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.
1448 Each of these options requires that the first device listed is the array
1449 to be acted upon, and the remainder are component devices to be added,
1450 removed, marked as faulty, etc. Several different operations can be
1451 specified for different devices, e.g.
1453 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1455 Each operation applies to all devices listed until the next
1458 If an array is using a write-intent bitmap, then devices which have
1459 been removed can be re\-added in a way that avoids a full
1460 reconstruction but instead just updates the blocks that have changed
1461 since the device was removed. For arrays with persistent metadata
1462 (superblocks) this is done automatically. For arrays created with
1464 mdadm needs to be told that this device we removed recently with
1467 Devices can only be removed from an array if they are not in active
1468 use, i.e. that must be spares or failed devices. To remove an active
1469 device, it must first be marked as
1475 .BR \-Q ", " \-\-query
1476 Examine a device to see
1477 (1) if it is an md device and (2) if it is a component of an md
1479 Information about what is discovered is presented.
1482 .BR \-D ", " \-\-detail
1483 Print details of one or more md devices.
1486 .BR \-\-detail\-platform
1487 Print details of the platform's RAID capabilities (firmware / hardware
1488 topology) for a given metadata format. If used without argument, mdadm
1489 will scan all controllers looking for their capabilities. Otherwise, mdadm
1490 will only look at the controller specified by the argument in form of an
1491 absolute filepath or a link, e.g.
1492 .IR /sys/devices/pci0000:00/0000:00:1f.2 .
1495 .BR \-Y ", " \-\-export
1498 .BR \-\-detail-platform ,
1502 output will be formatted as
1504 pairs for easy import into the environment.
1510 indicates whether an array was started
1512 or not, which may include a reason
1513 .RB ( unsafe ", " nothing ", " no ).
1516 indicates if the array is expected on this host
1518 or seems to be from elsewhere
1522 .BR \-E ", " \-\-examine
1523 Print contents of the metadata stored on the named device(s).
1524 Note the contrast between
1529 applies to devices which are components of an array, while
1531 applies to a whole array which is currently active.
1534 If an array was created on a SPARC machine with a 2.2 Linux kernel
1535 patched with RAID support, the superblock will have been created
1536 incorrectly, or at least incompatibly with 2.4 and later kernels.
1541 will fix the superblock before displaying it. If this appears to do
1542 the right thing, then the array can be successfully assembled using
1543 .BR "\-\-assemble \-\-update=sparc2.2" .
1546 .BR \-X ", " \-\-examine\-bitmap
1547 Report information about a bitmap file.
1548 The argument is either an external bitmap file or an array component
1549 in case of an internal bitmap. Note that running this on an array
1552 does not report the bitmap for that array.
1555 .B \-\-examine\-badblocks
1556 List the bad-blocks recorded for the device, if a bad-blocks list has
1557 been configured. Currently only
1559 metadata supports bad-blocks lists.
1562 .BI \-\-dump= directory
1564 .BI \-\-restore= directory
1565 Save metadata from lists devices, or restore metadata to listed devices.
1568 .BR \-R ", " \-\-run
1569 start a partially assembled array. If
1571 did not find enough devices to fully start the array, it might leaving
1572 it partially assembled. If you wish, you can then use
1574 to start the array in degraded mode.
1577 .BR \-S ", " \-\-stop
1578 deactivate array, releasing all resources.
1581 .BR \-o ", " \-\-readonly
1582 mark array as readonly.
1585 .BR \-w ", " \-\-readwrite
1586 mark array as readwrite.
1589 .B \-\-zero\-superblock
1590 If the device contains a valid md superblock, the block is
1591 overwritten with zeros. With
1593 the block where the superblock would be is overwritten even if it
1594 doesn't appear to be valid.
1597 .B \-\-kill\-subarray=
1598 If the device is a container and the argument to \-\-kill\-subarray
1599 specifies an inactive subarray in the container, then the subarray is
1600 deleted. Deleting all subarrays will leave an 'empty-container' or
1601 spare superblock on the drives. See
1602 .B \-\-zero\-superblock
1604 removing a superblock. Note that some formats depend on the subarray
1605 index for generating a UUID, this command will fail if it would change
1606 the UUID of an active subarray.
1609 .B \-\-update\-subarray=
1610 If the device is a container and the argument to \-\-update\-subarray
1611 specifies a subarray in the container, then attempt to update the given
1612 superblock field in the subarray. See below in
1617 .BR \-t ", " \-\-test
1622 is set to reflect the status of the device. See below in
1627 .BR \-W ", " \-\-wait
1628 For each md device given, wait for any resync, recovery, or reshape
1629 activity to finish before returning.
1631 will return with success if it actually waited for every device
1632 listed, otherwise it will return failure.
1636 For each md device given, or each device in /proc/mdstat if
1638 is given, arrange for the array to be marked clean as soon as possible.
1640 will return with success if the array uses external metadata and we
1641 successfully waited. For native arrays this returns immediately as the
1642 kernel handles dirty-clean transitions at shutdown. No action is taken
1643 if safe-mode handling is disabled.
1647 Set the "sync_action" for all md devices given to one of
1654 will abort any currently running action though some actions will
1655 automatically restart.
1658 will abort any current action and ensure no other action starts
1668 .BR "SCRUBBING AND MISMATCHES" .
1670 .SH For Incremental Assembly mode:
1672 .BR \-\-rebuild\-map ", " \-r
1673 Rebuild the map file
1677 uses to help track which arrays are currently being assembled.
1680 .BR \-\-run ", " \-R
1681 Run any array assembled as soon as a minimal number of devices are
1682 available, rather than waiting until all expected devices are present.
1685 .BR \-\-scan ", " \-s
1686 Only meaningful with
1690 file for arrays that are being incrementally assembled and will try to
1691 start any that are not already started. If any such array is listed
1694 as requiring an external bitmap, that bitmap will be attached first.
1697 .BR \-\-fail ", " \-f
1698 This allows the hot-plug system to remove devices that have fully disappeared
1699 from the kernel. It will first fail and then remove the device from any
1700 array it belongs to.
1701 The device name given should be a kernel device name such as "sda",
1707 Only used with \-\-fail. The 'path' given will be recorded so that if
1708 a new device appears at the same location it can be automatically
1709 added to the same array. This allows the failed device to be
1710 automatically replaced by a new device without metadata if it appears
1711 at specified path. This option is normally only set by a
1715 .SH For Monitor mode:
1717 .BR \-m ", " \-\-mail
1718 Give a mail address to send alerts to.
1721 .BR \-p ", " \-\-program ", " \-\-alert
1722 Give a program to be run whenever an event is detected.
1725 .BR \-y ", " \-\-syslog
1726 Cause all events to be reported through 'syslog'. The messages have
1727 facility of 'daemon' and varying priorities.
1730 .BR \-d ", " \-\-delay
1731 Give a delay in seconds.
1733 polls the md arrays and then waits this many seconds before polling
1734 again. The default is 60 seconds. Since 2.6.16, there is no need to
1735 reduce this as the kernel alerts
1737 immediately when there is any change.
1740 .BR \-r ", " \-\-increment
1741 Give a percentage increment.
1743 will generate RebuildNN events with the given percentage increment.
1746 .BR \-f ", " \-\-daemonise
1749 to run as a background daemon if it decides to monitor anything. This
1750 causes it to fork and run in the child, and to disconnect from the
1751 terminal. The process id of the child is written to stdout.
1754 which will only continue monitoring if a mail address or alert program
1755 is found in the config file.
1758 .BR \-i ", " \-\-pid\-file
1761 is running in daemon mode, write the pid of the daemon process to
1762 the specified file, instead of printing it on standard output.
1765 .BR \-1 ", " \-\-oneshot
1766 Check arrays only once. This will generate
1768 events and more significantly
1774 .B " mdadm \-\-monitor \-\-scan \-1"
1776 from a cron script will ensure regular notification of any degraded arrays.
1779 .BR \-t ", " \-\-test
1782 alert for every array found at startup. This alert gets mailed and
1783 passed to the alert program. This can be used for testing that alert
1784 message do get through successfully.
1788 This inhibits the functionality for moving spares between arrays.
1789 Only one monitoring process started with
1791 but without this flag is allowed, otherwise the two could interfere
1798 .B mdadm \-\-assemble
1799 .I md-device options-and-component-devices...
1802 .B mdadm \-\-assemble \-\-scan
1803 .I md-devices-and-options...
1806 .B mdadm \-\-assemble \-\-scan
1810 This usage assembles one or more RAID arrays from pre-existing components.
1811 For each array, mdadm needs to know the md device, the identity of the
1812 array, and a number of component-devices. These can be found in a number of ways.
1814 In the first usage example (without the
1816 the first device given is the md device.
1817 In the second usage example, all devices listed are treated as md
1818 devices and assembly is attempted.
1819 In the third (where no devices are listed) all md devices that are
1820 listed in the configuration file are assembled. If no arrays are
1821 described by the configuration file, then any arrays that
1822 can be found on unused devices will be assembled.
1824 If precisely one device is listed, but
1830 was given and identity information is extracted from the configuration file.
1832 The identity can be given with the
1838 option, will be taken from the md-device record in the config file, or
1839 will be taken from the super block of the first component-device
1840 listed on the command line.
1842 Devices can be given on the
1844 command line or in the config file. Only devices which have an md
1845 superblock which contains the right identity will be considered for
1848 The config file is only used if explicitly named with
1850 or requested with (a possibly implicit)
1855 .B /etc/mdadm/mdadm.conf
1860 is not given, then the config file will only be used to find the
1861 identity of md arrays.
1863 Normally the array will be started after it is assembled. However if
1865 is not given and not all expected drives were listed, then the array
1866 is not started (to guard against usage errors). To insist that the
1867 array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1876 does not create any entries in
1880 It does record information in
1884 to choose the correct name.
1888 detects that udev is not configured, it will create the devices in
1892 In Linux kernels prior to version 2.6.28 there were two distinctly
1893 different types of md devices that could be created: one that could be
1894 partitioned using standard partitioning tools and one that could not.
1895 Since 2.6.28 that distinction is no longer relevant as both type of
1896 devices can be partitioned.
1898 will normally create the type that originally could not be partitioned
1899 as it has a well defined major number (9).
1901 Prior to 2.6.28, it is important that mdadm chooses the correct type
1902 of array device to use. This can be controlled with the
1904 option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1905 to use a partitionable device rather than the default.
1907 In the no-udev case, the value given to
1909 can be suffixed by a number. This tells
1911 to create that number of partition devices rather than the default of 4.
1915 can also be given in the configuration file as a word starting
1917 on the ARRAY line for the relevant array.
1924 and no devices are listed,
1926 will first attempt to assemble all the arrays listed in the config
1929 If no arrays are listed in the config (other than those marked
1931 it will look through the available devices for possible arrays and
1932 will try to assemble anything that it finds. Arrays which are tagged
1933 as belonging to the given homehost will be assembled and started
1934 normally. Arrays which do not obviously belong to this host are given
1935 names that are expected not to conflict with anything local, and are
1936 started "read-auto" so that nothing is written to any device until the
1937 array is written to. i.e. automatic resync etc is delayed.
1941 finds a consistent set of devices that look like they should comprise
1942 an array, and if the superblock is tagged as belonging to the given
1943 home host, it will automatically choose a device name and try to
1944 assemble the array. If the array uses version-0.90 metadata, then the
1946 number as recorded in the superblock is used to create a name in
1950 If the array uses version-1 metadata, then the
1952 from the superblock is used to similarly create a name in
1954 (the name will have any 'host' prefix stripped first).
1956 This behaviour can be modified by the
1960 configuration file. This line can indicate that specific metadata
1961 type should, or should not, be automatically assembled. If an array
1962 is found which is not listed in
1964 and has a metadata format that is denied by the
1966 line, then it will not be assembled.
1969 line can also request that all arrays identified as being for this
1970 homehost should be assembled regardless of their metadata type.
1973 for further details.
1975 Note: Auto assembly cannot be used for assembling and activating some
1976 arrays which are undergoing reshape. In particular as the
1978 cannot be given, any reshape which requires a backup-file to continue
1979 cannot be started by auto assembly. An array which is growing to more
1980 devices and has passed the critical section can be assembled using
1991 .BI \-\-raid\-devices= Z
1995 This usage is similar to
1997 The difference is that it creates an array without a superblock. With
1998 these arrays there is no difference between initially creating the array and
1999 subsequently assembling the array, except that hopefully there is useful
2000 data there in the second case.
2002 The level may raid0, linear, raid1, raid10, multipath, or faulty, or
2003 one of their synonyms. All devices must be listed and the array will
2004 be started once complete. It will often be appropriate to use
2005 .B \-\-assume\-clean
2006 with levels raid1 or raid10.
2017 .BI \-\-raid\-devices= Z
2021 This usage will initialise a new md array, associate some devices with
2022 it, and activate the array.
2024 The named device will normally not exist when
2025 .I "mdadm \-\-create"
2026 is run, but will be created by
2028 once the array becomes active.
2030 As devices are added, they are checked to see if they contain RAID
2031 superblocks or filesystems. They are also checked to see if the variance in
2032 device size exceeds 1%.
2034 If any discrepancy is found, the array will not automatically be run, though
2037 can override this caution.
2039 To create a "degraded" array in which some devices are missing, simply
2040 give the word "\fBmissing\fP"
2041 in place of a device name. This will cause
2043 to leave the corresponding slot in the array empty.
2044 For a RAID4 or RAID5 array at most one slot can be
2045 "\fBmissing\fP"; for a RAID6 array at most two slots.
2046 For a RAID1 array, only one real device needs to be given. All of the
2050 When creating a RAID5 array,
2052 will automatically create a degraded array with an extra spare drive.
2053 This is because building the spare into a degraded array is in general
2054 faster than resyncing the parity on a non-degraded, but not clean,
2055 array. This feature can be overridden with the
2059 When creating an array with version-1 metadata a name for the array is
2061 If this is not given with the
2065 will choose a name based on the last component of the name of the
2066 device being created. So if
2068 is being created, then the name
2073 is being created, then the name
2077 When creating a partition based array, using
2079 with version-1.x metadata, the partition type should be set to
2081 (non fs-data). This type selection allows for greater precision since
2082 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
2083 might create problems in the event of array recovery through a live cdrom.
2085 A new array will normally get a randomly assigned 128bit UUID which is
2086 very likely to be unique. If you have a specific need, you can choose
2087 a UUID for the array by giving the
2089 option. Be warned that creating two arrays with the same UUID is a
2090 recipe for disaster. Also, using
2092 when creating a v0.90 array will silently override any
2097 .\"option is given, it is not necessary to list any component-devices in this command.
2098 .\"They can be added later, before a
2102 .\"is given, the apparent size of the smallest drive given is used.
2104 If the array type supports a write-intent bitmap, and if the devices
2105 in the array exceed 100G is size, an internal write-intent bitmap
2106 will automatically be added unless some other option is explicitly
2109 option. In any case space for a bitmap will be reserved so that one
2110 can be added layer with
2111 .BR "\-\-grow \-\-bitmap=internal" .
2113 If the metadata type supports it (currently only 1.x metadata), space
2114 will be allocated to store a bad block list. This allows a modest
2115 number of bad blocks to be recorded, allowing the drive to remain in
2116 service while only partially functional.
2118 When creating an array within a
2121 can be given either the list of devices to use, or simply the name of
2122 the container. The former case gives control over which devices in
2123 the container will be used for the array. The latter case allows
2125 to automatically choose which devices to use based on how much spare
2128 The General Management options that are valid with
2133 insist on running the array even if some devices look like they might
2138 start the array readonly \(em not supported yet.
2145 .I options... devices...
2148 This usage will allow individual devices in an array to be failed,
2149 removed or added. It is possible to perform multiple operations with
2150 on command. For example:
2152 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
2158 and will then remove it from the array and finally add it back
2159 in as a spare. However only one md array can be affected by a single
2162 When a device is added to an active array, mdadm checks to see if it
2163 has metadata on it which suggests that it was recently a member of the
2164 array. If it does, it tries to "re\-add" the device. If there have
2165 been no changes since the device was removed, or if the array has a
2166 write-intent bitmap which has recorded whatever changes there were,
2167 then the device will immediately become a full member of the array and
2168 those differences recorded in the bitmap will be resolved.
2178 MISC mode includes a number of distinct operations that
2179 operate on distinct devices. The operations are:
2182 The device is examined to see if it is
2183 (1) an active md array, or
2184 (2) a component of an md array.
2185 The information discovered is reported.
2189 The device should be an active md device.
2191 will display a detailed description of the array.
2195 will cause the output to be less detailed and the format to be
2196 suitable for inclusion in
2200 will normally be 0 unless
2202 failed to get useful information about the device(s); however, if the
2204 option is given, then the exit status will be:
2208 The array is functioning normally.
2211 The array has at least one failed device.
2214 The array has multiple failed devices such that it is unusable.
2217 There was an error while trying to get information about the device.
2221 .B \-\-detail\-platform
2222 Print detail of the platform's RAID capabilities (firmware / hardware
2223 topology). If the metadata is specified with
2227 then the return status will be:
2231 metadata successfully enumerated its platform components on this system
2234 metadata is platform independent
2237 metadata failed to find its platform components on this system
2241 .B \-\-update\-subarray=
2242 If the device is a container and the argument to \-\-update\-subarray
2243 specifies a subarray in the container, then attempt to update the given
2244 superblock field in the subarray. Similar to updating an array in
2245 "assemble" mode, the field to update is selected by
2249 option. Currently only
2255 option updates the subarray name in the metadata, it may not affect the
2256 device node name or the device node symlink until the subarray is
2257 re\-assembled. If updating
2259 would change the UUID of an active subarray this operation is blocked,
2260 and the command will end in an error.
2264 The device should be a component of an md array.
2266 will read the md superblock of the device and display the contents.
2271 is given, then multiple devices that are components of the one array
2272 are grouped together and reported in a single entry suitable
2278 without listing any devices will cause all devices listed in the
2279 config file to be examined.
2282 .BI \-\-dump= directory
2283 If the device contains RAID metadata, a file will be created in the
2285 and the metadata will be written to it. The file will be the same
2286 size as the device and have the metadata written in the file at the
2287 same locate that it exists in the device. However the file will be "sparse" so
2288 that only those blocks containing metadata will be allocated. The
2289 total space used will be small.
2291 The file name used in the
2293 will be the base name of the device. Further if any links appear in
2295 which point to the device, then hard links to the file will be created
2302 Multiple devices can be listed and their metadata will all be stored
2303 in the one directory.
2306 .BI \-\-restore= directory
2307 This is the reverse of
2310 will locate a file in the directory that has a name appropriate for
2311 the given device and will restore metadata from it. Names that match
2313 names are preferred, however if two of those refer to different files,
2315 will not choose between them but will abort the operation.
2317 If a file name is given instead of a
2321 will restore from that file to a single device, always provided the
2322 size of the file matches that of the device, and the file contains
2326 The devices should be active md arrays which will be deactivated, as
2327 long as they are not currently in use.
2331 This will fully activate a partially assembled md array.
2335 This will mark an active array as read-only, providing that it is
2336 not currently being used.
2342 array back to being read/write.
2346 For all operations except
2349 will cause the operation to be applied to all arrays listed in
2354 causes all devices listed in the config file to be examined.
2357 .BR \-b ", " \-\-brief
2358 Be less verbose. This is used with
2366 gives an intermediate level of verbosity.
2372 .B mdadm \-\-monitor
2373 .I options... devices...
2378 to periodically poll a number of md arrays and to report on any events
2381 will never exit once it decides that there are arrays to be checked,
2382 so it should normally be run in the background.
2384 As well as reporting events,
2386 may move a spare drive from one array to another if they are in the
2391 and if the destination array has a failed drive but no spares.
2393 If any devices are listed on the command line,
2395 will only monitor those devices. Otherwise all arrays listed in the
2396 configuration file will be monitored. Further, if
2398 is given, then any other md devices that appear in
2400 will also be monitored.
2402 The result of monitoring the arrays is the generation of events.
2403 These events are passed to a separate program (if specified) and may
2404 be mailed to a given E-mail address.
2406 When passing events to a program, the program is run once for each event,
2407 and is given 2 or 3 command-line arguments: the first is the
2408 name of the event (see below), the second is the name of the
2409 md device which is affected, and the third is the name of a related
2410 device if relevant (such as a component device that has failed).
2414 is given, then a program or an E-mail address must be specified on the
2415 command line or in the config file. If neither are available, then
2417 will not monitor anything.
2421 will continue monitoring as long as something was found to monitor. If
2422 no program or email is given, then each event is reported to
2425 The different events are:
2429 .B DeviceDisappeared
2430 An md array which previously was configured appears to no longer be
2431 configured. (syslog priority: Critical)
2435 was told to monitor an array which is RAID0 or Linear, then it will
2437 .B DeviceDisappeared
2438 with the extra information
2440 This is because RAID0 and Linear do not support the device-failed,
2441 hot-spare and resync operations which are monitored.
2445 An md array started reconstruction (e.g. recovery, resync, reshape,
2446 check, repair). (syslog priority: Warning)
2452 is a two-digit number (ie. 05, 48). This indicates that rebuild
2453 has passed that many percent of the total. The events are generated
2454 with fixed increment since 0. Increment size may be specified with
2455 a commandline option (default is 20). (syslog priority: Warning)
2459 An md array that was rebuilding, isn't any more, either because it
2460 finished normally or was aborted. (syslog priority: Warning)
2464 An active component device of an array has been marked as
2465 faulty. (syslog priority: Critical)
2469 A spare component device which was being rebuilt to replace a faulty
2470 device has failed. (syslog priority: Critical)
2474 A spare component device which was being rebuilt to replace a faulty
2475 device has been successfully rebuilt and has been made active.
2476 (syslog priority: Info)
2480 A new md array has been detected in the
2482 file. (syslog priority: Info)
2486 A newly noticed array appears to be degraded. This message is not
2489 notices a drive failure which causes degradation, but only when
2491 notices that an array is degraded when it first sees the array.
2492 (syslog priority: Critical)
2496 A spare drive has been moved from one array in a
2500 to another to allow a failed drive to be replaced.
2501 (syslog priority: Info)
2507 has been told, via the config file, that an array should have a certain
2508 number of spare devices, and
2510 detects that it has fewer than this number when it first sees the
2511 array, it will report a
2514 (syslog priority: Warning)
2518 An array was found at startup, and the
2521 (syslog priority: Info)
2531 cause Email to be sent. All events cause the program to be run.
2532 The program is run with two or three arguments: the event
2533 name, the array device and possibly a second device.
2535 Each event has an associated array device (e.g.
2537 and possibly a second device. For
2542 the second device is the relevant component device.
2545 the second device is the array that the spare was moved from.
2549 to move spares from one array to another, the different arrays need to
2550 be labeled with the same
2552 or the spares must be allowed to migrate through matching POLICY domains
2553 in the configuration file. The
2555 name can be any string; it is only necessary that different spare
2556 groups use different names.
2560 detects that an array in a spare group has fewer active
2561 devices than necessary for the complete array, and has no spare
2562 devices, it will look for another array in the same spare group that
2563 has a full complement of working drive and a spare. It will then
2564 attempt to remove the spare from the second drive and add it to the
2566 If the removal succeeds but the adding fails, then it is added back to
2569 If the spare group for a degraded array is not defined,
2571 will look at the rules of spare migration specified by POLICY lines in
2573 and then follow similar steps as above if a matching spare is found.
2576 The GROW mode is used for changing the size or shape of an active
2578 For this to work, the kernel must support the necessary change.
2579 Various types of growth are being added during 2.6 development.
2581 Currently the supported changes include
2583 change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
2585 increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
2588 change the chunk-size and layout of RAID0, RAID4, RAID5, RAID6 and RAID10.
2590 convert between RAID1 and RAID5, between RAID5 and RAID6, between
2591 RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
2593 add a write-intent bitmap to any array which supports these bitmaps, or
2594 remove a write-intent bitmap from such an array.
2597 Using GROW on containers is currently supported only for Intel's IMSM
2598 container format. The number of devices in a container can be
2599 increased - which affects all arrays in the container - or an array
2600 in a container can be converted between levels where those levels are
2601 supported by the container, and the conversion is on of those listed
2602 above. Resizing arrays in an IMSM container with
2604 is not yet supported.
2606 Grow functionality (e.g. expand a number of raid devices) for Intel's
2607 IMSM container format has an experimental status. It is guarded by the
2608 .B MDADM_EXPERIMENTAL
2609 environment variable which must be set to '1' for a GROW command to
2611 This is for the following reasons:
2614 Intel's native IMSM check-pointing is not fully tested yet.
2615 This can causes IMSM incompatibility during the grow process: an array
2616 which is growing cannot roam between Microsoft Windows(R) and Linux
2620 Interrupting a grow operation is not recommended, because it
2621 has not been fully tested for Intel's IMSM container format yet.
2624 Note: Intel's native checkpointing doesn't use
2626 option and it is transparent for assembly feature.
2629 Normally when an array is built the "size" is taken from the smallest
2630 of the drives. If all the small drives in an arrays are, one at a
2631 time, removed and replaced with larger drives, then you could have an
2632 array of large drives with only a small amount used. In this
2633 situation, changing the "size" with "GROW" mode will allow the extra
2634 space to start being used. If the size is increased in this way, a
2635 "resync" process will start to make sure the new parts of the array
2638 Note that when an array changes size, any filesystem that may be
2639 stored in the array will not automatically grow or shrink to use or
2640 vacate the space. The
2641 filesystem will need to be explicitly told to use the extra space
2642 after growing, or to reduce its size
2644 to shrinking the array.
2646 Also the size of an array cannot be changed while it has an active
2647 bitmap. If an array has a bitmap, it must be removed before the size
2648 can be changed. Once the change is complete a new bitmap can be created.
2650 .SS RAID\-DEVICES CHANGES
2652 A RAID1 array can work with any number of devices from 1 upwards
2653 (though 1 is not very useful). There may be times which you want to
2654 increase or decrease the number of active devices. Note that this is
2655 different to hot-add or hot-remove which changes the number of
2658 When reducing the number of devices in a RAID1 array, the slots which
2659 are to be removed from the array must already be vacant. That is, the
2660 devices which were in those slots must be failed and removed.
2662 When the number of devices is increased, any hot spares that are
2663 present will be activated immediately.
2665 Changing the number of active devices in a RAID5 or RAID6 is much more
2666 effort. Every block in the array will need to be read and written
2667 back to a new location. From 2.6.17, the Linux Kernel is able to
2668 increase the number of devices in a RAID5 safely, including restarting
2669 an interrupted "reshape". From 2.6.31, the Linux Kernel is able to
2670 increase or decrease the number of devices in a RAID5 or RAID6.
2672 From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4
2675 uses this functionality and the ability to add
2676 devices to a RAID4 to allow devices to be added to a RAID0. When
2677 requested to do this,
2679 will convert the RAID0 to a RAID4, add the necessary disks and make
2680 the reshape happen, and then convert the RAID4 back to RAID0.
2682 When decreasing the number of devices, the size of the array will also
2683 decrease. If there was data in the array, it could get destroyed and
2684 this is not reversible, so you should firstly shrink the filesystem on
2685 the array to fit within the new size. To help prevent accidents,
2687 requires that the size of the array be decreased first with
2688 .BR "mdadm --grow --array-size" .
2689 This is a reversible change which simply makes the end of the array
2690 inaccessible. The integrity of any data can then be checked before
2691 the non-reversible reduction in the number of devices is request.
2693 When relocating the first few stripes on a RAID5 or RAID6, it is not
2694 possible to keep the data on disk completely consistent and
2695 crash-proof. To provide the required safety, mdadm disables writes to
2696 the array while this "critical section" is reshaped, and takes a
2697 backup of the data that is in that section. For grows, this backup may be
2698 stored in any spare devices that the array has, however it can also be
2699 stored in a separate file specified with the
2701 option, and is required to be specified for shrinks, RAID level
2702 changes and layout changes. If this option is used, and the system
2703 does crash during the critical period, the same file must be passed to
2705 to restore the backup and reassemble the array. When shrinking rather
2706 than growing the array, the reshape is done from the end towards the
2707 beginning, so the "critical section" is at the end of the reshape.
2711 Changing the RAID level of any array happens instantaneously. However
2712 in the RAID5 to RAID6 case this requires a non-standard layout of the
2713 RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is
2714 required before the change can be accomplished. So while the level
2715 change is instant, the accompanying layout change can take quite a
2718 is required. If the array is not simultaneously being grown or
2719 shrunk, so that the array size will remain the same - for example,
2720 reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
2721 be used not just for a "cricital section" but throughout the reshape
2722 operation, as described below under LAYOUT CHANGES.
2724 .SS CHUNK-SIZE AND LAYOUT CHANGES
2726 Changing the chunk-size of layout without also changing the number of
2727 devices as the same time will involve re-writing all blocks in-place.
2728 To ensure against data loss in the case of a crash, a
2730 must be provided for these changes. Small sections of the array will
2731 be copied to the backup file while they are being rearranged. This
2732 means that all the data is copied twice, once to the backup and once
2733 to the new layout on the array, so this type of reshape will go very
2736 If the reshape is interrupted for any reason, this backup file must be
2738 .B "mdadm --assemble"
2739 so the array can be reassembled. Consequently the file cannot be
2740 stored on the device being reshaped.
2745 A write-intent bitmap can be added to, or removed from, an active
2746 array. Either internal bitmaps, or bitmaps stored in a separate file,
2747 can be added. Note that if you add a bitmap stored in a file which is
2748 in a filesystem that is on the RAID array being affected, the system
2749 will deadlock. The bitmap must be on a separate filesystem.
2751 .SH INCREMENTAL MODE
2755 .B mdadm \-\-incremental
2759 .RI [ optional-aliases-for-device ]
2762 .B mdadm \-\-incremental \-\-fail
2766 .B mdadm \-\-incremental \-\-rebuild\-map
2769 .B mdadm \-\-incremental \-\-run \-\-scan
2772 This mode is designed to be used in conjunction with a device
2773 discovery system. As devices are found in a system, they can be
2775 .B "mdadm \-\-incremental"
2776 to be conditionally added to an appropriate array.
2778 Conversely, it can also be used with the
2780 flag to do just the opposite and find whatever array a particular device
2781 is part of and remove the device from that array.
2783 If the device passed is a
2785 device created by a previous call to
2787 then rather than trying to add that device to an array, all the arrays
2788 described by the metadata of the container will be started.
2791 performs a number of tests to determine if the device is part of an
2792 array, and which array it should be part of. If an appropriate array
2793 is found, or can be created,
2795 adds the device to the array and conditionally starts the array.
2799 will normally only add devices to an array which were previously working
2800 (active or spare) parts of that array. The support for automatic
2801 inclusion of a new drive as a spare in some array requires
2802 a configuration through POLICY in config file.
2806 makes are as follow:
2808 Is the device permitted by
2810 That is, is it listed in a
2812 line in that file. If
2814 is absent then the default it to allow any device. Similarly if
2816 contains the special word
2818 then any device is allowed. Otherwise the device name given to
2820 or one of the aliases given, or an alias found in the filesystem,
2821 must match one of the names or patterns in a
2825 This is the only context where the aliases are used. They are
2826 usually provided by a
2832 Does the device have a valid md superblock? If a specific metadata
2833 version is requested with
2837 then only that style of metadata is accepted, otherwise
2839 finds any known version of metadata. If no
2841 metadata is found, the device may be still added to an array
2842 as a spare if POLICY allows.
2846 Does the metadata match an expected array?
2847 The metadata can match in two ways. Either there is an array listed
2850 which identifies the array (either by UUID, by name, by device list,
2851 or by minor-number), or the array was created with a
2857 or on the command line.
2860 is not able to positively identify the array as belonging to the
2861 current host, the device will be rejected.
2866 keeps a list of arrays that it has partially assembled in
2868 If no array exists which matches
2869 the metadata on the new device,
2871 must choose a device name and unit number. It does this based on any
2874 or any name information stored in the metadata. If this name
2875 suggests a unit number, that number will be used, otherwise a free
2876 unit number will be chosen. Normally
2878 will prefer to create a partitionable array, however if the
2882 suggests that a non-partitionable array is preferred, that will be
2885 If the array is not found in the config file and its metadata does not
2886 identify it as belonging to the "homehost", then
2888 will choose a name for the array which is certain not to conflict with
2889 any array which does belong to this host. It does this be adding an
2890 underscore and a small number to the name preferred by the metadata.
2892 Once an appropriate array is found or created and the device is added,
2894 must decide if the array is ready to be started. It will
2895 normally compare the number of available (non-spare) devices to the
2896 number of devices that the metadata suggests need to be active. If
2897 there are at least that many, the array will be started. This means
2898 that if any devices are missing the array will not be restarted.
2904 in which case the array will be run as soon as there are enough
2905 devices present for the data to be accessible. For a RAID1, that
2906 means one device will start the array. For a clean RAID5, the array
2907 will be started as soon as all but one drive is present.
2909 Note that neither of these approaches is really ideal. If it can
2910 be known that all device discovery has completed, then
2914 can be run which will try to start all arrays that are being
2915 incrementally assembled. They are started in "read-auto" mode in
2916 which they are read-only until the first write request. This means
2917 that no metadata updates are made and no attempt at resync or recovery
2918 happens. Further devices that are found before the first write can
2919 still be added safely.
2922 This section describes environment variables that affect how mdadm
2927 Setting this value to 1 will prevent mdadm from automatically launching
2928 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2934 does not create any device nodes in /dev, but leaves that task to
2938 appears not to be configured, or if this environment variable is set
2941 will create and devices that are needed.
2944 .B MDADM_NO_SYSTEMCTL
2949 is in use it will normally request
2951 to start various background tasks (particularly
2953 rather than forking and running them in the background. This can be
2954 suppressed by setting
2955 .BR MDADM_NO_SYSTEMCTL=1 .
2959 A key value of IMSM metadata is that it allows interoperability with
2960 boot ROMs on Intel platforms, and with other major operating systems.
2963 will only allow an IMSM array to be created or modified if detects
2964 that it is running on an Intel platform which supports IMSM, and
2965 supports the particular configuration of IMSM that is being requested
2966 (some functionality requires newer OROM support).
2968 These checks can be suppressed by setting IMSM_NO_PLATFORM=1 in the
2969 environment. This can be useful for testing or for disaster
2970 recovery. You should be aware that interoperability may be
2971 compromised by setting this value.
2974 .B MDADM_GROW_ALLOW_OLD
2975 If an array is stopped while it is performing a reshape and that
2976 reshape was making use of a backup file, then when the array is
2979 will sometimes complain that the backup file is too old. If this
2980 happens and you are certain it is the right backup file, you can
2981 over-ride this check by setting
2982 .B MDADM_GROW_ALLOW_OLD=1
2987 Any string given in this variable is added to the start of the
2989 line in the config file, or treated as the whole
2991 line if none is given. It can be used to disable certain metadata
2994 is called from a boot script. For example
2996 .B " export MDADM_CONF_AUTO='-ddf -imsm'
3000 does not automatically assemble any DDF or
3001 IMSM arrays that are found. This can be useful on systems configured
3002 to manage such arrays with
3008 .B " mdadm \-\-query /dev/name-of-device"
3010 This will find out if a given device is a RAID array, or is part of
3011 one, and will provide brief information about the device.
3013 .B " mdadm \-\-assemble \-\-scan"
3015 This will assemble and start all arrays listed in the standard config
3016 file. This command will typically go in a system startup file.
3018 .B " mdadm \-\-stop \-\-scan"
3020 This will shut down all arrays that can be shut down (i.e. are not
3021 currently in use). This will typically go in a system shutdown script.
3023 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
3025 If (and only if) there is an Email address or program given in the
3026 standard config file, then
3027 monitor the status of all arrays listed in that file by
3028 polling them ever 2 minutes.
3030 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
3032 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
3035 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
3037 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
3039 This will create a prototype config file that describes currently
3040 active arrays that are known to be made from partitions of IDE or SCSI drives.
3041 This file should be reviewed before being used as it may
3042 contain unwanted detail.
3044 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
3046 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
3048 This will find arrays which could be assembled from existing IDE and
3049 SCSI whole drives (not partitions), and store the information in the
3050 format of a config file.
3051 This file is very likely to contain unwanted detail, particularly
3054 entries. It should be reviewed and edited before being used as an
3057 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
3059 .B " mdadm \-Ebsc partitions"
3061 Create a list of devices by reading
3062 .BR /proc/partitions ,
3063 scan these for RAID superblocks, and printout a brief listing of all
3066 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
3068 Scan all partitions and devices listed in
3069 .BR /proc/partitions
3072 out of all such devices with a RAID superblock with a minor number of 0.
3074 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /run/mdadm/mon.pid"
3076 If config file contains a mail address or alert program, run mdadm in
3077 the background in monitor mode monitoring all md devices. Also write
3078 pid of mdadm daemon to
3079 .BR /run/mdadm/mon.pid .
3081 .B " mdadm \-Iq /dev/somedevice"
3083 Try to incorporate newly discovered device into some array as
3086 .B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan"
3088 Rebuild the array map from any current arrays, and then start any that
3091 .B " mdadm /dev/md4 --fail detached --remove detached"
3093 Any devices which are components of /dev/md4 will be marked as faulty
3094 and then remove from the array.
3096 .B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
3100 which is currently a RAID5 array will be converted to RAID6. There
3101 should normally already be a spare drive attached to the array as a
3102 RAID6 needs one more drive than a matching RAID5.
3104 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
3106 Create a DDF array over 6 devices.
3108 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
3110 Create a RAID5 array over any 3 devices in the given DDF set. Use
3111 only 30 gigabytes of each device.
3113 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
3115 Assemble a pre-exist ddf array.
3117 .B " mdadm -I /dev/md/ddf1"
3119 Assemble all arrays contained in the ddf array, assigning names as
3122 .B " mdadm \-\-create \-\-help"
3124 Provide help about the Create mode.
3126 .B " mdadm \-\-config \-\-help"
3128 Provide help about the format of the config file.
3130 .B " mdadm \-\-help"
3132 Provide general help.
3142 lists all active md devices with information about them.
3144 uses this to find arrays when
3146 is given in Misc mode, and to monitor array reconstruction
3151 The config file lists which devices may be scanned to see if
3152 they contain MD super block, and gives identifying information
3153 (e.g. UUID) about known MD arrays. See
3157 .SS /etc/mdadm.conf.d
3159 A directory containing configuration files which are read in lexical
3165 mode is used, this file gets a list of arrays currently being created.
3170 understand two sorts of names for array devices.
3172 The first is the so-called 'standard' format name, which matches the
3173 names used by the kernel and which appear in
3176 The second sort can be freely chosen, but must reside in
3178 When giving a device name to
3180 to create or assemble an array, either full path name such as
3184 can be given, or just the suffix of the second sort of name, such as
3190 chooses device names during auto-assembly or incremental assembly, it
3191 will sometimes add a small sequence number to the end of the name to
3192 avoid conflicted between multiple arrays that have the same name. If
3194 can reasonably determine that the array really is meant for this host,
3195 either by a hostname in the metadata, or by the presence of the array
3198 then it will leave off the suffix if possible.
3199 Also if the homehost is specified as
3202 will only use a suffix if a different array of the same name already
3203 exists or is listed in the config file.
3205 The standard names for non-partitioned arrays (the only sort of md
3206 array available in 2.4 and earlier) are of the form
3210 where NN is a number.
3211 The standard names for partitionable arrays (as available from 2.6
3212 onwards) are of the form:
3216 Partition numbers should be indicated by adding "pMM" to these, thus "/dev/md/d1p2".
3218 From kernel version 2.6.28 the "non-partitioned array" can actually
3219 be partitioned. So the "md_d\fBNN\fP"
3220 names are no longer needed, and
3221 partitions such as "/dev/md\fBNN\fPp\fBXX\fP"
3224 From kernel version 2.6.29 standard names can be non-numeric following
3231 is any string. These names are supported by
3233 since version 3.3 provided they are enabled in
3238 was previously known as
3242 For further information on mdadm usage, MD and the various levels of
3245 .B http://raid.wiki.kernel.org/
3247 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
3249 The latest version of
3251 should always be available from
3253 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob