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 Kibibytes) 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 'M' or 'G' can be given to indicate 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 'M' or 'G' can be given to indicate 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 kibibytes. 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 'M' or 'G' can be given to indicate 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 'M' or 'G' can be given to indicate 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 an 'M' or 'G' suffix is given.
815 can also be used with
817 for some RAID levels (initially on RAID10). This allows the
818 data\-offset to be changed as part of the reshape process. When the
819 data offset is changed, no backup file is required as the difference
820 in offsets is used to provide the same functionality.
822 When the new offset is earlier than the old offset, the number of
823 devices in the array cannot shrink. When it is after the old offset,
824 the number of devices in the array cannot increase.
826 When creating an array,
830 In the case each member device is expected to have a offset appended
831 to the name, separated by a colon. This makes it possible to recreate
832 exactly an array which has varying data offsets (as can happen when
833 different versions of
835 are used to add different devices).
839 This option is complementary to the
840 .B \-\-freeze-reshape
841 option for assembly. It is needed when
843 operation is interrupted and it is not restarted automatically due to
844 .B \-\-freeze-reshape
845 usage during array assembly. This option is used together with
849 ) command and device for a pending reshape to be continued.
850 All parameters required for reshape continuation will be read from array metadata.
854 .BR \-\-backup\-file=
855 option to be set, continuation option will require to have exactly the same
856 backup file given as well.
858 Any other parameter passed together with
860 option will be ignored.
863 .BR \-N ", " \-\-name=
866 for the array. This is currently only effective when creating an
867 array with a version-1 superblock, or an array in a DDF container.
868 The name is a simple textual string that can be used to identify array
869 components when assembling. If name is needed but not specified, it
870 is taken from the basename of the device that is being created.
882 run the array, even if some of the components
883 appear to be active in another array or filesystem. Normally
885 will ask for confirmation before including such components in an
886 array. This option causes that question to be suppressed.
889 .BR \-f ", " \-\-force
892 accept the geometry and layout specified without question. Normally
894 will not allow creation of an array with only one device, and will try
895 to create a RAID5 array with one missing drive (as this makes the
896 initial resync work faster). With
899 will not try to be so clever.
902 .BR \-o ", " \-\-readonly
905 rather than read-write as normal. No writes will be allowed to the
906 array, and no resync, recovery, or reshape will be started.
909 .BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
910 Instruct mdadm how to create the device file if needed, possibly allocating
911 an unused minor number. "md" causes a non-partitionable array
912 to be used (though since Linux 2.6.28, these array devices are in fact
913 partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
914 later) to be used. "yes" requires the named md device to have
915 a 'standard' format, and the type and minor number will be determined
916 from this. With mdadm 3.0, device creation is normally left up to
918 so this option is unlikely to be needed.
919 See DEVICE NAMES below.
921 The argument can also come immediately after
926 is not given on the command line or in the config file, then
932 is also given, then any
934 entries in the config file will override the
936 instruction given on the command line.
938 For partitionable arrays,
940 will create the device file for the whole array and for the first 4
941 partitions. A different number of partitions can be specified at the
942 end of this option (e.g.
944 If the device name ends with a digit, the partition names add a 'p',
946 .IR /dev/md/home1p3 .
947 If there is no trailing digit, then the partition names just have a
949 .IR /dev/md/scratch3 .
951 If the md device name is in a 'standard' format as described in DEVICE
952 NAMES, then it will be created, if necessary, with the appropriate
953 device number based on that name. If the device name is not in one of these
954 formats, then a unused device number will be allocated. The device
955 number will be considered unused if there is no active array for that
956 number, and there is no entry in /dev for that number and with a
957 non-standard name. Names that are not in 'standard' format are only
958 allowed in "/dev/md/".
960 This is meaningful with
966 .BR \-a ", " "\-\-add"
967 This option can be used in Grow mode in two cases.
969 If the target array is a Linear array, then
971 can be used to add one or more devices to the array. They
972 are simply catenated on to the end of the array. Once added, the
973 devices cannot be removed.
977 option is being used to increase the number of devices in an array,
980 can be used to add some extra devices to be included in the array.
981 In most cases this is not needed as the extra devices can be added as
982 spares first, and then the number of raid-disks can be changed.
983 However for RAID0, it is not possible to add spares. So to increase
984 the number of devices in a RAID0, it is necessary to set the new
985 number of devices, and to add the new devices, in the same command.
989 Only works when the array is for clustered environment. It specifies
990 the maximum number of nodes in the cluster that will use this device
991 simultaneously. If not specified, this defaults to 4.
994 .BR \-\-write-journal
995 Specify journal device for the RAID-4/5/6 array. The journal device
996 should be a SSD with reasonable lifetime.
1002 .BR \-u ", " \-\-uuid=
1003 uuid of array to assemble. Devices which don't have this uuid are
1007 .BR \-m ", " \-\-super\-minor=
1008 Minor number of device that array was created for. Devices which
1009 don't have this minor number are excluded. If you create an array as
1010 /dev/md1, then all superblocks will contain the minor number 1, even if
1011 the array is later assembled as /dev/md2.
1013 Giving the literal word "dev" for
1017 to use the minor number of the md device that is being assembled.
1018 e.g. when assembling
1020 .B \-\-super\-minor=dev
1021 will look for super blocks with a minor number of 0.
1024 is only relevant for v0.90 metadata, and should not normally be used.
1030 .BR \-N ", " \-\-name=
1031 Specify the name of the array to assemble. This must be the name
1032 that was specified when creating the array. It must either match
1033 the name stored in the superblock exactly, or it must match
1036 prefixed to the start of the given name.
1039 .BR \-f ", " \-\-force
1040 Assemble the array even if the metadata on some devices appears to be
1043 cannot find enough working devices to start the array, but can find
1044 some devices that are recorded as having failed, then it will mark
1045 those devices as working so that the array can be started.
1046 An array which requires
1048 to be started may contain data corruption. Use it carefully.
1051 .BR \-R ", " \-\-run
1052 Attempt to start the array even if fewer drives were given than were
1053 present last time the array was active. Normally if not all the
1054 expected drives are found and
1056 is not used, then the array will be assembled but not started.
1059 an attempt will be made to start it anyway.
1063 This is the reverse of
1065 in that it inhibits the startup of array unless all expected drives
1066 are present. This is only needed with
1068 and can be used if the physical connections to devices are
1069 not as reliable as you would like.
1072 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
1073 See this option under Create and Build options.
1076 .BR \-b ", " \-\-bitmap=
1077 Specify the bitmap file that was given when the array was created. If
1080 bitmap, there is no need to specify this when assembling the array.
1083 .BR \-\-backup\-file=
1086 was used while reshaping an array (e.g. changing number of devices or
1087 chunk size) and the system crashed during the critical section, then the same
1089 must be presented to
1091 to allow possibly corrupted data to be restored, and the reshape
1095 .BR \-\-invalid\-backup
1096 If the file needed for the above option is not available for any
1097 reason an empty file can be given together with this option to
1098 indicate that the backup file is invalid. In this case the data that
1099 was being rearranged at the time of the crash could be irrecoverably
1100 lost, but the rest of the array may still be recoverable. This option
1101 should only be used as a last resort if there is no way to recover the
1106 .BR \-U ", " \-\-update=
1107 Update the superblock on each device while assembling the array. The
1108 argument given to this flag can be one of
1128 option will adjust the superblock of an array what was created on a Sparc
1129 machine running a patched 2.2 Linux kernel. This kernel got the
1130 alignment of part of the superblock wrong. You can use the
1131 .B "\-\-examine \-\-sparc2.2"
1134 to see what effect this would have.
1138 option will update the
1139 .B "preferred minor"
1140 field on each superblock to match the minor number of the array being
1142 This can be useful if
1144 reports a different "Preferred Minor" to
1146 In some cases this update will be performed automatically
1147 by the kernel driver. In particular the update happens automatically
1148 at the first write to an array with redundancy (RAID level 1 or
1149 greater) on a 2.6 (or later) kernel.
1153 option will change the uuid of the array. If a UUID is given with the
1155 option that UUID will be used as a new UUID and will
1157 be used to help identify the devices in the array.
1160 is given, a random UUID is chosen.
1164 option will change the
1166 of the array as stored in the superblock and bitmap. This option only
1167 works for clustered environment.
1171 option will change the
1173 of the array as stored in the superblock. This is only supported for
1174 version-1 superblocks.
1178 option will change the
1180 as recorded in the superblock. For version-0 superblocks, this is the
1181 same as updating the UUID.
1182 For version-1 superblocks, this involves updating the name.
1186 option will change the cluster name as recorded in the superblock and
1187 bitmap. This option only works for clustered environment.
1191 option will cause the array to be marked
1193 meaning that any redundancy in the array (e.g. parity for RAID5,
1194 copies for RAID1) may be incorrect. This will cause the RAID system
1195 to perform a "resync" pass to make sure that all redundant information
1200 option allows arrays to be moved between machines with different
1202 When assembling such an array for the first time after a move, giving
1203 .B "\-\-update=byteorder"
1206 to expect superblocks to have their byteorder reversed, and will
1207 correct that order before assembling the array. This is only valid
1208 with original (Version 0.90) superblocks.
1212 option will correct the summaries in the superblock. That is the
1213 counts of total, working, active, failed, and spare devices.
1217 option will rarely be of use. It applies to version 1.1 and 1.2 metadata
1218 only (where the metadata is at the start of the device) and is only
1219 useful when the component device has changed size (typically become
1220 larger). The version 1 metadata records the amount of the device that
1221 can be used to store data, so if a device in a version 1.1 or 1.2
1222 array becomes larger, the metadata will still be visible, but the
1223 extra space will not. In this case it might be useful to assemble the
1225 .BR \-\-update=devicesize .
1228 to determine the maximum usable amount of space on each device and
1229 update the relevant field in the metadata.
1233 option only works on v0.90 metadata arrays and will convert them to
1234 v1.0 metadata. The array must not be dirty (i.e. it must not need a
1235 sync) and it must not have a write-intent bitmap.
1237 The old metadata will remain on the devices, but will appear older
1238 than the new metadata and so will usually be ignored. The old metadata
1239 (or indeed the new metadata) can be removed by giving the appropriate
1242 .BR \-\-zero\-superblock .
1246 option can be used when an array has an internal bitmap which is
1247 corrupt in some way so that assembling the array normally fails. It
1248 will cause any internal bitmap to be ignored.
1252 option will reserve space in each device for a bad block list. This
1253 will be 4K in size and positioned near the end of any free space
1254 between the superblock and the data.
1258 option will cause any reservation of space for a bad block list to be
1259 removed. If the bad block list contains entries, this will fail, as
1260 removing the list could cause data corruption.
1263 .BR \-\-freeze\-reshape
1264 Option is intended to be used in start-up scripts during initrd boot phase.
1265 When array under reshape is assembled during initrd phase, this option
1266 stops reshape after reshape critical section is being restored. This happens
1267 before file system pivot operation and avoids loss of file system context.
1268 Losing file system context would cause reshape to be broken.
1270 Reshape can be continued later using the
1272 option for the grow command.
1274 .SH For Manage mode:
1277 .BR \-t ", " \-\-test
1278 Unless a more serious error occurred,
1280 will exit with a status of 2 if no changes were made to the array and
1281 0 if at least one change was made.
1282 This can be useful when an indirect specifier such as
1287 is used in requesting an operation on the array.
1289 will report failure if these specifiers didn't find any match.
1292 .BR \-a ", " \-\-add
1293 hot-add listed devices.
1294 If a device appears to have recently been part of the array
1295 (possibly it failed or was removed) the device is re\-added as described
1297 If that fails or the device was never part of the array, the device is
1298 added as a hot-spare.
1299 If the array is degraded, it will immediately start to rebuild data
1302 Note that this and the following options are only meaningful on array
1303 with redundancy. They don't apply to RAID0 or Linear.
1307 re\-add a device that was previously removed from an array.
1308 If the metadata on the device reports that it is a member of the
1309 array, and the slot that it used is still vacant, then the device will
1310 be added back to the array in the same position. This will normally
1311 cause the data for that device to be recovered. However based on the
1312 event count on the device, the recovery may only require sections that
1313 are flagged a write-intent bitmap to be recovered or may not require
1314 any recovery at all.
1316 When used on an array that has no metadata (i.e. it was built with
1318 it will be assumed that bitmap-based recovery is enough to make the
1319 device fully consistent with the array.
1321 When used with v1.x metadata,
1323 can be accompanied by
1324 .BR \-\-update=devicesize ,
1325 .BR \-\-update=bbl ", or"
1326 .BR \-\-update=no\-bbl .
1327 See the description of these option when used in Assemble mode for an
1328 explanation of their use.
1330 If the device name given is
1334 will try to find any device that looks like it should be
1335 part of the array but isn't and will try to re\-add all such devices.
1337 If the device name given is
1341 will find all devices in the array that are marked
1343 remove them and attempt to immediately re\-add them. This can be
1344 useful if you are certain that the reason for failure has been
1349 Add a device as a spare. This is similar to
1351 except that it does not attempt
1353 first. The device will be added as a spare even if it looks like it
1354 could be an recent member of the array.
1357 .BR \-r ", " \-\-remove
1358 remove listed devices. They must not be active. i.e. they should
1359 be failed or spare devices.
1361 As well as the name of a device file
1371 The first causes all failed device to be removed. The second causes
1372 any device which is no longer connected to the system (i.e an 'open'
1376 The third will remove a set as describe below under
1380 .BR \-f ", " \-\-fail
1381 Mark listed devices as faulty.
1382 As well as the name of a device file, the word
1386 can be given. The former will cause any device that has been detached from
1387 the system to be marked as failed. It can then be removed.
1389 For RAID10 arrays where the number of copies evenly divides the number
1390 of devices, the devices can be conceptually divided into sets where
1391 each set contains a single complete copy of the data on the array.
1392 Sometimes a RAID10 array will be configured so that these sets are on
1393 separate controllers. In this case all the devices in one set can be
1394 failed by giving a name like
1400 The appropriate set names are reported by
1410 Mark listed devices as requiring replacement. As soon as a spare is
1411 available, it will be rebuilt and will replace the marked device.
1412 This is similar to marking a device as faulty, but the device remains
1413 in service during the recovery process to increase resilience against
1414 multiple failures. When the replacement process finishes, the
1415 replaced device will be marked as faulty.
1419 This can follow a list of
1421 devices. The devices listed after
1423 will be preferentially used to replace the devices listed after
1425 These device must already be spare devices in the array.
1428 .BR \-\-write\-mostly
1429 Subsequent devices that are added or re\-added will have the 'write-mostly'
1430 flag set. This is only valid for RAID1 and means that the 'md' driver
1431 will avoid reading from these devices if possible.
1434 Subsequent devices that are added or re\-added will have the 'write-mostly'
1437 .BR \-\-cluster\-confirm
1438 Confirm the existence of the device. This is issued in response to an \-\-add
1439 request by a node in a cluster. When a node adds a device it sends a message
1440 to all nodes in the cluster to look for a device with a UUID. This translates
1441 to a udev notification with the UUID of the device to be added and the slot
1442 number. The receiving node must acknowledge this message
1443 with \-\-cluster\-confirm. Valid arguments are <slot>:<devicename> in case
1444 the device is found or <slot>:missing in case the device is not found.
1447 Each of these options requires that the first device listed is the array
1448 to be acted upon, and the remainder are component devices to be added,
1449 removed, marked as faulty, etc. Several different operations can be
1450 specified for different devices, e.g.
1452 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1454 Each operation applies to all devices listed until the next
1457 If an array is using a write-intent bitmap, then devices which have
1458 been removed can be re\-added in a way that avoids a full
1459 reconstruction but instead just updates the blocks that have changed
1460 since the device was removed. For arrays with persistent metadata
1461 (superblocks) this is done automatically. For arrays created with
1463 mdadm needs to be told that this device we removed recently with
1466 Devices can only be removed from an array if they are not in active
1467 use, i.e. that must be spares or failed devices. To remove an active
1468 device, it must first be marked as
1474 .BR \-Q ", " \-\-query
1475 Examine a device to see
1476 (1) if it is an md device and (2) if it is a component of an md
1478 Information about what is discovered is presented.
1481 .BR \-D ", " \-\-detail
1482 Print details of one or more md devices.
1485 .BR \-\-detail\-platform
1486 Print details of the platform's RAID capabilities (firmware / hardware
1487 topology) for a given metadata format. If used without argument, mdadm
1488 will scan all controllers looking for their capabilities. Otherwise, mdadm
1489 will only look at the controller specified by the argument in form of an
1490 absolute filepath or a link, e.g.
1491 .IR /sys/devices/pci0000:00/0000:00:1f.2 .
1494 .BR \-Y ", " \-\-export
1497 .BR \-\-detail-platform ,
1501 output will be formatted as
1503 pairs for easy import into the environment.
1509 indicates whether an array was started
1511 or not, which may include a reason
1512 .RB ( unsafe ", " nothing ", " no ).
1515 indicates if the array is expected on this host
1517 or seems to be from elsewhere
1521 .BR \-E ", " \-\-examine
1522 Print contents of the metadata stored on the named device(s).
1523 Note the contrast between
1528 applies to devices which are components of an array, while
1530 applies to a whole array which is currently active.
1533 If an array was created on a SPARC machine with a 2.2 Linux kernel
1534 patched with RAID support, the superblock will have been created
1535 incorrectly, or at least incompatibly with 2.4 and later kernels.
1540 will fix the superblock before displaying it. If this appears to do
1541 the right thing, then the array can be successfully assembled using
1542 .BR "\-\-assemble \-\-update=sparc2.2" .
1545 .BR \-X ", " \-\-examine\-bitmap
1546 Report information about a bitmap file.
1547 The argument is either an external bitmap file or an array component
1548 in case of an internal bitmap. Note that running this on an array
1551 does not report the bitmap for that array.
1554 .B \-\-examine\-badblocks
1555 List the bad-blocks recorded for the device, if a bad-blocks list has
1556 been configured. Currently only
1558 metadata supports bad-blocks lists.
1561 .BI \-\-dump= directory
1563 .BI \-\-restore= directory
1564 Save metadata from lists devices, or restore metadata to listed devices.
1567 .BR \-R ", " \-\-run
1568 start a partially assembled array. If
1570 did not find enough devices to fully start the array, it might leaving
1571 it partially assembled. If you wish, you can then use
1573 to start the array in degraded mode.
1576 .BR \-S ", " \-\-stop
1577 deactivate array, releasing all resources.
1580 .BR \-o ", " \-\-readonly
1581 mark array as readonly.
1584 .BR \-w ", " \-\-readwrite
1585 mark array as readwrite.
1588 .B \-\-zero\-superblock
1589 If the device contains a valid md superblock, the block is
1590 overwritten with zeros. With
1592 the block where the superblock would be is overwritten even if it
1593 doesn't appear to be valid.
1596 .B \-\-kill\-subarray=
1597 If the device is a container and the argument to \-\-kill\-subarray
1598 specifies an inactive subarray in the container, then the subarray is
1599 deleted. Deleting all subarrays will leave an 'empty-container' or
1600 spare superblock on the drives. See
1601 .B \-\-zero\-superblock
1603 removing a superblock. Note that some formats depend on the subarray
1604 index for generating a UUID, this command will fail if it would change
1605 the UUID of an active subarray.
1608 .B \-\-update\-subarray=
1609 If the device is a container and the argument to \-\-update\-subarray
1610 specifies a subarray in the container, then attempt to update the given
1611 superblock field in the subarray. See below in
1616 .BR \-t ", " \-\-test
1621 is set to reflect the status of the device. See below in
1626 .BR \-W ", " \-\-wait
1627 For each md device given, wait for any resync, recovery, or reshape
1628 activity to finish before returning.
1630 will return with success if it actually waited for every device
1631 listed, otherwise it will return failure.
1635 For each md device given, or each device in /proc/mdstat if
1637 is given, arrange for the array to be marked clean as soon as possible.
1639 will return with success if the array uses external metadata and we
1640 successfully waited. For native arrays this returns immediately as the
1641 kernel handles dirty-clean transitions at shutdown. No action is taken
1642 if safe-mode handling is disabled.
1646 Set the "sync_action" for all md devices given to one of
1653 will abort any currently running action though some actions will
1654 automatically restart.
1657 will abort any current action and ensure no other action starts
1667 .BR "SCRUBBING AND MISMATCHES" .
1669 .SH For Incremental Assembly mode:
1671 .BR \-\-rebuild\-map ", " \-r
1672 Rebuild the map file
1676 uses to help track which arrays are currently being assembled.
1679 .BR \-\-run ", " \-R
1680 Run any array assembled as soon as a minimal number of devices are
1681 available, rather than waiting until all expected devices are present.
1684 .BR \-\-scan ", " \-s
1685 Only meaningful with
1689 file for arrays that are being incrementally assembled and will try to
1690 start any that are not already started. If any such array is listed
1693 as requiring an external bitmap, that bitmap will be attached first.
1696 .BR \-\-fail ", " \-f
1697 This allows the hot-plug system to remove devices that have fully disappeared
1698 from the kernel. It will first fail and then remove the device from any
1699 array it belongs to.
1700 The device name given should be a kernel device name such as "sda",
1706 Only used with \-\-fail. The 'path' given will be recorded so that if
1707 a new device appears at the same location it can be automatically
1708 added to the same array. This allows the failed device to be
1709 automatically replaced by a new device without metadata if it appears
1710 at specified path. This option is normally only set by a
1714 .SH For Monitor mode:
1716 .BR \-m ", " \-\-mail
1717 Give a mail address to send alerts to.
1720 .BR \-p ", " \-\-program ", " \-\-alert
1721 Give a program to be run whenever an event is detected.
1724 .BR \-y ", " \-\-syslog
1725 Cause all events to be reported through 'syslog'. The messages have
1726 facility of 'daemon' and varying priorities.
1729 .BR \-d ", " \-\-delay
1730 Give a delay in seconds.
1732 polls the md arrays and then waits this many seconds before polling
1733 again. The default is 60 seconds. Since 2.6.16, there is no need to
1734 reduce this as the kernel alerts
1736 immediately when there is any change.
1739 .BR \-r ", " \-\-increment
1740 Give a percentage increment.
1742 will generate RebuildNN events with the given percentage increment.
1745 .BR \-f ", " \-\-daemonise
1748 to run as a background daemon if it decides to monitor anything. This
1749 causes it to fork and run in the child, and to disconnect from the
1750 terminal. The process id of the child is written to stdout.
1753 which will only continue monitoring if a mail address or alert program
1754 is found in the config file.
1757 .BR \-i ", " \-\-pid\-file
1760 is running in daemon mode, write the pid of the daemon process to
1761 the specified file, instead of printing it on standard output.
1764 .BR \-1 ", " \-\-oneshot
1765 Check arrays only once. This will generate
1767 events and more significantly
1773 .B " mdadm \-\-monitor \-\-scan \-1"
1775 from a cron script will ensure regular notification of any degraded arrays.
1778 .BR \-t ", " \-\-test
1781 alert for every array found at startup. This alert gets mailed and
1782 passed to the alert program. This can be used for testing that alert
1783 message do get through successfully.
1787 This inhibits the functionality for moving spares between arrays.
1788 Only one monitoring process started with
1790 but without this flag is allowed, otherwise the two could interfere
1797 .B mdadm \-\-assemble
1798 .I md-device options-and-component-devices...
1801 .B mdadm \-\-assemble \-\-scan
1802 .I md-devices-and-options...
1805 .B mdadm \-\-assemble \-\-scan
1809 This usage assembles one or more RAID arrays from pre-existing components.
1810 For each array, mdadm needs to know the md device, the identity of the
1811 array, and a number of component-devices. These can be found in a number of ways.
1813 In the first usage example (without the
1815 the first device given is the md device.
1816 In the second usage example, all devices listed are treated as md
1817 devices and assembly is attempted.
1818 In the third (where no devices are listed) all md devices that are
1819 listed in the configuration file are assembled. If no arrays are
1820 described by the configuration file, then any arrays that
1821 can be found on unused devices will be assembled.
1823 If precisely one device is listed, but
1829 was given and identity information is extracted from the configuration file.
1831 The identity can be given with the
1837 option, will be taken from the md-device record in the config file, or
1838 will be taken from the super block of the first component-device
1839 listed on the command line.
1841 Devices can be given on the
1843 command line or in the config file. Only devices which have an md
1844 superblock which contains the right identity will be considered for
1847 The config file is only used if explicitly named with
1849 or requested with (a possibly implicit)
1854 .B /etc/mdadm/mdadm.conf
1859 is not given, then the config file will only be used to find the
1860 identity of md arrays.
1862 Normally the array will be started after it is assembled. However if
1864 is not given and not all expected drives were listed, then the array
1865 is not started (to guard against usage errors). To insist that the
1866 array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1875 does not create any entries in
1879 It does record information in
1883 to choose the correct name.
1887 detects that udev is not configured, it will create the devices in
1891 In Linux kernels prior to version 2.6.28 there were two distinctly
1892 different types of md devices that could be created: one that could be
1893 partitioned using standard partitioning tools and one that could not.
1894 Since 2.6.28 that distinction is no longer relevant as both type of
1895 devices can be partitioned.
1897 will normally create the type that originally could not be partitioned
1898 as it has a well defined major number (9).
1900 Prior to 2.6.28, it is important that mdadm chooses the correct type
1901 of array device to use. This can be controlled with the
1903 option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1904 to use a partitionable device rather than the default.
1906 In the no-udev case, the value given to
1908 can be suffixed by a number. This tells
1910 to create that number of partition devices rather than the default of 4.
1914 can also be given in the configuration file as a word starting
1916 on the ARRAY line for the relevant array.
1923 and no devices are listed,
1925 will first attempt to assemble all the arrays listed in the config
1928 If no arrays are listed in the config (other than those marked
1930 it will look through the available devices for possible arrays and
1931 will try to assemble anything that it finds. Arrays which are tagged
1932 as belonging to the given homehost will be assembled and started
1933 normally. Arrays which do not obviously belong to this host are given
1934 names that are expected not to conflict with anything local, and are
1935 started "read-auto" so that nothing is written to any device until the
1936 array is written to. i.e. automatic resync etc is delayed.
1940 finds a consistent set of devices that look like they should comprise
1941 an array, and if the superblock is tagged as belonging to the given
1942 home host, it will automatically choose a device name and try to
1943 assemble the array. If the array uses version-0.90 metadata, then the
1945 number as recorded in the superblock is used to create a name in
1949 If the array uses version-1 metadata, then the
1951 from the superblock is used to similarly create a name in
1953 (the name will have any 'host' prefix stripped first).
1955 This behaviour can be modified by the
1959 configuration file. This line can indicate that specific metadata
1960 type should, or should not, be automatically assembled. If an array
1961 is found which is not listed in
1963 and has a metadata format that is denied by the
1965 line, then it will not be assembled.
1968 line can also request that all arrays identified as being for this
1969 homehost should be assembled regardless of their metadata type.
1972 for further details.
1974 Note: Auto assembly cannot be used for assembling and activating some
1975 arrays which are undergoing reshape. In particular as the
1977 cannot be given, any reshape which requires a backup-file to continue
1978 cannot be started by auto assembly. An array which is growing to more
1979 devices and has passed the critical section can be assembled using
1990 .BI \-\-raid\-devices= Z
1994 This usage is similar to
1996 The difference is that it creates an array without a superblock. With
1997 these arrays there is no difference between initially creating the array and
1998 subsequently assembling the array, except that hopefully there is useful
1999 data there in the second case.
2001 The level may raid0, linear, raid1, raid10, multipath, or faulty, or
2002 one of their synonyms. All devices must be listed and the array will
2003 be started once complete. It will often be appropriate to use
2004 .B \-\-assume\-clean
2005 with levels raid1 or raid10.
2016 .BI \-\-raid\-devices= Z
2020 This usage will initialise a new md array, associate some devices with
2021 it, and activate the array.
2023 The named device will normally not exist when
2024 .I "mdadm \-\-create"
2025 is run, but will be created by
2027 once the array becomes active.
2029 As devices are added, they are checked to see if they contain RAID
2030 superblocks or filesystems. They are also checked to see if the variance in
2031 device size exceeds 1%.
2033 If any discrepancy is found, the array will not automatically be run, though
2036 can override this caution.
2038 To create a "degraded" array in which some devices are missing, simply
2039 give the word "\fBmissing\fP"
2040 in place of a device name. This will cause
2042 to leave the corresponding slot in the array empty.
2043 For a RAID4 or RAID5 array at most one slot can be
2044 "\fBmissing\fP"; for a RAID6 array at most two slots.
2045 For a RAID1 array, only one real device needs to be given. All of the
2049 When creating a RAID5 array,
2051 will automatically create a degraded array with an extra spare drive.
2052 This is because building the spare into a degraded array is in general
2053 faster than resyncing the parity on a non-degraded, but not clean,
2054 array. This feature can be overridden with the
2058 When creating an array with version-1 metadata a name for the array is
2060 If this is not given with the
2064 will choose a name based on the last component of the name of the
2065 device being created. So if
2067 is being created, then the name
2072 is being created, then the name
2076 When creating a partition based array, using
2078 with version-1.x metadata, the partition type should be set to
2080 (non fs-data). This type selection allows for greater precision since
2081 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
2082 might create problems in the event of array recovery through a live cdrom.
2084 A new array will normally get a randomly assigned 128bit UUID which is
2085 very likely to be unique. If you have a specific need, you can choose
2086 a UUID for the array by giving the
2088 option. Be warned that creating two arrays with the same UUID is a
2089 recipe for disaster. Also, using
2091 when creating a v0.90 array will silently override any
2096 .\"option is given, it is not necessary to list any component-devices in this command.
2097 .\"They can be added later, before a
2101 .\"is given, the apparent size of the smallest drive given is used.
2103 If the array type supports a write-intent bitmap, and if the devices
2104 in the array exceed 100G is size, an internal write-intent bitmap
2105 will automatically be added unless some other option is explicitly
2108 option. In any case space for a bitmap will be reserved so that one
2109 can be added layer with
2110 .BR "\-\-grow \-\-bitmap=internal" .
2112 If the metadata type supports it (currently only 1.x metadata), space
2113 will be allocated to store a bad block list. This allows a modest
2114 number of bad blocks to be recorded, allowing the drive to remain in
2115 service while only partially functional.
2117 When creating an array within a
2120 can be given either the list of devices to use, or simply the name of
2121 the container. The former case gives control over which devices in
2122 the container will be used for the array. The latter case allows
2124 to automatically choose which devices to use based on how much spare
2127 The General Management options that are valid with
2132 insist on running the array even if some devices look like they might
2137 start the array readonly \(em not supported yet.
2144 .I options... devices...
2147 This usage will allow individual devices in an array to be failed,
2148 removed or added. It is possible to perform multiple operations with
2149 on command. For example:
2151 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
2157 and will then remove it from the array and finally add it back
2158 in as a spare. However only one md array can be affected by a single
2161 When a device is added to an active array, mdadm checks to see if it
2162 has metadata on it which suggests that it was recently a member of the
2163 array. If it does, it tries to "re\-add" the device. If there have
2164 been no changes since the device was removed, or if the array has a
2165 write-intent bitmap which has recorded whatever changes there were,
2166 then the device will immediately become a full member of the array and
2167 those differences recorded in the bitmap will be resolved.
2177 MISC mode includes a number of distinct operations that
2178 operate on distinct devices. The operations are:
2181 The device is examined to see if it is
2182 (1) an active md array, or
2183 (2) a component of an md array.
2184 The information discovered is reported.
2188 The device should be an active md device.
2190 will display a detailed description of the array.
2194 will cause the output to be less detailed and the format to be
2195 suitable for inclusion in
2199 will normally be 0 unless
2201 failed to get useful information about the device(s); however, if the
2203 option is given, then the exit status will be:
2207 The array is functioning normally.
2210 The array has at least one failed device.
2213 The array has multiple failed devices such that it is unusable.
2216 There was an error while trying to get information about the device.
2220 .B \-\-detail\-platform
2221 Print detail of the platform's RAID capabilities (firmware / hardware
2222 topology). If the metadata is specified with
2226 then the return status will be:
2230 metadata successfully enumerated its platform components on this system
2233 metadata is platform independent
2236 metadata failed to find its platform components on this system
2240 .B \-\-update\-subarray=
2241 If the device is a container and the argument to \-\-update\-subarray
2242 specifies a subarray in the container, then attempt to update the given
2243 superblock field in the subarray. Similar to updating an array in
2244 "assemble" mode, the field to update is selected by
2248 option. Currently only
2254 option updates the subarray name in the metadata, it may not affect the
2255 device node name or the device node symlink until the subarray is
2256 re\-assembled. If updating
2258 would change the UUID of an active subarray this operation is blocked,
2259 and the command will end in an error.
2263 The device should be a component of an md array.
2265 will read the md superblock of the device and display the contents.
2270 is given, then multiple devices that are components of the one array
2271 are grouped together and reported in a single entry suitable
2277 without listing any devices will cause all devices listed in the
2278 config file to be examined.
2281 .BI \-\-dump= directory
2282 If the device contains RAID metadata, a file will be created in the
2284 and the metadata will be written to it. The file will be the same
2285 size as the device and have the metadata written in the file at the
2286 same locate that it exists in the device. However the file will be "sparse" so
2287 that only those blocks containing metadata will be allocated. The
2288 total space used will be small.
2290 The file name used in the
2292 will be the base name of the device. Further if any links appear in
2294 which point to the device, then hard links to the file will be created
2301 Multiple devices can be listed and their metadata will all be stored
2302 in the one directory.
2305 .BI \-\-restore= directory
2306 This is the reverse of
2309 will locate a file in the directory that has a name appropriate for
2310 the given device and will restore metadata from it. Names that match
2312 names are preferred, however if two of those refer to different files,
2314 will not choose between them but will abort the operation.
2316 If a file name is given instead of a
2320 will restore from that file to a single device, always provided the
2321 size of the file matches that of the device, and the file contains
2325 The devices should be active md arrays which will be deactivated, as
2326 long as they are not currently in use.
2330 This will fully activate a partially assembled md array.
2334 This will mark an active array as read-only, providing that it is
2335 not currently being used.
2341 array back to being read/write.
2345 For all operations except
2348 will cause the operation to be applied to all arrays listed in
2353 causes all devices listed in the config file to be examined.
2356 .BR \-b ", " \-\-brief
2357 Be less verbose. This is used with
2365 gives an intermediate level of verbosity.
2371 .B mdadm \-\-monitor
2372 .I options... devices...
2377 to periodically poll a number of md arrays and to report on any events
2380 will never exit once it decides that there are arrays to be checked,
2381 so it should normally be run in the background.
2383 As well as reporting events,
2385 may move a spare drive from one array to another if they are in the
2390 and if the destination array has a failed drive but no spares.
2392 If any devices are listed on the command line,
2394 will only monitor those devices. Otherwise all arrays listed in the
2395 configuration file will be monitored. Further, if
2397 is given, then any other md devices that appear in
2399 will also be monitored.
2401 The result of monitoring the arrays is the generation of events.
2402 These events are passed to a separate program (if specified) and may
2403 be mailed to a given E-mail address.
2405 When passing events to a program, the program is run once for each event,
2406 and is given 2 or 3 command-line arguments: the first is the
2407 name of the event (see below), the second is the name of the
2408 md device which is affected, and the third is the name of a related
2409 device if relevant (such as a component device that has failed).
2413 is given, then a program or an E-mail address must be specified on the
2414 command line or in the config file. If neither are available, then
2416 will not monitor anything.
2420 will continue monitoring as long as something was found to monitor. If
2421 no program or email is given, then each event is reported to
2424 The different events are:
2428 .B DeviceDisappeared
2429 An md array which previously was configured appears to no longer be
2430 configured. (syslog priority: Critical)
2434 was told to monitor an array which is RAID0 or Linear, then it will
2436 .B DeviceDisappeared
2437 with the extra information
2439 This is because RAID0 and Linear do not support the device-failed,
2440 hot-spare and resync operations which are monitored.
2444 An md array started reconstruction (e.g. recovery, resync, reshape,
2445 check, repair). (syslog priority: Warning)
2451 is a two-digit number (ie. 05, 48). This indicates that rebuild
2452 has passed that many percent of the total. The events are generated
2453 with fixed increment since 0. Increment size may be specified with
2454 a commandline option (default is 20). (syslog priority: Warning)
2458 An md array that was rebuilding, isn't any more, either because it
2459 finished normally or was aborted. (syslog priority: Warning)
2463 An active component device of an array has been marked as
2464 faulty. (syslog priority: Critical)
2468 A spare component device which was being rebuilt to replace a faulty
2469 device has failed. (syslog priority: Critical)
2473 A spare component device which was being rebuilt to replace a faulty
2474 device has been successfully rebuilt and has been made active.
2475 (syslog priority: Info)
2479 A new md array has been detected in the
2481 file. (syslog priority: Info)
2485 A newly noticed array appears to be degraded. This message is not
2488 notices a drive failure which causes degradation, but only when
2490 notices that an array is degraded when it first sees the array.
2491 (syslog priority: Critical)
2495 A spare drive has been moved from one array in a
2499 to another to allow a failed drive to be replaced.
2500 (syslog priority: Info)
2506 has been told, via the config file, that an array should have a certain
2507 number of spare devices, and
2509 detects that it has fewer than this number when it first sees the
2510 array, it will report a
2513 (syslog priority: Warning)
2517 An array was found at startup, and the
2520 (syslog priority: Info)
2530 cause Email to be sent. All events cause the program to be run.
2531 The program is run with two or three arguments: the event
2532 name, the array device and possibly a second device.
2534 Each event has an associated array device (e.g.
2536 and possibly a second device. For
2541 the second device is the relevant component device.
2544 the second device is the array that the spare was moved from.
2548 to move spares from one array to another, the different arrays need to
2549 be labeled with the same
2551 or the spares must be allowed to migrate through matching POLICY domains
2552 in the configuration file. The
2554 name can be any string; it is only necessary that different spare
2555 groups use different names.
2559 detects that an array in a spare group has fewer active
2560 devices than necessary for the complete array, and has no spare
2561 devices, it will look for another array in the same spare group that
2562 has a full complement of working drive and a spare. It will then
2563 attempt to remove the spare from the second drive and add it to the
2565 If the removal succeeds but the adding fails, then it is added back to
2568 If the spare group for a degraded array is not defined,
2570 will look at the rules of spare migration specified by POLICY lines in
2572 and then follow similar steps as above if a matching spare is found.
2575 The GROW mode is used for changing the size or shape of an active
2577 For this to work, the kernel must support the necessary change.
2578 Various types of growth are being added during 2.6 development.
2580 Currently the supported changes include
2582 change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
2584 increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
2587 change the chunk-size and layout of RAID0, RAID4, RAID5, RAID6 and RAID10.
2589 convert between RAID1 and RAID5, between RAID5 and RAID6, between
2590 RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
2592 add a write-intent bitmap to any array which supports these bitmaps, or
2593 remove a write-intent bitmap from such an array.
2596 Using GROW on containers is currently supported only for Intel's IMSM
2597 container format. The number of devices in a container can be
2598 increased - which affects all arrays in the container - or an array
2599 in a container can be converted between levels where those levels are
2600 supported by the container, and the conversion is on of those listed
2601 above. Resizing arrays in an IMSM container with
2603 is not yet supported.
2605 Grow functionality (e.g. expand a number of raid devices) for Intel's
2606 IMSM container format has an experimental status. It is guarded by the
2607 .B MDADM_EXPERIMENTAL
2608 environment variable which must be set to '1' for a GROW command to
2610 This is for the following reasons:
2613 Intel's native IMSM check-pointing is not fully tested yet.
2614 This can causes IMSM incompatibility during the grow process: an array
2615 which is growing cannot roam between Microsoft Windows(R) and Linux
2619 Interrupting a grow operation is not recommended, because it
2620 has not been fully tested for Intel's IMSM container format yet.
2623 Note: Intel's native checkpointing doesn't use
2625 option and it is transparent for assembly feature.
2628 Normally when an array is built the "size" is taken from the smallest
2629 of the drives. If all the small drives in an arrays are, one at a
2630 time, removed and replaced with larger drives, then you could have an
2631 array of large drives with only a small amount used. In this
2632 situation, changing the "size" with "GROW" mode will allow the extra
2633 space to start being used. If the size is increased in this way, a
2634 "resync" process will start to make sure the new parts of the array
2637 Note that when an array changes size, any filesystem that may be
2638 stored in the array will not automatically grow or shrink to use or
2639 vacate the space. The
2640 filesystem will need to be explicitly told to use the extra space
2641 after growing, or to reduce its size
2643 to shrinking the array.
2645 Also the size of an array cannot be changed while it has an active
2646 bitmap. If an array has a bitmap, it must be removed before the size
2647 can be changed. Once the change is complete a new bitmap can be created.
2649 .SS RAID\-DEVICES CHANGES
2651 A RAID1 array can work with any number of devices from 1 upwards
2652 (though 1 is not very useful). There may be times which you want to
2653 increase or decrease the number of active devices. Note that this is
2654 different to hot-add or hot-remove which changes the number of
2657 When reducing the number of devices in a RAID1 array, the slots which
2658 are to be removed from the array must already be vacant. That is, the
2659 devices which were in those slots must be failed and removed.
2661 When the number of devices is increased, any hot spares that are
2662 present will be activated immediately.
2664 Changing the number of active devices in a RAID5 or RAID6 is much more
2665 effort. Every block in the array will need to be read and written
2666 back to a new location. From 2.6.17, the Linux Kernel is able to
2667 increase the number of devices in a RAID5 safely, including restarting
2668 an interrupted "reshape". From 2.6.31, the Linux Kernel is able to
2669 increase or decrease the number of devices in a RAID5 or RAID6.
2671 From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4
2674 uses this functionality and the ability to add
2675 devices to a RAID4 to allow devices to be added to a RAID0. When
2676 requested to do this,
2678 will convert the RAID0 to a RAID4, add the necessary disks and make
2679 the reshape happen, and then convert the RAID4 back to RAID0.
2681 When decreasing the number of devices, the size of the array will also
2682 decrease. If there was data in the array, it could get destroyed and
2683 this is not reversible, so you should firstly shrink the filesystem on
2684 the array to fit within the new size. To help prevent accidents,
2686 requires that the size of the array be decreased first with
2687 .BR "mdadm --grow --array-size" .
2688 This is a reversible change which simply makes the end of the array
2689 inaccessible. The integrity of any data can then be checked before
2690 the non-reversible reduction in the number of devices is request.
2692 When relocating the first few stripes on a RAID5 or RAID6, it is not
2693 possible to keep the data on disk completely consistent and
2694 crash-proof. To provide the required safety, mdadm disables writes to
2695 the array while this "critical section" is reshaped, and takes a
2696 backup of the data that is in that section. For grows, this backup may be
2697 stored in any spare devices that the array has, however it can also be
2698 stored in a separate file specified with the
2700 option, and is required to be specified for shrinks, RAID level
2701 changes and layout changes. If this option is used, and the system
2702 does crash during the critical period, the same file must be passed to
2704 to restore the backup and reassemble the array. When shrinking rather
2705 than growing the array, the reshape is done from the end towards the
2706 beginning, so the "critical section" is at the end of the reshape.
2710 Changing the RAID level of any array happens instantaneously. However
2711 in the RAID5 to RAID6 case this requires a non-standard layout of the
2712 RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is
2713 required before the change can be accomplished. So while the level
2714 change is instant, the accompanying layout change can take quite a
2717 is required. If the array is not simultaneously being grown or
2718 shrunk, so that the array size will remain the same - for example,
2719 reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
2720 be used not just for a "cricital section" but throughout the reshape
2721 operation, as described below under LAYOUT CHANGES.
2723 .SS CHUNK-SIZE AND LAYOUT CHANGES
2725 Changing the chunk-size of layout without also changing the number of
2726 devices as the same time will involve re-writing all blocks in-place.
2727 To ensure against data loss in the case of a crash, a
2729 must be provided for these changes. Small sections of the array will
2730 be copied to the backup file while they are being rearranged. This
2731 means that all the data is copied twice, once to the backup and once
2732 to the new layout on the array, so this type of reshape will go very
2735 If the reshape is interrupted for any reason, this backup file must be
2737 .B "mdadm --assemble"
2738 so the array can be reassembled. Consequently the file cannot be
2739 stored on the device being reshaped.
2744 A write-intent bitmap can be added to, or removed from, an active
2745 array. Either internal bitmaps, or bitmaps stored in a separate file,
2746 can be added. Note that if you add a bitmap stored in a file which is
2747 in a filesystem that is on the RAID array being affected, the system
2748 will deadlock. The bitmap must be on a separate filesystem.
2750 .SH INCREMENTAL MODE
2754 .B mdadm \-\-incremental
2758 .RI [ optional-aliases-for-device ]
2761 .B mdadm \-\-incremental \-\-fail
2765 .B mdadm \-\-incremental \-\-rebuild\-map
2768 .B mdadm \-\-incremental \-\-run \-\-scan
2771 This mode is designed to be used in conjunction with a device
2772 discovery system. As devices are found in a system, they can be
2774 .B "mdadm \-\-incremental"
2775 to be conditionally added to an appropriate array.
2777 Conversely, it can also be used with the
2779 flag to do just the opposite and find whatever array a particular device
2780 is part of and remove the device from that array.
2782 If the device passed is a
2784 device created by a previous call to
2786 then rather than trying to add that device to an array, all the arrays
2787 described by the metadata of the container will be started.
2790 performs a number of tests to determine if the device is part of an
2791 array, and which array it should be part of. If an appropriate array
2792 is found, or can be created,
2794 adds the device to the array and conditionally starts the array.
2798 will normally only add devices to an array which were previously working
2799 (active or spare) parts of that array. The support for automatic
2800 inclusion of a new drive as a spare in some array requires
2801 a configuration through POLICY in config file.
2805 makes are as follow:
2807 Is the device permitted by
2809 That is, is it listed in a
2811 line in that file. If
2813 is absent then the default it to allow any device. Similarly if
2815 contains the special word
2817 then any device is allowed. Otherwise the device name given to
2819 or one of the aliases given, or an alias found in the filesystem,
2820 must match one of the names or patterns in a
2824 This is the only context where the aliases are used. They are
2825 usually provided by a
2831 Does the device have a valid md superblock? If a specific metadata
2832 version is requested with
2836 then only that style of metadata is accepted, otherwise
2838 finds any known version of metadata. If no
2840 metadata is found, the device may be still added to an array
2841 as a spare if POLICY allows.
2845 Does the metadata match an expected array?
2846 The metadata can match in two ways. Either there is an array listed
2849 which identifies the array (either by UUID, by name, by device list,
2850 or by minor-number), or the array was created with a
2856 or on the command line.
2859 is not able to positively identify the array as belonging to the
2860 current host, the device will be rejected.
2865 keeps a list of arrays that it has partially assembled in
2867 If no array exists which matches
2868 the metadata on the new device,
2870 must choose a device name and unit number. It does this based on any
2873 or any name information stored in the metadata. If this name
2874 suggests a unit number, that number will be used, otherwise a free
2875 unit number will be chosen. Normally
2877 will prefer to create a partitionable array, however if the
2881 suggests that a non-partitionable array is preferred, that will be
2884 If the array is not found in the config file and its metadata does not
2885 identify it as belonging to the "homehost", then
2887 will choose a name for the array which is certain not to conflict with
2888 any array which does belong to this host. It does this be adding an
2889 underscore and a small number to the name preferred by the metadata.
2891 Once an appropriate array is found or created and the device is added,
2893 must decide if the array is ready to be started. It will
2894 normally compare the number of available (non-spare) devices to the
2895 number of devices that the metadata suggests need to be active. If
2896 there are at least that many, the array will be started. This means
2897 that if any devices are missing the array will not be restarted.
2903 in which case the array will be run as soon as there are enough
2904 devices present for the data to be accessible. For a RAID1, that
2905 means one device will start the array. For a clean RAID5, the array
2906 will be started as soon as all but one drive is present.
2908 Note that neither of these approaches is really ideal. If it can
2909 be known that all device discovery has completed, then
2913 can be run which will try to start all arrays that are being
2914 incrementally assembled. They are started in "read-auto" mode in
2915 which they are read-only until the first write request. This means
2916 that no metadata updates are made and no attempt at resync or recovery
2917 happens. Further devices that are found before the first write can
2918 still be added safely.
2921 This section describes environment variables that affect how mdadm
2926 Setting this value to 1 will prevent mdadm from automatically launching
2927 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2933 does not create any device nodes in /dev, but leaves that task to
2937 appears not to be configured, or if this environment variable is set
2940 will create and devices that are needed.
2943 .B MDADM_NO_SYSTEMCTL
2948 is in use it will normally request
2950 to start various background tasks (particularly
2952 rather than forking and running them in the background. This can be
2953 suppressed by setting
2954 .BR MDADM_NO_SYSTEMCTL=1 .
2958 A key value of IMSM metadata is that it allows interoperability with
2959 boot ROMs on Intel platforms, and with other major operating systems.
2962 will only allow an IMSM array to be created or modified if detects
2963 that it is running on an Intel platform which supports IMSM, and
2964 supports the particular configuration of IMSM that is being requested
2965 (some functionality requires newer OROM support).
2967 These checks can be suppressed by setting IMSM_NO_PLATFORM=1 in the
2968 environment. This can be useful for testing or for disaster
2969 recovery. You should be aware that interoperability may be
2970 compromised by setting this value.
2973 .B MDADM_GROW_ALLOW_OLD
2974 If an array is stopped while it is performing a reshape and that
2975 reshape was making use of a backup file, then when the array is
2978 will sometimes complain that the backup file is too old. If this
2979 happens and you are certain it is the right backup file, you can
2980 over-ride this check by setting
2981 .B MDADM_GROW_ALLOW_OLD=1
2986 Any string given in this variable is added to the start of the
2988 line in the config file, or treated as the whole
2990 line if none is given. It can be used to disable certain metadata
2993 is called from a boot script. For example
2995 .B " export MDADM_CONF_AUTO='-ddf -imsm'
2999 does not automatically assemble any DDF or
3000 IMSM arrays that are found. This can be useful on systems configured
3001 to manage such arrays with
3007 .B " mdadm \-\-query /dev/name-of-device"
3009 This will find out if a given device is a RAID array, or is part of
3010 one, and will provide brief information about the device.
3012 .B " mdadm \-\-assemble \-\-scan"
3014 This will assemble and start all arrays listed in the standard config
3015 file. This command will typically go in a system startup file.
3017 .B " mdadm \-\-stop \-\-scan"
3019 This will shut down all arrays that can be shut down (i.e. are not
3020 currently in use). This will typically go in a system shutdown script.
3022 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
3024 If (and only if) there is an Email address or program given in the
3025 standard config file, then
3026 monitor the status of all arrays listed in that file by
3027 polling them ever 2 minutes.
3029 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
3031 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
3034 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
3036 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
3038 This will create a prototype config file that describes currently
3039 active arrays that are known to be made from partitions of IDE or SCSI drives.
3040 This file should be reviewed before being used as it may
3041 contain unwanted detail.
3043 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
3045 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
3047 This will find arrays which could be assembled from existing IDE and
3048 SCSI whole drives (not partitions), and store the information in the
3049 format of a config file.
3050 This file is very likely to contain unwanted detail, particularly
3053 entries. It should be reviewed and edited before being used as an
3056 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
3058 .B " mdadm \-Ebsc partitions"
3060 Create a list of devices by reading
3061 .BR /proc/partitions ,
3062 scan these for RAID superblocks, and printout a brief listing of all
3065 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
3067 Scan all partitions and devices listed in
3068 .BR /proc/partitions
3071 out of all such devices with a RAID superblock with a minor number of 0.
3073 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /run/mdadm/mon.pid"
3075 If config file contains a mail address or alert program, run mdadm in
3076 the background in monitor mode monitoring all md devices. Also write
3077 pid of mdadm daemon to
3078 .BR /run/mdadm/mon.pid .
3080 .B " mdadm \-Iq /dev/somedevice"
3082 Try to incorporate newly discovered device into some array as
3085 .B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan"
3087 Rebuild the array map from any current arrays, and then start any that
3090 .B " mdadm /dev/md4 --fail detached --remove detached"
3092 Any devices which are components of /dev/md4 will be marked as faulty
3093 and then remove from the array.
3095 .B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
3099 which is currently a RAID5 array will be converted to RAID6. There
3100 should normally already be a spare drive attached to the array as a
3101 RAID6 needs one more drive than a matching RAID5.
3103 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
3105 Create a DDF array over 6 devices.
3107 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
3109 Create a RAID5 array over any 3 devices in the given DDF set. Use
3110 only 30 gigabytes of each device.
3112 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
3114 Assemble a pre-exist ddf array.
3116 .B " mdadm -I /dev/md/ddf1"
3118 Assemble all arrays contained in the ddf array, assigning names as
3121 .B " mdadm \-\-create \-\-help"
3123 Provide help about the Create mode.
3125 .B " mdadm \-\-config \-\-help"
3127 Provide help about the format of the config file.
3129 .B " mdadm \-\-help"
3131 Provide general help.
3141 lists all active md devices with information about them.
3143 uses this to find arrays when
3145 is given in Misc mode, and to monitor array reconstruction
3150 The config file lists which devices may be scanned to see if
3151 they contain MD super block, and gives identifying information
3152 (e.g. UUID) about known MD arrays. See
3156 .SS /etc/mdadm.conf.d
3158 A directory containing configuration files which are read in lexical
3164 mode is used, this file gets a list of arrays currently being created.
3169 understand two sorts of names for array devices.
3171 The first is the so-called 'standard' format name, which matches the
3172 names used by the kernel and which appear in
3175 The second sort can be freely chosen, but must reside in
3177 When giving a device name to
3179 to create or assemble an array, either full path name such as
3183 can be given, or just the suffix of the second sort of name, such as
3189 chooses device names during auto-assembly or incremental assembly, it
3190 will sometimes add a small sequence number to the end of the name to
3191 avoid conflicted between multiple arrays that have the same name. If
3193 can reasonably determine that the array really is meant for this host,
3194 either by a hostname in the metadata, or by the presence of the array
3197 then it will leave off the suffix if possible.
3198 Also if the homehost is specified as
3201 will only use a suffix if a different array of the same name already
3202 exists or is listed in the config file.
3204 The standard names for non-partitioned arrays (the only sort of md
3205 array available in 2.4 and earlier) are of the form
3209 where NN is a number.
3210 The standard names for partitionable arrays (as available from 2.6
3211 onwards) are of the form:
3215 Partition numbers should be indicated by adding "pMM" to these, thus "/dev/md/d1p2".
3217 From kernel version 2.6.28 the "non-partitioned array" can actually
3218 be partitioned. So the "md_d\fBNN\fP"
3219 names are no longer needed, and
3220 partitions such as "/dev/md\fBNN\fPp\fBXX\fP"
3223 From kernel version 2.6.29 standard names can be non-numeric following
3230 is any string. These names are supported by
3232 since version 3.3 provided they are enabled in
3237 was previously known as
3241 For further information on mdadm usage, MD and the various levels of
3244 .B http://raid.wiki.kernel.org/
3246 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
3248 The latest version of
3250 should always be available from
3252 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob