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
765 .BR \-\-assume\-clean
768 that the array pre-existed and is known to be clean. It can be useful
769 when trying to recover from a major failure as you can be sure that no
770 data will be affected unless you actually write to the array. It can
771 also be used when creating a RAID1 or RAID10 if you want to avoid the
772 initial resync, however this practice \(em while normally safe \(em is not
773 recommended. Use this only if you really know what you are doing.
775 When the devices that will be part of a new array were filled
776 with zeros before creation the operator knows the array is
777 actually clean. If that is the case, such as after running
778 badblocks, this argument can be used to tell mdadm the
779 facts the operator knows.
781 When an array is resized to a larger size with
782 .B "\-\-grow \-\-size="
783 the new space is normally resynced in that same way that the whole
784 array is resynced at creation. From Linux version 3.0,
786 can be used with that command to avoid the automatic resync.
789 .BR \-\-backup\-file=
792 is used to increase the number of raid-devices in a RAID5 or RAID6 if
793 there are no spare devices available, or to shrink, change RAID level
794 or layout. See the GROW MODE section below on RAID\-DEVICES CHANGES.
795 The file must be stored on a separate device, not on the RAID array
800 Arrays with 1.x metadata can leave a gap between the start of the
801 device and the start of array data. This gap can be used for various
802 metadata. The start of data is known as the
804 Normally an appropriate data offset is computed automatically.
805 However it can be useful to set it explicitly such as when re-creating
806 an array which was originally created using a different version of
808 which computed a different offset.
810 Setting the offset explicitly over-rides the default. The value given
811 is in Kilobytes unless a suffix of 'K', 'M' or 'G' is used to explicitly
812 indicate Kilobytes, Megabytes or Gigabytes respectively.
816 can also be used with
818 for some RAID levels (initially on RAID10). This allows the
819 data\-offset to be changed as part of the reshape process. When the
820 data offset is changed, no backup file is required as the difference
821 in offsets is used to provide the same functionality.
823 When the new offset is earlier than the old offset, the number of
824 devices in the array cannot shrink. When it is after the old offset,
825 the number of devices in the array cannot increase.
827 When creating an array,
831 In the case each member device is expected to have a offset appended
832 to the name, separated by a colon. This makes it possible to recreate
833 exactly an array which has varying data offsets (as can happen when
834 different versions of
836 are used to add different devices).
840 This option is complementary to the
841 .B \-\-freeze-reshape
842 option for assembly. It is needed when
844 operation is interrupted and it is not restarted automatically due to
845 .B \-\-freeze-reshape
846 usage during array assembly. This option is used together with
850 ) command and device for a pending reshape to be continued.
851 All parameters required for reshape continuation will be read from array metadata.
855 .BR \-\-backup\-file=
856 option to be set, continuation option will require to have exactly the same
857 backup file given as well.
859 Any other parameter passed together with
861 option will be ignored.
864 .BR \-N ", " \-\-name=
867 for the array. This is currently only effective when creating an
868 array with a version-1 superblock, or an array in a DDF container.
869 The name is a simple textual string that can be used to identify array
870 components when assembling. If name is needed but not specified, it
871 is taken from the basename of the device that is being created.
883 run the array, even if some of the components
884 appear to be active in another array or filesystem. Normally
886 will ask for confirmation before including such components in an
887 array. This option causes that question to be suppressed.
890 .BR \-f ", " \-\-force
893 accept the geometry and layout specified without question. Normally
895 will not allow creation of an array with only one device, and will try
896 to create a RAID5 array with one missing drive (as this makes the
897 initial resync work faster). With
900 will not try to be so clever.
903 .BR \-o ", " \-\-readonly
906 rather than read-write as normal. No writes will be allowed to the
907 array, and no resync, recovery, or reshape will be started.
910 .BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
911 Instruct mdadm how to create the device file if needed, possibly allocating
912 an unused minor number. "md" causes a non-partitionable array
913 to be used (though since Linux 2.6.28, these array devices are in fact
914 partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
915 later) to be used. "yes" requires the named md device to have
916 a 'standard' format, and the type and minor number will be determined
917 from this. With mdadm 3.0, device creation is normally left up to
919 so this option is unlikely to be needed.
920 See DEVICE NAMES below.
922 The argument can also come immediately after
927 is not given on the command line or in the config file, then
933 is also given, then any
935 entries in the config file will override the
937 instruction given on the command line.
939 For partitionable arrays,
941 will create the device file for the whole array and for the first 4
942 partitions. A different number of partitions can be specified at the
943 end of this option (e.g.
945 If the device name ends with a digit, the partition names add a 'p',
947 .IR /dev/md/home1p3 .
948 If there is no trailing digit, then the partition names just have a
950 .IR /dev/md/scratch3 .
952 If the md device name is in a 'standard' format as described in DEVICE
953 NAMES, then it will be created, if necessary, with the appropriate
954 device number based on that name. If the device name is not in one of these
955 formats, then a unused device number will be allocated. The device
956 number will be considered unused if there is no active array for that
957 number, and there is no entry in /dev for that number and with a
958 non-standard name. Names that are not in 'standard' format are only
959 allowed in "/dev/md/".
961 This is meaningful with
967 .BR \-a ", " "\-\-add"
968 This option can be used in Grow mode in two cases.
970 If the target array is a Linear array, then
972 can be used to add one or more devices to the array. They
973 are simply catenated on to the end of the array. Once added, the
974 devices cannot be removed.
978 option is being used to increase the number of devices in an array,
981 can be used to add some extra devices to be included in the array.
982 In most cases this is not needed as the extra devices can be added as
983 spares first, and then the number of raid-disks can be changed.
984 However for RAID0, it is not possible to add spares. So to increase
985 the number of devices in a RAID0, it is necessary to set the new
986 number of devices, and to add the new devices, in the same command.
990 Only works when the array is for clustered environment. It specifies
991 the maximum number of nodes in the cluster that will use this device
992 simultaneously. If not specified, this defaults to 4.
995 .BR \-\-write-journal
996 Specify journal device for the RAID-4/5/6 array. The journal device
997 should be a SSD with reasonable lifetime.
1003 .BR \-u ", " \-\-uuid=
1004 uuid of array to assemble. Devices which don't have this uuid are
1008 .BR \-m ", " \-\-super\-minor=
1009 Minor number of device that array was created for. Devices which
1010 don't have this minor number are excluded. If you create an array as
1011 /dev/md1, then all superblocks will contain the minor number 1, even if
1012 the array is later assembled as /dev/md2.
1014 Giving the literal word "dev" for
1018 to use the minor number of the md device that is being assembled.
1019 e.g. when assembling
1021 .B \-\-super\-minor=dev
1022 will look for super blocks with a minor number of 0.
1025 is only relevant for v0.90 metadata, and should not normally be used.
1031 .BR \-N ", " \-\-name=
1032 Specify the name of the array to assemble. This must be the name
1033 that was specified when creating the array. It must either match
1034 the name stored in the superblock exactly, or it must match
1037 prefixed to the start of the given name.
1040 .BR \-f ", " \-\-force
1041 Assemble the array even if the metadata on some devices appears to be
1044 cannot find enough working devices to start the array, but can find
1045 some devices that are recorded as having failed, then it will mark
1046 those devices as working so that the array can be started.
1047 An array which requires
1049 to be started may contain data corruption. Use it carefully.
1052 .BR \-R ", " \-\-run
1053 Attempt to start the array even if fewer drives were given than were
1054 present last time the array was active. Normally if not all the
1055 expected drives are found and
1057 is not used, then the array will be assembled but not started.
1060 an attempt will be made to start it anyway.
1064 This is the reverse of
1066 in that it inhibits the startup of array unless all expected drives
1067 are present. This is only needed with
1069 and can be used if the physical connections to devices are
1070 not as reliable as you would like.
1073 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
1074 See this option under Create and Build options.
1077 .BR \-b ", " \-\-bitmap=
1078 Specify the bitmap file that was given when the array was created. If
1081 bitmap, there is no need to specify this when assembling the array.
1084 .BR \-\-backup\-file=
1087 was used while reshaping an array (e.g. changing number of devices or
1088 chunk size) and the system crashed during the critical section, then the same
1090 must be presented to
1092 to allow possibly corrupted data to be restored, and the reshape
1096 .BR \-\-invalid\-backup
1097 If the file needed for the above option is not available for any
1098 reason an empty file can be given together with this option to
1099 indicate that the backup file is invalid. In this case the data that
1100 was being rearranged at the time of the crash could be irrecoverably
1101 lost, but the rest of the array may still be recoverable. This option
1102 should only be used as a last resort if there is no way to recover the
1107 .BR \-U ", " \-\-update=
1108 Update the superblock on each device while assembling the array. The
1109 argument given to this flag can be one of
1129 option will adjust the superblock of an array what was created on a Sparc
1130 machine running a patched 2.2 Linux kernel. This kernel got the
1131 alignment of part of the superblock wrong. You can use the
1132 .B "\-\-examine \-\-sparc2.2"
1135 to see what effect this would have.
1139 option will update the
1140 .B "preferred minor"
1141 field on each superblock to match the minor number of the array being
1143 This can be useful if
1145 reports a different "Preferred Minor" to
1147 In some cases this update will be performed automatically
1148 by the kernel driver. In particular the update happens automatically
1149 at the first write to an array with redundancy (RAID level 1 or
1150 greater) on a 2.6 (or later) kernel.
1154 option will change the uuid of the array. If a UUID is given with the
1156 option that UUID will be used as a new UUID and will
1158 be used to help identify the devices in the array.
1161 is given, a random UUID is chosen.
1165 option will change the
1167 of the array as stored in the superblock. This is only supported for
1168 version-1 superblocks.
1172 option will change the
1174 of the array as stored in the bitmap superblock. This option only
1175 works for a clustered environment.
1179 option will change the
1181 as recorded in the superblock. For version-0 superblocks, this is the
1182 same as updating the UUID.
1183 For version-1 superblocks, this involves updating the name.
1187 option will change the cluster name as recorded in the superblock and
1188 bitmap. This option only works for clustered environment.
1192 option will cause the array to be marked
1194 meaning that any redundancy in the array (e.g. parity for RAID5,
1195 copies for RAID1) may be incorrect. This will cause the RAID system
1196 to perform a "resync" pass to make sure that all redundant information
1201 option allows arrays to be moved between machines with different
1203 When assembling such an array for the first time after a move, giving
1204 .B "\-\-update=byteorder"
1207 to expect superblocks to have their byteorder reversed, and will
1208 correct that order before assembling the array. This is only valid
1209 with original (Version 0.90) superblocks.
1213 option will correct the summaries in the superblock. That is the
1214 counts of total, working, active, failed, and spare devices.
1218 option will rarely be of use. It applies to version 1.1 and 1.2 metadata
1219 only (where the metadata is at the start of the device) and is only
1220 useful when the component device has changed size (typically become
1221 larger). The version 1 metadata records the amount of the device that
1222 can be used to store data, so if a device in a version 1.1 or 1.2
1223 array becomes larger, the metadata will still be visible, but the
1224 extra space will not. In this case it might be useful to assemble the
1226 .BR \-\-update=devicesize .
1229 to determine the maximum usable amount of space on each device and
1230 update the relevant field in the metadata.
1234 option only works on v0.90 metadata arrays and will convert them to
1235 v1.0 metadata. The array must not be dirty (i.e. it must not need a
1236 sync) and it must not have a write-intent bitmap.
1238 The old metadata will remain on the devices, but will appear older
1239 than the new metadata and so will usually be ignored. The old metadata
1240 (or indeed the new metadata) can be removed by giving the appropriate
1243 .BR \-\-zero\-superblock .
1247 option can be used when an array has an internal bitmap which is
1248 corrupt in some way so that assembling the array normally fails. It
1249 will cause any internal bitmap to be ignored.
1253 option will reserve space in each device for a bad block list. This
1254 will be 4K in size and positioned near the end of any free space
1255 between the superblock and the data.
1259 option will cause any reservation of space for a bad block list to be
1260 removed. If the bad block list contains entries, this will fail, as
1261 removing the list could cause data corruption.
1264 .BR \-\-freeze\-reshape
1265 Option is intended to be used in start-up scripts during initrd boot phase.
1266 When array under reshape is assembled during initrd phase, this option
1267 stops reshape after reshape critical section is being restored. This happens
1268 before file system pivot operation and avoids loss of file system context.
1269 Losing file system context would cause reshape to be broken.
1271 Reshape can be continued later using the
1273 option for the grow command.
1275 .SH For Manage mode:
1278 .BR \-t ", " \-\-test
1279 Unless a more serious error occurred,
1281 will exit with a status of 2 if no changes were made to the array and
1282 0 if at least one change was made.
1283 This can be useful when an indirect specifier such as
1288 is used in requesting an operation on the array.
1290 will report failure if these specifiers didn't find any match.
1293 .BR \-a ", " \-\-add
1294 hot-add listed devices.
1295 If a device appears to have recently been part of the array
1296 (possibly it failed or was removed) the device is re\-added as described
1298 If that fails or the device was never part of the array, the device is
1299 added as a hot-spare.
1300 If the array is degraded, it will immediately start to rebuild data
1303 Note that this and the following options are only meaningful on array
1304 with redundancy. They don't apply to RAID0 or Linear.
1308 re\-add a device that was previously removed from an array.
1309 If the metadata on the device reports that it is a member of the
1310 array, and the slot that it used is still vacant, then the device will
1311 be added back to the array in the same position. This will normally
1312 cause the data for that device to be recovered. However based on the
1313 event count on the device, the recovery may only require sections that
1314 are flagged a write-intent bitmap to be recovered or may not require
1315 any recovery at all.
1317 When used on an array that has no metadata (i.e. it was built with
1319 it will be assumed that bitmap-based recovery is enough to make the
1320 device fully consistent with the array.
1322 When used with v1.x metadata,
1324 can be accompanied by
1325 .BR \-\-update=devicesize ,
1326 .BR \-\-update=bbl ", or"
1327 .BR \-\-update=no\-bbl .
1328 See the description of these option when used in Assemble mode for an
1329 explanation of their use.
1331 If the device name given is
1335 will try to find any device that looks like it should be
1336 part of the array but isn't and will try to re\-add all such devices.
1338 If the device name given is
1342 will find all devices in the array that are marked
1344 remove them and attempt to immediately re\-add them. This can be
1345 useful if you are certain that the reason for failure has been
1350 Add a device as a spare. This is similar to
1352 except that it does not attempt
1354 first. The device will be added as a spare even if it looks like it
1355 could be an recent member of the array.
1358 .BR \-r ", " \-\-remove
1359 remove listed devices. They must not be active. i.e. they should
1360 be failed or spare devices.
1362 As well as the name of a device file
1372 The first causes all failed device to be removed. The second causes
1373 any device which is no longer connected to the system (i.e an 'open'
1377 The third will remove a set as describe below under
1381 .BR \-f ", " \-\-fail
1382 Mark listed devices as faulty.
1383 As well as the name of a device file, the word
1387 can be given. The former will cause any device that has been detached from
1388 the system to be marked as failed. It can then be removed.
1390 For RAID10 arrays where the number of copies evenly divides the number
1391 of devices, the devices can be conceptually divided into sets where
1392 each set contains a single complete copy of the data on the array.
1393 Sometimes a RAID10 array will be configured so that these sets are on
1394 separate controllers. In this case all the devices in one set can be
1395 failed by giving a name like
1401 The appropriate set names are reported by
1411 Mark listed devices as requiring replacement. As soon as a spare is
1412 available, it will be rebuilt and will replace the marked device.
1413 This is similar to marking a device as faulty, but the device remains
1414 in service during the recovery process to increase resilience against
1415 multiple failures. When the replacement process finishes, the
1416 replaced device will be marked as faulty.
1420 This can follow a list of
1422 devices. The devices listed after
1424 will be preferentially used to replace the devices listed after
1426 These device must already be spare devices in the array.
1429 .BR \-\-write\-mostly
1430 Subsequent devices that are added or re\-added will have the 'write-mostly'
1431 flag set. This is only valid for RAID1 and means that the 'md' driver
1432 will avoid reading from these devices if possible.
1435 Subsequent devices that are added or re\-added will have the 'write-mostly'
1438 .BR \-\-cluster\-confirm
1439 Confirm the existence of the device. This is issued in response to an \-\-add
1440 request by a node in a cluster. When a node adds a device it sends a message
1441 to all nodes in the cluster to look for a device with a UUID. This translates
1442 to a udev notification with the UUID of the device to be added and the slot
1443 number. The receiving node must acknowledge this message
1444 with \-\-cluster\-confirm. Valid arguments are <slot>:<devicename> in case
1445 the device is found or <slot>:missing in case the device is not found.
1449 Recreate journal for RAID-4/5/6 array that lost a journal device. In the
1450 current implementation, this command cannot add a journal to an array
1451 that had a failed journal. To avoid interrupting on-going write opertions,
1453 only works for array in Read-Only state.
1456 Each of these options requires that the first device listed is the array
1457 to be acted upon, and the remainder are component devices to be added,
1458 removed, marked as faulty, etc. Several different operations can be
1459 specified for different devices, e.g.
1461 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1463 Each operation applies to all devices listed until the next
1466 If an array is using a write-intent bitmap, then devices which have
1467 been removed can be re\-added in a way that avoids a full
1468 reconstruction but instead just updates the blocks that have changed
1469 since the device was removed. For arrays with persistent metadata
1470 (superblocks) this is done automatically. For arrays created with
1472 mdadm needs to be told that this device we removed recently with
1475 Devices can only be removed from an array if they are not in active
1476 use, i.e. that must be spares or failed devices. To remove an active
1477 device, it must first be marked as
1483 .BR \-Q ", " \-\-query
1484 Examine a device to see
1485 (1) if it is an md device and (2) if it is a component of an md
1487 Information about what is discovered is presented.
1490 .BR \-D ", " \-\-detail
1491 Print details of one or more md devices.
1494 .BR \-\-detail\-platform
1495 Print details of the platform's RAID capabilities (firmware / hardware
1496 topology) for a given metadata format. If used without argument, mdadm
1497 will scan all controllers looking for their capabilities. Otherwise, mdadm
1498 will only look at the controller specified by the argument in form of an
1499 absolute filepath or a link, e.g.
1500 .IR /sys/devices/pci0000:00/0000:00:1f.2 .
1503 .BR \-Y ", " \-\-export
1506 .BR \-\-detail-platform ,
1510 output will be formatted as
1512 pairs for easy import into the environment.
1518 indicates whether an array was started
1520 or not, which may include a reason
1521 .RB ( unsafe ", " nothing ", " no ).
1524 indicates if the array is expected on this host
1526 or seems to be from elsewhere
1530 .BR \-E ", " \-\-examine
1531 Print contents of the metadata stored on the named device(s).
1532 Note the contrast between
1537 applies to devices which are components of an array, while
1539 applies to a whole array which is currently active.
1542 If an array was created on a SPARC machine with a 2.2 Linux kernel
1543 patched with RAID support, the superblock will have been created
1544 incorrectly, or at least incompatibly with 2.4 and later kernels.
1549 will fix the superblock before displaying it. If this appears to do
1550 the right thing, then the array can be successfully assembled using
1551 .BR "\-\-assemble \-\-update=sparc2.2" .
1554 .BR \-X ", " \-\-examine\-bitmap
1555 Report information about a bitmap file.
1556 The argument is either an external bitmap file or an array component
1557 in case of an internal bitmap. Note that running this on an array
1560 does not report the bitmap for that array.
1563 .B \-\-examine\-badblocks
1564 List the bad-blocks recorded for the device, if a bad-blocks list has
1565 been configured. Currently only
1567 metadata supports bad-blocks lists.
1570 .BI \-\-dump= directory
1572 .BI \-\-restore= directory
1573 Save metadata from lists devices, or restore metadata to listed devices.
1576 .BR \-R ", " \-\-run
1577 start a partially assembled array. If
1579 did not find enough devices to fully start the array, it might leaving
1580 it partially assembled. If you wish, you can then use
1582 to start the array in degraded mode.
1585 .BR \-S ", " \-\-stop
1586 deactivate array, releasing all resources.
1589 .BR \-o ", " \-\-readonly
1590 mark array as readonly.
1593 .BR \-w ", " \-\-readwrite
1594 mark array as readwrite.
1597 .B \-\-zero\-superblock
1598 If the device contains a valid md superblock, the block is
1599 overwritten with zeros. With
1601 the block where the superblock would be is overwritten even if it
1602 doesn't appear to be valid.
1605 .B \-\-kill\-subarray=
1606 If the device is a container and the argument to \-\-kill\-subarray
1607 specifies an inactive subarray in the container, then the subarray is
1608 deleted. Deleting all subarrays will leave an 'empty-container' or
1609 spare superblock on the drives. See
1610 .B \-\-zero\-superblock
1612 removing a superblock. Note that some formats depend on the subarray
1613 index for generating a UUID, this command will fail if it would change
1614 the UUID of an active subarray.
1617 .B \-\-update\-subarray=
1618 If the device is a container and the argument to \-\-update\-subarray
1619 specifies a subarray in the container, then attempt to update the given
1620 superblock field in the subarray. See below in
1625 .BR \-t ", " \-\-test
1630 is set to reflect the status of the device. See below in
1635 .BR \-W ", " \-\-wait
1636 For each md device given, wait for any resync, recovery, or reshape
1637 activity to finish before returning.
1639 will return with success if it actually waited for every device
1640 listed, otherwise it will return failure.
1644 For each md device given, or each device in /proc/mdstat if
1646 is given, arrange for the array to be marked clean as soon as possible.
1648 will return with success if the array uses external metadata and we
1649 successfully waited. For native arrays this returns immediately as the
1650 kernel handles dirty-clean transitions at shutdown. No action is taken
1651 if safe-mode handling is disabled.
1655 Set the "sync_action" for all md devices given to one of
1662 will abort any currently running action though some actions will
1663 automatically restart.
1666 will abort any current action and ensure no other action starts
1676 .BR "SCRUBBING AND MISMATCHES" .
1678 .SH For Incremental Assembly mode:
1680 .BR \-\-rebuild\-map ", " \-r
1681 Rebuild the map file
1685 uses to help track which arrays are currently being assembled.
1688 .BR \-\-run ", " \-R
1689 Run any array assembled as soon as a minimal number of devices are
1690 available, rather than waiting until all expected devices are present.
1693 .BR \-\-scan ", " \-s
1694 Only meaningful with
1698 file for arrays that are being incrementally assembled and will try to
1699 start any that are not already started. If any such array is listed
1702 as requiring an external bitmap, that bitmap will be attached first.
1705 .BR \-\-fail ", " \-f
1706 This allows the hot-plug system to remove devices that have fully disappeared
1707 from the kernel. It will first fail and then remove the device from any
1708 array it belongs to.
1709 The device name given should be a kernel device name such as "sda",
1715 Only used with \-\-fail. The 'path' given will be recorded so that if
1716 a new device appears at the same location it can be automatically
1717 added to the same array. This allows the failed device to be
1718 automatically replaced by a new device without metadata if it appears
1719 at specified path. This option is normally only set by a
1723 .SH For Monitor mode:
1725 .BR \-m ", " \-\-mail
1726 Give a mail address to send alerts to.
1729 .BR \-p ", " \-\-program ", " \-\-alert
1730 Give a program to be run whenever an event is detected.
1733 .BR \-y ", " \-\-syslog
1734 Cause all events to be reported through 'syslog'. The messages have
1735 facility of 'daemon' and varying priorities.
1738 .BR \-d ", " \-\-delay
1739 Give a delay in seconds.
1741 polls the md arrays and then waits this many seconds before polling
1742 again. The default is 60 seconds. Since 2.6.16, there is no need to
1743 reduce this as the kernel alerts
1745 immediately when there is any change.
1748 .BR \-r ", " \-\-increment
1749 Give a percentage increment.
1751 will generate RebuildNN events with the given percentage increment.
1754 .BR \-f ", " \-\-daemonise
1757 to run as a background daemon if it decides to monitor anything. This
1758 causes it to fork and run in the child, and to disconnect from the
1759 terminal. The process id of the child is written to stdout.
1762 which will only continue monitoring if a mail address or alert program
1763 is found in the config file.
1766 .BR \-i ", " \-\-pid\-file
1769 is running in daemon mode, write the pid of the daemon process to
1770 the specified file, instead of printing it on standard output.
1773 .BR \-1 ", " \-\-oneshot
1774 Check arrays only once. This will generate
1776 events and more significantly
1782 .B " mdadm \-\-monitor \-\-scan \-1"
1784 from a cron script will ensure regular notification of any degraded arrays.
1787 .BR \-t ", " \-\-test
1790 alert for every array found at startup. This alert gets mailed and
1791 passed to the alert program. This can be used for testing that alert
1792 message do get through successfully.
1796 This inhibits the functionality for moving spares between arrays.
1797 Only one monitoring process started with
1799 but without this flag is allowed, otherwise the two could interfere
1806 .B mdadm \-\-assemble
1807 .I md-device options-and-component-devices...
1810 .B mdadm \-\-assemble \-\-scan
1811 .I md-devices-and-options...
1814 .B mdadm \-\-assemble \-\-scan
1818 This usage assembles one or more RAID arrays from pre-existing components.
1819 For each array, mdadm needs to know the md device, the identity of the
1820 array, and a number of component-devices. These can be found in a number of ways.
1822 In the first usage example (without the
1824 the first device given is the md device.
1825 In the second usage example, all devices listed are treated as md
1826 devices and assembly is attempted.
1827 In the third (where no devices are listed) all md devices that are
1828 listed in the configuration file are assembled. If no arrays are
1829 described by the configuration file, then any arrays that
1830 can be found on unused devices will be assembled.
1832 If precisely one device is listed, but
1838 was given and identity information is extracted from the configuration file.
1840 The identity can be given with the
1846 option, will be taken from the md-device record in the config file, or
1847 will be taken from the super block of the first component-device
1848 listed on the command line.
1850 Devices can be given on the
1852 command line or in the config file. Only devices which have an md
1853 superblock which contains the right identity will be considered for
1856 The config file is only used if explicitly named with
1858 or requested with (a possibly implicit)
1863 .B /etc/mdadm/mdadm.conf
1868 is not given, then the config file will only be used to find the
1869 identity of md arrays.
1871 Normally the array will be started after it is assembled. However if
1873 is not given and not all expected drives were listed, then the array
1874 is not started (to guard against usage errors). To insist that the
1875 array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1884 does not create any entries in
1888 It does record information in
1892 to choose the correct name.
1896 detects that udev is not configured, it will create the devices in
1900 In Linux kernels prior to version 2.6.28 there were two distinctly
1901 different types of md devices that could be created: one that could be
1902 partitioned using standard partitioning tools and one that could not.
1903 Since 2.6.28 that distinction is no longer relevant as both type of
1904 devices can be partitioned.
1906 will normally create the type that originally could not be partitioned
1907 as it has a well defined major number (9).
1909 Prior to 2.6.28, it is important that mdadm chooses the correct type
1910 of array device to use. This can be controlled with the
1912 option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1913 to use a partitionable device rather than the default.
1915 In the no-udev case, the value given to
1917 can be suffixed by a number. This tells
1919 to create that number of partition devices rather than the default of 4.
1923 can also be given in the configuration file as a word starting
1925 on the ARRAY line for the relevant array.
1932 and no devices are listed,
1934 will first attempt to assemble all the arrays listed in the config
1937 If no arrays are listed in the config (other than those marked
1939 it will look through the available devices for possible arrays and
1940 will try to assemble anything that it finds. Arrays which are tagged
1941 as belonging to the given homehost will be assembled and started
1942 normally. Arrays which do not obviously belong to this host are given
1943 names that are expected not to conflict with anything local, and are
1944 started "read-auto" so that nothing is written to any device until the
1945 array is written to. i.e. automatic resync etc is delayed.
1949 finds a consistent set of devices that look like they should comprise
1950 an array, and if the superblock is tagged as belonging to the given
1951 home host, it will automatically choose a device name and try to
1952 assemble the array. If the array uses version-0.90 metadata, then the
1954 number as recorded in the superblock is used to create a name in
1958 If the array uses version-1 metadata, then the
1960 from the superblock is used to similarly create a name in
1962 (the name will have any 'host' prefix stripped first).
1964 This behaviour can be modified by the
1968 configuration file. This line can indicate that specific metadata
1969 type should, or should not, be automatically assembled. If an array
1970 is found which is not listed in
1972 and has a metadata format that is denied by the
1974 line, then it will not be assembled.
1977 line can also request that all arrays identified as being for this
1978 homehost should be assembled regardless of their metadata type.
1981 for further details.
1983 Note: Auto assembly cannot be used for assembling and activating some
1984 arrays which are undergoing reshape. In particular as the
1986 cannot be given, any reshape which requires a backup-file to continue
1987 cannot be started by auto assembly. An array which is growing to more
1988 devices and has passed the critical section can be assembled using
1999 .BI \-\-raid\-devices= Z
2003 This usage is similar to
2005 The difference is that it creates an array without a superblock. With
2006 these arrays there is no difference between initially creating the array and
2007 subsequently assembling the array, except that hopefully there is useful
2008 data there in the second case.
2010 The level may raid0, linear, raid1, raid10, multipath, or faulty, or
2011 one of their synonyms. All devices must be listed and the array will
2012 be started once complete. It will often be appropriate to use
2013 .B \-\-assume\-clean
2014 with levels raid1 or raid10.
2025 .BI \-\-raid\-devices= Z
2029 This usage will initialise a new md array, associate some devices with
2030 it, and activate the array.
2032 The named device will normally not exist when
2033 .I "mdadm \-\-create"
2034 is run, but will be created by
2036 once the array becomes active.
2038 As devices are added, they are checked to see if they contain RAID
2039 superblocks or filesystems. They are also checked to see if the variance in
2040 device size exceeds 1%.
2042 If any discrepancy is found, the array will not automatically be run, though
2045 can override this caution.
2047 To create a "degraded" array in which some devices are missing, simply
2048 give the word "\fBmissing\fP"
2049 in place of a device name. This will cause
2051 to leave the corresponding slot in the array empty.
2052 For a RAID4 or RAID5 array at most one slot can be
2053 "\fBmissing\fP"; for a RAID6 array at most two slots.
2054 For a RAID1 array, only one real device needs to be given. All of the
2058 When creating a RAID5 array,
2060 will automatically create a degraded array with an extra spare drive.
2061 This is because building the spare into a degraded array is in general
2062 faster than resyncing the parity on a non-degraded, but not clean,
2063 array. This feature can be overridden with the
2067 When creating an array with version-1 metadata a name for the array is
2069 If this is not given with the
2073 will choose a name based on the last component of the name of the
2074 device being created. So if
2076 is being created, then the name
2081 is being created, then the name
2085 When creating a partition based array, using
2087 with version-1.x metadata, the partition type should be set to
2089 (non fs-data). This type selection allows for greater precision since
2090 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
2091 might create problems in the event of array recovery through a live cdrom.
2093 A new array will normally get a randomly assigned 128bit UUID which is
2094 very likely to be unique. If you have a specific need, you can choose
2095 a UUID for the array by giving the
2097 option. Be warned that creating two arrays with the same UUID is a
2098 recipe for disaster. Also, using
2100 when creating a v0.90 array will silently override any
2105 .\"option is given, it is not necessary to list any component-devices in this command.
2106 .\"They can be added later, before a
2110 .\"is given, the apparent size of the smallest drive given is used.
2112 If the array type supports a write-intent bitmap, and if the devices
2113 in the array exceed 100G is size, an internal write-intent bitmap
2114 will automatically be added unless some other option is explicitly
2117 option. In any case space for a bitmap will be reserved so that one
2118 can be added layer with
2119 .BR "\-\-grow \-\-bitmap=internal" .
2121 If the metadata type supports it (currently only 1.x metadata), space
2122 will be allocated to store a bad block list. This allows a modest
2123 number of bad blocks to be recorded, allowing the drive to remain in
2124 service while only partially functional.
2126 When creating an array within a
2129 can be given either the list of devices to use, or simply the name of
2130 the container. The former case gives control over which devices in
2131 the container will be used for the array. The latter case allows
2133 to automatically choose which devices to use based on how much spare
2136 The General Management options that are valid with
2141 insist on running the array even if some devices look like they might
2146 start the array readonly \(em not supported yet.
2153 .I options... devices...
2156 This usage will allow individual devices in an array to be failed,
2157 removed or added. It is possible to perform multiple operations with
2158 on command. For example:
2160 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
2166 and will then remove it from the array and finally add it back
2167 in as a spare. However only one md array can be affected by a single
2170 When a device is added to an active array, mdadm checks to see if it
2171 has metadata on it which suggests that it was recently a member of the
2172 array. If it does, it tries to "re\-add" the device. If there have
2173 been no changes since the device was removed, or if the array has a
2174 write-intent bitmap which has recorded whatever changes there were,
2175 then the device will immediately become a full member of the array and
2176 those differences recorded in the bitmap will be resolved.
2186 MISC mode includes a number of distinct operations that
2187 operate on distinct devices. The operations are:
2190 The device is examined to see if it is
2191 (1) an active md array, or
2192 (2) a component of an md array.
2193 The information discovered is reported.
2197 The device should be an active md device.
2199 will display a detailed description of the array.
2203 will cause the output to be less detailed and the format to be
2204 suitable for inclusion in
2208 will normally be 0 unless
2210 failed to get useful information about the device(s); however, if the
2212 option is given, then the exit status will be:
2216 The array is functioning normally.
2219 The array has at least one failed device.
2222 The array has multiple failed devices such that it is unusable.
2225 There was an error while trying to get information about the device.
2229 .B \-\-detail\-platform
2230 Print detail of the platform's RAID capabilities (firmware / hardware
2231 topology). If the metadata is specified with
2235 then the return status will be:
2239 metadata successfully enumerated its platform components on this system
2242 metadata is platform independent
2245 metadata failed to find its platform components on this system
2249 .B \-\-update\-subarray=
2250 If the device is a container and the argument to \-\-update\-subarray
2251 specifies a subarray in the container, then attempt to update the given
2252 superblock field in the subarray. Similar to updating an array in
2253 "assemble" mode, the field to update is selected by
2257 option. Currently only
2263 option updates the subarray name in the metadata, it may not affect the
2264 device node name or the device node symlink until the subarray is
2265 re\-assembled. If updating
2267 would change the UUID of an active subarray this operation is blocked,
2268 and the command will end in an error.
2272 The device should be a component of an md array.
2274 will read the md superblock of the device and display the contents.
2279 is given, then multiple devices that are components of the one array
2280 are grouped together and reported in a single entry suitable
2286 without listing any devices will cause all devices listed in the
2287 config file to be examined.
2290 .BI \-\-dump= directory
2291 If the device contains RAID metadata, a file will be created in the
2293 and the metadata will be written to it. The file will be the same
2294 size as the device and have the metadata written in the file at the
2295 same locate that it exists in the device. However the file will be "sparse" so
2296 that only those blocks containing metadata will be allocated. The
2297 total space used will be small.
2299 The file name used in the
2301 will be the base name of the device. Further if any links appear in
2303 which point to the device, then hard links to the file will be created
2310 Multiple devices can be listed and their metadata will all be stored
2311 in the one directory.
2314 .BI \-\-restore= directory
2315 This is the reverse of
2318 will locate a file in the directory that has a name appropriate for
2319 the given device and will restore metadata from it. Names that match
2321 names are preferred, however if two of those refer to different files,
2323 will not choose between them but will abort the operation.
2325 If a file name is given instead of a
2329 will restore from that file to a single device, always provided the
2330 size of the file matches that of the device, and the file contains
2334 The devices should be active md arrays which will be deactivated, as
2335 long as they are not currently in use.
2339 This will fully activate a partially assembled md array.
2343 This will mark an active array as read-only, providing that it is
2344 not currently being used.
2350 array back to being read/write.
2354 For all operations except
2357 will cause the operation to be applied to all arrays listed in
2362 causes all devices listed in the config file to be examined.
2365 .BR \-b ", " \-\-brief
2366 Be less verbose. This is used with
2374 gives an intermediate level of verbosity.
2380 .B mdadm \-\-monitor
2381 .I options... devices...
2386 to periodically poll a number of md arrays and to report on any events
2389 will never exit once it decides that there are arrays to be checked,
2390 so it should normally be run in the background.
2392 As well as reporting events,
2394 may move a spare drive from one array to another if they are in the
2399 and if the destination array has a failed drive but no spares.
2401 If any devices are listed on the command line,
2403 will only monitor those devices. Otherwise all arrays listed in the
2404 configuration file will be monitored. Further, if
2406 is given, then any other md devices that appear in
2408 will also be monitored.
2410 The result of monitoring the arrays is the generation of events.
2411 These events are passed to a separate program (if specified) and may
2412 be mailed to a given E-mail address.
2414 When passing events to a program, the program is run once for each event,
2415 and is given 2 or 3 command-line arguments: the first is the
2416 name of the event (see below), the second is the name of the
2417 md device which is affected, and the third is the name of a related
2418 device if relevant (such as a component device that has failed).
2422 is given, then a program or an E-mail address must be specified on the
2423 command line or in the config file. If neither are available, then
2425 will not monitor anything.
2429 will continue monitoring as long as something was found to monitor. If
2430 no program or email is given, then each event is reported to
2433 The different events are:
2437 .B DeviceDisappeared
2438 An md array which previously was configured appears to no longer be
2439 configured. (syslog priority: Critical)
2443 was told to monitor an array which is RAID0 or Linear, then it will
2445 .B DeviceDisappeared
2446 with the extra information
2448 This is because RAID0 and Linear do not support the device-failed,
2449 hot-spare and resync operations which are monitored.
2453 An md array started reconstruction (e.g. recovery, resync, reshape,
2454 check, repair). (syslog priority: Warning)
2460 is a two-digit number (ie. 05, 48). This indicates that rebuild
2461 has passed that many percent of the total. The events are generated
2462 with fixed increment since 0. Increment size may be specified with
2463 a commandline option (default is 20). (syslog priority: Warning)
2467 An md array that was rebuilding, isn't any more, either because it
2468 finished normally or was aborted. (syslog priority: Warning)
2472 An active component device of an array has been marked as
2473 faulty. (syslog priority: Critical)
2477 A spare component device which was being rebuilt to replace a faulty
2478 device has failed. (syslog priority: Critical)
2482 A spare component device which was being rebuilt to replace a faulty
2483 device has been successfully rebuilt and has been made active.
2484 (syslog priority: Info)
2488 A new md array has been detected in the
2490 file. (syslog priority: Info)
2494 A newly noticed array appears to be degraded. This message is not
2497 notices a drive failure which causes degradation, but only when
2499 notices that an array is degraded when it first sees the array.
2500 (syslog priority: Critical)
2504 A spare drive has been moved from one array in a
2508 to another to allow a failed drive to be replaced.
2509 (syslog priority: Info)
2515 has been told, via the config file, that an array should have a certain
2516 number of spare devices, and
2518 detects that it has fewer than this number when it first sees the
2519 array, it will report a
2522 (syslog priority: Warning)
2526 An array was found at startup, and the
2529 (syslog priority: Info)
2539 cause Email to be sent. All events cause the program to be run.
2540 The program is run with two or three arguments: the event
2541 name, the array device and possibly a second device.
2543 Each event has an associated array device (e.g.
2545 and possibly a second device. For
2550 the second device is the relevant component device.
2553 the second device is the array that the spare was moved from.
2557 to move spares from one array to another, the different arrays need to
2558 be labeled with the same
2560 or the spares must be allowed to migrate through matching POLICY domains
2561 in the configuration file. The
2563 name can be any string; it is only necessary that different spare
2564 groups use different names.
2568 detects that an array in a spare group has fewer active
2569 devices than necessary for the complete array, and has no spare
2570 devices, it will look for another array in the same spare group that
2571 has a full complement of working drive and a spare. It will then
2572 attempt to remove the spare from the second drive and add it to the
2574 If the removal succeeds but the adding fails, then it is added back to
2577 If the spare group for a degraded array is not defined,
2579 will look at the rules of spare migration specified by POLICY lines in
2581 and then follow similar steps as above if a matching spare is found.
2584 The GROW mode is used for changing the size or shape of an active
2586 For this to work, the kernel must support the necessary change.
2587 Various types of growth are being added during 2.6 development.
2589 Currently the supported changes include
2591 change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
2593 increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
2596 change the chunk-size and layout of RAID0, RAID4, RAID5, RAID6 and RAID10.
2598 convert between RAID1 and RAID5, between RAID5 and RAID6, between
2599 RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
2601 add a write-intent bitmap to any array which supports these bitmaps, or
2602 remove a write-intent bitmap from such an array.
2605 Using GROW on containers is currently supported only for Intel's IMSM
2606 container format. The number of devices in a container can be
2607 increased - which affects all arrays in the container - or an array
2608 in a container can be converted between levels where those levels are
2609 supported by the container, and the conversion is on of those listed
2610 above. Resizing arrays in an IMSM container with
2612 is not yet supported.
2614 Grow functionality (e.g. expand a number of raid devices) for Intel's
2615 IMSM container format has an experimental status. It is guarded by the
2616 .B MDADM_EXPERIMENTAL
2617 environment variable which must be set to '1' for a GROW command to
2619 This is for the following reasons:
2622 Intel's native IMSM check-pointing is not fully tested yet.
2623 This can causes IMSM incompatibility during the grow process: an array
2624 which is growing cannot roam between Microsoft Windows(R) and Linux
2628 Interrupting a grow operation is not recommended, because it
2629 has not been fully tested for Intel's IMSM container format yet.
2632 Note: Intel's native checkpointing doesn't use
2634 option and it is transparent for assembly feature.
2637 Normally when an array is built the "size" is taken from the smallest
2638 of the drives. If all the small drives in an arrays are, one at a
2639 time, removed and replaced with larger drives, then you could have an
2640 array of large drives with only a small amount used. In this
2641 situation, changing the "size" with "GROW" mode will allow the extra
2642 space to start being used. If the size is increased in this way, a
2643 "resync" process will start to make sure the new parts of the array
2646 Note that when an array changes size, any filesystem that may be
2647 stored in the array will not automatically grow or shrink to use or
2648 vacate the space. The
2649 filesystem will need to be explicitly told to use the extra space
2650 after growing, or to reduce its size
2652 to shrinking the array.
2654 Also the size of an array cannot be changed while it has an active
2655 bitmap. If an array has a bitmap, it must be removed before the size
2656 can be changed. Once the change is complete a new bitmap can be created.
2658 .SS RAID\-DEVICES CHANGES
2660 A RAID1 array can work with any number of devices from 1 upwards
2661 (though 1 is not very useful). There may be times which you want to
2662 increase or decrease the number of active devices. Note that this is
2663 different to hot-add or hot-remove which changes the number of
2666 When reducing the number of devices in a RAID1 array, the slots which
2667 are to be removed from the array must already be vacant. That is, the
2668 devices which were in those slots must be failed and removed.
2670 When the number of devices is increased, any hot spares that are
2671 present will be activated immediately.
2673 Changing the number of active devices in a RAID5 or RAID6 is much more
2674 effort. Every block in the array will need to be read and written
2675 back to a new location. From 2.6.17, the Linux Kernel is able to
2676 increase the number of devices in a RAID5 safely, including restarting
2677 an interrupted "reshape". From 2.6.31, the Linux Kernel is able to
2678 increase or decrease the number of devices in a RAID5 or RAID6.
2680 From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4
2683 uses this functionality and the ability to add
2684 devices to a RAID4 to allow devices to be added to a RAID0. When
2685 requested to do this,
2687 will convert the RAID0 to a RAID4, add the necessary disks and make
2688 the reshape happen, and then convert the RAID4 back to RAID0.
2690 When decreasing the number of devices, the size of the array will also
2691 decrease. If there was data in the array, it could get destroyed and
2692 this is not reversible, so you should firstly shrink the filesystem on
2693 the array to fit within the new size. To help prevent accidents,
2695 requires that the size of the array be decreased first with
2696 .BR "mdadm --grow --array-size" .
2697 This is a reversible change which simply makes the end of the array
2698 inaccessible. The integrity of any data can then be checked before
2699 the non-reversible reduction in the number of devices is request.
2701 When relocating the first few stripes on a RAID5 or RAID6, it is not
2702 possible to keep the data on disk completely consistent and
2703 crash-proof. To provide the required safety, mdadm disables writes to
2704 the array while this "critical section" is reshaped, and takes a
2705 backup of the data that is in that section. For grows, this backup may be
2706 stored in any spare devices that the array has, however it can also be
2707 stored in a separate file specified with the
2709 option, and is required to be specified for shrinks, RAID level
2710 changes and layout changes. If this option is used, and the system
2711 does crash during the critical period, the same file must be passed to
2713 to restore the backup and reassemble the array. When shrinking rather
2714 than growing the array, the reshape is done from the end towards the
2715 beginning, so the "critical section" is at the end of the reshape.
2719 Changing the RAID level of any array happens instantaneously. However
2720 in the RAID5 to RAID6 case this requires a non-standard layout of the
2721 RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is
2722 required before the change can be accomplished. So while the level
2723 change is instant, the accompanying layout change can take quite a
2726 is required. If the array is not simultaneously being grown or
2727 shrunk, so that the array size will remain the same - for example,
2728 reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
2729 be used not just for a "cricital section" but throughout the reshape
2730 operation, as described below under LAYOUT CHANGES.
2732 .SS CHUNK-SIZE AND LAYOUT CHANGES
2734 Changing the chunk-size of layout without also changing the number of
2735 devices as the same time will involve re-writing all blocks in-place.
2736 To ensure against data loss in the case of a crash, a
2738 must be provided for these changes. Small sections of the array will
2739 be copied to the backup file while they are being rearranged. This
2740 means that all the data is copied twice, once to the backup and once
2741 to the new layout on the array, so this type of reshape will go very
2744 If the reshape is interrupted for any reason, this backup file must be
2746 .B "mdadm --assemble"
2747 so the array can be reassembled. Consequently the file cannot be
2748 stored on the device being reshaped.
2753 A write-intent bitmap can be added to, or removed from, an active
2754 array. Either internal bitmaps, or bitmaps stored in a separate file,
2755 can be added. Note that if you add a bitmap stored in a file which is
2756 in a filesystem that is on the RAID array being affected, the system
2757 will deadlock. The bitmap must be on a separate filesystem.
2759 .SH INCREMENTAL MODE
2763 .B mdadm \-\-incremental
2767 .RI [ optional-aliases-for-device ]
2770 .B mdadm \-\-incremental \-\-fail
2774 .B mdadm \-\-incremental \-\-rebuild\-map
2777 .B mdadm \-\-incremental \-\-run \-\-scan
2780 This mode is designed to be used in conjunction with a device
2781 discovery system. As devices are found in a system, they can be
2783 .B "mdadm \-\-incremental"
2784 to be conditionally added to an appropriate array.
2786 Conversely, it can also be used with the
2788 flag to do just the opposite and find whatever array a particular device
2789 is part of and remove the device from that array.
2791 If the device passed is a
2793 device created by a previous call to
2795 then rather than trying to add that device to an array, all the arrays
2796 described by the metadata of the container will be started.
2799 performs a number of tests to determine if the device is part of an
2800 array, and which array it should be part of. If an appropriate array
2801 is found, or can be created,
2803 adds the device to the array and conditionally starts the array.
2807 will normally only add devices to an array which were previously working
2808 (active or spare) parts of that array. The support for automatic
2809 inclusion of a new drive as a spare in some array requires
2810 a configuration through POLICY in config file.
2814 makes are as follow:
2816 Is the device permitted by
2818 That is, is it listed in a
2820 line in that file. If
2822 is absent then the default it to allow any device. Similarly if
2824 contains the special word
2826 then any device is allowed. Otherwise the device name given to
2828 or one of the aliases given, or an alias found in the filesystem,
2829 must match one of the names or patterns in a
2833 This is the only context where the aliases are used. They are
2834 usually provided by a
2840 Does the device have a valid md superblock? If a specific metadata
2841 version is requested with
2845 then only that style of metadata is accepted, otherwise
2847 finds any known version of metadata. If no
2849 metadata is found, the device may be still added to an array
2850 as a spare if POLICY allows.
2854 Does the metadata match an expected array?
2855 The metadata can match in two ways. Either there is an array listed
2858 which identifies the array (either by UUID, by name, by device list,
2859 or by minor-number), or the array was created with a
2865 or on the command line.
2868 is not able to positively identify the array as belonging to the
2869 current host, the device will be rejected.
2874 keeps a list of arrays that it has partially assembled in
2876 If no array exists which matches
2877 the metadata on the new device,
2879 must choose a device name and unit number. It does this based on any
2882 or any name information stored in the metadata. If this name
2883 suggests a unit number, that number will be used, otherwise a free
2884 unit number will be chosen. Normally
2886 will prefer to create a partitionable array, however if the
2890 suggests that a non-partitionable array is preferred, that will be
2893 If the array is not found in the config file and its metadata does not
2894 identify it as belonging to the "homehost", then
2896 will choose a name for the array which is certain not to conflict with
2897 any array which does belong to this host. It does this be adding an
2898 underscore and a small number to the name preferred by the metadata.
2900 Once an appropriate array is found or created and the device is added,
2902 must decide if the array is ready to be started. It will
2903 normally compare the number of available (non-spare) devices to the
2904 number of devices that the metadata suggests need to be active. If
2905 there are at least that many, the array will be started. This means
2906 that if any devices are missing the array will not be restarted.
2912 in which case the array will be run as soon as there are enough
2913 devices present for the data to be accessible. For a RAID1, that
2914 means one device will start the array. For a clean RAID5, the array
2915 will be started as soon as all but one drive is present.
2917 Note that neither of these approaches is really ideal. If it can
2918 be known that all device discovery has completed, then
2922 can be run which will try to start all arrays that are being
2923 incrementally assembled. They are started in "read-auto" mode in
2924 which they are read-only until the first write request. This means
2925 that no metadata updates are made and no attempt at resync or recovery
2926 happens. Further devices that are found before the first write can
2927 still be added safely.
2930 This section describes environment variables that affect how mdadm
2935 Setting this value to 1 will prevent mdadm from automatically launching
2936 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2942 does not create any device nodes in /dev, but leaves that task to
2946 appears not to be configured, or if this environment variable is set
2949 will create and devices that are needed.
2952 .B MDADM_NO_SYSTEMCTL
2957 is in use it will normally request
2959 to start various background tasks (particularly
2961 rather than forking and running them in the background. This can be
2962 suppressed by setting
2963 .BR MDADM_NO_SYSTEMCTL=1 .
2967 A key value of IMSM metadata is that it allows interoperability with
2968 boot ROMs on Intel platforms, and with other major operating systems.
2971 will only allow an IMSM array to be created or modified if detects
2972 that it is running on an Intel platform which supports IMSM, and
2973 supports the particular configuration of IMSM that is being requested
2974 (some functionality requires newer OROM support).
2976 These checks can be suppressed by setting IMSM_NO_PLATFORM=1 in the
2977 environment. This can be useful for testing or for disaster
2978 recovery. You should be aware that interoperability may be
2979 compromised by setting this value.
2982 .B MDADM_GROW_ALLOW_OLD
2983 If an array is stopped while it is performing a reshape and that
2984 reshape was making use of a backup file, then when the array is
2987 will sometimes complain that the backup file is too old. If this
2988 happens and you are certain it is the right backup file, you can
2989 over-ride this check by setting
2990 .B MDADM_GROW_ALLOW_OLD=1
2995 Any string given in this variable is added to the start of the
2997 line in the config file, or treated as the whole
2999 line if none is given. It can be used to disable certain metadata
3002 is called from a boot script. For example
3004 .B " export MDADM_CONF_AUTO='-ddf -imsm'
3008 does not automatically assemble any DDF or
3009 IMSM arrays that are found. This can be useful on systems configured
3010 to manage such arrays with
3016 .B " mdadm \-\-query /dev/name-of-device"
3018 This will find out if a given device is a RAID array, or is part of
3019 one, and will provide brief information about the device.
3021 .B " mdadm \-\-assemble \-\-scan"
3023 This will assemble and start all arrays listed in the standard config
3024 file. This command will typically go in a system startup file.
3026 .B " mdadm \-\-stop \-\-scan"
3028 This will shut down all arrays that can be shut down (i.e. are not
3029 currently in use). This will typically go in a system shutdown script.
3031 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
3033 If (and only if) there is an Email address or program given in the
3034 standard config file, then
3035 monitor the status of all arrays listed in that file by
3036 polling them ever 2 minutes.
3038 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
3040 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
3043 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
3045 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
3047 This will create a prototype config file that describes currently
3048 active arrays that are known to be made from partitions of IDE or SCSI drives.
3049 This file should be reviewed before being used as it may
3050 contain unwanted detail.
3052 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
3054 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
3056 This will find arrays which could be assembled from existing IDE and
3057 SCSI whole drives (not partitions), and store the information in the
3058 format of a config file.
3059 This file is very likely to contain unwanted detail, particularly
3062 entries. It should be reviewed and edited before being used as an
3065 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
3067 .B " mdadm \-Ebsc partitions"
3069 Create a list of devices by reading
3070 .BR /proc/partitions ,
3071 scan these for RAID superblocks, and printout a brief listing of all
3074 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
3076 Scan all partitions and devices listed in
3077 .BR /proc/partitions
3080 out of all such devices with a RAID superblock with a minor number of 0.
3082 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /run/mdadm/mon.pid"
3084 If config file contains a mail address or alert program, run mdadm in
3085 the background in monitor mode monitoring all md devices. Also write
3086 pid of mdadm daemon to
3087 .BR /run/mdadm/mon.pid .
3089 .B " mdadm \-Iq /dev/somedevice"
3091 Try to incorporate newly discovered device into some array as
3094 .B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan"
3096 Rebuild the array map from any current arrays, and then start any that
3099 .B " mdadm /dev/md4 --fail detached --remove detached"
3101 Any devices which are components of /dev/md4 will be marked as faulty
3102 and then remove from the array.
3104 .B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
3108 which is currently a RAID5 array will be converted to RAID6. There
3109 should normally already be a spare drive attached to the array as a
3110 RAID6 needs one more drive than a matching RAID5.
3112 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
3114 Create a DDF array over 6 devices.
3116 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
3118 Create a RAID5 array over any 3 devices in the given DDF set. Use
3119 only 30 gigabytes of each device.
3121 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
3123 Assemble a pre-exist ddf array.
3125 .B " mdadm -I /dev/md/ddf1"
3127 Assemble all arrays contained in the ddf array, assigning names as
3130 .B " mdadm \-\-create \-\-help"
3132 Provide help about the Create mode.
3134 .B " mdadm \-\-config \-\-help"
3136 Provide help about the format of the config file.
3138 .B " mdadm \-\-help"
3140 Provide general help.
3150 lists all active md devices with information about them.
3152 uses this to find arrays when
3154 is given in Misc mode, and to monitor array reconstruction
3159 The config file lists which devices may be scanned to see if
3160 they contain MD super block, and gives identifying information
3161 (e.g. UUID) about known MD arrays. See
3165 .SS /etc/mdadm.conf.d
3167 A directory containing configuration files which are read in lexical
3173 mode is used, this file gets a list of arrays currently being created.
3178 understand two sorts of names for array devices.
3180 The first is the so-called 'standard' format name, which matches the
3181 names used by the kernel and which appear in
3184 The second sort can be freely chosen, but must reside in
3186 When giving a device name to
3188 to create or assemble an array, either full path name such as
3192 can be given, or just the suffix of the second sort of name, such as
3198 chooses device names during auto-assembly or incremental assembly, it
3199 will sometimes add a small sequence number to the end of the name to
3200 avoid conflicted between multiple arrays that have the same name. If
3202 can reasonably determine that the array really is meant for this host,
3203 either by a hostname in the metadata, or by the presence of the array
3206 then it will leave off the suffix if possible.
3207 Also if the homehost is specified as
3210 will only use a suffix if a different array of the same name already
3211 exists or is listed in the config file.
3213 The standard names for non-partitioned arrays (the only sort of md
3214 array available in 2.4 and earlier) are of the form
3218 where NN is a number.
3219 The standard names for partitionable arrays (as available from 2.6
3220 onwards) are of the form:
3224 Partition numbers should be indicated by adding "pMM" to these, thus "/dev/md/d1p2".
3226 From kernel version 2.6.28 the "non-partitioned array" can actually
3227 be partitioned. So the "md_d\fBNN\fP"
3228 names are no longer needed, and
3229 partitions such as "/dev/md\fBNN\fPp\fBXX\fP"
3232 From kernel version 2.6.29 standard names can be non-numeric following
3239 is any string. These names are supported by
3241 since version 3.3 provided they are enabled in
3246 was previously known as
3250 For further information on mdadm usage, MD and the various levels of
3253 .B http://raid.wiki.kernel.org/
3255 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
3257 The latest version of
3259 should always be available from
3261 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob