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" .
400 needs to print the name for a device it normally finds the name in
402 which refers to the device and is shortest. When a path component is
406 will prefer a longer name if it contains that component. For example
407 .B \-\-prefer=by-uuid
408 will prefer a name in a subdirectory of
413 This functionality is currently only provided by
419 .B \-\-home\-cluster=
420 specifies the cluster name for the md device. The md device can be assembled
421 only on the cluster which matches the name specified. If this option is not
422 provided, mdadm tries to detect the cluster name automatically.
424 .SH For create, build, or grow:
427 .BR \-n ", " \-\-raid\-devices=
428 Specify the number of active devices in the array. This, plus the
429 number of spare devices (see below) must equal the number of
431 (including "\fBmissing\fP" devices)
432 that are listed on the command line for
434 Setting a value of 1 is probably
435 a mistake and so requires that
437 be specified first. A value of 1 will then be allowed for linear,
438 multipath, RAID0 and RAID1. It is never allowed for RAID4, RAID5 or RAID6.
440 This number can only be changed using
442 for RAID1, RAID4, RAID5 and RAID6 arrays, and only on kernels which provide
443 the necessary support.
446 .BR \-x ", " \-\-spare\-devices=
447 Specify the number of spare (eXtra) devices in the initial array.
448 Spares can also be added
449 and removed later. The number of component devices listed
450 on the command line must equal the number of RAID devices plus the
451 number of spare devices.
454 .BR \-z ", " \-\-size=
455 Amount (in Kibibytes) of space to use from each drive in RAID levels 1/4/5/6.
456 This must be a multiple of the chunk size, and must leave about 128Kb
457 of space at the end of the drive for the RAID superblock.
458 If this is not specified
459 (as it normally is not) the smallest drive (or partition) sets the
460 size, though if there is a variance among the drives of greater than 1%, a warning is
463 A suffix of 'M' or 'G' can be given to indicate Megabytes or
464 Gigabytes respectively.
466 Sometimes a replacement drive can be a little smaller than the
467 original drives though this should be minimised by IDEMA standards.
468 Such a replacement drive will be rejected by
470 To guard against this it can be useful to set the initial size
471 slightly smaller than the smaller device with the aim that it will
472 still be larger than any replacement.
474 This value can be set with
476 for RAID level 1/4/5/6 though
478 based arrays such as those with IMSM metadata may not be able to
480 If the array was created with a size smaller than the currently
481 active drives, the extra space can be accessed using
483 The size can be given as
485 which means to choose the largest size that fits on all current drives.
487 Before reducing the size of the array (with
488 .BR "\-\-grow \-\-size=" )
489 you should make sure that space isn't needed. If the device holds a
490 filesystem, you would need to resize the filesystem to use less space.
492 After reducing the array size you should check that the data stored in
493 the device is still available. If the device holds a filesystem, then
494 an 'fsck' of the filesystem is a minimum requirement. If there are
495 problems the array can be made bigger again with no loss with another
496 .B "\-\-grow \-\-size="
499 This value cannot be used when creating a
501 such as with DDF and IMSM metadata, though it perfectly valid when
502 creating an array inside a container.
505 .BR \-Z ", " \-\-array\-size=
506 This is only meaningful with
508 and its effect is not persistent: when the array is stopped and
509 restarted the default array size will be restored.
511 Setting the array-size causes the array to appear smaller to programs
512 that access the data. This is particularly needed before reshaping an
513 array so that it will be smaller. As the reshape is not reversible,
514 but setting the size with
516 is, it is required that the array size is reduced as appropriate
517 before the number of devices in the array is reduced.
519 Before reducing the size of the array you should make sure that space
520 isn't needed. If the device holds a filesystem, you would need to
521 resize the filesystem to use less space.
523 After reducing the array size you should check that the data stored in
524 the device is still available. If the device holds a filesystem, then
525 an 'fsck' of the filesystem is a minimum requirement. If there are
526 problems the array can be made bigger again with no loss with another
527 .B "\-\-grow \-\-array\-size="
530 A suffix of 'M' or 'G' can be given to indicate Megabytes or
531 Gigabytes respectively.
534 restores the apparent size of the array to be whatever the real
535 amount of available space is.
538 .BR \-c ", " \-\-chunk=
539 Specify chunk size of kibibytes. The default when creating an
540 array is 512KB. To ensure compatibility with earlier versions, the
541 default when building an array with no persistent metadata is 64KB.
542 This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
544 RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a power
545 of 2. In any case it must be a multiple of 4KB.
547 A suffix of 'M' or 'G' can be given to indicate Megabytes or
548 Gigabytes respectively.
552 Specify rounding factor for a Linear array. The size of each
553 component will be rounded down to a multiple of this size.
554 This is a synonym for
556 but highlights the different meaning for Linear as compared to other
557 RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in
558 use, and is 0K (i.e. no rounding) in later kernels.
561 .BR \-l ", " \-\-level=
562 Set RAID level. When used with
564 options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
565 raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
566 Obviously some of these are synonymous.
570 metadata type is requested, only the
572 level is permitted, and it does not need to be explicitly given.
576 only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
580 to change the RAID level in some cases. See LEVEL CHANGES below.
583 .BR \-p ", " \-\-layout=
584 This option configures the fine details of data layout for RAID5, RAID6,
585 and RAID10 arrays, and controls the failure modes for
588 The layout of the RAID5 parity block can be one of
589 .BR left\-asymmetric ,
590 .BR left\-symmetric ,
591 .BR right\-asymmetric ,
592 .BR right\-symmetric ,
593 .BR la ", " ra ", " ls ", " rs .
595 .BR left\-symmetric .
597 It is also possible to cause RAID5 to use a RAID4-like layout by
603 Finally for RAID5 there are DDF\-compatible layouts,
604 .BR ddf\-zero\-restart ,
605 .BR ddf\-N\-restart ,
607 .BR ddf\-N\-continue .
609 These same layouts are available for RAID6. There are also 4 layouts
610 that will provide an intermediate stage for converting between RAID5
611 and RAID6. These provide a layout which is identical to the
612 corresponding RAID5 layout on the first N\-1 devices, and has the 'Q'
613 syndrome (the second 'parity' block used by RAID6) on the last device.
615 .BR left\-symmetric\-6 ,
616 .BR right\-symmetric\-6 ,
617 .BR left\-asymmetric\-6 ,
618 .BR right\-asymmetric\-6 ,
620 .BR parity\-first\-6 .
622 When setting the failure mode for level
625 .BR write\-transient ", " wt ,
626 .BR read\-transient ", " rt ,
627 .BR write\-persistent ", " wp ,
628 .BR read\-persistent ", " rp ,
630 .BR read\-fixable ", " rf ,
631 .BR clear ", " flush ", " none .
633 Each failure mode can be followed by a number, which is used as a period
634 between fault generation. Without a number, the fault is generated
635 once on the first relevant request. With a number, the fault will be
636 generated after that many requests, and will continue to be generated
637 every time the period elapses.
639 Multiple failure modes can be current simultaneously by using the
641 option to set subsequent failure modes.
643 "clear" or "none" will remove any pending or periodic failure modes,
644 and "flush" will clear any persistent faults.
646 Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
647 by a small number. The default is 'n2'. The supported options are:
650 signals 'near' copies. Multiple copies of one data block are at
651 similar offsets in different devices.
654 signals 'offset' copies. Rather than the chunks being duplicated
655 within a stripe, whole stripes are duplicated but are rotated by one
656 device so duplicate blocks are on different devices. Thus subsequent
657 copies of a block are in the next drive, and are one chunk further
662 (multiple copies have very different offsets).
663 See md(4) for more detail about 'near', 'offset', and 'far'.
665 The number is the number of copies of each datablock. 2 is normal, 3
666 can be useful. This number can be at most equal to the number of
667 devices in the array. It does not need to divide evenly into that
668 number (e.g. it is perfectly legal to have an 'n2' layout for an array
669 with an odd number of devices).
671 When an array is converted between RAID5 and RAID6 an intermediate
672 RAID6 layout is used in which the second parity block (Q) is always on
673 the last device. To convert a RAID5 to RAID6 and leave it in this new
674 layout (which does not require re-striping) use
675 .BR \-\-layout=preserve .
676 This will try to avoid any restriping.
678 The converse of this is
679 .B \-\-layout=normalise
680 which will change a non-standard RAID6 layout into a more standard
687 (thus explaining the p of
691 .BR \-b ", " \-\-bitmap=
692 Specify a file to store a write-intent bitmap in. The file should not
695 is also given. The same file should be provided
696 when assembling the array. If the word
698 is given, then the bitmap is stored with the metadata on the array,
699 and so is replicated on all devices. If the word
703 mode, then any bitmap that is present is removed. If the word
705 is given, the array is created for a clustered environment. One bitmap
706 is created for each node as defined by the
708 parameter and are stored internally.
710 To help catch typing errors, the filename must contain at least one
711 slash ('/') if it is a real file (not 'internal' or 'none').
713 Note: external bitmaps are only known to work on ext2 and ext3.
714 Storing bitmap files on other filesystems may result in serious problems.
716 When creating an array on devices which are 100G or larger,
718 automatically adds an internal bitmap as it will usually be
719 beneficial. This can be suppressed with
720 .B "\-\-bitmap=none".
723 .BR \-\-bitmap\-chunk=
724 Set the chunksize of the bitmap. Each bit corresponds to that many
725 Kilobytes of storage.
726 When using a file based bitmap, the default is to use the smallest
727 size that is at-least 4 and requires no more than 2^21 chunks.
730 bitmap, the chunksize defaults to 64Meg, or larger if necessary to
731 fit the bitmap into the available space.
733 A suffix of 'M' or 'G' can be given to indicate Megabytes or
734 Gigabytes respectively.
737 .BR \-W ", " \-\-write\-mostly
738 subsequent devices listed in a
743 command will be flagged as 'write-mostly'. This is valid for RAID1
744 only and means that the 'md' driver will avoid reading from these
745 devices if at all possible. This can be useful if mirroring over a
749 .BR \-\-write\-behind=
750 Specify that write-behind mode should be enabled (valid for RAID1
751 only). If an argument is specified, it will set the maximum number
752 of outstanding writes allowed. The default value is 256.
753 A write-intent bitmap is required in order to use write-behind
754 mode, and write-behind is only attempted on drives marked as
758 .BR \-\-assume\-clean
761 that the array pre-existed and is known to be clean. It can be useful
762 when trying to recover from a major failure as you can be sure that no
763 data will be affected unless you actually write to the array. It can
764 also be used when creating a RAID1 or RAID10 if you want to avoid the
765 initial resync, however this practice \(em while normally safe \(em is not
766 recommended. Use this only if you really know what you are doing.
768 When the devices that will be part of a new array were filled
769 with zeros before creation the operator knows the array is
770 actually clean. If that is the case, such as after running
771 badblocks, this argument can be used to tell mdadm the
772 facts the operator knows.
774 When an array is resized to a larger size with
775 .B "\-\-grow \-\-size="
776 the new space is normally resynced in that same way that the whole
777 array is resynced at creation. From Linux version 3.0,
779 can be used with that command to avoid the automatic resync.
782 .BR \-\-backup\-file=
785 is used to increase the number of raid-devices in a RAID5 or RAID6 if
786 there are no spare devices available, or to shrink, change RAID level
787 or layout. See the GROW MODE section below on RAID\-DEVICES CHANGES.
788 The file must be stored on a separate device, not on the RAID array
793 Arrays with 1.x metadata can leave a gap between the start of the
794 device and the start of array data. This gap can be used for various
795 metadata. The start of data is known as the
797 Normally an appropriate data offset is computed automatically.
798 However it can be useful to set it explicitly such as when re-creating
799 an array which was originally created using a different version of
801 which computed a different offset.
803 Setting the offset explicitly over-rides the default. The value given
804 is in Kilobytes unless an 'M' or 'G' suffix is given.
808 can also be used with
810 for some RAID levels (initially on RAID10). This allows the
811 data\-offset to be changed as part of the reshape process. When the
812 data offset is changed, no backup file is required as the difference
813 in offsets is used to provide the same functionality.
815 When the new offset is earlier than the old offset, the number of
816 devices in the array cannot shrink. When it is after the old offset,
817 the number of devices in the array cannot increase.
819 When creating an array,
823 In the case each member device is expected to have a offset appended
824 to the name, separated by a colon. This makes it possible to recreate
825 exactly an array which has varying data offsets (as can happen when
826 different versions of
828 are used to add different devices).
832 This option is complementary to the
833 .B \-\-freeze-reshape
834 option for assembly. It is needed when
836 operation is interrupted and it is not restarted automatically due to
837 .B \-\-freeze-reshape
838 usage during array assembly. This option is used together with
842 ) command and device for a pending reshape to be continued.
843 All parameters required for reshape continuation will be read from array metadata.
847 .BR \-\-backup\-file=
848 option to be set, continuation option will require to have exactly the same
849 backup file given as well.
851 Any other parameter passed together with
853 option will be ignored.
856 .BR \-N ", " \-\-name=
859 for the array. This is currently only effective when creating an
860 array with a version-1 superblock, or an array in a DDF container.
861 The name is a simple textual string that can be used to identify array
862 components when assembling. If name is needed but not specified, it
863 is taken from the basename of the device that is being created.
875 run the array, even if some of the components
876 appear to be active in another array or filesystem. Normally
878 will ask for confirmation before including such components in an
879 array. This option causes that question to be suppressed.
882 .BR \-f ", " \-\-force
885 accept the geometry and layout specified without question. Normally
887 will not allow creation of an array with only one device, and will try
888 to create a RAID5 array with one missing drive (as this makes the
889 initial resync work faster). With
892 will not try to be so clever.
895 .BR \-o ", " \-\-readonly
898 rather than read-write as normal. No writes will be allowed to the
899 array, and no resync, recovery, or reshape will be started.
902 .BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
903 Instruct mdadm how to create the device file if needed, possibly allocating
904 an unused minor number. "md" causes a non-partitionable array
905 to be used (though since Linux 2.6.28, these array devices are in fact
906 partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
907 later) to be used. "yes" requires the named md device to have
908 a 'standard' format, and the type and minor number will be determined
909 from this. With mdadm 3.0, device creation is normally left up to
911 so this option is unlikely to be needed.
912 See DEVICE NAMES below.
914 The argument can also come immediately after
919 is not given on the command line or in the config file, then
925 is also given, then any
927 entries in the config file will override the
929 instruction given on the command line.
931 For partitionable arrays,
933 will create the device file for the whole array and for the first 4
934 partitions. A different number of partitions can be specified at the
935 end of this option (e.g.
937 If the device name ends with a digit, the partition names add a 'p',
939 .IR /dev/md/home1p3 .
940 If there is no trailing digit, then the partition names just have a
942 .IR /dev/md/scratch3 .
944 If the md device name is in a 'standard' format as described in DEVICE
945 NAMES, then it will be created, if necessary, with the appropriate
946 device number based on that name. If the device name is not in one of these
947 formats, then a unused device number will be allocated. The device
948 number will be considered unused if there is no active array for that
949 number, and there is no entry in /dev for that number and with a
950 non-standard name. Names that are not in 'standard' format are only
951 allowed in "/dev/md/".
953 This is meaningful with
959 .BR \-a ", " "\-\-add"
960 This option can be used in Grow mode in two cases.
962 If the target array is a Linear array, then
964 can be used to add one or more devices to the array. They
965 are simply catenated on to the end of the array. Once added, the
966 devices cannot be removed.
970 option is being used to increase the number of devices in an array,
973 can be used to add some extra devices to be included in the array.
974 In most cases this is not needed as the extra devices can be added as
975 spares first, and then the number of raid-disks can be changed.
976 However for RAID0, it is not possible to add spares. So to increase
977 the number of devices in a RAID0, it is necessary to set the new
978 number of devices, and to add the new devices, in the same command.
982 Only works when the array is for clustered environment. It specifies
983 the maximum number of nodes in the cluster that will use this device
984 simultaneously. If not specified, this defaults to 4.
989 .BR \-u ", " \-\-uuid=
990 uuid of array to assemble. Devices which don't have this uuid are
994 .BR \-m ", " \-\-super\-minor=
995 Minor number of device that array was created for. Devices which
996 don't have this minor number are excluded. If you create an array as
997 /dev/md1, then all superblocks will contain the minor number 1, even if
998 the array is later assembled as /dev/md2.
1000 Giving the literal word "dev" for
1004 to use the minor number of the md device that is being assembled.
1005 e.g. when assembling
1007 .B \-\-super\-minor=dev
1008 will look for super blocks with a minor number of 0.
1011 is only relevant for v0.90 metadata, and should not normally be used.
1017 .BR \-N ", " \-\-name=
1018 Specify the name of the array to assemble. This must be the name
1019 that was specified when creating the array. It must either match
1020 the name stored in the superblock exactly, or it must match
1023 prefixed to the start of the given name.
1026 .BR \-f ", " \-\-force
1027 Assemble the array even if the metadata on some devices appears to be
1030 cannot find enough working devices to start the array, but can find
1031 some devices that are recorded as having failed, then it will mark
1032 those devices as working so that the array can be started.
1033 An array which requires
1035 to be started may contain data corruption. Use it carefully.
1038 .BR \-R ", " \-\-run
1039 Attempt to start the array even if fewer drives were given than were
1040 present last time the array was active. Normally if not all the
1041 expected drives are found and
1043 is not used, then the array will be assembled but not started.
1046 an attempt will be made to start it anyway.
1050 This is the reverse of
1052 in that it inhibits the startup of array unless all expected drives
1053 are present. This is only needed with
1055 and can be used if the physical connections to devices are
1056 not as reliable as you would like.
1059 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
1060 See this option under Create and Build options.
1063 .BR \-b ", " \-\-bitmap=
1064 Specify the bitmap file that was given when the array was created. If
1067 bitmap, there is no need to specify this when assembling the array.
1070 .BR \-\-backup\-file=
1073 was used while reshaping an array (e.g. changing number of devices or
1074 chunk size) and the system crashed during the critical section, then the same
1076 must be presented to
1078 to allow possibly corrupted data to be restored, and the reshape
1082 .BR \-\-invalid\-backup
1083 If the file needed for the above option is not available for any
1084 reason an empty file can be given together with this option to
1085 indicate that the backup file is invalid. In this case the data that
1086 was being rearranged at the time of the crash could be irrecoverably
1087 lost, but the rest of the array may still be recoverable. This option
1088 should only be used as a last resort if there is no way to recover the
1093 .BR \-U ", " \-\-update=
1094 Update the superblock on each device while assembling the array. The
1095 argument given to this flag can be one of
1113 option will adjust the superblock of an array what was created on a Sparc
1114 machine running a patched 2.2 Linux kernel. This kernel got the
1115 alignment of part of the superblock wrong. You can use the
1116 .B "\-\-examine \-\-sparc2.2"
1119 to see what effect this would have.
1123 option will update the
1124 .B "preferred minor"
1125 field on each superblock to match the minor number of the array being
1127 This can be useful if
1129 reports a different "Preferred Minor" to
1131 In some cases this update will be performed automatically
1132 by the kernel driver. In particular the update happens automatically
1133 at the first write to an array with redundancy (RAID level 1 or
1134 greater) on a 2.6 (or later) kernel.
1138 option will change the uuid of the array. If a UUID is given with the
1140 option that UUID will be used as a new UUID and will
1142 be used to help identify the devices in the array.
1145 is given, a random UUID is chosen.
1149 option will change the
1151 of the array as stored in the superblock. This is only supported for
1152 version-1 superblocks.
1156 option will change the
1158 as recorded in the superblock. For version-0 superblocks, this is the
1159 same as updating the UUID.
1160 For version-1 superblocks, this involves updating the name.
1164 option will cause the array to be marked
1166 meaning that any redundancy in the array (e.g. parity for RAID5,
1167 copies for RAID1) may be incorrect. This will cause the RAID system
1168 to perform a "resync" pass to make sure that all redundant information
1173 option allows arrays to be moved between machines with different
1175 When assembling such an array for the first time after a move, giving
1176 .B "\-\-update=byteorder"
1179 to expect superblocks to have their byteorder reversed, and will
1180 correct that order before assembling the array. This is only valid
1181 with original (Version 0.90) superblocks.
1185 option will correct the summaries in the superblock. That is the
1186 counts of total, working, active, failed, and spare devices.
1190 option will rarely be of use. It applies to version 1.1 and 1.2 metadata
1191 only (where the metadata is at the start of the device) and is only
1192 useful when the component device has changed size (typically become
1193 larger). The version 1 metadata records the amount of the device that
1194 can be used to store data, so if a device in a version 1.1 or 1.2
1195 array becomes larger, the metadata will still be visible, but the
1196 extra space will not. In this case it might be useful to assemble the
1198 .BR \-\-update=devicesize .
1201 to determine the maximum usable amount of space on each device and
1202 update the relevant field in the metadata.
1206 option only works on v0.90 metadata arrays and will convert them to
1207 v1.0 metadata. The array must not be dirty (i.e. it must not need a
1208 sync) and it must not have a write-intent bitmap.
1210 The old metadata will remain on the devices, but will appear older
1211 than the new metadata and so will usually be ignored. The old metadata
1212 (or indeed the new metadata) can be removed by giving the appropriate
1215 .BR \-\-zero\-superblock .
1219 option can be used when an array has an internal bitmap which is
1220 corrupt in some way so that assembling the array normally fails. It
1221 will cause any internal bitmap to be ignored.
1225 option will reserve space in each device for a bad block list. This
1226 will be 4K in size and positioned near the end of any free space
1227 between the superblock and the data.
1231 option will cause any reservation of space for a bad block list to be
1232 removed. If the bad block list contains entries, this will fail, as
1233 removing the list could cause data corruption.
1236 .BR \-\-freeze\-reshape
1237 Option is intended to be used in start-up scripts during initrd boot phase.
1238 When array under reshape is assembled during initrd phase, this option
1239 stops reshape after reshape critical section is being restored. This happens
1240 before file system pivot operation and avoids loss of file system context.
1241 Losing file system context would cause reshape to be broken.
1243 Reshape can be continued later using the
1245 option for the grow command.
1247 .SH For Manage mode:
1250 .BR \-t ", " \-\-test
1251 Unless a more serious error occurred,
1253 will exit with a status of 2 if no changes were made to the array and
1254 0 if at least one change was made.
1255 This can be useful when an indirect specifier such as
1260 is used in requesting an operation on the array.
1262 will report failure if these specifiers didn't find any match.
1265 .BR \-a ", " \-\-add
1266 hot-add listed devices.
1267 If a device appears to have recently been part of the array
1268 (possibly it failed or was removed) the device is re\-added as described
1270 If that fails or the device was never part of the array, the device is
1271 added as a hot-spare.
1272 If the array is degraded, it will immediately start to rebuild data
1275 Note that this and the following options are only meaningful on array
1276 with redundancy. They don't apply to RAID0 or Linear.
1280 re\-add a device that was previously removed from an array.
1281 If the metadata on the device reports that it is a member of the
1282 array, and the slot that it used is still vacant, then the device will
1283 be added back to the array in the same position. This will normally
1284 cause the data for that device to be recovered. However based on the
1285 event count on the device, the recovery may only require sections that
1286 are flagged a write-intent bitmap to be recovered or may not require
1287 any recovery at all.
1289 When used on an array that has no metadata (i.e. it was built with
1291 it will be assumed that bitmap-based recovery is enough to make the
1292 device fully consistent with the array.
1294 When used with v1.x metadata,
1296 can be accompanied by
1297 .BR \-\-update=devicesize ,
1298 .BR \-\-update=bbl ", or"
1299 .BR \-\-update=no\-bbl .
1300 See the description of these option when used in Assemble mode for an
1301 explanation of their use.
1303 If the device name given is
1307 will try to find any device that looks like it should be
1308 part of the array but isn't and will try to re\-add all such devices.
1310 If the device name given is
1314 will find all devices in the array that are marked
1316 remove them and attempt to immediately re\-add them. This can be
1317 useful if you are certain that the reason for failure has been
1322 Add a device as a spare. This is similar to
1324 except that it does not attempt
1326 first. The device will be added as a spare even if it looks like it
1327 could be an recent member of the array.
1330 .BR \-r ", " \-\-remove
1331 remove listed devices. They must not be active. i.e. they should
1332 be failed or spare devices.
1334 As well as the name of a device file
1344 The first causes all failed device to be removed. The second causes
1345 any device which is no longer connected to the system (i.e an 'open'
1349 The third will remove a set as describe below under
1353 .BR \-f ", " \-\-fail
1354 Mark listed devices as faulty.
1355 As well as the name of a device file, the word
1359 can be given. The former will cause any device that has been detached from
1360 the system to be marked as failed. It can then be removed.
1362 For RAID10 arrays where the number of copies evenly divides the number
1363 of devices, the devices can be conceptually divided into sets where
1364 each set contains a single complete copy of the data on the array.
1365 Sometimes a RAID10 array will be configured so that these sets are on
1366 separate controllers. In this case all the devices in one set can be
1367 failed by giving a name like
1373 The appropriate set names are reported by
1383 Mark listed devices as requiring replacement. As soon as a spare is
1384 available, it will be rebuilt and will replace the marked device.
1385 This is similar to marking a device as faulty, but the device remains
1386 in service during the recovery process to increase resilience against
1387 multiple failures. When the replacement process finishes, the
1388 replaced device will be marked as faulty.
1392 This can follow a list of
1394 devices. The devices listed after
1396 will be preferentially used to replace the devices listed after
1398 These device must already be spare devices in the array.
1401 .BR \-\-write\-mostly
1402 Subsequent devices that are added or re\-added will have the 'write-mostly'
1403 flag set. This is only valid for RAID1 and means that the 'md' driver
1404 will avoid reading from these devices if possible.
1407 Subsequent devices that are added or re\-added will have the 'write-mostly'
1410 .BR \-\-cluster\-confirm
1411 Confirm the existence of the device. This is issued in response to an \-\-add
1412 request by a node in a cluster. When a node adds a device it sends a message
1413 to all nodes in the cluster to look for a device with a UUID. This translates
1414 to a udev notification with the UUID of the device to be added and the slot
1415 number. The receiving node must acknowledge this message
1416 with \-\-cluster\-confirm. Valid arguments are <slot>:<devicename> in case
1417 the device is found or <slot>:missing in case the device is not found.
1420 Each of these options requires that the first device listed is the array
1421 to be acted upon, and the remainder are component devices to be added,
1422 removed, marked as faulty, etc. Several different operations can be
1423 specified for different devices, e.g.
1425 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1427 Each operation applies to all devices listed until the next
1430 If an array is using a write-intent bitmap, then devices which have
1431 been removed can be re\-added in a way that avoids a full
1432 reconstruction but instead just updates the blocks that have changed
1433 since the device was removed. For arrays with persistent metadata
1434 (superblocks) this is done automatically. For arrays created with
1436 mdadm needs to be told that this device we removed recently with
1439 Devices can only be removed from an array if they are not in active
1440 use, i.e. that must be spares or failed devices. To remove an active
1441 device, it must first be marked as
1447 .BR \-Q ", " \-\-query
1448 Examine a device to see
1449 (1) if it is an md device and (2) if it is a component of an md
1451 Information about what is discovered is presented.
1454 .BR \-D ", " \-\-detail
1455 Print details of one or more md devices.
1458 .BR \-\-detail\-platform
1459 Print details of the platform's RAID capabilities (firmware / hardware
1460 topology) for a given metadata format. If used without argument, mdadm
1461 will scan all controllers looking for their capabilities. Otherwise, mdadm
1462 will only look at the controller specified by the argument in form of an
1463 absolute filepath or a link, e.g.
1464 .IR /sys/devices/pci0000:00/0000:00:1f.2 .
1467 .BR \-Y ", " \-\-export
1470 .BR \-\-detail-platform ,
1474 output will be formatted as
1476 pairs for easy import into the environment.
1482 indicates whether an array was started
1484 or not, which may include a reason
1485 .RB ( unsafe ", " nothing ", " no ).
1488 indicates if the array is expected on this host
1490 or seems to be from elsewhere
1494 .BR \-E ", " \-\-examine
1495 Print contents of the metadata stored on the named device(s).
1496 Note the contrast between
1501 applies to devices which are components of an array, while
1503 applies to a whole array which is currently active.
1506 If an array was created on a SPARC machine with a 2.2 Linux kernel
1507 patched with RAID support, the superblock will have been created
1508 incorrectly, or at least incompatibly with 2.4 and later kernels.
1513 will fix the superblock before displaying it. If this appears to do
1514 the right thing, then the array can be successfully assembled using
1515 .BR "\-\-assemble \-\-update=sparc2.2" .
1518 .BR \-X ", " \-\-examine\-bitmap
1519 Report information about a bitmap file.
1520 The argument is either an external bitmap file or an array component
1521 in case of an internal bitmap. Note that running this on an array
1524 does not report the bitmap for that array.
1527 .B \-\-examine\-badblocks
1528 List the bad-blocks recorded for the device, if a bad-blocks list has
1529 been configured. Currently only
1531 metadata supports bad-blocks lists.
1534 .BI \-\-dump= directory
1536 .BI \-\-restore= directory
1537 Save metadata from lists devices, or restore metadata to listed devices.
1540 .BR \-R ", " \-\-run
1541 start a partially assembled array. If
1543 did not find enough devices to fully start the array, it might leaving
1544 it partially assembled. If you wish, you can then use
1546 to start the array in degraded mode.
1549 .BR \-S ", " \-\-stop
1550 deactivate array, releasing all resources.
1553 .BR \-o ", " \-\-readonly
1554 mark array as readonly.
1557 .BR \-w ", " \-\-readwrite
1558 mark array as readwrite.
1561 .B \-\-zero\-superblock
1562 If the device contains a valid md superblock, the block is
1563 overwritten with zeros. With
1565 the block where the superblock would be is overwritten even if it
1566 doesn't appear to be valid.
1569 .B \-\-kill\-subarray=
1570 If the device is a container and the argument to \-\-kill\-subarray
1571 specifies an inactive subarray in the container, then the subarray is
1572 deleted. Deleting all subarrays will leave an 'empty-container' or
1573 spare superblock on the drives. See
1574 .B \-\-zero\-superblock
1576 removing a superblock. Note that some formats depend on the subarray
1577 index for generating a UUID, this command will fail if it would change
1578 the UUID of an active subarray.
1581 .B \-\-update\-subarray=
1582 If the device is a container and the argument to \-\-update\-subarray
1583 specifies a subarray in the container, then attempt to update the given
1584 superblock field in the subarray. See below in
1589 .BR \-t ", " \-\-test
1594 is set to reflect the status of the device. See below in
1599 .BR \-W ", " \-\-wait
1600 For each md device given, wait for any resync, recovery, or reshape
1601 activity to finish before returning.
1603 will return with success if it actually waited for every device
1604 listed, otherwise it will return failure.
1608 For each md device given, or each device in /proc/mdstat if
1610 is given, arrange for the array to be marked clean as soon as possible.
1612 will return with success if the array uses external metadata and we
1613 successfully waited. For native arrays this returns immediately as the
1614 kernel handles dirty-clean transitions at shutdown. No action is taken
1615 if safe-mode handling is disabled.
1619 Set the "sync_action" for all md devices given to one of
1626 will abort any currently running action though some actions will
1627 automatically restart.
1630 will abort any current action and ensure no other action starts
1640 .BR "SCRUBBING AND MISMATCHES" .
1642 .SH For Incremental Assembly mode:
1644 .BR \-\-rebuild\-map ", " \-r
1645 Rebuild the map file
1649 uses to help track which arrays are currently being assembled.
1652 .BR \-\-run ", " \-R
1653 Run any array assembled as soon as a minimal number of devices are
1654 available, rather than waiting until all expected devices are present.
1657 .BR \-\-scan ", " \-s
1658 Only meaningful with
1662 file for arrays that are being incrementally assembled and will try to
1663 start any that are not already started. If any such array is listed
1666 as requiring an external bitmap, that bitmap will be attached first.
1669 .BR \-\-fail ", " \-f
1670 This allows the hot-plug system to remove devices that have fully disappeared
1671 from the kernel. It will first fail and then remove the device from any
1672 array it belongs to.
1673 The device name given should be a kernel device name such as "sda",
1679 Only used with \-\-fail. The 'path' given will be recorded so that if
1680 a new device appears at the same location it can be automatically
1681 added to the same array. This allows the failed device to be
1682 automatically replaced by a new device without metadata if it appears
1683 at specified path. This option is normally only set by a
1687 .SH For Monitor mode:
1689 .BR \-m ", " \-\-mail
1690 Give a mail address to send alerts to.
1693 .BR \-p ", " \-\-program ", " \-\-alert
1694 Give a program to be run whenever an event is detected.
1697 .BR \-y ", " \-\-syslog
1698 Cause all events to be reported through 'syslog'. The messages have
1699 facility of 'daemon' and varying priorities.
1702 .BR \-d ", " \-\-delay
1703 Give a delay in seconds.
1705 polls the md arrays and then waits this many seconds before polling
1706 again. The default is 60 seconds. Since 2.6.16, there is no need to
1707 reduce this as the kernel alerts
1709 immediately when there is any change.
1712 .BR \-r ", " \-\-increment
1713 Give a percentage increment.
1715 will generate RebuildNN events with the given percentage increment.
1718 .BR \-f ", " \-\-daemonise
1721 to run as a background daemon if it decides to monitor anything. This
1722 causes it to fork and run in the child, and to disconnect from the
1723 terminal. The process id of the child is written to stdout.
1726 which will only continue monitoring if a mail address or alert program
1727 is found in the config file.
1730 .BR \-i ", " \-\-pid\-file
1733 is running in daemon mode, write the pid of the daemon process to
1734 the specified file, instead of printing it on standard output.
1737 .BR \-1 ", " \-\-oneshot
1738 Check arrays only once. This will generate
1740 events and more significantly
1746 .B " mdadm \-\-monitor \-\-scan \-1"
1748 from a cron script will ensure regular notification of any degraded arrays.
1751 .BR \-t ", " \-\-test
1754 alert for every array found at startup. This alert gets mailed and
1755 passed to the alert program. This can be used for testing that alert
1756 message do get through successfully.
1760 This inhibits the functionality for moving spares between arrays.
1761 Only one monitoring process started with
1763 but without this flag is allowed, otherwise the two could interfere
1770 .B mdadm \-\-assemble
1771 .I md-device options-and-component-devices...
1774 .B mdadm \-\-assemble \-\-scan
1775 .I md-devices-and-options...
1778 .B mdadm \-\-assemble \-\-scan
1782 This usage assembles one or more RAID arrays from pre-existing components.
1783 For each array, mdadm needs to know the md device, the identity of the
1784 array, and a number of component-devices. These can be found in a number of ways.
1786 In the first usage example (without the
1788 the first device given is the md device.
1789 In the second usage example, all devices listed are treated as md
1790 devices and assembly is attempted.
1791 In the third (where no devices are listed) all md devices that are
1792 listed in the configuration file are assembled. If no arrays are
1793 described by the configuration file, then any arrays that
1794 can be found on unused devices will be assembled.
1796 If precisely one device is listed, but
1802 was given and identity information is extracted from the configuration file.
1804 The identity can be given with the
1810 option, will be taken from the md-device record in the config file, or
1811 will be taken from the super block of the first component-device
1812 listed on the command line.
1814 Devices can be given on the
1816 command line or in the config file. Only devices which have an md
1817 superblock which contains the right identity will be considered for
1820 The config file is only used if explicitly named with
1822 or requested with (a possibly implicit)
1827 .B /etc/mdadm/mdadm.conf
1832 is not given, then the config file will only be used to find the
1833 identity of md arrays.
1835 Normally the array will be started after it is assembled. However if
1837 is not given and not all expected drives were listed, then the array
1838 is not started (to guard against usage errors). To insist that the
1839 array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1848 does not create any entries in
1852 It does record information in
1856 to choose the correct name.
1860 detects that udev is not configured, it will create the devices in
1864 In Linux kernels prior to version 2.6.28 there were two distinctly
1865 different types of md devices that could be created: one that could be
1866 partitioned using standard partitioning tools and one that could not.
1867 Since 2.6.28 that distinction is no longer relevant as both type of
1868 devices can be partitioned.
1870 will normally create the type that originally could not be partitioned
1871 as it has a well defined major number (9).
1873 Prior to 2.6.28, it is important that mdadm chooses the correct type
1874 of array device to use. This can be controlled with the
1876 option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1877 to use a partitionable device rather than the default.
1879 In the no-udev case, the value given to
1881 can be suffixed by a number. This tells
1883 to create that number of partition devices rather than the default of 4.
1887 can also be given in the configuration file as a word starting
1889 on the ARRAY line for the relevant array.
1896 and no devices are listed,
1898 will first attempt to assemble all the arrays listed in the config
1901 If no arrays are listed in the config (other than those marked
1903 it will look through the available devices for possible arrays and
1904 will try to assemble anything that it finds. Arrays which are tagged
1905 as belonging to the given homehost will be assembled and started
1906 normally. Arrays which do not obviously belong to this host are given
1907 names that are expected not to conflict with anything local, and are
1908 started "read-auto" so that nothing is written to any device until the
1909 array is written to. i.e. automatic resync etc is delayed.
1913 finds a consistent set of devices that look like they should comprise
1914 an array, and if the superblock is tagged as belonging to the given
1915 home host, it will automatically choose a device name and try to
1916 assemble the array. If the array uses version-0.90 metadata, then the
1918 number as recorded in the superblock is used to create a name in
1922 If the array uses version-1 metadata, then the
1924 from the superblock is used to similarly create a name in
1926 (the name will have any 'host' prefix stripped first).
1928 This behaviour can be modified by the
1932 configuration file. This line can indicate that specific metadata
1933 type should, or should not, be automatically assembled. If an array
1934 is found which is not listed in
1936 and has a metadata format that is denied by the
1938 line, then it will not be assembled.
1941 line can also request that all arrays identified as being for this
1942 homehost should be assembled regardless of their metadata type.
1945 for further details.
1947 Note: Auto assembly cannot be used for assembling and activating some
1948 arrays which are undergoing reshape. In particular as the
1950 cannot be given, any reshape which requires a backup-file to continue
1951 cannot be started by auto assembly. An array which is growing to more
1952 devices and has passed the critical section can be assembled using
1963 .BI \-\-raid\-devices= Z
1967 This usage is similar to
1969 The difference is that it creates an array without a superblock. With
1970 these arrays there is no difference between initially creating the array and
1971 subsequently assembling the array, except that hopefully there is useful
1972 data there in the second case.
1974 The level may raid0, linear, raid1, raid10, multipath, or faulty, or
1975 one of their synonyms. All devices must be listed and the array will
1976 be started once complete. It will often be appropriate to use
1977 .B \-\-assume\-clean
1978 with levels raid1 or raid10.
1989 .BI \-\-raid\-devices= Z
1993 This usage will initialise a new md array, associate some devices with
1994 it, and activate the array.
1996 The named device will normally not exist when
1997 .I "mdadm \-\-create"
1998 is run, but will be created by
2000 once the array becomes active.
2002 As devices are added, they are checked to see if they contain RAID
2003 superblocks or filesystems. They are also checked to see if the variance in
2004 device size exceeds 1%.
2006 If any discrepancy is found, the array will not automatically be run, though
2009 can override this caution.
2011 To create a "degraded" array in which some devices are missing, simply
2012 give the word "\fBmissing\fP"
2013 in place of a device name. This will cause
2015 to leave the corresponding slot in the array empty.
2016 For a RAID4 or RAID5 array at most one slot can be
2017 "\fBmissing\fP"; for a RAID6 array at most two slots.
2018 For a RAID1 array, only one real device needs to be given. All of the
2022 When creating a RAID5 array,
2024 will automatically create a degraded array with an extra spare drive.
2025 This is because building the spare into a degraded array is in general
2026 faster than resyncing the parity on a non-degraded, but not clean,
2027 array. This feature can be overridden with the
2031 When creating an array with version-1 metadata a name for the array is
2033 If this is not given with the
2037 will choose a name based on the last component of the name of the
2038 device being created. So if
2040 is being created, then the name
2045 is being created, then the name
2049 When creating a partition based array, using
2051 with version-1.x metadata, the partition type should be set to
2053 (non fs-data). This type selection allows for greater precision since
2054 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
2055 might create problems in the event of array recovery through a live cdrom.
2057 A new array will normally get a randomly assigned 128bit UUID which is
2058 very likely to be unique. If you have a specific need, you can choose
2059 a UUID for the array by giving the
2061 option. Be warned that creating two arrays with the same UUID is a
2062 recipe for disaster. Also, using
2064 when creating a v0.90 array will silently override any
2069 .\"option is given, it is not necessary to list any component-devices in this command.
2070 .\"They can be added later, before a
2074 .\"is given, the apparent size of the smallest drive given is used.
2076 If the array type supports a write-intent bitmap, and if the devices
2077 in the array exceed 100G is size, an internal write-intent bitmap
2078 will automatically be added unless some other option is explicitly
2081 option. In any case space for a bitmap will be reserved so that one
2082 can be added layer with
2083 .BR "\-\-grow \-\-bitmap=internal" .
2085 If the metadata type supports it (currently only 1.x metadata), space
2086 will be allocated to store a bad block list. This allows a modest
2087 number of bad blocks to be recorded, allowing the drive to remain in
2088 service while only partially functional.
2090 When creating an array within a
2093 can be given either the list of devices to use, or simply the name of
2094 the container. The former case gives control over which devices in
2095 the container will be used for the array. The latter case allows
2097 to automatically choose which devices to use based on how much spare
2100 The General Management options that are valid with
2105 insist on running the array even if some devices look like they might
2110 start the array readonly \(em not supported yet.
2117 .I options... devices...
2120 This usage will allow individual devices in an array to be failed,
2121 removed or added. It is possible to perform multiple operations with
2122 on command. For example:
2124 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
2130 and will then remove it from the array and finally add it back
2131 in as a spare. However only one md array can be affected by a single
2134 When a device is added to an active array, mdadm checks to see if it
2135 has metadata on it which suggests that it was recently a member of the
2136 array. If it does, it tries to "re\-add" the device. If there have
2137 been no changes since the device was removed, or if the array has a
2138 write-intent bitmap which has recorded whatever changes there were,
2139 then the device will immediately become a full member of the array and
2140 those differences recorded in the bitmap will be resolved.
2150 MISC mode includes a number of distinct operations that
2151 operate on distinct devices. The operations are:
2154 The device is examined to see if it is
2155 (1) an active md array, or
2156 (2) a component of an md array.
2157 The information discovered is reported.
2161 The device should be an active md device.
2163 will display a detailed description of the array.
2167 will cause the output to be less detailed and the format to be
2168 suitable for inclusion in
2172 will normally be 0 unless
2174 failed to get useful information about the device(s); however, if the
2176 option is given, then the exit status will be:
2180 The array is functioning normally.
2183 The array has at least one failed device.
2186 The array has multiple failed devices such that it is unusable.
2189 There was an error while trying to get information about the device.
2193 .B \-\-detail\-platform
2194 Print detail of the platform's RAID capabilities (firmware / hardware
2195 topology). If the metadata is specified with
2199 then the return status will be:
2203 metadata successfully enumerated its platform components on this system
2206 metadata is platform independent
2209 metadata failed to find its platform components on this system
2213 .B \-\-update\-subarray=
2214 If the device is a container and the argument to \-\-update\-subarray
2215 specifies a subarray in the container, then attempt to update the given
2216 superblock field in the subarray. Similar to updating an array in
2217 "assemble" mode, the field to update is selected by
2221 option. Currently only
2227 option updates the subarray name in the metadata, it may not affect the
2228 device node name or the device node symlink until the subarray is
2229 re\-assembled. If updating
2231 would change the UUID of an active subarray this operation is blocked,
2232 and the command will end in an error.
2236 The device should be a component of an md array.
2238 will read the md superblock of the device and display the contents.
2243 is given, then multiple devices that are components of the one array
2244 are grouped together and reported in a single entry suitable
2250 without listing any devices will cause all devices listed in the
2251 config file to be examined.
2254 .BI \-\-dump= directory
2255 If the device contains RAID metadata, a file will be created in the
2257 and the metadata will be written to it. The file will be the same
2258 size as the device and have the metadata written in the file at the
2259 same locate that it exists in the device. However the file will be "sparse" so
2260 that only those blocks containing metadata will be allocated. The
2261 total space used will be small.
2263 The file name used in the
2265 will be the base name of the device. Further if any links appear in
2267 which point to the device, then hard links to the file will be created
2274 Multiple devices can be listed and their metadata will all be stored
2275 in the one directory.
2278 .BI \-\-restore= directory
2279 This is the reverse of
2282 will locate a file in the directory that has a name appropriate for
2283 the given device and will restore metadata from it. Names that match
2285 names are preferred, however if two of those refer to different files,
2287 will not choose between them but will abort the operation.
2289 If a file name is given instead of a
2293 will restore from that file to a single device, always provided the
2294 size of the file matches that of the device, and the file contains
2298 The devices should be active md arrays which will be deactivated, as
2299 long as they are not currently in use.
2303 This will fully activate a partially assembled md array.
2307 This will mark an active array as read-only, providing that it is
2308 not currently being used.
2314 array back to being read/write.
2318 For all operations except
2321 will cause the operation to be applied to all arrays listed in
2326 causes all devices listed in the config file to be examined.
2329 .BR \-b ", " \-\-brief
2330 Be less verbose. This is used with
2338 gives an intermediate level of verbosity.
2344 .B mdadm \-\-monitor
2345 .I options... devices...
2350 to periodically poll a number of md arrays and to report on any events
2353 will never exit once it decides that there are arrays to be checked,
2354 so it should normally be run in the background.
2356 As well as reporting events,
2358 may move a spare drive from one array to another if they are in the
2363 and if the destination array has a failed drive but no spares.
2365 If any devices are listed on the command line,
2367 will only monitor those devices. Otherwise all arrays listed in the
2368 configuration file will be monitored. Further, if
2370 is given, then any other md devices that appear in
2372 will also be monitored.
2374 The result of monitoring the arrays is the generation of events.
2375 These events are passed to a separate program (if specified) and may
2376 be mailed to a given E-mail address.
2378 When passing events to a program, the program is run once for each event,
2379 and is given 2 or 3 command-line arguments: the first is the
2380 name of the event (see below), the second is the name of the
2381 md device which is affected, and the third is the name of a related
2382 device if relevant (such as a component device that has failed).
2386 is given, then a program or an E-mail address must be specified on the
2387 command line or in the config file. If neither are available, then
2389 will not monitor anything.
2393 will continue monitoring as long as something was found to monitor. If
2394 no program or email is given, then each event is reported to
2397 The different events are:
2401 .B DeviceDisappeared
2402 An md array which previously was configured appears to no longer be
2403 configured. (syslog priority: Critical)
2407 was told to monitor an array which is RAID0 or Linear, then it will
2409 .B DeviceDisappeared
2410 with the extra information
2412 This is because RAID0 and Linear do not support the device-failed,
2413 hot-spare and resync operations which are monitored.
2417 An md array started reconstruction (e.g. recovery, resync, reshape,
2418 check, repair). (syslog priority: Warning)
2424 is a two-digit number (ie. 05, 48). This indicates that rebuild
2425 has passed that many percent of the total. The events are generated
2426 with fixed increment since 0. Increment size may be specified with
2427 a commandline option (default is 20). (syslog priority: Warning)
2431 An md array that was rebuilding, isn't any more, either because it
2432 finished normally or was aborted. (syslog priority: Warning)
2436 An active component device of an array has been marked as
2437 faulty. (syslog priority: Critical)
2441 A spare component device which was being rebuilt to replace a faulty
2442 device has failed. (syslog priority: Critical)
2446 A spare component device which was being rebuilt to replace a faulty
2447 device has been successfully rebuilt and has been made active.
2448 (syslog priority: Info)
2452 A new md array has been detected in the
2454 file. (syslog priority: Info)
2458 A newly noticed array appears to be degraded. This message is not
2461 notices a drive failure which causes degradation, but only when
2463 notices that an array is degraded when it first sees the array.
2464 (syslog priority: Critical)
2468 A spare drive has been moved from one array in a
2472 to another to allow a failed drive to be replaced.
2473 (syslog priority: Info)
2479 has been told, via the config file, that an array should have a certain
2480 number of spare devices, and
2482 detects that it has fewer than this number when it first sees the
2483 array, it will report a
2486 (syslog priority: Warning)
2490 An array was found at startup, and the
2493 (syslog priority: Info)
2503 cause Email to be sent. All events cause the program to be run.
2504 The program is run with two or three arguments: the event
2505 name, the array device and possibly a second device.
2507 Each event has an associated array device (e.g.
2509 and possibly a second device. For
2514 the second device is the relevant component device.
2517 the second device is the array that the spare was moved from.
2521 to move spares from one array to another, the different arrays need to
2522 be labeled with the same
2524 or the spares must be allowed to migrate through matching POLICY domains
2525 in the configuration file. The
2527 name can be any string; it is only necessary that different spare
2528 groups use different names.
2532 detects that an array in a spare group has fewer active
2533 devices than necessary for the complete array, and has no spare
2534 devices, it will look for another array in the same spare group that
2535 has a full complement of working drive and a spare. It will then
2536 attempt to remove the spare from the second drive and add it to the
2538 If the removal succeeds but the adding fails, then it is added back to
2541 If the spare group for a degraded array is not defined,
2543 will look at the rules of spare migration specified by POLICY lines in
2545 and then follow similar steps as above if a matching spare is found.
2548 The GROW mode is used for changing the size or shape of an active
2550 For this to work, the kernel must support the necessary change.
2551 Various types of growth are being added during 2.6 development.
2553 Currently the supported changes include
2555 change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
2557 increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
2560 change the chunk-size and layout of RAID0, RAID4, RAID5, RAID6 and RAID10.
2562 convert between RAID1 and RAID5, between RAID5 and RAID6, between
2563 RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
2565 add a write-intent bitmap to any array which supports these bitmaps, or
2566 remove a write-intent bitmap from such an array.
2569 Using GROW on containers is currently supported only for Intel's IMSM
2570 container format. The number of devices in a container can be
2571 increased - which affects all arrays in the container - or an array
2572 in a container can be converted between levels where those levels are
2573 supported by the container, and the conversion is on of those listed
2574 above. Resizing arrays in an IMSM container with
2576 is not yet supported.
2578 Grow functionality (e.g. expand a number of raid devices) for Intel's
2579 IMSM container format has an experimental status. It is guarded by the
2580 .B MDADM_EXPERIMENTAL
2581 environment variable which must be set to '1' for a GROW command to
2583 This is for the following reasons:
2586 Intel's native IMSM check-pointing is not fully tested yet.
2587 This can causes IMSM incompatibility during the grow process: an array
2588 which is growing cannot roam between Microsoft Windows(R) and Linux
2592 Interrupting a grow operation is not recommended, because it
2593 has not been fully tested for Intel's IMSM container format yet.
2596 Note: Intel's native checkpointing doesn't use
2598 option and it is transparent for assembly feature.
2601 Normally when an array is built the "size" is taken from the smallest
2602 of the drives. If all the small drives in an arrays are, one at a
2603 time, removed and replaced with larger drives, then you could have an
2604 array of large drives with only a small amount used. In this
2605 situation, changing the "size" with "GROW" mode will allow the extra
2606 space to start being used. If the size is increased in this way, a
2607 "resync" process will start to make sure the new parts of the array
2610 Note that when an array changes size, any filesystem that may be
2611 stored in the array will not automatically grow or shrink to use or
2612 vacate the space. The
2613 filesystem will need to be explicitly told to use the extra space
2614 after growing, or to reduce its size
2616 to shrinking the array.
2618 Also the size of an array cannot be changed while it has an active
2619 bitmap. If an array has a bitmap, it must be removed before the size
2620 can be changed. Once the change is complete a new bitmap can be created.
2622 .SS RAID\-DEVICES CHANGES
2624 A RAID1 array can work with any number of devices from 1 upwards
2625 (though 1 is not very useful). There may be times which you want to
2626 increase or decrease the number of active devices. Note that this is
2627 different to hot-add or hot-remove which changes the number of
2630 When reducing the number of devices in a RAID1 array, the slots which
2631 are to be removed from the array must already be vacant. That is, the
2632 devices which were in those slots must be failed and removed.
2634 When the number of devices is increased, any hot spares that are
2635 present will be activated immediately.
2637 Changing the number of active devices in a RAID5 or RAID6 is much more
2638 effort. Every block in the array will need to be read and written
2639 back to a new location. From 2.6.17, the Linux Kernel is able to
2640 increase the number of devices in a RAID5 safely, including restarting
2641 an interrupted "reshape". From 2.6.31, the Linux Kernel is able to
2642 increase or decrease the number of devices in a RAID5 or RAID6.
2644 From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4
2647 uses this functionality and the ability to add
2648 devices to a RAID4 to allow devices to be added to a RAID0. When
2649 requested to do this,
2651 will convert the RAID0 to a RAID4, add the necessary disks and make
2652 the reshape happen, and then convert the RAID4 back to RAID0.
2654 When decreasing the number of devices, the size of the array will also
2655 decrease. If there was data in the array, it could get destroyed and
2656 this is not reversible, so you should firstly shrink the filesystem on
2657 the array to fit within the new size. To help prevent accidents,
2659 requires that the size of the array be decreased first with
2660 .BR "mdadm --grow --array-size" .
2661 This is a reversible change which simply makes the end of the array
2662 inaccessible. The integrity of any data can then be checked before
2663 the non-reversible reduction in the number of devices is request.
2665 When relocating the first few stripes on a RAID5 or RAID6, it is not
2666 possible to keep the data on disk completely consistent and
2667 crash-proof. To provide the required safety, mdadm disables writes to
2668 the array while this "critical section" is reshaped, and takes a
2669 backup of the data that is in that section. For grows, this backup may be
2670 stored in any spare devices that the array has, however it can also be
2671 stored in a separate file specified with the
2673 option, and is required to be specified for shrinks, RAID level
2674 changes and layout changes. If this option is used, and the system
2675 does crash during the critical period, the same file must be passed to
2677 to restore the backup and reassemble the array. When shrinking rather
2678 than growing the array, the reshape is done from the end towards the
2679 beginning, so the "critical section" is at the end of the reshape.
2683 Changing the RAID level of any array happens instantaneously. However
2684 in the RAID5 to RAID6 case this requires a non-standard layout of the
2685 RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is
2686 required before the change can be accomplished. So while the level
2687 change is instant, the accompanying layout change can take quite a
2690 is required. If the array is not simultaneously being grown or
2691 shrunk, so that the array size will remain the same - for example,
2692 reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
2693 be used not just for a "cricital section" but throughout the reshape
2694 operation, as described below under LAYOUT CHANGES.
2696 .SS CHUNK-SIZE AND LAYOUT CHANGES
2698 Changing the chunk-size of layout without also changing the number of
2699 devices as the same time will involve re-writing all blocks in-place.
2700 To ensure against data loss in the case of a crash, a
2702 must be provided for these changes. Small sections of the array will
2703 be copied to the backup file while they are being rearranged. This
2704 means that all the data is copied twice, once to the backup and once
2705 to the new layout on the array, so this type of reshape will go very
2708 If the reshape is interrupted for any reason, this backup file must be
2710 .B "mdadm --assemble"
2711 so the array can be reassembled. Consequently the file cannot be
2712 stored on the device being reshaped.
2717 A write-intent bitmap can be added to, or removed from, an active
2718 array. Either internal bitmaps, or bitmaps stored in a separate file,
2719 can be added. Note that if you add a bitmap stored in a file which is
2720 in a filesystem that is on the RAID array being affected, the system
2721 will deadlock. The bitmap must be on a separate filesystem.
2723 .SH INCREMENTAL MODE
2727 .B mdadm \-\-incremental
2731 .RI [ optional-aliases-for-device ]
2734 .B mdadm \-\-incremental \-\-fail
2738 .B mdadm \-\-incremental \-\-rebuild\-map
2741 .B mdadm \-\-incremental \-\-run \-\-scan
2744 This mode is designed to be used in conjunction with a device
2745 discovery system. As devices are found in a system, they can be
2747 .B "mdadm \-\-incremental"
2748 to be conditionally added to an appropriate array.
2750 Conversely, it can also be used with the
2752 flag to do just the opposite and find whatever array a particular device
2753 is part of and remove the device from that array.
2755 If the device passed is a
2757 device created by a previous call to
2759 then rather than trying to add that device to an array, all the arrays
2760 described by the metadata of the container will be started.
2763 performs a number of tests to determine if the device is part of an
2764 array, and which array it should be part of. If an appropriate array
2765 is found, or can be created,
2767 adds the device to the array and conditionally starts the array.
2771 will normally only add devices to an array which were previously working
2772 (active or spare) parts of that array. The support for automatic
2773 inclusion of a new drive as a spare in some array requires
2774 a configuration through POLICY in config file.
2778 makes are as follow:
2780 Is the device permitted by
2782 That is, is it listed in a
2784 line in that file. If
2786 is absent then the default it to allow any device. Similarly if
2788 contains the special word
2790 then any device is allowed. Otherwise the device name given to
2792 or one of the aliases given, or an alias found in the filesystem,
2793 must match one of the names or patterns in a
2797 This is the only context where the aliases are used. They are
2798 usually provided by a
2804 Does the device have a valid md superblock? If a specific metadata
2805 version is requested with
2809 then only that style of metadata is accepted, otherwise
2811 finds any known version of metadata. If no
2813 metadata is found, the device may be still added to an array
2814 as a spare if POLICY allows.
2818 Does the metadata match an expected array?
2819 The metadata can match in two ways. Either there is an array listed
2822 which identifies the array (either by UUID, by name, by device list,
2823 or by minor-number), or the array was created with a
2829 or on the command line.
2832 is not able to positively identify the array as belonging to the
2833 current host, the device will be rejected.
2838 keeps a list of arrays that it has partially assembled in
2840 If no array exists which matches
2841 the metadata on the new device,
2843 must choose a device name and unit number. It does this based on any
2846 or any name information stored in the metadata. If this name
2847 suggests a unit number, that number will be used, otherwise a free
2848 unit number will be chosen. Normally
2850 will prefer to create a partitionable array, however if the
2854 suggests that a non-partitionable array is preferred, that will be
2857 If the array is not found in the config file and its metadata does not
2858 identify it as belonging to the "homehost", then
2860 will choose a name for the array which is certain not to conflict with
2861 any array which does belong to this host. It does this be adding an
2862 underscore and a small number to the name preferred by the metadata.
2864 Once an appropriate array is found or created and the device is added,
2866 must decide if the array is ready to be started. It will
2867 normally compare the number of available (non-spare) devices to the
2868 number of devices that the metadata suggests need to be active. If
2869 there are at least that many, the array will be started. This means
2870 that if any devices are missing the array will not be restarted.
2876 in which case the array will be run as soon as there are enough
2877 devices present for the data to be accessible. For a RAID1, that
2878 means one device will start the array. For a clean RAID5, the array
2879 will be started as soon as all but one drive is present.
2881 Note that neither of these approaches is really ideal. If it can
2882 be known that all device discovery has completed, then
2886 can be run which will try to start all arrays that are being
2887 incrementally assembled. They are started in "read-auto" mode in
2888 which they are read-only until the first write request. This means
2889 that no metadata updates are made and no attempt at resync or recovery
2890 happens. Further devices that are found before the first write can
2891 still be added safely.
2894 This section describes environment variables that affect how mdadm
2899 Setting this value to 1 will prevent mdadm from automatically launching
2900 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2906 does not create any device nodes in /dev, but leaves that task to
2910 appears not to be configured, or if this environment variable is set
2913 will create and devices that are needed.
2916 .B MDADM_NO_SYSTEMCTL
2921 is in use it will normally request
2923 to start various background tasks (particularly
2925 rather than forking and running them in the background. This can be
2926 suppressed by setting
2927 .BR MDADM_NO_SYSTEMCTL=1 .
2931 A key value of IMSM metadata is that it allows interoperability with
2932 boot ROMs on Intel platforms, and with other major operating systems.
2935 will only allow an IMSM array to be created or modified if detects
2936 that it is running on an Intel platform which supports IMSM, and
2937 supports the particular configuration of IMSM that is being requested
2938 (some functionality requires newer OROM support).
2940 These checks can be suppressed by setting IMSM_NO_PLATFORM=1 in the
2941 environment. This can be useful for testing or for disaster
2942 recovery. You should be aware that interoperability may be
2943 compromised by setting this value.
2946 .B MDADM_GROW_ALLOW_OLD
2947 If an array is stopped while it is performing a reshape and that
2948 reshape was making use of a backup file, then when the array is
2951 will sometimes complain that the backup file is too old. If this
2952 happens and you are certain it is the right backup file, you can
2953 over-ride this check by setting
2954 .B MDADM_GROW_ALLOW_OLD=1
2959 Any string given in this variable is added to the start of the
2961 line in the config file, or treated as the whole
2963 line if none is given. It can be used to disable certain metadata
2966 is called from a boot script. For example
2968 .B " export MDADM_CONF_AUTO='-ddf -imsm'
2972 does not automatically assemble any DDF or
2973 IMSM arrays that are found. This can be useful on systems configured
2974 to manage such arrays with
2980 .B " mdadm \-\-query /dev/name-of-device"
2982 This will find out if a given device is a RAID array, or is part of
2983 one, and will provide brief information about the device.
2985 .B " mdadm \-\-assemble \-\-scan"
2987 This will assemble and start all arrays listed in the standard config
2988 file. This command will typically go in a system startup file.
2990 .B " mdadm \-\-stop \-\-scan"
2992 This will shut down all arrays that can be shut down (i.e. are not
2993 currently in use). This will typically go in a system shutdown script.
2995 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
2997 If (and only if) there is an Email address or program given in the
2998 standard config file, then
2999 monitor the status of all arrays listed in that file by
3000 polling them ever 2 minutes.
3002 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
3004 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
3007 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
3009 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
3011 This will create a prototype config file that describes currently
3012 active arrays that are known to be made from partitions of IDE or SCSI drives.
3013 This file should be reviewed before being used as it may
3014 contain unwanted detail.
3016 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
3018 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
3020 This will find arrays which could be assembled from existing IDE and
3021 SCSI whole drives (not partitions), and store the information in the
3022 format of a config file.
3023 This file is very likely to contain unwanted detail, particularly
3026 entries. It should be reviewed and edited before being used as an
3029 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
3031 .B " mdadm \-Ebsc partitions"
3033 Create a list of devices by reading
3034 .BR /proc/partitions ,
3035 scan these for RAID superblocks, and printout a brief listing of all
3038 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
3040 Scan all partitions and devices listed in
3041 .BR /proc/partitions
3044 out of all such devices with a RAID superblock with a minor number of 0.
3046 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /run/mdadm/mon.pid"
3048 If config file contains a mail address or alert program, run mdadm in
3049 the background in monitor mode monitoring all md devices. Also write
3050 pid of mdadm daemon to
3051 .BR /run/mdadm/mon.pid .
3053 .B " mdadm \-Iq /dev/somedevice"
3055 Try to incorporate newly discovered device into some array as
3058 .B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan"
3060 Rebuild the array map from any current arrays, and then start any that
3063 .B " mdadm /dev/md4 --fail detached --remove detached"
3065 Any devices which are components of /dev/md4 will be marked as faulty
3066 and then remove from the array.
3068 .B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
3072 which is currently a RAID5 array will be converted to RAID6. There
3073 should normally already be a spare drive attached to the array as a
3074 RAID6 needs one more drive than a matching RAID5.
3076 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
3078 Create a DDF array over 6 devices.
3080 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
3082 Create a RAID5 array over any 3 devices in the given DDF set. Use
3083 only 30 gigabytes of each device.
3085 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
3087 Assemble a pre-exist ddf array.
3089 .B " mdadm -I /dev/md/ddf1"
3091 Assemble all arrays contained in the ddf array, assigning names as
3094 .B " mdadm \-\-create \-\-help"
3096 Provide help about the Create mode.
3098 .B " mdadm \-\-config \-\-help"
3100 Provide help about the format of the config file.
3102 .B " mdadm \-\-help"
3104 Provide general help.
3114 lists all active md devices with information about them.
3116 uses this to find arrays when
3118 is given in Misc mode, and to monitor array reconstruction
3123 The config file lists which devices may be scanned to see if
3124 they contain MD super block, and gives identifying information
3125 (e.g. UUID) about known MD arrays. See
3129 .SS /etc/mdadm.conf.d
3131 A directory containing configuration files which are read in lexical
3137 mode is used, this file gets a list of arrays currently being created.
3142 understand two sorts of names for array devices.
3144 The first is the so-called 'standard' format name, which matches the
3145 names used by the kernel and which appear in
3148 The second sort can be freely chosen, but must reside in
3150 When giving a device name to
3152 to create or assemble an array, either full path name such as
3156 can be given, or just the suffix of the second sort of name, such as
3162 chooses device names during auto-assembly or incremental assembly, it
3163 will sometimes add a small sequence number to the end of the name to
3164 avoid conflicted between multiple arrays that have the same name. If
3166 can reasonably determine that the array really is meant for this host,
3167 either by a hostname in the metadata, or by the presence of the array
3170 then it will leave off the suffix if possible.
3171 Also if the homehost is specified as
3174 will only use a suffix if a different array of the same name already
3175 exists or is listed in the config file.
3177 The standard names for non-partitioned arrays (the only sort of md
3178 array available in 2.4 and earlier) are of the form
3182 where NN is a number.
3183 The standard names for partitionable arrays (as available from 2.6
3184 onwards) are of the form:
3188 Partition numbers should be indicated by adding "pMM" to these, thus "/dev/md/d1p2".
3190 From kernel version 2.6.28 the "non-partitioned array" can actually
3191 be partitioned. So the "md_d\fBNN\fP"
3192 names are no longer needed, and
3193 partitions such as "/dev/md\fBNN\fPp\fBXX\fP"
3196 From kernel version 2.6.29 standard names can be non-numeric following
3203 is any string. These names are supported by
3205 since version 3.3 provided they are enabled in
3210 was previously known as
3214 For further information on mdadm usage, MD and the various levels of
3217 .B http://raid.wiki.kernel.org/
3219 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
3221 The latest version of
3223 should always be available from
3225 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob