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-rc1
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 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 superblocks.
107 .\"in several step create-add-add-run or it can all happen with one command.
110 .B "Follow or Monitor"
111 Monitor one or more md devices and act on any state changes. This is
112 only meaningful for raid1, 4, 5, 6, 10 or multipath arrays, as
113 only these have interesting state. raid0 or linear never have
114 missing, spare, or failed drives, so there is nothing to monitor.
118 Grow (or shrink) an array, or otherwise reshape it in some way.
119 Currently supported growth options including changing the active size
120 of component devices and changing the number of active devices in RAID
121 levels 1/4/5/6, as well as adding or removing a write-intent bitmap.
124 .B "Incremental Assembly"
125 Add a single device to an appropriate array. If the addition of the
126 device makes the array runnable, the array will be started.
127 This provides a convenient interface to a
129 system. As each device is detected,
131 has a chance to include it in some array as appropriate.
137 in this mode, then any arrays within that container will be assembled
142 This is for doing things to specific components of an array such as
143 adding new spares and removing faulty devices.
147 This is an 'everything else' mode that supports operations on active
148 arrays, operations on component devices such as erasing old superblocks, and
149 information gathering operations.
150 .\"This mode allows operations on independent devices such as examine MD
151 .\"superblocks, erasing old superblocks and stopping active arrays.
155 This mode does not act on a specific device or array, but rather it
156 requests the Linux Kernel to activate any auto-detected arrays.
159 .SH Options for selecting a mode are:
162 .BR \-A ", " \-\-assemble
163 Assemble a pre-existing array.
166 .BR \-B ", " \-\-build
167 Build a legacy array without superblocks.
170 .BR \-C ", " \-\-create
174 .BR \-F ", " \-\-follow ", " \-\-monitor
180 .BR \-G ", " \-\-grow
181 Change the size or shape of an active array.
184 .BR \-I ", " \-\-incremental
185 Add a single device into an appropriate array, and possibly start the array.
189 Request that the kernel starts any auto-detected arrays. This can only
192 is compiled into the kernel \(em not if it is a module.
193 Arrays can be auto-detected by the kernel if all the components are in
194 primary MS-DOS partitions with partition type
196 In-kernel autodetect is not recommended for new installations. Using
198 to detect and assemble arrays \(em possibly in an
200 \(em is substantially more flexible and should be preferred.
203 If a device is given before any options, or if the first option is
208 then the MANAGE mode is assume.
209 Anything other than these will cause the
213 .SH Options that are not mode-specific are:
216 .BR \-h ", " \-\-help
217 Display general help message or, after one of the above options, a
218 mode-specific help message.
222 Display more detailed help about command line parsing and some commonly
226 .BR \-V ", " \-\-version
227 Print version information for mdadm.
230 .BR \-v ", " \-\-verbose
231 Be more verbose about what is happening. This can be used twice to be
233 The extra verbosity currently only affects
234 .B \-\-detail \-\-scan
236 .BR "\-\-examine \-\-scan" .
239 .BR \-q ", " \-\-quiet
240 Avoid printing purely informative messages. With this,
242 will be silent unless there is something really important to report.
245 .BR \-b ", " \-\-brief
246 Be less verbose. This is used with
254 gives an intermediate level of verbosity.
257 .BR \-f ", " \-\-force
258 Be more forceful about certain operations. See the various modes for
259 the exact meaning of this option in different contexts.
262 .BR \-c ", " \-\-config=
263 Specify the config file. Default is to use
264 .BR /etc/mdadm.conf ,
265 or if that is missing then
266 .BR /etc/mdadm/mdadm.conf .
267 If the config file given is
269 then nothing will be read, but
271 will act as though the config file contained exactly
272 .B "DEVICE partitions containers"
275 to find a list of devices to scan, and
277 to find a list of containers to examine.
280 is given for the config file, then
282 will act as though the config file were empty.
285 .BR \-s ", " \-\-scan
288 for missing information.
289 In general, this option gives
291 permission to get any missing information (like component devices,
292 array devices, array identities, and alert destination) from the
293 configuration file (see previous option);
294 one exception is MISC mode when using
300 says to get a list of array devices from
304 .B \-e ", " \-\-metadata=
305 Declare the style of superblock (raid metadata) to be used. The
308 and to guess for other operations.
309 The default can be overridden by setting the
318 .IP "0, 0.90, default"
319 Use the original 0.90 format superblock. This format limits arrays to
320 28 component devices and limits component devices of levels 1 and
321 greater to 2 terabytes.
322 .IP "1, 1.0, 1.1, 1.2"
323 Use the new version-1 format superblock. This has few restrictions.
324 The different sub-versions store the superblock at different locations
325 on the device, either at the end (for 1.0), at the start (for 1.1) or
326 4K from the start (for 1.2).
328 Use the "Industry Standard" DDF (Disk Data Format) format. When
329 creating a DDF array a
331 will be created, and normal arrays can be created in that container.
333 Use the Intel(R) Matrix Storage Manager metadata format. This creates a
335 which is managed in a similar manner to DDF, and is supported by an
336 option-rom on some platforms:
338 .B http://www.intel.com/design/chipsets/matrixstorage_sb.htm
344 This will override any
346 setting in the config file and provides the identity of the host which
347 should be considered the home for any arrays.
349 When creating an array, the
351 will be recorded in the superblock. For version-1 superblocks, it will
352 be prefixed to the array name. For version-0.90 superblocks, part of
353 the SHA1 hash of the hostname will be stored in the later half of the
356 When reporting information about an array, any array which is tagged
357 for the given homehost will be reported as such.
359 When using Auto-Assemble, only arrays tagged for the given homehost
360 will be allowed to use 'local' names (i.e. not ending in '_' followed
363 .SH For create, build, or grow:
366 .BR \-n ", " \-\-raid\-devices=
367 Specify the number of active devices in the array. This, plus the
368 number of spare devices (see below) must equal the number of
370 (including "\fBmissing\fP" devices)
371 that are listed on the command line for
373 Setting a value of 1 is probably
374 a mistake and so requires that
376 be specified first. A value of 1 will then be allowed for linear,
377 multipath, raid0 and raid1. It is never allowed for raid4 or raid5.
379 This number can only be changed using
381 for RAID1, RAID5 and RAID6 arrays, and only on kernels which provide
385 .BR \-x ", " \-\-spare\-devices=
386 Specify the number of spare (eXtra) devices in the initial array.
387 Spares can also be added
388 and removed later. The number of component devices listed
389 on the command line must equal the number of raid devices plus the
390 number of spare devices.
394 .BR \-z ", " \-\-size=
395 Amount (in Kibibytes) of space to use from each drive in RAID level 1/4/5/6.
396 This must be a multiple of the chunk size, and must leave about 128Kb
397 of space at the end of the drive for the RAID superblock.
398 If this is not specified
399 (as it normally is not) the smallest drive (or partition) sets the
400 size, though if there is a variance among the drives of greater than 1%, a warning is
403 This value can be set with
405 for RAID level 1/4/5/6. If the array was created with a size smaller
406 than the currently active drives, the extra space can be accessed
409 The size can be given as
411 which means to choose the largest size that fits on all current drives.
413 This value can not be used with
415 metadata such as DDF and IMSM.
418 .BR \-c ", " \-\-chunk=
419 Specify chunk size of kibibytes. The default is 64.
423 Specify rounding factor for linear array (==chunk size)
426 .BR \-l ", " \-\-level=
427 Set raid level. When used with
429 options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
430 raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
431 Obviously some of these are synonymous.
435 metadata type is requested, only the
437 level is permitted, and it does not need to be explicitly given.
441 only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
443 Not yet supported with
447 .BR \-p ", " \-\-layout=
448 This option configures the fine details of data layout for raid5,
449 and raid10 arrays, and controls the failure modes for
452 The layout of the raid5 parity block can be one of
453 .BR left\-asymmetric ,
454 .BR left\-symmetric ,
455 .BR right\-asymmetric ,
456 .BR right\-symmetric ,
457 .BR la ", " ra ", " ls ", " rs .
459 .BR left\-symmetric .
461 When setting the failure mode for level
464 .BR write\-transient ", " wt ,
465 .BR read\-transient ", " rt ,
466 .BR write\-persistent ", " wp ,
467 .BR read\-persistent ", " rp ,
469 .BR read\-fixable ", " rf ,
470 .BR clear ", " flush ", " none .
472 Each failure mode can be followed by a number, which is used as a period
473 between fault generation. Without a number, the fault is generated
474 once on the first relevant request. With a number, the fault will be
475 generated after that many requests, and will continue to be generated
476 every time the period elapses.
478 Multiple failure modes can be current simultaneously by using the
480 option to set subsequent failure modes.
482 "clear" or "none" will remove any pending or periodic failure modes,
483 and "flush" will clear any persistent faults.
485 Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
486 by a small number. The default is 'n2'. The supported options are:
489 signals 'near' copies. Multiple copies of one data block are at
490 similar offsets in different devices.
493 signals 'offset' copies. Rather than the chunks being duplicated
494 within a stripe, whole stripes are duplicated but are rotated by one
495 device so duplicate blocks are on different devices. Thus subsequent
496 copies of a block are in the next drive, and are one chunk further
501 (multiple copies have very different offsets).
502 See md(4) for more detail about 'near' and 'far'.
504 The number is the number of copies of each datablock. 2 is normal, 3
505 can be useful. This number can be at most equal to the number of
506 devices in the array. It does not need to divide evenly into that
507 number (e.g. it is perfectly legal to have an 'n2' layout for an array
508 with an odd number of devices).
514 (thus explaining the p of
518 .BR \-b ", " \-\-bitmap=
519 Specify a file to store a write-intent bitmap in. The file should not
522 is also given. The same file should be provided
523 when assembling the array. If the word
525 is given, then the bitmap is stored with the metadata on the array,
526 and so is replicated on all devices. If the word
530 mode, then any bitmap that is present is removed.
532 To help catch typing errors, the filename must contain at least one
533 slash ('/') if it is a real file (not 'internal' or 'none').
535 Note: external bitmaps are only known to work on ext2 and ext3.
536 Storing bitmap files on other filesystems may result in serious problems.
539 .BR \-\-bitmap\-chunk=
540 Set the chunksize of the bitmap. Each bit corresponds to that many
541 Kilobytes of storage.
542 When using a file based bitmap, the default is to use the smallest
543 size that is at-least 4 and requires no more than 2^21 chunks.
546 bitmap, the chunksize is automatically determined to make best use of
551 .BR \-W ", " \-\-write\-mostly
552 subsequent devices lists in a
557 command will be flagged as 'write-mostly'. This is valid for RAID1
558 only and means that the 'md' driver will avoid reading from these
559 devices if at all possible. This can be useful if mirroring over a
563 .BR \-\-write\-behind=
564 Specify that write-behind mode should be enabled (valid for RAID1
565 only). If an argument is specified, it will set the maximum number
566 of outstanding writes allowed. The default value is 256.
567 A write-intent bitmap is required in order to use write-behind
568 mode, and write-behind is only attempted on drives marked as
572 .BR \-\-assume\-clean
575 that the array pre-existed and is known to be clean. It can be useful
576 when trying to recover from a major failure as you can be sure that no
577 data will be affected unless you actually write to the array. It can
578 also be used when creating a RAID1 or RAID10 if you want to avoid the
579 initial resync, however this practice \(em while normally safe \(em is not
580 recommended. Use this only if you really know what you are doing.
583 .BR \-\-backup\-file=
586 is used to increase the number of
587 raid-devices in a RAID5 if there are no spare devices available.
588 See the section below on RAID_DEVICE CHANGES. The file should be
589 stored on a separate device, not on the raid array being reshaped.
592 .BR \-\-array-size= ", " \-Z
593 Set the size of the array which is seen by users of the device such as
594 filesystems. This can be less that the real size, but never greater.
595 The size set this way does not persist across restarts of the array.
597 This is most useful when reducing the number of devices in a RAID5 or
598 RAID6. Such arrays require the array-size to be reduced before a
599 reshape can be performed that reduces the real size.
603 restores the apparent size of the array to be whatever the real
604 amount of available space is.
607 .BR \-N ", " \-\-name=
610 for the array. This is currently only effective when creating an
611 array with a version-1 superblock. The name is a simple textual
612 string that can be used to identify array components when assembling.
618 run the array, even if some of the components
619 appear to be active in another array or filesystem. Normally
621 will ask for confirmation before including such components in an
622 array. This option causes that question to be suppressed.
625 .BR \-f ", " \-\-force
628 accept the geometry and layout specified without question. Normally
630 will not allow creation of an array with only one device, and will try
631 to create a raid5 array with one missing drive (as this makes the
632 initial resync work faster). With
635 will not try to be so clever.
638 .BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
639 Instruct mdadm how to create the device file if needed, possibly allocating
640 an unused minor number. "md" causes a non-partitionable array
641 to be used (though since Linux 2.6.28, these array devices are in fact
642 partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
643 later) to be used. "yes" requires the named md device to have
644 a 'standard' format, and the type and minor number will be determined
645 from this. With mdadm 3.0, device creation is normally left up to
647 so this option is unlikely to be needed.
648 See DEVICE NAMES below.
650 The argument can also come immediately after
655 is not given on the command line or in the config file, then
661 is also given, then any
663 entries in the config file will override the
665 instruction given on the command line.
667 For partitionable arrays,
669 will create the device file for the whole array and for the first 4
670 partitions. A different number of partitions can be specified at the
671 end of this option (e.g.
673 If the device name ends with a digit, the partition names add a 'p',
674 and a number, e.g. "/dev/md/home1p3". If there is no
675 trailing digit, then the partition names just have a number added,
676 e.g. "/dev/md/scratch3".
678 If the md device name is in a 'standard' format as described in DEVICE
679 NAMES, then it will be created, if necessary, with the appropriate
680 number based on that name. If the device name is not in one of these
681 formats, then a unused minor number will be allocated. The minor
682 number will be considered unused if there is no active array for that
683 number, and there is no entry in /dev for that number and with a
684 non-standard name. Name that are not in 'standard' format are only
685 allowed in "/dev/md/".
688 \".BR \-\-symlink = no
693 \"to create devices in
695 \"it will also create symlinks from
697 \"with names starting with
703 \"to suppress this, or
705 \"to enforce this even if it is suppressing
712 .BR \-u ", " \-\-uuid=
713 uuid of array to assemble. Devices which don't have this uuid are
717 .BR \-m ", " \-\-super\-minor=
718 Minor number of device that array was created for. Devices which
719 don't have this minor number are excluded. If you create an array as
720 /dev/md1, then all superblocks will contain the minor number 1, even if
721 the array is later assembled as /dev/md2.
723 Giving the literal word "dev" for
727 to use the minor number of the md device that is being assembled.
730 .B \-\-super\-minor=dev
731 will look for super blocks with a minor number of 0.
734 .BR \-N ", " \-\-name=
735 Specify the name of the array to assemble. This must be the name
736 that was specified when creating the array. It must either match
737 the name stored in the superblock exactly, or it must match
740 prefixed to the start of the given name.
743 .BR \-f ", " \-\-force
744 Assemble the array even if some superblocks appear out-of-date
748 Attempt to start the array even if fewer drives were given than were
749 present last time the array was active. Normally if not all the
750 expected drives are found and
752 is not used, then the array will be assembled but not started.
755 an attempt will be made to start it anyway.
759 This is the reverse of
761 in that it inhibits the startup of array unless all expected drives
762 are present. This is only needed with
764 and can be used if the physical connections to devices are
765 not as reliable as you would like.
768 .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
769 See this option under Create and Build options.
772 .BR \-b ", " \-\-bitmap=
773 Specify the bitmap file that was given when the array was created. If
776 bitmap, there is no need to specify this when assembling the array.
779 .BR \-\-backup\-file=
782 was used to grow the number of raid-devices in a RAID5, and the system
783 crashed during the critical section, then the same
787 to allow possibly corrupted data to be restored.
790 .BR \-U ", " \-\-update=
791 Update the superblock on each device while assembling the array. The
792 argument given to this flag can be one of
806 option will adjust the superblock of an array what was created on a Sparc
807 machine running a patched 2.2 Linux kernel. This kernel got the
808 alignment of part of the superblock wrong. You can use the
809 .B "\-\-examine \-\-sparc2.2"
812 to see what effect this would have.
816 option will update the
818 field on each superblock to match the minor number of the array being
820 This can be useful if
822 reports a different "Preferred Minor" to
824 In some cases this update will be performed automatically
825 by the kernel driver. In particular the update happens automatically
826 at the first write to an array with redundancy (RAID level 1 or
827 greater) on a 2.6 (or later) kernel.
831 option will change the uuid of the array. If a UUID is given with the
833 option that UUID will be used as a new UUID and will
835 be used to help identify the devices in the array.
838 is given, a random UUID is chosen.
842 option will change the
844 of the array as stored in the superblock. This is only supported for
845 version-1 superblocks.
849 option will change the
851 as recorded in the superblock. For version-0 superblocks, this is the
852 same as updating the UUID.
853 For version-1 superblocks, this involves updating the name.
857 option will cause the array to be marked
859 meaning that any redundancy in the array (e.g. parity for raid5,
860 copies for raid1) may be incorrect. This will cause the raid system
861 to perform a "resync" pass to make sure that all redundant information
866 option allows arrays to be moved between machines with different
868 When assembling such an array for the first time after a move, giving
869 .B "\-\-update=byteorder"
872 to expect superblocks to have their byteorder reversed, and will
873 correct that order before assembling the array. This is only valid
874 with original (Version 0.90) superblocks.
878 option will correct the summaries in the superblock. That is the
879 counts of total, working, active, failed, and spare devices.
883 will rarely be of use. It applies to version 1.1 and 1.2 metadata
884 only (where the metadata is at the start of the device) and is only
885 useful when the component device has changed size (typically become
886 larger). The version 1 metadata records the amount of the device that
887 can be used to store data, so if a device in a version 1.1 or 1.2
888 array becomes larger, the metadata will still be visible, but the
889 extra space will not. In this case it might be useful to assemble the
891 .BR \-\-update=devicesize .
894 to determine the maximum usable amount of space on each device and
895 update the relevant field in the metadata.
898 .B \-\-auto\-update\-homehost
899 This flag is only meaningful with auto-assembly (see discussion below).
900 In that situation, if no suitable arrays are found for this homehost,
902 will rescan for any arrays at all and will assemble them and update the
903 homehost to match the current host.
909 hot-add listed devices.
913 re-add a device that was recently removed from an array.
916 .BR \-r ", " \-\-remove
917 remove listed devices. They must not be active. i.e. they should
918 be failed or spare devices. As well as the name of a device file
927 The first causes all failed device to be removed. The second causes
928 any device which is no longer connected to the system (i.e an 'open'
931 to be removed. This will only succeed for devices that are spares or
932 have already been marked as failed.
935 .BR \-f ", " \-\-fail
936 mark listed devices as faulty.
937 As well as the name of a device file, the word
939 can be given. This will cause any device that has been detached from
940 the system to be marked as failed. It can then be removed.
948 .BR \-\-write\-mostly
949 Subsequent devices that are added or re-added will have the 'write-mostly'
950 flag set. This is only valid for RAID! and means that the 'md' driver
951 will avoid reading from these devices if possible.
954 Subsequent devices that are added or re-added will have the 'write-mostly'
959 Each of these options require that the first device listed is the array
960 to be acted upon, and the remainder are component devices to be added,
961 removed, or marked as faulty. Several different operations can be
962 specified for different devices, e.g.
964 mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
966 Each operation applies to all devices listed until the next
969 If an array is using a write-intent bitmap, then devices which have
970 been removed can be re-added in a way that avoids a full
971 reconstruction but instead just updates the blocks that have changed
972 since the device was removed. For arrays with persistent metadata
973 (superblocks) this is done automatically. For arrays created with
975 mdadm needs to be told that this device we removed recently with
978 Devices can only be removed from an array if they are not in active
979 use, i.e. that must be spares or failed devices. To remove an active
980 device, it must first be marked as
986 .BR \-Q ", " \-\-query
987 Examine a device to see
988 (1) if it is an md device and (2) if it is a component of an md
990 Information about what is discovered is presented.
993 .BR \-D ", " \-\-detail
994 Print detail of one or more md devices.
997 .BR \-\-detail\-platform
998 Print detail of the platform's raid capabilities (firmware / hardware
999 topology) for a given metadata format.
1002 .BR \-Y ", " \-\-export
1007 output will be formatted as
1009 pairs for easy import into the environment.
1012 .BR \-E ", " \-\-examine
1013 Print content of md superblock on device(s).
1016 If an array was created on a 2.2 Linux kernel patched with RAID
1017 support, the superblock will have been created incorrectly, or at
1018 least incompatibly with 2.4 and later kernels. Using the
1022 will fix the superblock before displaying it. If this appears to do
1023 the right thing, then the array can be successfully assembled using
1024 .BR "\-\-assemble \-\-update=sparc2.2" .
1027 .BR \-X ", " \-\-examine\-bitmap
1028 Report information about a bitmap file.
1029 The argument is either an external bitmap file or an array component
1030 in case of an internal bitmap.
1033 .BR \-R ", " \-\-run
1034 start a partially built array.
1037 .BR \-S ", " \-\-stop
1038 deactivate array, releasing all resources.
1041 .BR \-o ", " \-\-readonly
1042 mark array as readonly.
1045 .BR \-w ", " \-\-readwrite
1046 mark array as readwrite.
1049 .B \-\-zero\-superblock
1050 If the device contains a valid md superblock, the block is
1051 overwritten with zeros. With
1053 the block where the superblock would be is overwritten even if it
1054 doesn't appear to be valid.
1057 .BR \-t ", " \-\-test
1062 is set to reflect the status of the device.
1065 .BR \-W ", " \-\-wait
1066 For each md device given, wait for any resync, recovery, or reshape
1067 activity to finish before returning.
1069 will return with success if it actually waited for every device
1070 listed, otherwise it will return failure.
1074 For each md device given, or each device in /proc/mdstat if
1076 is given, arrange for the array to be marked clean as soon as possible.
1077 Also, quiesce resync so that the monitor for external metadata arrays
1078 (mdmon) has an opportunity to checkpoint the resync position.
1080 will return with success if the array uses external metadata and we
1081 successfully waited. For native arrays this returns immediately as the
1082 kernel handles both dirty-clean transitions and resync checkpointing in
1083 the kernel at shutdown. No action is taken if safe-mode handling is
1086 .SH For Incremental Assembly mode:
1088 .BR \-\-rebuild\-map ", " \-r
1089 Rebuild the map file
1090 .RB ( /var/run/mdadm/map )
1093 uses to help track which arrays are currently being assembled.
1096 .BR \-\-run ", " \-R
1097 Run any array assembled as soon as a minimal number of devices are
1098 available, rather than waiting until all expected devices are present.
1102 This allows the hot-plug system to prevent arrays from running when it knows
1103 that more disks may arrive later in the discovery process.
1106 .BR \-\-scan ", " \-s
1107 Only meaningful with
1111 file for arrays that are being incrementally assembled and will try to
1112 start any that are not already started. If any such array is listed
1115 as requiring an external bitmap, that bitmap will be attached first.
1117 .SH For Monitor mode:
1119 .BR \-m ", " \-\-mail
1120 Give a mail address to send alerts to.
1123 .BR \-p ", " \-\-program ", " \-\-alert
1124 Give a program to be run whenever an event is detected.
1127 .BR \-y ", " \-\-syslog
1128 Cause all events to be reported through 'syslog'. The messages have
1129 facility of 'daemon' and varying priorities.
1132 .BR \-d ", " \-\-delay
1133 Give a delay in seconds.
1135 polls the md arrays and then waits this many seconds before polling
1136 again. The default is 60 seconds.
1139 .BR \-f ", " \-\-daemonise
1142 to run as a background daemon if it decides to monitor anything. This
1143 causes it to fork and run in the child, and to disconnect form the
1144 terminal. The process id of the child is written to stdout.
1147 which will only continue monitoring if a mail address or alert program
1148 is found in the config file.
1151 .BR \-i ", " \-\-pid\-file
1154 is running in daemon mode, write the pid of the daemon process to
1155 the specified file, instead of printing it on standard output.
1158 .BR \-1 ", " \-\-oneshot
1159 Check arrays only once. This will generate
1161 events and more significantly
1167 .B " mdadm \-\-monitor \-\-scan \-1"
1169 from a cron script will ensure regular notification of any degraded arrays.
1172 .BR \-t ", " \-\-test
1175 alert for every array found at startup. This alert gets mailed and
1176 passed to the alert program. This can be used for testing that alert
1177 message do get through successfully.
1183 .B mdadm \-\-assemble
1184 .I md-device options-and-component-devices...
1187 .B mdadm \-\-assemble \-\-scan
1188 .I md-devices-and-options...
1191 .B mdadm \-\-assemble \-\-scan
1195 This usage assembles one or more raid arrays from pre-existing components.
1196 For each array, mdadm needs to know the md device, the identity of the
1197 array, and a number of component-devices. These can be found in a number of ways.
1199 In the first usage example (without the
1201 the first device given is the md device.
1202 In the second usage example, all devices listed are treated as md
1203 devices and assembly is attempted.
1204 In the third (where no devices are listed) all md devices that are
1205 listed in the configuration file are assembled. Then any arrays that
1206 can be found on unused devices will also be assembled.
1208 If precisely one device is listed, but
1214 was given and identity information is extracted from the configuration file.
1216 The identity can be given with the
1220 option, will be taken from the md-device record in the config file, or
1221 will be taken from the super block of the first component-device
1222 listed on the command line.
1224 Devices can be given on the
1226 command line or in the config file. Only devices which have an md
1227 superblock which contains the right identity will be considered for
1230 The config file is only used if explicitly named with
1232 or requested with (a possibly implicit)
1237 .B /etc/mdadm/mdadm.conf
1242 is not given, then the config file will only be used to find the
1243 identity of md arrays.
1245 Normally the array will be started after it is assembled. However if
1247 is not given and insufficient drives were listed to start a complete
1248 (non-degraded) array, then the array is not started (to guard against
1249 usage errors). To insist that the array be started in this case (as
1250 may work for RAID1, 4, 5, 6, or 10), give the
1254 If the md device does not exist, then it will be created providing the
1255 intent is clear. i.e. the name must be in a standard form, or the
1257 option must be given to clarify how and whether the device should be
1259 This can be useful for handling partitioned devices (which don't have
1260 a stable device number \(em it can change after a reboot) and when using
1261 "udev" to manage your
1263 tree (udev cannot handle md devices because of the unusual device
1264 initialisation conventions).
1266 If the option to "auto" is "mdp" or "part" or (on the command line
1267 only) "p", then mdadm will create a partitionable array, using the
1268 first free one that is not in use and does not already have an entry
1269 in /dev (apart from numeric /dev/md* entries).
1271 If the option to "auto" is "yes" or "md" or (on the command line)
1272 nothing, then mdadm will create a traditional, non-partitionable md
1275 It is expected that the "auto" functionality will be used to create
1276 device entries with meaningful names such as "/dev/md/home" or
1277 "/dev/md/root", rather than names based on the numerical array number.
1279 When using option "auto" to create a partitionable array, the device
1280 files for the first 4 partitions are also created. If a different
1281 number is required it can be simply appended to the auto option.
1282 e.g. "auto=part8". Partition names are created by appending a digit
1283 string to the device name, with an intervening "p" if the device name
1288 option is also available in Build and Create modes. As those modes do
1289 not use a config file, the "auto=" config option does not apply to
1297 and no devices are listed,
1299 will first attempt to assemble all the arrays listed in the config
1302 It will then look further for possible arrays and will try to assemble
1303 anything that it finds. Arrays which are tagged as belonging to the given
1304 homehost will be assembled and started normally. Arrays which do not
1305 obviously belong to this host are given names that are expected not to
1306 conflict with anything local, and are started "read-auto" so that
1307 nothing is written to any device until the array is written to. i.e.
1308 automatic resync etc is delayed.
1312 finds a consistent set of devices that look like they should comprise
1313 an array, and if the superblock is tagged as belonging to the given
1314 home host, it will automatically choose a device name and try to
1315 assemble the array. If the array uses version-0.90 metadata, then the
1317 number as recorded in the superblock is used to create a name in
1321 If the array uses version-1 metadata, then the
1323 from the superblock is used to similarly create a name in
1325 (the name will have any 'host' prefix stripped first).
1329 cannot find any array for the given host at all, and if
1330 .B \-\-auto\-update\-homehost
1333 will search again for any array (not just an array created for this
1334 host) and will assemble each assuming
1335 .BR \-\-update=homehost .
1336 This will change the host tag in the superblock so that on the next run,
1337 these arrays will be found without the second pass. The intention of
1338 this feature is to support transitioning a set of md arrays to using
1341 The reason for requiring arrays to be tagged with the homehost for
1342 auto assembly is to guard against problems that can arise when moving
1343 devices from one host to another.
1353 .BI \-\-raid\-devices= Z
1357 This usage is similar to
1359 The difference is that it creates an array without a superblock. With
1360 these arrays there is no difference between initially creating the array and
1361 subsequently assembling the array, except that hopefully there is useful
1362 data there in the second case.
1364 The level may raid0, linear, multipath, or faulty, or one of their
1365 synonyms. All devices must be listed and the array will be started
1377 .BI \-\-raid\-devices= Z
1381 This usage will initialise a new md array, associate some devices with
1382 it, and activate the array.
1386 option is given (as described in more detail in the section on
1387 Assemble mode), then the md device will be created with a suitable
1388 device number if necessary.
1390 As devices are added, they are checked to see if they contain raid
1391 superblocks or filesystems. They are also checked to see if the variance in
1392 device size exceeds 1%.
1394 If any discrepancy is found, the array will not automatically be run, though
1397 can override this caution.
1399 To create a "degraded" array in which some devices are missing, simply
1400 give the word "\fBmissing\fP"
1401 in place of a device name. This will cause
1403 to leave the corresponding slot in the array empty.
1404 For a RAID4 or RAID5 array at most one slot can be
1405 "\fBmissing\fP"; for a RAID6 array at most two slots.
1406 For a RAID1 array, only one real device needs to be given. All of the
1410 When creating a RAID5 array,
1412 will automatically create a degraded array with an extra spare drive.
1413 This is because building the spare into a degraded array is in general faster than resyncing
1414 the parity on a non-degraded, but not clean, array. This feature can
1415 be overridden with the
1419 When creating an array with version-1 metadata a name for the array is
1421 If this is not given with the
1425 will choose a name based on the last component of the name of the
1426 device being created. So if
1428 is being created, then the name
1433 is being created, then the name
1437 When creating a partition based array, using
1439 with version-1.x metadata, the partition type should be set to
1441 (non fs-data). This type selection allows for greater precision since
1442 using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
1443 might create problems in the event of array recovery through a live cdrom.
1445 A new array will normally get a randomly assigned 128bit UUID which is
1446 very likely to be unique. If you have a specific need, you can choose
1447 a UUID for the array by giving the
1449 option. Be warned that creating two arrays with the same UUID is a
1450 recipe for disaster. Also, using
1452 when creating a v0.90 array will silently override any
1457 .\"option is given, it is not necessary to list any component-devices in this command.
1458 .\"They can be added later, before a
1462 .\"is given, the apparent size of the smallest drive given is used.
1464 When creating an array within a
1467 can be given either the list of devices to use, or simply the name of
1468 the container. The former case gives control over which devices in
1469 the container will be used for the array. The latter case allows
1471 to automatically choose which devices to use based on how much spare
1474 The General Management options that are valid with
1479 insist on running the array even if some devices look like they might
1484 start the array readonly \(em not supported yet.
1492 .I options... devices...
1495 This usage will allow individual devices in an array to be failed,
1496 removed or added. It is possible to perform multiple operations with
1497 on command. For example:
1499 .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
1505 and will then remove it from the array and finally add it back
1506 in as a spare. However only one md array can be affected by a single
1517 MISC mode includes a number of distinct operations that
1518 operate on distinct devices. The operations are:
1521 The device is examined to see if it is
1522 (1) an active md array, or
1523 (2) a component of an md array.
1524 The information discovered is reported.
1528 The device should be an active md device.
1530 will display a detailed description of the array.
1534 will cause the output to be less detailed and the format to be
1535 suitable for inclusion in
1536 .BR /etc/mdadm.conf .
1539 will normally be 0 unless
1541 failed to get useful information about the device(s); however, if the
1543 option is given, then the exit status will be:
1547 The array is functioning normally.
1550 The array has at least one failed device.
1553 The array has multiple failed devices such that it is unusable.
1556 There was an error while trying to get information about the device.
1560 .B \-\-detail\-platform
1561 Print detail of the platform's raid capabilities (firmware / hardware
1562 topology). If the metadata is specified with
1566 then the return status will be:
1570 metadata successfully enumerated its platform components on this system
1573 metadata is platform independent
1576 metadata failed to find its platform components on this system
1581 The device should be a component of an md array.
1583 will read the md superblock of the device and display the contents.
1588 is given, then multiple devices that are components of the one array
1589 are grouped together and reported in a single entry suitable
1591 .BR /etc/mdadm.conf .
1595 without listing any devices will cause all devices listed in the
1596 config file to be examined.
1600 The devices should be active md arrays which will be deactivated, as
1601 long as they are not currently in use.
1605 This will fully activate a partially assembled md array.
1609 This will mark an active array as read-only, providing that it is
1610 not currently being used.
1616 array back to being read/write.
1620 For all operations except
1623 will cause the operation to be applied to all arrays listed in
1628 causes all devices listed in the config file to be examined.
1635 .B mdadm \-\-monitor
1636 .I options... devices...
1641 to periodically poll a number of md arrays and to report on any events
1644 will never exit once it decides that there are arrays to be checked,
1645 so it should normally be run in the background.
1647 As well as reporting events,
1649 may move a spare drive from one array to another if they are in the
1652 and if the destination array has a failed drive but no spares.
1654 If any devices are listed on the command line,
1656 will only monitor those devices. Otherwise all arrays listed in the
1657 configuration file will be monitored. Further, if
1659 is given, then any other md devices that appear in
1661 will also be monitored.
1663 The result of monitoring the arrays is the generation of events.
1664 These events are passed to a separate program (if specified) and may
1665 be mailed to a given E-mail address.
1667 When passing events to a program, the program is run once for each event,
1668 and is given 2 or 3 command-line arguments: the first is the
1669 name of the event (see below), the second is the name of the
1670 md device which is affected, and the third is the name of a related
1671 device if relevant (such as a component device that has failed).
1675 is given, then a program or an E-mail address must be specified on the
1676 command line or in the config file. If neither are available, then
1678 will not monitor anything.
1682 will continue monitoring as long as something was found to monitor. If
1683 no program or email is given, then each event is reported to
1686 The different events are:
1690 .B DeviceDisappeared
1691 An md array which previously was configured appears to no longer be
1692 configured. (syslog priority: Critical)
1696 was told to monitor an array which is RAID0 or Linear, then it will
1698 .B DeviceDisappeared
1699 with the extra information
1701 This is because RAID0 and Linear do not support the device-failed,
1702 hot-spare and resync operations which are monitored.
1706 An md array started reconstruction. (syslog priority: Warning)
1712 is 20, 40, 60, or 80, this indicates that rebuild has passed that many
1713 percentage of the total. (syslog priority: Warning)
1717 An md array that was rebuilding, isn't any more, either because it
1718 finished normally or was aborted. (syslog priority: Warning)
1722 An active component device of an array has been marked as
1723 faulty. (syslog priority: Critical)
1727 A spare component device which was being rebuilt to replace a faulty
1728 device has failed. (syslog priority: Critical)
1732 A spare component device which was being rebuilt to replace a faulty
1733 device has been successfully rebuilt and has been made active.
1734 (syslog priority: Info)
1738 A new md array has been detected in the
1740 file. (syslog priority: Info)
1744 A newly noticed array appears to be degraded. This message is not
1747 notices a drive failure which causes degradation, but only when
1749 notices that an array is degraded when it first sees the array.
1750 (syslog priority: Critical)
1754 A spare drive has been moved from one array in a
1756 to another to allow a failed drive to be replaced.
1757 (syslog priority: Info)
1763 has been told, via the config file, that an array should have a certain
1764 number of spare devices, and
1766 detects that it has fewer than this number when it first sees the
1767 array, it will report a
1770 (syslog priority: Warning)
1774 An array was found at startup, and the
1777 (syslog priority: Info)
1787 cause Email to be sent. All events cause the program to be run.
1788 The program is run with two or three arguments: the event
1789 name, the array device and possibly a second device.
1791 Each event has an associated array device (e.g.
1793 and possibly a second device. For
1798 the second device is the relevant component device.
1801 the second device is the array that the spare was moved from.
1805 to move spares from one array to another, the different arrays need to
1806 be labeled with the same
1808 in the configuration file. The
1810 name can be any string; it is only necessary that different spare
1811 groups use different names.
1815 detects that an array in a spare group has fewer active
1816 devices than necessary for the complete array, and has no spare
1817 devices, it will look for another array in the same spare group that
1818 has a full complement of working drive and a spare. It will then
1819 attempt to remove the spare from the second drive and add it to the
1821 If the removal succeeds but the adding fails, then it is added back to
1825 The GROW mode is used for changing the size or shape of an active
1827 For this to work, the kernel must support the necessary change.
1828 Various types of growth are being added during 2.6 development,
1829 including restructuring a raid5 array to have more active devices.
1831 Currently the only support available is to
1833 change the "size" attribute
1834 for RAID1, RAID5 and RAID6.
1836 increase the "raid\-devices" attribute of RAID1, RAID5, and RAID6.
1838 add a write-intent bitmap to any array which supports these bitmaps, or
1839 remove a write-intent bitmap from such an array.
1842 GROW mode is not currently supported for
1844 or arrays inside containers.
1847 Normally when an array is built the "size" it taken from the smallest
1848 of the drives. If all the small drives in an arrays are, one at a
1849 time, removed and replaced with larger drives, then you could have an
1850 array of large drives with only a small amount used. In this
1851 situation, changing the "size" with "GROW" mode will allow the extra
1852 space to start being used. If the size is increased in this way, a
1853 "resync" process will start to make sure the new parts of the array
1856 Note that when an array changes size, any filesystem that may be
1857 stored in the array will not automatically grow to use the space. The
1858 filesystem will need to be explicitly told to use the extra space.
1860 .SS RAID-DEVICES CHANGES
1862 A RAID1 array can work with any number of devices from 1 upwards
1863 (though 1 is not very useful). There may be times which you want to
1864 increase or decrease the number of active devices. Note that this is
1865 different to hot-add or hot-remove which changes the number of
1868 When reducing the number of devices in a RAID1 array, the slots which
1869 are to be removed from the array must already be vacant. That is, the
1870 devices which were in those slots must be failed and removed.
1872 When the number of devices is increased, any hot spares that are
1873 present will be activated immediately.
1875 Increasing the number of active devices in a RAID5 is much more
1876 effort. Every block in the array will need to be read and written
1877 back to a new location. From 2.6.17, the Linux Kernel is able to do
1878 this safely, including restart and interrupted "reshape".
1880 When relocating the first few stripes on a raid5, it is not possible
1881 to keep the data on disk completely consistent and crash-proof. To
1882 provide the required safety, mdadm disables writes to the array while
1883 this "critical section" is reshaped, and takes a backup of the data
1884 that is in that section. This backup is normally stored in any spare
1885 devices that the array has, however it can also be stored in a
1886 separate file specified with the
1888 option. If this option is used, and the system does crash during the
1889 critical period, the same file must be passed to
1891 to restore the backup and reassemble the array.
1895 A write-intent bitmap can be added to, or removed from, an active
1896 array. Either internal bitmaps, or bitmaps stored in a separate file,
1897 can be added. Note that if you add a bitmap stored in a file which is
1898 in a filesystem that is on the raid array being affected, the system
1899 will deadlock. The bitmap must be on a separate filesystem.
1901 .SH INCREMENTAL MODE
1905 .B mdadm \-\-incremental
1911 .B mdadm \-\-incremental \-\-rebuild
1914 .B mdadm \-\-incremental \-\-run \-\-scan
1918 This mode is designed to be used in conjunction with a device
1919 discovery system. As devices are found in a system, they can be
1921 .B "mdadm \-\-incremental"
1922 to be conditionally added to an appropriate array.
1924 If the device passed is a
1926 device created by a previous call to
1928 then rather than trying to add that device to an array, all the arrays
1929 described by the metadata of the container will be started.
1932 performs a number of tests to determine if the device is part of an
1933 array, and which array it should be part of. If an appropriate array
1934 is found, or can be created,
1936 adds the device to the array and conditionally starts the array.
1940 will only add devices to an array which were previously working
1941 (active or spare) parts of that array. It does not currently support
1942 automatic inclusion of a new drive as a spare in some array.
1946 makes are as follow:
1948 Is the device permitted by
1950 That is, is it listed in a
1952 line in that file. If
1954 is absent then the default it to allow any device. Similar if
1956 contains the special word
1958 then any device is allowed. Otherwise the device name given to
1960 must match one of the names or patterns in a
1965 Does the device have a valid md superblock. If a specific metadata
1966 version is request with
1970 then only that style of metadata is accepted, otherwise
1972 finds any known version of metadata. If no
1974 metadata is found, the device is rejected.
1977 Does the metadata match an expected array?
1978 The metadata can match in two ways. Either there is an array listed
1981 which identifies the array (either by UUID, by name, by device list,
1982 or by minor-number), or the array was created with a
1988 or on the command line.
1991 is not able to positively identify the array as belonging to the
1992 current host, the device will be rejected.
1996 keeps a list of arrays that it has partially assembled in
1997 .B /var/run/mdadm/map
1999 .B /var/run/mdadm.map
2000 if the directory doesn't exist). If no array exists which matches
2001 the metadata on the new device,
2003 must choose a device name and unit number. It does this based on any
2006 or any name information stored in the metadata. If this name
2007 suggests a unit number, that number will be used, otherwise a free
2008 unit number will be chosen. Normally
2010 will prefer to create a partitionable array, however if the
2014 suggests that a non-partitionable array is preferred, that will be
2018 Once an appropriate array is found or created and the device is added,
2020 must decide if the array is ready to be started. It will
2021 normally compare the number of available (non-spare) devices to the
2022 number of devices that the metadata suggests need to be active. If
2023 there are at least that many, the array will be started. This means
2024 that if any devices are missing the array will not be restarted.
2030 in which case the array will be run as soon as there are enough
2031 devices present for the data to be accessible. For a raid1, that
2032 means one device will start the array. For a clean raid5, the array
2033 will be started as soon as all but one drive is present.
2035 Note that neither of these approaches is really ideal. If it can
2036 be known that all device discovery has completed, then
2040 can be run which will try to start all arrays that are being
2041 incrementally assembled. They are started in "read-auto" mode in
2042 which they are read-only until the first write request. This means
2043 that no metadata updates are made and no attempt at resync or recovery
2044 happens. Further devices that are found before the first write can
2045 still be added safely.
2049 This section describes environment variables that affect how mdadm
2054 Setting this value to 1 will prevent mdadm from automatically launching
2055 mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2061 does not create any device nodes in /dev, but leaves that task to
2065 appears not to be configured, or if this environment variable is set
2068 will create and devices that are needed.
2072 .B " mdadm \-\-query /dev/name-of-device"
2074 This will find out if a given device is a raid array, or is part of
2075 one, and will provide brief information about the device.
2077 .B " mdadm \-\-assemble \-\-scan"
2079 This will assemble and start all arrays listed in the standard config
2080 file. This command will typically go in a system startup file.
2082 .B " mdadm \-\-stop \-\-scan"
2084 This will shut down all arrays that can be shut down (i.e. are not
2085 currently in use). This will typically go in a system shutdown script.
2087 .B " mdadm \-\-follow \-\-scan \-\-delay=120"
2089 If (and only if) there is an Email address or program given in the
2090 standard config file, then
2091 monitor the status of all arrays listed in that file by
2092 polling them ever 2 minutes.
2094 .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
2096 Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
2099 .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
2101 .B " mdadm \-\-detail \-\-scan >> mdadm.conf"
2103 This will create a prototype config file that describes currently
2104 active arrays that are known to be made from partitions of IDE or SCSI drives.
2105 This file should be reviewed before being used as it may
2106 contain unwanted detail.
2108 .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
2110 .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
2112 This will find arrays which could be assembled from existing IDE and
2113 SCSI whole drives (not partitions), and store the information in the
2114 format of a config file.
2115 This file is very likely to contain unwanted detail, particularly
2118 entries. It should be reviewed and edited before being used as an
2121 .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
2123 .B " mdadm \-Ebsc partitions"
2125 Create a list of devices by reading
2126 .BR /proc/partitions ,
2127 scan these for RAID superblocks, and printout a brief listing of all
2130 .B " mdadm \-Ac partitions \-m 0 /dev/md0"
2132 Scan all partitions and devices listed in
2133 .BR /proc/partitions
2136 out of all such devices with a RAID superblock with a minor number of 0.
2138 .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /var/run/mdadm"
2140 If config file contains a mail address or alert program, run mdadm in
2141 the background in monitor mode monitoring all md devices. Also write
2142 pid of mdadm daemon to
2143 .BR /var/run/mdadm .
2145 .B " mdadm \-Iq /dev/somedevice"
2147 Try to incorporate newly discovered device into some array as
2150 .B " mdadm \-\-incremental \-\-rebuild \-\-run \-\-scan"
2152 Rebuild the array map from any current arrays, and then start any that
2155 .B " mdadm /dev/md4 --fail detached --remove detached"
2157 Any devices which are components of /dev/md4 will be marked as faulty
2158 and then remove from the array.
2160 .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
2162 Create a DDF array over 6 devices.
2164 .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
2166 Create a raid5 array over any 3 devices in the given DDF set. Use
2167 only 30 gigabytes of each device.
2169 .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
2171 Assemble a pre-exist ddf array.
2173 .B " mdadm -I /dev/md/ddf1"
2175 Assemble all arrays contained in the ddf array, assigning names as
2178 .B " mdadm \-\-create \-\-help"
2180 Provide help about the Create mode.
2182 .B " mdadm \-\-config \-\-help"
2184 Provide help about the format of the config file.
2186 .B " mdadm \-\-help"
2188 Provide general help.
2199 lists all active md devices with information about them.
2201 uses this to find arrays when
2203 is given in Misc mode, and to monitor array reconstruction
2209 The config file lists which devices may be scanned to see if
2210 they contain MD super block, and gives identifying information
2211 (e.g. UUID) about known MD arrays. See
2215 .SS /var/run/mdadm/map
2218 mode is used, this file gets a list of arrays currently being created.
2221 does not exist as a directory, then
2222 .B /var/run/mdadm.map
2228 understand two sorts of names for array devices.
2230 The first is the so-called 'standard' format name, which matches the
2231 names used by the kernel and which appear in
2234 The second sort can be freely chosen, but must reside in
2236 When giving a device name to
2238 to create or assemble an array, either full path name such as
2242 can be given, or just the suffix of the second sort of name, such as
2248 chooses device names during auto-assembly, it will normally add a
2249 small sequence number to the end of the name to avoid conflicted
2250 between multiple arrays that have the same name. If
2252 can reasonably determine that the array really is meant for this host,
2253 either by a hostname in the metadata, or by the presence of the array
2254 in /etc/mdadm.conf, then it will leave of the suffix if possible.
2256 The standard names for non-partitioned arrays (the only sort of md
2257 array available in 2.4 and earlier) are of the form
2261 where NN is a number.
2262 The standard names for partitionable arrays (as available from 2.6
2263 onwards) are of the form
2267 Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
2269 From kernel version, 2.6.28 the "non-partitioned array" can actually
2270 be partitioned. So the "md_dNN" names are no longer needed, and
2271 partitions such as "/dev/mdNNpXX" are possible.
2275 was previously known as
2279 is completely separate from the
2281 package, and does not use the
2283 configuration file at all.
2286 For further information on mdadm usage, MD and the various levels of
2289 .B http://linux\-raid.osdl.org/
2291 (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
2293 .\"for new releases of the RAID driver check out:
2296 .\".UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2297 .\"ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2302 .\".UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2303 .\"http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2306 The latest version of
2308 should always be available from
2310 .B http://www.kernel.org/pub/linux/utils/raid/mdadm/
projects / thirdparty / mdadm.git / blob