checked to see if the variance in
2079 device size exceeds 1%.
2081 If any discrepancy is found, the array will not automatically be run, though
2084 can override this caution.
2086 To create a "degraded" array in which some devices are missing, simply
2087 give the word "\fBmissing\fP"
2088 in place of a device name. This will cause
2090 to leave the corresponding slot in the array empty.
2091 For a RAID4 or RAID5 array at most one slot can be
2092 "\fBmissing\fP"; for a RAID6 array at most two slots.
2093 For a RAID1 array, only one real device needs to be given. All of the
2097 When creating a RAID5 array,
2099 will automatically create a degraded array with an extra spare drive.
2100 This is because building the spare into a degraded array is in general
2101 faster than resyncing the parity on a non-degraded, but not clean,
2102 array. This feature can be overridden with the
2106 When creating an array with version-1 metadata a name for the array is
2108 If this is not given with the
2112 will choose a name based on the last component of the name of the
2113 device being created. So if
2115 is being created, then the name
2120 is being created, then the name
2124 When creating a partition based array, using
2126 with version-1.x metadata, the partition type should be set to
2128 (non fs-data). This type selection allows for greater precision since
2129 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
2130 might create problems in the event of array recovery through a live cdrom.
2132 A new array will normally get a randomly assigned 128bit UUID which is
2133 very likely to be unique. If you have a specific need, you can choose
2134 a UUID for the array by giving the
2136 option. Be warned that creating two arrays with the same UUID is a
2137 recipe for disaster. Also, using
2139 when creating a v0.90 array will silently override any
2144 .\"option is given, it is not necessary to list any component-devices in this command.
2145 .\"They can be added later, before a
2149 .\"is given, the apparent size of the smallest drive given is used.
2151 If the array type supports a write-intent bitmap, and if the devices
2152 in the array exceed 100G is size, an internal write-intent bitmap
2153 will automatically be added unless some other option is explicitly
2156 option. In any case space for a bitmap will be reserved so that one
2157 can be added layer with
2158 .BR "\-\-grow \-\-bitmap=internal" .
2160 If the metadata type supports it (currently only 1.x metadata), space
2161 will be allocated to store a bad block list. This allows a modest
2162 number of bad blocks to be recorded, allowing the drive to remain in
2163 service while only partially functional.
2165 When creating an array within a
2168 can be given either the list of devices to use, or simply the name of
2169 the container. The former case gives control over which devices in
2170 the container will be used for the array. The latter case allows
2172 to automatically choose which devices to use based on how much spare
2175 The General Management options that are valid with
2180 insist on running the array even if some devices look like they might
2185 start the array readonly \(em not supported yet.
2192 .I options... devices...
2195 This usage will allow individual devices in an array to be failed,
2196 removed or added. It is possible to perform multiple operations with
2197 on command. For example:
2199 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
2205 and will then remove it from the array and finally add it back
2206 in as a spare. However only one md array can be affected by a single
2209 When a device is added to an active array, mdadm checks to see if it
2210 has metadata on it which suggests that it was recently a member of the
2211 array. If it does, it tries to "re\-add" the device. If there have
2212 been no changes since the device was removed, or if the array has a
2213 write-intent bitmap which has recorded whatever changes there were,
2214 then the device will immediately become a full member of the array and
2215 those differences recorded in the bitmap will be resolved.
2225 MISC mode includes a number of distinct operations that
2226 operate on distinct devices. The operations are:
2229 The device is examined to see if it is
2230 (1) an active md array, or
2231 (2) a component of an md array.
2232 The information discovered is reported.
2236 The device should be an active md device.
2238 will display a detailed description of the array.
2242 will cause the output to be less detailed and the format to be
2243 suitable for inclusion in
2247 will normally be 0 unless
2249 failed to get useful information about the device(s); however, if the
2251 option is given, then the exit status will be:
2255 The array is functioning normally.
2258 The array has at least one failed device.
2261 The array has multiple failed devices such that it is unusable.
2264 There was an error while trying to get information about the device.
2268 .B \-\-detail\-platform
2269 Print detail of the platform's RAID capabilities (firmware / hardware
2270 topology). If the metadata is specified with
2274 then the return status will be:
2278 metadata successfully enumerated its platform components on this system
2281 metadata is platform independent
2284 metadata failed to find its platform components on this system
2288 .B \-\-update\-subarray=
2289 If the device is a container and the argument to \-\-update\-subarray
2290 specifies a subarray in the container, then attempt to update the given
2291 superblock field in the subarray. Similar to updating an array in
2292 "assemble" mode, the field to update is selected by
2296 option. Currently only
2302 option updates the subarray name in the metadata, it may not affect the
2303 device node name or the device node symlink until the subarray is
2304 re\-assembled. If updating
2306 would change the UUID of an active subarray this operation is blocked,
2307 and the command will end in an error.
2311 The device should be a component of an md array.
2313 will read the md superblock of the device and display the contents.
2318 is given, then multiple devices that are components of the one array
2319 are grouped together and reported in a single entry suitable
2325 without listing any devices will cause all devices listed in the
2326 config file to be examined.
2329 .BI \-\-dump= directory
2330 If the device contains RAID metadata, a file will be created in the
2332 and the metadata will be written to it. The file will be the same
2333 size as the device and have the metadata written in the file at the
2334 same locate that it exists in the device. However the file will be "sparse" so
2335 that only those blocks containing metadata will be allocated. The
2336 total space used will be small.
2338 The file name used in the
2340 will be the base name of the device. Further if any links appear in
2342 which point to the device, then hard links to the file will be created
2349 Multiple devices can be listed and their metadata will all be stored
2350 in the one directory.
2353 .BI \-\-restore= directory
2354 This is the reverse of
2357 will locate a file in the directory that has a name appropriate for
2358 the given device and will restore metadata from it. Names that match
2360 names are preferred, however if two of those refer to different files,
2362 will not choose between them but will abort the operation.
2364 If a file name is given instead of a
2368 will restore from that file to a single device, always provided the
2369 size of the file matches that of the device, and the file contains
2373 The devices should be active md arrays which will be deactivated, as
2374 long as they are not currently in use.
2378 This will fully activate a partially assembled md array.
2382 This will mark an active array as read-only, providing that it is
2383 not currently being used.
2389 array back to being read/write.
2393 For all operations except
2396 will cause the operation to be applied to all arrays listed in
2401 causes all devices listed in the config file to be examined.
2404 .BR \-b ", " \-\-brief
2405 Be less verbose. This is used with
2413 gives an intermediate level of verbosity.
2419 .B mdadm \-\-monitor
2420 .I options... devices...
2425 to periodically poll a number of md arrays and to report on any events
2428 will never exit once it decides that there are arrays to be checked,
2429 so it should normally be run in the background.
2431 As well as reporting events,
2433 may move a spare drive from one array to another if they are in the
2438 and if the destination array has a failed drive but no spares.
2440 If any devices are listed on the command line,
2442 will only monitor those devices. Otherwise all arrays listed in the
2443 configuration file will be monitored. Further, if
2445 is given, then any other md devices that appear in
2447 will also be monitored.
2449 The result of monitoring the arrays is the generation of events.
2450 These events are passed to a separate program (if specified) and may
2451 be mailed to a given E-mail address.
2453 When passing events to a program, the program is run once for each event,
2454 and is given 2 or 3 command-line arguments: the first is the
2455 name of the event (see below), the second is the name of the
2456 md device which is affected, and the third is the name of a related
2457 device if relevant (such as a component device that has failed).
2461 is given, then a program or an E-mail address must be specified on the
2462 command line or in the config file. If neither are available, then
2464 will not monitor anything.
2468 will continue monitoring as long as something was found to monitor. If
2469 no program or email is given, then each event is reported to
2472 The different events are:
2476 .B DeviceDisappeared
2477 An md array which previously was configured appears to no longer be
2478 configured. (syslog priority: Critical)
2482 was told to monitor an array which is RAID0 or Linear, then it will
2484 .B DeviceDisappeared
2485 with the extra information
2487 This is because RAID0 and Linear do not support the device-failed,
2488 hot-spare and resync operations which are monitored.
2492 An md array started reconstruction (e.g. recovery, resync, reshape,
2493 check, repair). (syslog priority: Warning)
2499 is a two-digit number (ie. 05, 48). This indicates that rebuild
2500 has passed that many percent of the total. The events are generated
2501 with fixed increment since 0. Increment size may be specified with
2502 a commandline option (default is 20). (syslog priority: Warning)
2506 An md array that was rebuilding, isn't any more, either because it
2507 finished normally or was aborted. (syslog priority: Warning)
2511 An active component device of an array has been marked as
2512 faulty. (syslog priority: Critical)
2516 A spare component device which was being rebuilt to replace a faulty
2517 device has failed. (syslog priority: Critical)
2521 A spare component device which was being rebuilt to replace a faulty
2522 device has been successfully rebuilt and has been made active.
2523 (syslog priority: Info)
2527 A new md array has been detected in the
2529 file. (syslog priority: Info)
2533 A newly noticed array appears to be degraded. This message is not
2536 notices a drive failure which causes degradation, but only when
2538 notices that an array is degraded when it first sees the array.
2539 (syslog priority: Critical)
2543 A spare drive has been moved from one array in a
2547 to another to allow a failed drive to be replaced.
2548 (syslog priority: Info)
2554 has been told, via the config file, that an array should have a certain
2555 number of spare devices, and
2557 detects that it has fewer than this number when it first sees the
2558 array, it will report a
2561 (syslog priority: Warning)
2565 An array was found at startup, and the
2568 (syslog priority: Info)
2578 cause Email to be sent. All events cause the program to be run.
2579 The program is run with two or three arguments: the event
2580 name, the array device and possibly a second device.
2582 Each event has an associated array device (e.g.
2584 and possibly a second device. For
2589 the second device is the relevant component device.
2592 the second device is the array that the spare was moved from.
2596 to move spares from one array to another, the different arrays need to
2597 be labeled with the same
2599 or the spares must be allowed to migrate through matching POLICY domains
2600 in the configuration file. The
2602 name can be any string; it is only necessary that different spare
2603 groups use different names.
2607 detects that an array in a spare group has fewer active
2608 devices than necessary for the complete array, and has no spare
2609 devices, it will look for another array in the same spare group that
2610 has a full complement of working drive and a spare. It will then
2611 attempt to remove the spare from the second drive and add it to the
2613 If the removal succeeds but the adding fails, then it is added back to
2616 If the spare group for a degraded array is not defined,
2618 will look at the rules of spare migration specified by POLICY lines in
2620 and then follow similar steps as above if a matching spare is found.
2623 The GROW mode is used for changing the size or shape of an active
2625 For this to work, the kernel must support the necessary change.
2626 Various types of growth are being added during 2.6 development.
2628 Currently the supported changes include
2630 change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
2632 increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
2635 change the chunk-size and layout of RAID0, RAID4, RAID5, RAID6 and RAID10.
2637 convert between RAID1 and RAID5, between RAID5 and RAID6, between
2638 RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
2640 add a write-intent bitmap to any array which supports these bitmaps, or
2641 remove a write-intent bitmap from such an array.
2644 Using GROW on containers is currently supported only for Intel's IMSM
2645 container format. The number of devices in a container can be
2646 increased - which affects all arrays in the container - or an array
2647 in a container can be converted between levels where those levels are
2648 supported by the container, and the conversion is on of those listed
2649 above. Resizing arrays in an IMSM container with
2651 is not yet supported.
2653 Grow functionality (e.g. expand a number of raid devices) for Intel's
2654 IMSM container format has an experimental status. It is guarded by the
2655 .B MDADM_EXPERIMENTAL
2656 environment variable which must be set to '1' for a GROW command to
2658 This is for the following reasons:
2661 Intel's native IMSM check-pointing is not fully tested yet.
2662 This can causes IMSM incompatibility during the grow process: an array
2663 which is growing cannot roam between Microsoft Windows(R) and Linux
2667 Interrupting a grow operation is not recommended, because it
2668 has not been fully tested for Intel's IMSM container format yet.
2671 Note: Intel's native checkpointing doesn't use
2673 option and it is transparent for assembly feature.
2676 Normally when an array is built the "size" is taken from the smallest
2677 of the drives. If all the small drives in an arrays are, one at a
2678 time, removed and replaced with larger drives, then you could have an
2679 array of large drives with only a small amount used. In this
2680 situation, changing the "size" with "GROW" mode will allow the extra
2681 space to start being used. If the size is increased in this way, a
2682 "resync" process will start to make sure the new parts of the array
2685 Note that when an array changes size, any filesystem that may be
2686 stored in the array will not automatically grow or shrink to use or
2687 vacate the space. The
2688 filesystem will need to be explicitly told to use the extra space
2689 after growing, or to reduce its size
2691 to shrinking the array.
2693 Also the size of an array cannot be changed while it has an active
2694 bitmap. If an array has a bitmap, it must be removed before the size
2695 can be changed. Once the change is complete a new bitmap can be created.
2697 .SS RAID\-DEVICES CHANGES
2699 A RAID1 array can work with any number of devices from 1 upwards
2700 (though 1 is not very useful). There may be times which you want to
2701 increase or decrease the number of active devices. Note that this is
2702 different to hot-add or hot-remove which changes the number of
2705 When reducing the number of devices in a RAID1 array, the slots which
2706 are to be removed from the array must already be vacant. That is, the
2707 devices which were in those slots must be failed and removed.
2709 When the number of devices is increased, any hot spares that are
2710 present will be activated immediately.
2712 Changing the number of active devices in a RAID5 or RAID6 is much more
2713 effort. Every block in the array will need to be read and written
2714 back to a new location. From 2.6.17, the Linux Kernel is able to
2715 increase the number of devices in a RAID5 safely, including restarting
2716 an interrupted "reshape". From 2.6.31, the Linux Kernel is able to
2717 increase or decrease the number of devices in a RAID5 or RAID6.
2719 From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4
2722 uses this functionality and the ability to add
2723 devices to a RAID4 to allow devices to be added to a RAID0. When
2724 requested to do this,
2726 will convert the RAID0 to a RAID4, add the necessary disks and make
2727 the reshape happen, and then convert the RAID4 back to RAID0.
2729 When decreasing the number of devices, the size of the array will also
2730 decrease. If there was data in the array, it could get destroyed and
2731 this is not reversible, so you should firstly shrink the filesystem on
2732 the array to fit within the new size. To help prevent accidents,
2734 requires that the size of the array be decreased first with
2735 .BR "mdadm --grow --array-size" .
2736 This is a reversible change which simply makes the end of the array
2737 inaccessible. The integrity of any data can then be checked before
2738 the non-reversible reduction in the number of devices is request.
2740 When relocating the first few stripes on a RAID5 or RAID6, it is not
2741 possible to keep the data on disk completely consistent and
2742 crash-proof. To provide the required safety, mdadm disables writes to
2743 the array while this "critical section" is reshaped, and takes a
2744 backup of the data that is in that section. For grows, this backup may be
2745 stored in any spare devices that the array has, however it can also be
2746 stored in a separate file specified with the
2748 option, and is required to be specified for shrinks, RAID level
2749 changes and layout changes. If this option is used, and the system
2750 does crash during the critical period, the same file must be passed to
2752 to restore the backup and reassemble the array. When shrinking rather
2753 than growing the array, the reshape is done from the end towards the
2754 beginning, so the "critical section" is at the end of the reshape.
2758 Changing the RAID level of any array happens instantaneously. However
2759 in the RAID5 to RAID6 case this requires a non-standard layout of the
2760 RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is
2761 required before the change can be accomplished. So while the level
2762 change is instant, the accompanying layout change can take quite a
2765 is required. If the array is not simultaneously being grown or
2766 shrunk, so that the array size will remain the same - for example,
2767 reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
2768 be used not just for a "cricital section" but throughout the reshape
2769 operation, as described below under LAYOUT CHANGES.
2771 .SS CHUNK-SIZE AND LAYOUT CHANGES
2773 Changing the chunk-size of layout without also changing the number of
2774 devices as the same time will involve re-writing all blocks in-place.
2775 To ensure against data loss in the case of a crash, a
2777 must be provided for these changes. Small sections of the array will
2778 be copied to the backup file while they are being rearranged. This
2779 means that all the data is copied twice, once to the backup and once
2780 to the new layout on the array, so this type of reshape will go very
2783 If the reshape is interrupted for any reason, this backup file must be
2785 .B "mdadm --assemble"
2786 so the array can be reassembled. Consequently the file cannot be
2787 stored on the device being reshaped.
2792 A write-intent bitmap can be added to, or removed from, an active
2793 array. Either internal bitmaps, or bitmaps stored in a separate file,
2794 can be added. Note that if you add a bitmap stored in a file which is
2795 in a filesystem that is on the RAID array being affected, the system
2796 will deadlock. The bitmap must be on a separate filesystem.
2798 .SH INCREMENTAL MODE
2802 .B mdadm \-\-incremental
2806 .RI [ optional-aliases-for-device ]
2809 .B mdadm \-\-incremental \-\-fail
2813 .B mdadm \-\-incremental \-\-rebuild\-map
2816 .B mdadm \-\-incremental \-\-run \-\-scan
2819 This mode is designed to be used in conjunction with a device
2820 discovery system. As devices are found in a system, they can be
2822 .B "mdadm \-\-incremental"
2823 to be conditionally added to an appropriate array.
2825 Conversely, it can also be used with the
2827 flag to do just the opposite and find whatever array a particular device
2828 is part of and remove the device from that array.
2830 If the device passed is a
2832 device created by a previous call to
2834 then rather than trying to add that device to an array, all the arrays
2835 described by the metadata of the container will be started.
2838 performs a number of tests to determine if the device is part of an
2839 array, and which array it should be part of. If an appropriate array
2840 is found, or can be created,
2842 adds the device to the array and conditionally starts the array.
2846 will normally only add devices to an array which were previously working
2847 (active or spare) parts of that array. The support for automatic
2848 inclusion of a new drive as a spare in some array requires
2849 a configuration through POLICY in config file.
2853 makes are as follow:
2855 Is the device permitted by
2857 That is, is it listed in a
2859 line in that file. If
2861 is absent then the default it to allow any device. Similarly if
2863 contains the special word
2865 then any device is allowed. Otherwise the device name given to
2867 or one of the aliases given, or an alias found in the filesystem,
2868 must match one of the names or patterns in a
2872 This is the only context where the aliases are used. They are
2873 usually provided by a
2879 Does the device have a valid md superblock? If a specific metadata
2880 version is requested with
2884 then only that style of metadata is accepted, otherwise
2886 finds any known version of metadata. If no
2888 metadata is found, the device may be still added to an array
2889 as a spare if POLICY allows.
2893 Does the metadata match an expected array?
2894 The metadata can match in two ways. Either there is an array listed
2897 which identifies the array (either by UUID, by name, by device list,
2898 or by minor-number), or the array was created with a
2904 or on the command line.
2907 is not able to positively identify the array as belonging to the
2908 current host, the device will be rejected.
2913 keeps a list of arrays that it has partially assembled in
2915 If no array exists which matches
2916 the metadata on the new device,
2918 must choose a device name and unit number. It does this based on any
2921 or any name information stored in the metadata. If this name
2922 suggests a unit number, that number will be used, otherwise a free
2923 unit number will be chosen. Normally
2925 will prefer to create a partitionable array, however if the
2929 suggests that a non-partitionable array is preferred, that will be
2932 If the array is not found in the config file and its metadata does not
2933 identify it as belonging to the "homehost", then
2935 will choose a name for the array which is certain not to conflict with
2936 any array which does belong to this host. It does this be adding an
2937 underscore and a small number to the name preferred by the metadata.
2939 Once an appropriate array is found or created and the device is added,
2941 must decide if the array is ready to be started. It will
2942 normally compare the number of available (non-spare) devices to the
2943 number of devices that the metadata suggests need to be active. If
2944 there are at least that many, the array will be started. This means
2945 that if any devices are missing the array will not be restarted.
2951 in which case the array will be run as soon as there are enough
2952 devices present for the data to be accessible. For a RAID1, that
2953 means one device will start the array. For a clean RAID5, the array
2954 will be started as soon as all but one drive is present.
2956 Note that neither of these approaches is really ideal. If it can
2957 be known that all device discovery has completed, then
2961 can be run which will try to start all arrays that are being
2962 incrementally assembled. They are started in "read-auto" mode in
2963 which they are read-only until the first write request. This means
2964 that no metadata updates are made and no attempt at resync or recovery
2965 happens. Further devices that are found before the first write can
2966 still be added safely.
2969 This section describes environment variables that affect how mdadm
2974 Setting this value to 1 will prevent mdadm from automatically launching
2975 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2981 does not create any device nodes in /dev, but leaves that task to
2985 appears not to be configured, or if this environment variable is set
2988 will create and devices that are needed.
2991 .B MDADM_NO_SYSTEMCTL
2996 is in use it will normally request
2998 to start various background tasks (particularly
3000 rather than forking and running them in the background. This can be
3001 suppressed by setting
3002 .BR MDADM_NO_SYSTEMCTL=1 .
3006 A key value of IMSM metadata is that it allows interoperability with
3007 boot ROMs on Intel platforms, and with other major operating systems.
3010 will only allow an IMSM array to be created or modified if detects
3011 that it is running on an Intel platform which supports IMSM, and
3012 supports the particular configuration of IMSM that is being requested
3013 (some functionality requires newer OROM support).
3015 These checks can be suppressed by setting IMSM_NO_PLATFORM=1 in the
3016 environment. This can be useful for testing or for disaster
3017 recovery. You should be aware that interoperability may be
3018 compromised by setting this value.
3021 .B MDADM_GROW_ALLOW_OLD
3022 If an array is stopped while it is performing a reshape and that
3023 reshape was making use of a backup file, then when the array is
3026 will sometimes complain that the backup file is too old. If this
3027 happens and you are certain it is the right backup file, you can
3028 over-ride this check by setting
3029 .B MDADM_GROW_ALLOW_OLD=1
3034 Any string given in this variable is added to the start of the
3036 line in the config file, or treated as the whole
3038 line if none is given. It can be used to disable certain metadata
3041 is called from a boot script. For example
3043 .B " export MDADM_CONF_AUTO='-ddf -imsm'
3047 does not automatically assemble any DDF or
3048 IMSM arrays that are found. This can be useful on systems configured
3049 to manage such arrays with
3055 .B " mdadm \-\-query /dev/name-of-device"
3057 This will find out if a given device is a RAID array, or is part of
3058 one, and will provide brief information about the device.
3060 .B " mdadm \-\-assemble \-\-scan"
3062 This will assemble and start all arrays listed in the standard config
3063 file. This command will typically go in a system startup file.
3065 .B " mdadm \-\-stop \-\-scan"
3067 This will shut down all arrays that can be shut down (i.e. are not
3068 currently in use). This will typically go in a system shutdown script.
3070 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
3072 If (and only if) there is an Email address or program given in the
3073 standard config file, then
3074 monitor the status of all arrays listed in that file by
3075 polling them ever 2 minutes.
3077 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
3079 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
3082 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
3084 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
3086 This will create a prototype config file that describes currently
3087 active arrays that are known to be made from partitions of IDE or SCSI drives.
3088 This file should be reviewed before being used as it may
3089 contain unwanted detail.
3091 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
3093 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
3095 This will find arrays which could be assembled from existing IDE and
3096 SCSI whole drives (not partitions), and store the information in the
3097 format of a config file.
3098 This file is very likely to contain unwanted detail, particularly
3101 entries. It should be reviewed and edited before being used as an
3104 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
3106 .B " mdadm \-Ebsc partitions"
3108 Create a list of devices by reading
3109 .BR /proc/partitions ,
3110 scan these for RAID superblocks, and printout a brief listing of all
3113 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
3115 Scan all partitions and devices listed in
3116 .BR /proc/partitions
3119 out of all such devices with a RAID superblock with a minor number of 0.
3121 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /run/mdadm/mon.pid"
3123 If config file contains a mail address or alert program, run mdadm in
3124 the background in monitor mode monitoring all md devices. Also write
3125 pid of mdadm daemon to
3126 .BR /run/mdadm/mon.pid .
3128 .B " mdadm \-Iq /dev/somedevice"
3130 Try to incorporate newly discovered device into some array as
3133 .B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan"
3135 Rebuild the array map from any current arrays, and then start any that
3138 .B " mdadm /dev/md4 --fail detached --remove detached"
3140 Any devices which are components of /dev/md4 will be marked as faulty
3141 and then remove from the array.
3143 .B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
3147 which is currently a RAID5 array will be converted to RAID6. There
3148 should normally already be a spare drive attached to the array as a
3149 RAID6 needs one more drive than a matching RAID5.
3151 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
3153 Create a DDF array over 6 devices.
3155 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
3157 Create a RAID5 array over any 3 devices in the given DDF set. Use
3158 only 30 gigabytes of each device.
3160 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
3162 Assemble a pre-exist ddf array.
3164 .B " mdadm -I /dev/md/ddf1"
3166 Assemble all arrays contained in the ddf array, assigning names as
3169 .B " mdadm \-\-create \-\-help"
3171 Provide help about the Create mode.
3173 .B " mdadm \-\-config \-\-help"
3175 Provide help about the format of the config file.
3177 .B " mdadm \-\-help"
3179 Provide general help.
3189 lists all active md devices with information about them.
3191 uses this to find arrays when
3193 is given in Misc mode, and to monitor array reconstruction
3198 The config file lists which devices may be scanned to see if
3199 they contain MD super block, and gives identifying information
3200 (e.g. UUID) about known MD arrays. See
3204 .SS /etc/mdadm.conf.d
3206 A directory containing configuration files which are read in lexical
3212 mode is used, this file gets a list of arrays currently being created.
3217 understand two sorts of names for array devices.
3219 The first is the so-called 'standard' format name, which matches the
3220 names used by the kernel and which appear in
3223 The second sort can be freely chosen, but must reside in
3225 When giving a device name to
3227 to create or assemble an array, either full path name such as
3231 can be given, or just the suffix of the second sort of name, such as
3237 chooses device names during auto-assembly or incremental assembly, it
3238 will sometimes add a small sequence number to the end of the name to
3239 avoid conflicted between multiple arrays that have the same name. If
3241 can reasonably determine that the array really is meant for this host,
3242 either by a hostname in the metadata, or by the presence of the array
3245 then it will leave off the suffix if possible.
3246 Also if the homehost is specified as
3249 will only use a suffix if a different array of the same name already
3250 exists or is listed in the config file.
3252 The standard names for non-partitioned arrays (the only sort of md
3253 array available in 2.4 and earlier) are of the form
3257 where NN is a number.
3258 The standard names for partitionable arrays (as available from 2.6
3259 onwards) are of the form:
3263 Partition numbers should be indicated by adding "pMM" to these, thus "/dev/md/d1p2".
3265 From kernel version 2.6.28 the "non-partitioned array" can actually
3266 be partitioned. So the "md_d\fBNN\fP"
3267 names are no longer needed, and
3268 partitions such as "/dev/md\fBNN\fPp\fBXX\fP"
3271 From kernel version 2.6.29 standard names can be non-numeric following
3278 is any string. These names are supported by
3280 since version 3.3 provided they are enabled in
3285 was previously known as
3289 For further information on mdadm usage, MD and the various levels of
3292 .B http://raid.wiki.kernel.org/
3294 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
3296 The latest version of
3298 should always be available from
3300 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob