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.
8 .TH MDADM 8 "" v3.0-devel2
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.
51 is also not true RAID, and it only involves one device. It
52 provides a layer over a true device that can be used to inject faults.
57 is a collection of devices that are
58 managed as a set. This is similar to the set of devices connected to
59 a hardware RAID controller. The set of devices may contain a number
60 of different RAID arrays each utilising some (or all) blocks from a
61 number of the devices in the set. For example, two devices in a 5-device set
62 might form a RAID1 used the whole devices. The remaining three might
63 have a RAID5 over the first half of each device, and a RAID0 over the
68 there is one set of metadata that describes all of
69 the arrays in the container. So when
73 device, it just represents the metadata. Other normal arrays (RAID1
74 etc) can be created inside that container.
78 .\"is a program that can be used to create, manage, and monitor
80 .\"such it provides a similar set of functionality to the
83 .\"The key differences between
90 .\"is a single program and not a collection of programs.
93 .\"can perform (almost) all of its functions without having a
94 .\"configuration file and does not use one by default. Also
96 .\"helps with management of the configuration
100 .\"can provide information about your arrays (through Query, Detail, and Examine)
107 .\".IR /etc/raidtab ,
110 .\"configuration file, at all. It has a different configuration file
111 .\"with a different format and a different purpose.
114 mdadm has several major modes of operation:
117 Assemble the components of a previously created
118 array into an active array. Components can be explicitly given
119 or can be searched for.
121 checks that the components
122 do form a bona fide array, and can, on request, fiddle superblock
123 information so as to assemble a faulty array.
127 Build an array that doesn't have per-device superblocks. For these
130 cannot differentiate between initial creation and subsequent assembly
131 of an array. It also cannot perform any checks that appropriate
132 components have been requested. Because of this, the
134 mode should only be used together with a complete understanding of
139 Create a new array with per-device superblocks.
141 .\"in several step create-add-add-run or it can all happen with one command.
144 .B "Follow or Monitor"
145 Monitor one or more md devices and act on any state changes. This is
146 only meaningful for raid1, 4, 5, 6, 10 or multipath arrays, as
147 only these have interesting state. raid0 or linear never have
148 missing, spare, or failed drives, so there is nothing to monitor.
152 Grow (or shrink) an array, or otherwise reshape it in some way.
153 Currently supported growth options including changing the active size
154 of component devices and changing the number of active devices in RAID
155 levels 1/4/5/6, as well as adding or removing a write-intent bitmap.
158 .B "Incremental Assembly"
159 Add a single device to an appropriate array. If the addition of the
160 device makes the array runnable, the array will be started.
161 This provides a convenient interface to a
163 system. As each device is detected,
165 has a chance to include it in some array as appropriate.
171 in this mode, then any arrays within that container will be assembled
176 This is for doing things to specific components of an array such as
177 adding new spares and removing faulty devices.
181 This is an 'everything else' mode that supports operations on active
182 arrays, operations on component devices such as erasing old superblocks, and
183 information gathering operations.
184 .\"This mode allows operations on independent devices such as examine MD
185 .\"superblocks, erasing old superblocks and stopping active arrays.
189 This mode does not act on a specific device or array, but rather it
190 requests the Linux Kernel to activate any auto-detected arrays.
193 .SH Options for selecting a mode are:
196 .BR \-A ", " \-\-assemble
197 Assemble a pre-existing array.
200 .BR \-B ", " \-\-build
201 Build a legacy array without superblocks.
204 .BR \-C ", " \-\-create
208 .BR \-F ", " \-\-follow ", " \-\-monitor
214 .BR \-G ", " \-\-grow
215 Change the size or shape of an active array.
218 .BR \-I ", " \-\-incremental
219 Add a single device into an appropriate array, and possibly start the array.
223 Request that the kernel starts any auto-detected arrays. This can only
226 is compiled into the kernel \(em not if it is a module.
227 Arrays can be auto-detected by the kernel if all the components are in
228 primary MS-DOS partitions with partition type
230 In-kernel autodetect is not recommended for new installations. Using
232 to detect and assemble arrays \(em possibly in an
234 \(em is substantially more flexible and should be preferred.
237 If a device is given before any options, or if the first option is
242 then the MANAGE mode is assume.
243 Anything other than these will cause the
247 .SH Options that are not mode-specific are:
250 .BR \-h ", " \-\-help
251 Display general help message or, after one of the above options, a
252 mode-specific help message.
256 Display more detailed help about command line parsing and some commonly
260 .BR \-V ", " \-\-version
261 Print version information for mdadm.
264 .BR \-v ", " \-\-verbose
265 Be more verbose about what is happening. This can be used twice to be
267 The extra verbosity currently only affects
268 .B \-\-detail \-\-scan
270 .BR "\-\-examine \-\-scan" .
273 .BR \-q ", " \-\-quiet
274 Avoid printing purely informative messages. With this,
276 will be silent unless there is something really important to report.
279 .BR \-b ", " \-\-brief
280 Be less verbose. This is used with
288 gives an intermediate level of verbosity.
291 .BR \-f ", " \-\-force
292 Be more forceful about certain operations. See the various modes for
293 the exact meaning of this option in different contexts.
296 .BR \-c ", " \-\-config=
297 Specify the config file. Default is to use
298 .BR /etc/mdadm.conf ,
299 or if that is missing then
300 .BR /etc/mdadm/mdadm.conf .
301 If the config file given is
303 then nothing will be read, but
305 will act as though the config file contained exactly
306 .B "DEVICE partitions containers"
309 to find a list of devices to scan, and
311 to find a list of containers to examine.
314 is given for the config file, then
316 will act as though the config file were empty.
319 .BR \-s ", " \-\-scan
322 for missing information.
323 In general, this option gives
325 permission to get any missing information (like component devices,
326 array devices, array identities, and alert destination) from the
327 configuration file (see previous option);
328 one exception is MISC mode when using
334 says to get a list of array devices from
338 .B \-e ", " \-\-metadata=
339 Declare the style of superblock (raid metadata) to be used. The
342 and to guess for other operations.
343 The default can be overridden by setting the
352 .IP "0, 0.90, default"
353 Use the original 0.90 format superblock. This format limits arrays to
354 28 component devices and limits component devices of levels 1 and
355 greater to 2 terabytes.
356 .IP "1, 1.0, 1.1, 1.2"
357 Use the new version-1 format superblock. This has few restrictions.
358 The different sub-versions store the superblock at different locations
359 on the device, either at the end (for 1.0), at the start (for 1.1) or
360 4K from the start (for 1.2).
362 Use the "Industry Standard" DDF (Disk Data Format) format. When
363 creating a DDF array a
365 will be created, and normal arrays can be created in that container.
367 Use the Intel Matrix Storage Manager metadata format. This creates a
369 which is managed in a similar manner to DDF.
374 This will override any
376 setting in the config file and provides the identity of the host which
377 should be considered the home for any arrays.
379 When creating an array, the
381 will be recorded in the superblock. For version-1 superblocks, it will
382 be prefixed to the array name. For version-0.90 superblocks, part of
383 the SHA1 hash of the hostname will be stored in the later half of the
386 When reporting information about an array, any array which is tagged
387 for the given homehost will be reported as such.
389 When using Auto-Assemble, only arrays tagged for the given homehost
392 .SH For create, build, or grow:
395 .BR \-n ", " \-\-raid\-devices=
396 Specify the number of active devices in the array. This, plus the
397 number of spare devices (see below) must equal the number of
399 (including "\fBmissing\fP" devices)
400 that are listed on the command line for
402 Setting a value of 1 is probably
403 a mistake and so requires that
405 be specified first. A value of 1 will then be allowed for linear,
406 multipath, raid0 and raid1. It is never allowed for raid4 or raid5.
408 This number can only be changed using
410 for RAID1, RAID5 and RAID6 arrays, and only on kernels which provide
414 .BR \-x ", " \-\-spare\-devices=
415 Specify the number of spare (eXtra) devices in the initial array.
416 Spares can also be added
417 and removed later. The number of component devices listed
418 on the command line must equal the number of raid devices plus the
419 number of spare devices.
423 .BR \-z ", " \-\-size=
424 Amount (in Kibibytes) of space to use from each drive in RAID level 1/4/5/6.
425 This must be a multiple of the chunk size, and must leave about 128Kb
426 of space at the end of the drive for the RAID superblock.
427 If this is not specified
428 (as it normally is not) the smallest drive (or partition) sets the
429 size, though if there is a variance among the drives of greater than 1%, a warning is
432 This value can be set with
434 for RAID level 1/4/5/6. If the array was created with a size smaller
435 than the currently active drives, the extra space can be accessed
438 The size can be given as
440 which means to choose the largest size that fits on all current drives.
442 This value can not be used with
444 metadata such as DDF and IMSM.
447 .BR \-c ", " \-\-chunk=
448 Specify chunk size of kibibytes. The default is 64.
452 Specify rounding factor for linear array (==chunk size)
455 .BR \-l ", " \-\-level=
456 Set raid level. When used with
458 options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
459 raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
460 Obviously some of these are synonymous.
464 metadata type is requested, only the
466 level is permitted, and it does not need to be explicitly given.
470 only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
472 Not yet supported with
476 .BR \-p ", " \-\-layout=
477 This option configures the fine details of data layout for raid5,
478 and raid10 arrays, and controls the failure modes for
481 The layout of the raid5 parity block can be one of
482 .BR left\-asymmetric ,
483 .BR left\-symmetric ,
484 .BR right\-asymmetric ,
485 .BR right\-symmetric ,
486 .BR la ", " ra ", " ls ", " rs .
488 .BR left\-symmetric .
490 When setting the failure mode for level
493 .BR write\-transient ", " wt ,
494 .BR read\-transient ", " rt ,
495 .BR write\-persistent ", " wp ,
496 .BR read\-persistent ", " rp ,
498 .BR read\-fixable ", " rf ,
499 .BR clear ", " flush ", " none .
501 Each failure mode can be followed by a number, which is used as a period
502 between fault generation. Without a number, the fault is generated
503 once on the first relevant request. With a number, the fault will be
504 generated after that many requests, and will continue to be generated
505 every time the period elapses.
507 Multiple failure modes can be current simultaneously by using the
509 option to set subsequent failure modes.
511 "clear" or "none" will remove any pending or periodic failure modes,
512 and "flush" will clear any persistent faults.
514 To set the parity with
516 the level of the array ("faulty")
517 must be specified before the fault mode is specified.
519 Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
520 by a small number. The default is 'n2'. The supported options are:
523 signals 'near' copies. Multiple copies of one data block are at
524 similar offsets in different devices.
527 signals 'offset' copies. Rather than the chunks being duplicated
528 within a stripe, whole stripes are duplicated but are rotated by one
529 device so duplicate blocks are on different devices. Thus subsequent
530 copies of a block are in the next drive, and are one chunk further
535 (multiple copies have very different offsets).
536 See md(4) for more detail about 'near' and 'far'.
538 The number is the number of copies of each datablock. 2 is normal, 3
539 can be useful. This number can be at most equal to the number of
540 devices in the array. It does not need to divide evenly into that
541 number (e.g. it is perfectly legal to have an 'n2' layout for an array
542 with an odd number of devices).
548 (thus explaining the p of
552 .BR \-b ", " \-\-bitmap=
553 Specify a file to store a write-intent bitmap in. The file should not
556 is also given. The same file should be provided
557 when assembling the array. If the word
559 is given, then the bitmap is stored with the metadata on the array,
560 and so is replicated on all devices. If the word
564 mode, then any bitmap that is present is removed.
566 To help catch typing errors, the filename must contain at least one
567 slash ('/') if it is a real file (not 'internal' or 'none').
569 Note: external bitmaps are only known to work on ext2 and ext3.
570 Storing bitmap files on other filesystems may result in serious problems.
573 .BR \-\-bitmap\-chunk=
574 Set the chunksize of the bitmap. Each bit corresponds to that many
575 Kilobytes of storage.
576 When using a file based bitmap, the default is to use the smallest
577 size that is at-least 4 and requires no more than 2^21 chunks.
580 bitmap, the chunksize is automatically determined to make best use of
585 .BR \-W ", " \-\-write\-mostly
586 subsequent devices lists in a
591 command will be flagged as 'write-mostly'. This is valid for RAID1
592 only and means that the 'md' driver will avoid reading from these
593 devices if at all possible. This can be useful if mirroring over a
597 .BR \-\-write\-behind=
598 Specify that write-behind mode should be enabled (valid for RAID1
599 only). If an argument is specified, it will set the maximum number
600 of outstanding writes allowed. The default value is 256.
601 A write-intent bitmap is required in order to use write-behind
602 mode, and write-behind is only attempted on drives marked as
606 .BR \-\-assume\-clean
609 that the array pre-existed and is known to be clean. It can be useful
610 when trying to recover from a major failure as you can be sure that no
611 data will be affected unless you actually write to the array. It can
612 also be used when creating a RAID1 or RAID10 if you want to avoid the
613 initial resync, however this practice \(em while normally safe \(em is not
614 recommended. Use this only if you really know what you are doing.
617 .BR \-\-backup\-file=
620 is used to increase the number of
621 raid-devices in a RAID5 if there are no spare devices available.
622 See the section below on RAID_DEVICE CHANGES. The file should be
623 stored on a separate device, not on the raid array being reshaped.
626 .BR \-N ", " \-\-name=
629 for the array. This is currently only effective when creating an
630 array with a version-1 superblock. The name is a simple textual
631 string that can be used to identify array components when assembling.
637 run the array, even if some of the components
638 appear to be active in another array or filesystem. Normally
640 will ask for confirmation before including such components in an
641 array. This option causes that question to be suppressed.
644 .BR \-f ", " \-\-force
647 accept the geometry and layout specified without question. Normally
649 will not allow creation of an array with only one device, and will try
650 to create a raid5 array with one missing drive (as this makes the
651 initial resync work faster). With
654 will not try to be so clever.
657 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part,p}{NN}"
658 Instruct mdadm to create the device file if needed, possibly allocating
659 an unused minor number. "md" causes a non-partitionable array
660 to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and
661 later) to be used. "yes" requires the named md device to have
662 a 'standard' format, and the type and minor number will be determined
663 from this. See DEVICE NAMES below.
665 The argument can also come immediately after
670 is not given on the command line or in the config file, then
676 is also given, then any
678 entries in the config file will override the
680 instruction given on the command line.
682 For partitionable arrays,
684 will create the device file for the whole array and for the first 4
685 partitions. A different number of partitions can be specified at the
686 end of this option (e.g.
688 If the device name ends with a digit, the partition names add a 'p',
689 and a number, e.g. "/dev/md/home1p3". If there is no
690 trailing digit, then the partition names just have a number added,
691 e.g. "/dev/md/scratch3".
693 If the md device name is in a 'standard' format as described in DEVICE
694 NAMES, then it will be created, if necessary, with the appropriate
695 number based on that name. If the device name is not in one of these
696 formats, then a unused minor number will be allocated. The minor
697 number will be considered unused if there is no active array for that
698 number, and there is no entry in /dev for that number and with a
699 non-standard name. Name that are not in 'standard' format are only
700 allowed in "/dev/md/".
703 \".BR \-\-symlink = no
708 \"to create devices in
710 \"it will also create symlinks from
712 \"with names starting with
718 \"to suppress this, or
720 \"to enforce this even if it is suppressing
727 .BR \-u ", " \-\-uuid=
728 uuid of array to assemble. Devices which don't have this uuid are
732 .BR \-m ", " \-\-super\-minor=
733 Minor number of device that array was created for. Devices which
734 don't have this minor number are excluded. If you create an array as
735 /dev/md1, then all superblocks will contain the minor number 1, even if
736 the array is later assembled as /dev/md2.
738 Giving the literal word "dev" for
742 to use the minor number of the md device that is being assembled.
745 .B \-\-super\-minor=dev
746 will look for super blocks with a minor number of 0.
749 .BR \-N ", " \-\-name=
750 Specify the name of the array to assemble. This must be the name
751 that was specified when creating the array. It must either match
752 the name stored in the superblock exactly, or it must match
755 prefixed to the start of the given name.
758 .BR \-f ", " \-\-force
759 Assemble the array even if some superblocks appear out-of-date
763 Attempt to start the array even if fewer drives were given than were
764 present last time the array was active. Normally if not all the
765 expected drives are found and
767 is not used, then the array will be assembled but not started.
770 an attempt will be made to start it anyway.
774 This is the reverse of
776 in that it inhibits the startup of array unless all expected drives
777 are present. This is only needed with
779 and can be used if the physical connections to devices are
780 not as reliable as you would like.
783 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
784 See this option under Create and Build options.
787 .BR \-b ", " \-\-bitmap=
788 Specify the bitmap file that was given when the array was created. If
791 bitmap, there is no need to specify this when assembling the array.
794 .BR \-\-backup\-file=
797 was used to grow the number of raid-devices in a RAID5, and the system
798 crashed during the critical section, then the same
802 to allow possibly corrupted data to be restored.
805 .BR \-U ", " \-\-update=
806 Update the superblock on each device while assembling the array. The
807 argument given to this flag can be one of
821 option will adjust the superblock of an array what was created on a Sparc
822 machine running a patched 2.2 Linux kernel. This kernel got the
823 alignment of part of the superblock wrong. You can use the
824 .B "\-\-examine \-\-sparc2.2"
827 to see what effect this would have.
831 option will update the
833 field on each superblock to match the minor number of the array being
835 This can be useful if
837 reports a different "Preferred Minor" to
839 In some cases this update will be performed automatically
840 by the kernel driver. In particular the update happens automatically
841 at the first write to an array with redundancy (RAID level 1 or
842 greater) on a 2.6 (or later) kernel.
846 option will change the uuid of the array. If a UUID is given with the
848 option that UUID will be used as a new UUID and will
850 be used to help identify the devices in the array.
853 is given, a random UUID is chosen.
857 option will change the
859 of the array as stored in the superblock. This is only supported for
860 version-1 superblocks.
864 option will change the
866 as recorded in the superblock. For version-0 superblocks, this is the
867 same as updating the UUID.
868 For version-1 superblocks, this involves updating the name.
872 option will cause the array to be marked
874 meaning that any redundancy in the array (e.g. parity for raid5,
875 copies for raid1) may be incorrect. This will cause the raid system
876 to perform a "resync" pass to make sure that all redundant information
881 option allows arrays to be moved between machines with different
883 When assembling such an array for the first time after a move, giving
884 .B "\-\-update=byteorder"
887 to expect superblocks to have their byteorder reversed, and will
888 correct that order before assembling the array. This is only valid
889 with original (Version 0.90) superblocks.
893 option will correct the summaries in the superblock. That is the
894 counts of total, working, active, failed, and spare devices.
898 will rarely be of use. It applies to version 1.1 and 1.2 metadata
899 only (where the metadata is at the start of the device) and is only
900 useful when the component device has changed size (typically become
901 larger). The version 1 metadata records the amount of the device that
902 can be used to store data, so if a device in a version 1.1 or 1.2
903 array becomes larger, the metadata will still be visible, but the
904 extra space will not. In this case it might be useful to assemble the
906 .BR \-\-update=devicesize .
909 to determine the maximum usable amount of space on each device and
910 update the relevant field in the metadata.
913 .B \-\-auto\-update\-homehost
914 This flag is only meaningful with auto-assembly (see discussion below).
915 In that situation, if no suitable arrays are found for this homehost,
917 will rescan for any arrays at all and will assemble them and update the
918 homehost to match the current host.
924 hot-add listed devices.
928 re-add a device that was recently removed from an array.
931 .BR \-r ", " \-\-remove
932 remove listed devices. They must not be active. i.e. they should
933 be failed or spare devices. As well as the name of a device file
942 The first causes all failed device to be removed. The second causes
943 any device which is no longer connected to the system (i.e an 'open'
946 to be removed. This will only succeed for devices that are spares or
947 have already been marked as failed.
950 .BR \-f ", " \-\-fail
951 mark listed devices as faulty.
952 As well as the name of a device file, the word
954 can be given. This will cause any device that has been detached from
955 the system to be marked as failed. It can then be removed.
963 .BR \-\-write\-mostly
964 Subsequent devices that are added or re-added will have the 'write-mostly'
965 flag set. This is only valid for RAID! and means that the 'md' driver
966 will avoid reading from these devices if possible.
969 Subsequent devices that are added or re-added will have the 'write-mostly'
974 Each of these options require that the first device listed is the array
975 to be acted upon, and the remainder are component devices to be added,
976 removed, or marked as faulty. Several different operations can be
977 specified for different devices, e.g.
979 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
981 Each operation applies to all devices listed until the next
984 If an array is using a write-intent bitmap, then devices which have
985 been removed can be re-added in a way that avoids a full
986 reconstruction but instead just updates the blocks that have changed
987 since the device was removed. For arrays with persistent metadata
988 (superblocks) this is done automatically. For arrays created with
990 mdadm needs to be told that this device we removed recently with
993 Devices can only be removed from an array if they are not in active
994 use, i.e. that must be spares or failed devices. To remove an active
995 device, it must first be marked as
1001 .BR \-Q ", " \-\-query
1002 Examine a device to see
1003 (1) if it is an md device and (2) if it is a component of an md
1005 Information about what is discovered is presented.
1008 .BR \-D ", " \-\-detail
1009 Print detail of one or more md devices.
1012 .BR \-Y ", " \-\-export
1017 output will be formatted as
1019 pairs for easy import into the environment.
1022 .BR \-E ", " \-\-examine
1023 Print content of md superblock on device(s).
1026 If an array was created on a 2.2 Linux kernel patched with RAID
1027 support, the superblock will have been created incorrectly, or at
1028 least incompatibly with 2.4 and later kernels. Using the
1032 will fix the superblock before displaying it. If this appears to do
1033 the right thing, then the array can be successfully assembled using
1034 .BR "\-\-assemble \-\-update=sparc2.2" .
1037 .BR \-X ", " \-\-examine\-bitmap
1038 Report information about a bitmap file.
1039 The argument is either an external bitmap file or an array component
1040 in case of an internal bitmap.
1043 .BR \-R ", " \-\-run
1044 start a partially built array.
1047 .BR \-S ", " \-\-stop
1048 deactivate array, releasing all resources.
1051 .BR \-o ", " \-\-readonly
1052 mark array as readonly.
1055 .BR \-w ", " \-\-readwrite
1056 mark array as readwrite.
1059 .B \-\-zero\-superblock
1060 If the device contains a valid md superblock, the block is
1061 overwritten with zeros. With
1063 the block where the superblock would be is overwritten even if it
1064 doesn't appear to be valid.
1067 .BR \-t ", " \-\-test
1072 is set to reflect the status of the device.
1075 .BR \-W ", " \-\-wait
1076 For each md device given, wait for any resync, recovery, or reshape
1077 activity to finish before returning.
1079 will return with success if it actually waited for every device
1080 listed, otherwise it will return failure.
1084 For each md device given, or each device in /proc/mdstat if
1086 is given, arrange for the array to be marked clean as soon as possible.
1087 Also, quiesce resync so that the monitor for external metadata arrays
1088 (mdmon) has an opportunity to checkpoint the resync position.
1090 will return with success if the array uses external metadata and we
1091 successfully waited. For native arrays this returns immediately as the
1092 kernel handles both dirty-clean transitions and resync checkpointing in
1093 the kernel at shutdown. No action is taken if safe-mode handling is
1096 .SH For Incremental Assembly mode:
1098 .BR \-\-rebuild\-map ", " \-r
1099 Rebuild the map file
1100 .RB ( /var/run/mdadm/map )
1103 uses to help track which arrays are currently being assembled.
1106 .BR \-\-run ", " \-R
1107 Run any array assembled as soon as a minimal number of devices are
1108 available, rather than waiting until all expected devices are present.
1111 .BR \-\-scan ", " \-s
1112 Only meaningful with
1116 file for arrays that are being incrementally assembled and will try to
1117 start any that are not already started. If any such array is listed
1120 as requiring an external bitmap, that bitmap will be attached first.
1122 .SH For Monitor mode:
1124 .BR \-m ", " \-\-mail
1125 Give a mail address to send alerts to.
1128 .BR \-p ", " \-\-program ", " \-\-alert
1129 Give a program to be run whenever an event is detected.
1132 .BR \-y ", " \-\-syslog
1133 Cause all events to be reported through 'syslog'. The messages have
1134 facility of 'daemon' and varying priorities.
1137 .BR \-d ", " \-\-delay
1138 Give a delay in seconds.
1140 polls the md arrays and then waits this many seconds before polling
1141 again. The default is 60 seconds.
1144 .BR \-f ", " \-\-daemonise
1147 to run as a background daemon if it decides to monitor anything. This
1148 causes it to fork and run in the child, and to disconnect form the
1149 terminal. The process id of the child is written to stdout.
1152 which will only continue monitoring if a mail address or alert program
1153 is found in the config file.
1156 .BR \-i ", " \-\-pid\-file
1159 is running in daemon mode, write the pid of the daemon process to
1160 the specified file, instead of printing it on standard output.
1163 .BR \-1 ", " \-\-oneshot
1164 Check arrays only once. This will generate
1166 events and more significantly
1172 .B " mdadm \-\-monitor \-\-scan \-1"
1174 from a cron script will ensure regular notification of any degraded arrays.
1177 .BR \-t ", " \-\-test
1180 alert for every array found at startup. This alert gets mailed and
1181 passed to the alert program. This can be used for testing that alert
1182 message do get through successfully.
1188 .B mdadm \-\-assemble
1189 .I md-device options-and-component-devices...
1192 .B mdadm \-\-assemble \-\-scan
1193 .I md-devices-and-options...
1196 .B mdadm \-\-assemble \-\-scan
1200 This usage assembles one or more raid arrays from pre-existing components.
1201 For each array, mdadm needs to know the md device, the identity of the
1202 array, and a number of component-devices. These can be found in a number of ways.
1204 In the first usage example (without the
1206 the first device given is the md device.
1207 In the second usage example, all devices listed are treated as md
1208 devices and assembly is attempted.
1209 In the third (where no devices are listed) all md devices that are
1210 listed in the configuration file are assembled. Then any arrays that
1211 can be found on unused devices will also be assembled.
1213 If precisely one device is listed, but
1219 was given and identity information is extracted from the configuration file.
1221 The identity can be given with the
1225 option, will be taken from the md-device record in the config file, or
1226 will be taken from the super block of the first component-device
1227 listed on the command line.
1229 Devices can be given on the
1231 command line or in the config file. Only devices which have an md
1232 superblock which contains the right identity will be considered for
1235 The config file is only used if explicitly named with
1237 or requested with (a possibly implicit)
1242 .B /etc/mdadm/mdadm.conf
1247 is not given, then the config file will only be used to find the
1248 identity of md arrays.
1250 Normally the array will be started after it is assembled. However if
1252 is not given and insufficient drives were listed to start a complete
1253 (non-degraded) array, then the array is not started (to guard against
1254 usage errors). To insist that the array be started in this case (as
1255 may work for RAID1, 4, 5, 6, or 10), give the
1259 If the md device does not exist, then it will be created providing the
1260 intent is clear. i.e. the name must be in a standard form, or the
1262 option must be given to clarify how and whether the device should be
1264 This can be useful for handling partitioned devices (which don't have
1265 a stable device number \(em it can change after a reboot) and when using
1266 "udev" to manage your
1268 tree (udev cannot handle md devices because of the unusual device
1269 initialisation conventions).
1271 If the option to "auto" is "mdp" or "part" or (on the command line
1272 only) "p", then mdadm will create a partitionable array, using the
1273 first free one that is not in use and does not already have an entry
1274 in /dev (apart from numeric /dev/md* entries).
1276 If the option to "auto" is "yes" or "md" or (on the command line)
1277 nothing, then mdadm will create a traditional, non-partitionable md
1280 It is expected that the "auto" functionality will be used to create
1281 device entries with meaningful names such as "/dev/md/home" or
1282 "/dev/md/root", rather than names based on the numerical array number.
1284 When using option "auto" to create a partitionable array, the device
1285 files for the first 4 partitions are also created. If a different
1286 number is required it can be simply appended to the auto option.
1287 e.g. "auto=part8". Partition names are created by appending a digit
1288 string to the device name, with an intervening "p" if the device name
1293 option is also available in Build and Create modes. As those modes do
1294 not use a config file, the "auto=" config option does not apply to
1302 and no devices are listed,
1304 will first attempt to assemble all the arrays listed in the config
1307 It will then look further for possible arrays and will try to assemble
1308 anything that it finds. Arrays which are tagged as belonging to the given
1309 homehost will be assembled and started normally. Arrays which do not
1310 obviously belong to this host are given names that are expected not to
1311 conflict with anything local, and are started "read-auto" so that
1312 nothing is written to any device until the array is written to. i.e.
1313 automatic resync etc is delayed.
1317 finds a consistent set of devices that look like they should comprise
1318 an array, and if the superblock is tagged as belonging to the given
1319 home host, it will automatically choose a device name and try to
1320 assemble the array. If the array uses version-0.90 metadata, then the
1322 number as recorded in the superblock is used to create a name in
1326 If the array uses version-1 metadata, then the
1328 from the superblock is used to similarly create a name in
1330 (the name will have any 'host' prefix stripped first).
1334 cannot find any array for the given host at all, and if
1335 .B \-\-auto\-update\-homehost
1338 will search again for any array (not just an array created for this
1339 host) and will assemble each assuming
1340 .BR \-\-update=homehost .
1341 This will change the host tag in the superblock so that on the next run,
1342 these arrays will be found without the second pass. The intention of
1343 this feature is to support transitioning a set of md arrays to using
1346 The reason for requiring arrays to be tagged with the homehost for
1347 auto assembly is to guard against problems that can arise when moving
1348 devices from one host to another.
1358 .BI \-\-raid\-devices= Z
1362 This usage is similar to
1364 The difference is that it creates an array without a superblock. With
1365 these arrays there is no difference between initially creating the array and
1366 subsequently assembling the array, except that hopefully there is useful
1367 data there in the second case.
1369 The level may raid0, linear, multipath, or faulty, or one of their
1370 synonyms. All devices must be listed and the array will be started
1382 .BI \-\-raid\-devices= Z
1386 This usage will initialise a new md array, associate some devices with
1387 it, and activate the array.
1391 option is given (as described in more detail in the section on
1392 Assemble mode), then the md device will be created with a suitable
1393 device number if necessary.
1395 As devices are added, they are checked to see if they contain raid
1396 superblocks or filesystems. They are also checked to see if the variance in
1397 device size exceeds 1%.
1399 If any discrepancy is found, the array will not automatically be run, though
1402 can override this caution.
1404 To create a "degraded" array in which some devices are missing, simply
1405 give the word "\fBmissing\fP"
1406 in place of a device name. This will cause
1408 to leave the corresponding slot in the array empty.
1409 For a RAID4 or RAID5 array at most one slot can be
1410 "\fBmissing\fP"; for a RAID6 array at most two slots.
1411 For a RAID1 array, only one real device needs to be given. All of the
1415 When creating a RAID5 array,
1417 will automatically create a degraded array with an extra spare drive.
1418 This is because building the spare into a degraded array is in general faster than resyncing
1419 the parity on a non-degraded, but not clean, array. This feature can
1420 be overridden with the
1424 When creating an array with version-1 metadata a name for the array is
1426 If this is not given with the
1430 will choose a name based on the last component of the name of the
1431 device being created. So if
1433 is being created, then the name
1438 is being created, then the name
1442 When creating a partition based array, using
1444 with version-1.x metadata, the partition type should be set to
1446 (non fs-data). This type selection allows for greater precision since
1447 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
1448 might create problems in the event of array recovery through a live cdrom.
1450 A new array will normally get a randomly assigned 128bit UUID which is
1451 very likely to be unique. If you have a specific need, you can choose
1452 a UUID for the array by giving the
1454 option. Be warned that creating two arrays with the same UUID is a
1455 recipe for disaster. Also, using
1457 when creating a v0.90 array will silently override any
1462 .\"option is given, it is not necessary to list any component-devices in this command.
1463 .\"They can be added later, before a
1467 .\"is given, the apparent size of the smallest drive given is used.
1469 When creating an array within a
1472 can be given either the list of devices to use, or simply the name of
1473 the container. The former case gives control over which devices in
1474 the container will be used for the array. The latter case allows
1476 to automatically choose which devices to use based on how much spare
1479 The General Management options that are valid with
1484 insist on running the array even if some devices look like they might
1489 start the array readonly \(em not supported yet.
1497 .I options... devices...
1500 This usage will allow individual devices in an array to be failed,
1501 removed or added. It is possible to perform multiple operations with
1502 on command. For example:
1504 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
1510 and will then remove it from the array and finally add it back
1511 in as a spare. However only one md array can be affected by a single
1522 MISC mode includes a number of distinct operations that
1523 operate on distinct devices. The operations are:
1526 The device is examined to see if it is
1527 (1) an active md array, or
1528 (2) a component of an md array.
1529 The information discovered is reported.
1533 The device should be an active md device.
1535 will display a detailed description of the array.
1539 will cause the output to be less detailed and the format to be
1540 suitable for inclusion in
1541 .BR /etc/mdadm.conf .
1544 will normally be 0 unless
1546 failed to get useful information about the device(s); however, if the
1548 option is given, then the exit status will be:
1552 The array is functioning normally.
1555 The array has at least one failed device.
1558 The array has multiple failed devices such that it is unusable.
1561 There was an error while trying to get information about the device.
1566 The device should be a component of an md array.
1568 will read the md superblock of the device and display the contents.
1573 is given, then multiple devices that are components of the one array
1574 are grouped together and reported in a single entry suitable
1576 .BR /etc/mdadm.conf .
1580 without listing any devices will cause all devices listed in the
1581 config file to be examined.
1585 The devices should be active md arrays which will be deactivated, as
1586 long as they are not currently in use.
1590 This will fully activate a partially assembled md array.
1594 This will mark an active array as read-only, providing that it is
1595 not currently being used.
1601 array back to being read/write.
1605 For all operations except
1608 will cause the operation to be applied to all arrays listed in
1613 causes all devices listed in the config file to be examined.
1620 .B mdadm \-\-monitor
1621 .I options... devices...
1626 to periodically poll a number of md arrays and to report on any events
1629 will never exit once it decides that there are arrays to be checked,
1630 so it should normally be run in the background.
1632 As well as reporting events,
1634 may move a spare drive from one array to another if they are in the
1637 and if the destination array has a failed drive but no spares.
1639 If any devices are listed on the command line,
1641 will only monitor those devices. Otherwise all arrays listed in the
1642 configuration file will be monitored. Further, if
1644 is given, then any other md devices that appear in
1646 will also be monitored.
1648 The result of monitoring the arrays is the generation of events.
1649 These events are passed to a separate program (if specified) and may
1650 be mailed to a given E-mail address.
1652 When passing events to a program, the program is run once for each event,
1653 and is given 2 or 3 command-line arguments: the first is the
1654 name of the event (see below), the second is the name of the
1655 md device which is affected, and the third is the name of a related
1656 device if relevant (such as a component device that has failed).
1660 is given, then a program or an E-mail address must be specified on the
1661 command line or in the config file. If neither are available, then
1663 will not monitor anything.
1667 will continue monitoring as long as something was found to monitor. If
1668 no program or email is given, then each event is reported to
1671 The different events are:
1675 .B DeviceDisappeared
1676 An md array which previously was configured appears to no longer be
1677 configured. (syslog priority: Critical)
1681 was told to monitor an array which is RAID0 or Linear, then it will
1683 .B DeviceDisappeared
1684 with the extra information
1686 This is because RAID0 and Linear do not support the device-failed,
1687 hot-spare and resync operations which are monitored.
1691 An md array started reconstruction. (syslog priority: Warning)
1697 is 20, 40, 60, or 80, this indicates that rebuild has passed that many
1698 percentage of the total. (syslog priority: Warning)
1702 An md array that was rebuilding, isn't any more, either because it
1703 finished normally or was aborted. (syslog priority: Warning)
1707 An active component device of an array has been marked as
1708 faulty. (syslog priority: Critical)
1712 A spare component device which was being rebuilt to replace a faulty
1713 device has failed. (syslog priority: Critical)
1717 A spare component device which was being rebuilt to replace a faulty
1718 device has been successfully rebuilt and has been made active.
1719 (syslog priority: Info)
1723 A new md array has been detected in the
1725 file. (syslog priority: Info)
1729 A newly noticed array appears to be degraded. This message is not
1732 notices a drive failure which causes degradation, but only when
1734 notices that an array is degraded when it first sees the array.
1735 (syslog priority: Critical)
1739 A spare drive has been moved from one array in a
1741 to another to allow a failed drive to be replaced.
1742 (syslog priority: Info)
1748 has been told, via the config file, that an array should have a certain
1749 number of spare devices, and
1751 detects that it has fewer than this number when it first sees the
1752 array, it will report a
1755 (syslog priority: Warning)
1759 An array was found at startup, and the
1762 (syslog priority: Info)
1772 cause Email to be sent. All events cause the program to be run.
1773 The program is run with two or three arguments: the event
1774 name, the array device and possibly a second device.
1776 Each event has an associated array device (e.g.
1778 and possibly a second device. For
1783 the second device is the relevant component device.
1786 the second device is the array that the spare was moved from.
1790 to move spares from one array to another, the different arrays need to
1791 be labeled with the same
1793 in the configuration file. The
1795 name can be any string; it is only necessary that different spare
1796 groups use different names.
1800 detects that an array in a spare group has fewer active
1801 devices than necessary for the complete array, and has no spare
1802 devices, it will look for another array in the same spare group that
1803 has a full complement of working drive and a spare. It will then
1804 attempt to remove the spare from the second drive and add it to the
1806 If the removal succeeds but the adding fails, then it is added back to
1810 The GROW mode is used for changing the size or shape of an active
1812 For this to work, the kernel must support the necessary change.
1813 Various types of growth are being added during 2.6 development,
1814 including restructuring a raid5 array to have more active devices.
1816 Currently the only support available is to
1818 change the "size" attribute
1819 for RAID1, RAID5 and RAID6.
1821 increase the "raid\-devices" attribute of RAID1, RAID5, and RAID6.
1823 add a write-intent bitmap to any array which supports these bitmaps, or
1824 remove a write-intent bitmap from such an array.
1827 GROW mode is not currently supported for
1829 or arrays inside containers.
1832 Normally when an array is built the "size" it taken from the smallest
1833 of the drives. If all the small drives in an arrays are, one at a
1834 time, removed and replaced with larger drives, then you could have an
1835 array of large drives with only a small amount used. In this
1836 situation, changing the "size" with "GROW" mode will allow the extra
1837 space to start being used. If the size is increased in this way, a
1838 "resync" process will start to make sure the new parts of the array
1841 Note that when an array changes size, any filesystem that may be
1842 stored in the array will not automatically grow to use the space. The
1843 filesystem will need to be explicitly told to use the extra space.
1845 .SS RAID-DEVICES CHANGES
1847 A RAID1 array can work with any number of devices from 1 upwards
1848 (though 1 is not very useful). There may be times which you want to
1849 increase or decrease the number of active devices. Note that this is
1850 different to hot-add or hot-remove which changes the number of
1853 When reducing the number of devices in a RAID1 array, the slots which
1854 are to be removed from the array must already be vacant. That is, the
1855 devices which were in those slots must be failed and removed.
1857 When the number of devices is increased, any hot spares that are
1858 present will be activated immediately.
1860 Increasing the number of active devices in a RAID5 is much more
1861 effort. Every block in the array will need to be read and written
1862 back to a new location. From 2.6.17, the Linux Kernel is able to do
1863 this safely, including restart and interrupted "reshape".
1865 When relocating the first few stripes on a raid5, it is not possible
1866 to keep the data on disk completely consistent and crash-proof. To
1867 provide the required safety, mdadm disables writes to the array while
1868 this "critical section" is reshaped, and takes a backup of the data
1869 that is in that section. This backup is normally stored in any spare
1870 devices that the array has, however it can also be stored in a
1871 separate file specified with the
1873 option. If this option is used, and the system does crash during the
1874 critical period, the same file must be passed to
1876 to restore the backup and reassemble the array.
1880 A write-intent bitmap can be added to, or removed from, an active
1881 array. Either internal bitmaps, or bitmaps stored in a separate file,
1882 can be added. Note that if you add a bitmap stored in a file which is
1883 in a filesystem that is on the raid array being affected, the system
1884 will deadlock. The bitmap must be on a separate filesystem.
1886 .SH INCREMENTAL MODE
1890 .B mdadm \-\-incremental
1896 .B mdadm \-\-incremental \-\-rebuild
1899 .B mdadm \-\-incremental \-\-run \-\-scan
1903 This mode is designed to be used in conjunction with a device
1904 discovery system. As devices are found in a system, they can be
1906 .B "mdadm \-\-incremental"
1907 to be conditionally added to an appropriate array.
1909 If the device passed is a
1911 device created by a previous call to
1913 then rather than trying to add that device to an array, all the arrays
1914 described by the metadata of the container will be started.
1917 performs a number of tests to determine if the device is part of an
1918 array, and which array it should be part of. If an appropriate array
1919 is found, or can be created,
1921 adds the device to the array and conditionally starts the array.
1925 will only add devices to an array which were previously working
1926 (active or spare) parts of that array. It does not currently support
1927 automatic inclusion of a new drive as a spare in some array.
1931 makes are as follow:
1933 Is the device permitted by
1935 That is, is it listed in a
1937 line in that file. If
1939 is absent then the default it to allow any device. Similar if
1941 contains the special word
1943 then any device is allowed. Otherwise the device name given to
1945 must match one of the names or patterns in a
1950 Does the device have a valid md superblock. If a specific metadata
1951 version is request with
1955 then only that style of metadata is accepted, otherwise
1957 finds any known version of metadata. If no
1959 metadata is found, the device is rejected.
1962 Does the metadata match an expected array?
1963 The metadata can match in two ways. Either there is an array listed
1966 which identifies the array (either by UUID, by name, by device list,
1967 or by minor-number), or the array was created with a
1973 or on the command line.
1976 is not able to positively identify the array as belonging to the
1977 current host, the device will be rejected.
1981 keeps a list of arrays that it has partially assembled in
1982 .B /var/run/mdadm/map
1984 .B /var/run/mdadm.map
1985 if the directory doesn't exist). If no array exists which matches
1986 the metadata on the new device,
1988 must choose a device name and unit number. It does this based on any
1991 or any name information stored in the metadata. If this name
1992 suggests a unit number, that number will be used, otherwise a free
1993 unit number will be chosen. Normally
1995 will prefer to create a partitionable array, however if the
1999 suggests that a non-partitionable array is preferred, that will be
2003 Once an appropriate array is found or created and the device is added,
2005 must decide if the array is ready to be started. It will
2006 normally compare the number of available (non-spare) devices to the
2007 number of devices that the metadata suggests need to be active. If
2008 there are at least that many, the array will be started. This means
2009 that if any devices are missing the array will not be restarted.
2015 in which case the array will be run as soon as there are enough
2016 devices present for the data to be accessible. For a raid1, that
2017 means one device will start the array. For a clean raid5, the array
2018 will be started as soon as all but one drive is present.
2020 Note that neither of these approaches is really ideal. If it can
2021 be known that all device discovery has completed, then
2025 can be run which will try to start all arrays that are being
2026 incrementally assembled. They are started in "read-auto" mode in
2027 which they are read-only until the first write request. This means
2028 that no metadata updates are made and no attempt at resync or recovery
2029 happens. Further devices that are found before the first write can
2030 still be added safely.
2034 This section describes environment variables that affect how mdadm
2039 Setting this value to 1 will prevent mdadm from automatically launching
2040 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2046 does not create any device nodes in /dev, but leaves that task to
2050 appears not to be configured, or if this environment variable is set
2053 will create and devices that are needed.
2057 .B " mdadm \-\-query /dev/name-of-device"
2059 This will find out if a given device is a raid array, or is part of
2060 one, and will provide brief information about the device.
2062 .B " mdadm \-\-assemble \-\-scan"
2064 This will assemble and start all arrays listed in the standard config
2065 file. This command will typically go in a system startup file.
2067 .B " mdadm \-\-stop \-\-scan"
2069 This will shut down all arrays that can be shut down (i.e. are not
2070 currently in use). This will typically go in a system shutdown script.
2072 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
2074 If (and only if) there is an Email address or program given in the
2075 standard config file, then
2076 monitor the status of all arrays listed in that file by
2077 polling them ever 2 minutes.
2079 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
2081 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
2084 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
2086 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
2088 This will create a prototype config file that describes currently
2089 active arrays that are known to be made from partitions of IDE or SCSI drives.
2090 This file should be reviewed before being used as it may
2091 contain unwanted detail.
2093 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
2095 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
2097 This will find arrays which could be assembled from existing IDE and
2098 SCSI whole drives (not partitions), and store the information in the
2099 format of a config file.
2100 This file is very likely to contain unwanted detail, particularly
2103 entries. It should be reviewed and edited before being used as an
2106 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
2108 .B " mdadm \-Ebsc partitions"
2110 Create a list of devices by reading
2111 .BR /proc/partitions ,
2112 scan these for RAID superblocks, and printout a brief listing of all
2115 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
2117 Scan all partitions and devices listed in
2118 .BR /proc/partitions
2121 out of all such devices with a RAID superblock with a minor number of 0.
2123 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /var/run/mdadm"
2125 If config file contains a mail address or alert program, run mdadm in
2126 the background in monitor mode monitoring all md devices. Also write
2127 pid of mdadm daemon to
2128 .BR /var/run/mdadm .
2130 .B " mdadm \-Iq /dev/somedevice"
2132 Try to incorporate newly discovered device into some array as
2135 .B " mdadm \-\-incremental \-\-rebuild \-\-run \-\-scan"
2137 Rebuild the array map from any current arrays, and then start any that
2140 .B " mdadm /dev/md4 --fail detached --remove detached"
2142 Any devices which are components of /dev/md4 will be marked as faulty
2143 and then remove from the array.
2145 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
2147 Create a DDF array over 6 devices.
2149 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
2151 Create a raid5 array over any 3 devices in the given DDF set. Use
2152 only 30 gigabytes of each device.
2154 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
2156 Assemble a pre-exist ddf array.
2158 .B " mdadm -I /dev/md/ddf1"
2160 Assemble all arrays contained in the ddf array, assigning names as
2163 .B " mdadm \-\-create \-\-help"
2165 Provide help about the Create mode.
2167 .B " mdadm \-\-config \-\-help"
2169 Provide help about the format of the config file.
2171 .B " mdadm \-\-help"
2173 Provide general help.
2184 lists all active md devices with information about them.
2186 uses this to find arrays when
2188 is given in Misc mode, and to monitor array reconstruction
2194 The config file lists which devices may be scanned to see if
2195 they contain MD super block, and gives identifying information
2196 (e.g. UUID) about known MD arrays. See
2200 .SS /var/run/mdadm/map
2203 mode is used, this file gets a list of arrays currently being created.
2206 does not exist as a directory, then
2207 .B /var/run/mdadm.map
2213 understand two sorts of names for array devices.
2215 The first is the so-called 'standard' format name, which matches the
2216 names used by the kernel and which appear in
2219 The second sort can be freely chosen, but must reside in
2221 When giving a device name to
2223 to create or assemble an array, either full path name such as
2227 can be given, or just the suffix of the second sort of name, such as
2233 chooses device names during auto-assembly, it will normally add a
2234 small sequence number to the end of the name to avoid conflicted
2235 between multiple arrays that have the same name. If
2237 can reasonably determine that the array really is meant for this host,
2238 either by a hostname in the metadata, or by the presence of the array
2239 in /etc/mdadm.conf, then it will leave of the suffix if possible.
2241 The standard names for non-partitioned arrays (the only sort of md
2242 array available in 2.4 and earlier) are of the form
2246 where NN is a number.
2247 The standard names for partitionable arrays (as available from 2.6
2248 onwards) are of the form
2252 Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
2254 From kernel version, 2.6.28 the "non-partitioned array" can actually
2255 be partitioned. So the "md_dNN" names are no longer needed, and
2256 partitions such as "/dev/mdNNpXX" are possible.
2260 was previously known as
2264 is completely separate from the
2266 package, and does not use the
2268 configuration file at all.
2271 For further information on mdadm usage, MD and the various levels of
2274 .B http://linux\-raid.osdl.org/
2276 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
2278 .\"for new releases of the RAID driver check out:
2281 .\".UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2282 .\"ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2287 .\".UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2288 .\"http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2291 The latest version of
2293 should always be available from
2295 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob