mdadm-1.6.0
[thirdparty/mdadm.git] / mdadm.8
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52826846 1.\" -*- nroff -*-
dd0781e5 2.TH MDADM 8 "" v1.6.0
52826846 3.SH NAME
9a9dab36 4mdadm \- manage MD devices
cd29a5c8
NB
5.I aka
6Linux Software Raid.
7
52826846
NB
8.SH SYNOPSIS
9
e0d19036 10.BI mdadm " [mode] <raiddevice> [options] <component-devices>"
52826846
NB
11
12.SH DESCRIPTION
13RAID devices are virtual devices created from two or more
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NB
14real block devices. This allows multiple devices (typically disk
15drives or partitions there-of) to be combined into a single device to
16hold (for example) a single filesystem.
2d465520 17Some RAID levels include redundancy and so can survive some degree of
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NB
18device failure.
19
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NB
20Linux Software RAID devices are implemented through the md (Multiple
21Devices) device driver.
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NB
22
23Currently, Linux supports
24.B LINEAR
25md devices,
26.B RAID0
27(striping),
28.B RAID1
29(mirroring),
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NB
30.BR RAID4 ,
31.BR RAID5 ,
98c6faba 32.BR RAID6 ,
cd29a5c8 33and
cd29a5c8 34.BR MULTIPATH .
d013a55e
NB
35
36.B MULTIPATH is not a Software RAID mechanism, but does involve
37multiple devices. For
38.B MULTIPATH
39each device is a path to one common physical storage device.
40
52826846 41
9a9dab36 42.B mdadm
11a3e71d
NB
43is a program that can be used to create, manage, and monitor
44MD devices. As
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NB
45such it provides a similar set of functionality to the
46.B raidtools
47packages.
48The key differences between
9a9dab36 49.B mdadm
cd29a5c8
NB
50and
51.B raidtools
52are:
53.IP \(bu 4
9a9dab36 54.B mdadm
cd29a5c8
NB
55is a single program and not a collection of programs.
56.IP \(bu 4
9a9dab36 57.B mdadm
cd29a5c8 58can perform (almost) all of its functions without having a
5787fa49 59configuration file and does not use one by default. Also
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NB
60.B mdadm
61helps with management of the configuration
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62file.
63.IP \(bu 4
9a9dab36 64.B mdadm
e0d19036 65can provide information about your arrays (through Query, Detail, and Examine)
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NB
66that
67.B raidtools
68cannot.
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NB
69.P
70.I mdadm
71does not use
72.IR /etc/raidtab ,
73the
74.B raidtools
75configuration file, at all. It has a different configuration file
76with a different format and an different purpose.
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NB
77
78.SH MODES
dd0781e5 79mdadm has 7 major modes of operation:
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NB
80.TP
81.B Assemble
82Assemble the parts of a previously created
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83array into an active array. Components can be explicitly given
84or can be searched for.
9a9dab36 85.B mdadm
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NB
86checks that the components
87do form a bona fide array, and can, on request, fiddle superblock
88information so as to assemble a faulty array.
89
90.TP
91.B Build
92Build a legacy array without per-device superblocks.
93
94.TP
95.B Create
96Create a new array with per-device superblocks.
97'''It can progress
98'''in several step create-add-add-run or it can all happen with one command.
99
100.TP
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NB
101.B Manage
102This is for doing things to specific components of an array such as
103adding new spares and removing faulty devices.
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104
105.TP
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106.B Misc
107This mode allows operations on independent devices such as examine MD
108superblocks, erasing old superblocks and stopping active arrays.
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NB
109
110.TP
111.B "Follow or Monitor"
5787fa49 112Monitor one or more md devices and act on any state changes. This is
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NB
113only meaningful for raid1, 4, 5, 6 or multipath arrays as
114only these have interesting state. raid0 or linear never have
115missing, spare, or failed drives, so there is nothing to monitor.
5787fa49 116
dd0781e5
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117.TP
118.B "Grow"
119Grow (or shrink) an array, or otherwise reshape it in some way.
120Currently supported growth options including changing the active size
121of componenet devices in RAID level 1/4/5/6 and changing the number of
122active devices in RAID1.
cd29a5c8 123
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124.SH OPTIONS
125
126Available options are:
127
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128.TP
129.BR -A ", " --assemble
2d465520 130Assemble a pre-existing array.
52826846 131
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132.TP
133.BR -B ", " --build
134Build a legacy array without superblocks.
52826846 135
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NB
136.TP
137.BR -C ", " --create
138Create a new array.
52826846 139
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NB
140.TP
141.BR -Q ", " --query
142Examine a device to see
143(1) if it is an md device and (2) if it is a component of an md
144array.
145Information about what is discovered is presented.
146
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NB
147.TP
148.BR -D ", " --detail
149Print detail of one or more md devices.
52826846 150
cd29a5c8
NB
151.TP
152.BR -E ", " --examine
153Print content of md superblock on device(s).
52826846 154
cd29a5c8
NB
155.TP
156.BR -F ", " --follow ", " --monitor
157Select
158.B Monitor
159mode.
52826846 160
dd0781e5
NB
161.TP
162.BR -G ", " --grow
163Change the size or shape of an active array.
164
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NB
165.TP
166.BR -h ", " --help
56eedc1a
NB
167Display help message or, after above option, mode specific help
168message.
169
170.TP
171.B --help-options
172Display more detailed help about command line parsing and some commonly
173used options.
52826846 174
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NB
175.TP
176.BR -V ", " --version
9a9dab36 177Print version information for mdadm.
52826846 178
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179.TP
180.BR -v ", " --verbose
181Be more verbose about what is happening.
52826846 182
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NB
183.TP
184.BR -b ", " --brief
185Be less verbose. This is used with
186.B --detail
187and
188.BR --examine .
52826846 189
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NB
190.TP
191.BR -f ", " --force
192Be more forceful about certain operations. See the various modes of
193the exact meaning of this option in different contexts.
194
195.TP
196.BR -c ", " --config=
197Specify the config file. Default is
198.BR /etc/mdadm.conf .
5787fa49
NB
199If the config file given is
200.B partitions
201then nothing will be read, but
202.I mdadm
203will act as though the config file contained exactly
204.B "DEVICE partitions"
205and will read
206.B /proc/partitions
207to find a list of devices to scan.
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NB
208If the word
209.B none
210is given for the config file, then
211.I mdadm
212will act as though the config file were empty.
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NB
213
214.TP
215.BR -s ", " --scan
216scan config file or
217.B /proc/mdstat
218for missing information.
219In general, this option gives
220.B mdadm
221permission to get any missing information, like component devices,
222array devices, array identities, and alert destination from the
223configuration file:
224.BR /etc/mdadm.conf .
225One exception is MISC mode when using
226.B --detail
227or
228.B --stop
229in which case
230.B --scan
231says to get a list of array devices from
232.BR /proc/mdstat .
233
cd29a5c8 234.SH For create or build:
52826846 235
cd29a5c8
NB
236.TP
237.BR -c ", " --chunk=
238Specify chunk size of kibibytes. The default is 64.
52826846 239
cd29a5c8
NB
240.TP
241.BR --rounding=
242Specify rounding factor for linear array (==chunk size)
52826846 243
cd29a5c8
NB
244.TP
245.BR -l ", " --level=
aa88f531
NB
246Set raid level. When used with
247.IR --create ,
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NB
248options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
249raid5, 5, raid6, 6, multipath, mp. Obviously some of these are synonymous.
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NB
250
251When used with
252.IR --build ,
253only linear, raid0, 0, stripe are valid.
52826846 254
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NB
255.TP
256.BR -p ", " --parity=
257Set raid5 parity algorithm. Options are:
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NB
258left-asymmetric,
259left-symmetric,
260right-asymmetric,
261right-symmetric,
262la, ra, ls, rs. The default is left-symmetric.
52826846 263
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NB
264.TP
265.BR --layout=
266same as --parity
52826846 267
cd29a5c8 268.TP
b83d95f3 269.BR -n ", " --raid-devices=
5787fa49
NB
270Specify the number of active devices in the array. This, plus the
271number of spare devices (see below) must equal the number of
272.I component-devices
d013a55e 273(including "\fBmissing\fP" devices)
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274that are listed on the command line for
275.BR --create .
276Setting a value of 1 is probably
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277a mistake and so requires that
278.B --force
279be specified first. A value of 1 will then be allowed for linear,
280multipath, raid0 and raid1. It is never allowed for raid4 or raid5.
281.br
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282This number can only be changed using
283.B --grow
284for RAID1 arrays, and only on kernels which provide necessary support.
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NB
285
286.TP
b83d95f3 287.BR -x ", " --spare-devices=
5787fa49
NB
288Specify the number of spare (eXtra) devices in the initial array.
289Spares can also be added
290and removed later. The number of component devices listed
291on the command line must equal the number of raid devices plus the
292number of spare devices.
293
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NB
294
295.TP
296.BR -z ", " --size=
98c6faba 297Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6.
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NB
298This must be a multiple of the chunk size, and must leave about 128Kb
299of space at the end of the drive for the RAID superblock.
300If this is not specified
301(as it normally is not) the smallest drive (or partition) sets the
302size, though if there is a variance among the drives of greater than 1%, a warning is
303issued.
52826846 304
dd0781e5
NB
305This value can be set with
306.B --grow
307for RAID level 1/4/5/6. If the array was created with a size smaller
308than the currently active drives, the extra space can be accessed
309using
310.BR --grow .
311
312.TP
313.BR --assume-clean
314Tell
315.I mdadm
316that the array pre-existed and is known to be clean. This is only
317really useful for Building RAID1 array. Only use this if you really
318know what you are doing. This is currently only supported for --build.
319
320.TP
321.BR -R ", " --run
322Insist that
323.I mdadm
324run the array, even if some of the components
325appear to be active in another array or filesystem. Normally
326.I mdadm
327will ask for confirmation before including such components in an
328array. This option causes that question to be suppressed.
329
330.TP
331.BR -f ", " --force
332Insist that
333.I mdadm
334accept the geometry and layout specified without question. Normally
335.I mdadm
336will not allow creation of an array with only one device, and will try
337to create a raid5 array with one missing drive (as this makes the
338initial resync work faster). With
339.BR --force ,
340.I mdadm
341will not try to be so clever.
342
343.TP
344.BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}"
345Instruct mdadm to create the device file if needed, and to allocate
346an unused minor number. "yes" or "md" causes a non-partitionable array
347to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and
348later) to be used. The argumentment can also come immediately after
349"-a". e.g. "-ap".
350
351For partitionable arrays,
352.I mdadm
353will create the device file for the whole array and for the first 4
354partitions. A different number of partitions can be specified at the
355end of this option (e.g.
356.BR --auto=p7 ).
357If the device name ends with a digit, the partition names add an
358underscore, a 'p', and a number, e.g. "/dev/home1_p3". If there is no
359trailing digit, then the partition names just have a number added,
360e.g. "/dev/scratch3".
361
52826846
NB
362.SH For assemble:
363
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NB
364.TP
365.BR -u ", " --uuid=
366uuid of array to assemble. Devices which don't have this uuid are
367excluded
368
369.TP
370.BR -m ", " --super-minor=
371Minor number of device that array was created for. Devices which
372don't have this minor number are excluded. If you create an array as
2d465520 373/dev/md1, then all superblocks will contain the minor number 1, even if
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NB
374the array is later assembled as /dev/md2.
375
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NB
376Giving the literal word "dev" for
377.B --super-minor
378will cause
379.I mdadm
380to use the minor number of the md device that is being assembled.
381e.g. when assembling
382.BR /dev/md0 ,
383.M --super-minor=dev
384will look for super blocks with a minor number of 0.
385
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NB
386.TP
387.BR -f ", " --force
52826846
NB
388Assemble the array even if some superblocks appear out-of-date
389
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NB
390.TP
391.BR -R ", " --run
392Attempt to start the array even if fewer drives were given than are
393needed for a full array. Normally if not all drives are found and
394.B --scan
395is not used, then the array will be assembled but not started.
396With
397.B --run
398an attempt will be made to start it anyway.
52826846 399
dd0781e5
NB
400.TP
401.BR -a ", " "--auto{=no,yes,md,mdp,part}"
402See this option under Create and Build options.
403
5787fa49
NB
404.TP
405.BR -U ", " --update=
406Update the superblock on each device while assembling the array. The
feb716e9
NB
407argument given to this flag can be one of
408.BR sparc2.2 ,
409.BR summaries ,
5787fa49
NB
410or
411.BR super-minor .
412
413The
414.B sparc2.2
415option will adjust the superblock of an array what was created on a Sparc
416machine running a patched 2.2 Linux kernel. This kernel got the
417alignment of part of the superblock wrong. You can use the
418.B "--examine --sparc2.2"
419option to
420.I mdadm
421to see what effect this would have.
422
423The
424.B super-minor
425option will update the
426.B "prefered minor"
427field on each superblock to match the minor number of the array being
feb716e9 428assembled. This is not needed on 2.6 and later kernels as they make
5787fa49
NB
429this adjustment automatically.
430
feb716e9
NB
431The
432.B summaries
433option will correct the summaries in the superblock. That is the
434counts of total, working, active, failed, and spare devices.
5787fa49 435
e0d19036 436.SH For Manage mode:
52826846 437
cd29a5c8
NB
438.TP
439.BR -a ", " --add
440'''add, or
441hotadd listed devices.
52826846 442
cd29a5c8
NB
443.TP
444.BR -r ", " --remove
2d465520 445remove listed devices. They must not be active. i.e. they should
cd29a5c8 446be failed or spare devices.
52826846 447
cd29a5c8
NB
448.TP
449.BR -f ", " --fail
450mark listed devices as faulty.
52826846 451
cd29a5c8
NB
452.TP
453.BR --set-faulty
454same as --fail.
52826846 455
5787fa49
NB
456.SH For Examine mode:
457
458.TP
459.B --sparc2.2
460In an array was created on a 2.2 Linux kernel patched with RAID
461support, the superblock will have been created incorrectly, or at
462least incompatibly with 2.4 and later kernels. Using the
463.B --sparc2.2
464flag with
465.B --examine
466will fix the superblock before displaying it. If this appears to do
467the right thing, then the array can be successfully assembled using
468.BR "--assemble --update=sparc2.2" .
469
e0d19036
NB
470.SH For Misc mode:
471
cd29a5c8
NB
472.TP
473.BR -R ", " --run
474start a partially built array.
52826846 475
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NB
476.TP
477.BR -S ", " --stop
478deactivate array, releasing all resources.
52826846 479
cd29a5c8
NB
480.TP
481.BR -o ", " --readonly
482mark array as readonly.
52826846 483
cd29a5c8
NB
484.TP
485.BR -w ", " --readwrite
486mark array as readwrite.
52826846 487
e0d19036
NB
488.TP
489.B --zero-superblock
490If the device contains a valid md superblock, the block is
491over-written with zeros. With
492--force
493the block where the superblock would be is over-written even if it
494doesn't appear to be valid.
52826846 495
feb716e9
NB
496.TP
497.BR -t ", " --test
498When used with
499.BR --detail ,
500the exit status of
501.I mdadm
502is set to reflect the status of the device.
503
e0d19036
NB
504.SH For Monitor mode:
505.TP
506.BR -m ", " --mail
507Give a mail address to send alerts to.
508
509.TP
510.BR -p ", " --program ", " --alert
511Give a program to be run whenever an event is detected.
512
513.TP
514.BR -d ", " --delay
515Give a delay in seconds.
516.B mdadm
517polls the md arrays and then waits this many seconds before polling
518again. The default is 60 seconds.
519
d013a55e
NB
520.TP
521.BR -f ", " --daemonise
522Tell
523.B mdadm
524to run as a background daemon if it decides to monitor anything. This
525causes it to fork and run in the child, and to disconnect form the
526terminal. The process id of the child is written to stdout.
527This is useful with
528.B --scan
529which will only continue monitoring if a mail address or alert program
530is found in the config file.
531
aa88f531
NB
532.TP
533.BR -1 ", " --oneshot
534Check arrays only once. This will generate
535.B NewArray
536events and more significantly
537.B DegradedArray
538events. Running
539.in +5
540.B " mdadm --monitor --scan -1"
541.in -5
542from a cron script will ensure regular notification of any degraded arrays.
543
98c6faba
NB
544.TP
545.BR -t ", " --test
546Generate a
547.B TestMessage
548alert for every array found at startup. This alert gets mailed and
549passed to the alert program. This can be used for testing that alert
550message to get through successfully.
551
e0d19036 552.SH ASSEMBLE MODE
52826846 553
cd29a5c8
NB
554.HP 12
555Usage:
9a9dab36 556.B mdadm --assemble
5787fa49
NB
557.I md-device options-and-component-devices...
558.HP 12
559Usage:
560.B mdadm --assemble --scan
561.I md-devices-and-options...
cd29a5c8
NB
562.HP 12
563Usage:
9a9dab36 564.B mdadm --assemble --scan
cd29a5c8 565.I options...
52826846 566
cd29a5c8 567.PP
52826846 568This usage assembles one or more raid arrays from pre-existing components.
9a9dab36 569For each array, mdadm needs to know the md device, the identity of the
e0d19036 570array, and a number of component-devices. These can be found in a number of ways.
52826846 571
5787fa49
NB
572In the first usage example (without the
573.BR --scan )
574the first device given is the md device.
575In the second usage example, all devices listed are treated as md
576devices and assembly is attempted.
577In the third (where no devices are listed) all md devices that are
578listed in the configuration file are assembled.
52826846 579
d013a55e
NB
580If precisely one device is listed, but
581.B --scan
dd0781e5 582is not given, then
d013a55e
NB
583.I mdadm
584acts as though
585.B --scan
586was given and identify information is extracted from the configuration file.
587
cd29a5c8 588The identity can be given with the
52826846 589.B --uuid
cd29a5c8
NB
590option, with the
591.B --super-minor
5787fa49 592option, can be found in the config file, or will be taken from the
e0d19036 593super block on the first component-device listed on the command line.
52826846
NB
594
595Devices can be given on the
596.B --assemble
5787fa49
NB
597command line or in the config file. Only devices which have an md
598superblock which contains the right identity will be considered for
599any array.
52826846
NB
600
601The config file is only used if explicitly named with
602.B --config
d013a55e 603or requested with (a possibly implicit)
52826846
NB
604.B --scan.
605In the later case,
9a9dab36 606.B /etc/mdadm.conf
52826846
NB
607is used.
608
609If
610.B --scan
cd29a5c8
NB
611is not given, then the config file will only be used to find the
612identity of md arrays.
52826846 613
2d465520 614Normally the array will be started after it is assembled. However if
cd29a5c8 615.B --scan
2d465520 616is not given and insufficient drives were listed to start a complete
cd29a5c8
NB
617(non-degraded) array, then the array is not started (to guard against
618usage errors). To insist that the array be started in this case (as
98c6faba 619may work for RAID1, 4, 5 or 6), give the
cd29a5c8
NB
620.B --run
621flag.
52826846 622
dd0781e5
NB
623If an
624.B auto
625option is given, either on the command line (--auto) or in the
626configuration file (e.g. auto=part), then
627.I mdadm
628will create the md device if necessary or will re-create it if it
629doesn't look usable as it is.
630
631This can be useful for handling partitioned devices (which don't have
632a stable device number - it can change after a reboot) and when using
633"udev" to manage your
634.B /dev
635tree (udev cannot handle md devices because of the unusual device
636initialisation conventions).
637
638If the option to "auto" is "mdp" or "part" or (on the command line
639only) "p", then mdadm will create a partitionable array, using the
640first free one that is not inuse, and does not already have an entry
641in /dev (apart from numeric /dev/md* entries).
642
643If the option to "auto" is "yes" or "md" or (on the command line)
644nothing, then mdadm will create a traditional, non-partitionable md
645array.
646
647It is expected that the "auto" functionality will be used to create
648device entries with meaningful names such as "/dev/md/home" or
649"/dev/md/root", rather than names based on the numerical array number.
650
651When using this option to create a partitionable array, the device
652files for the first 4 partitions are also created. If a different
653number is required it can be simply appended to the auto option.
654e.g. "auto=part8". Partition names are created by appending a digit
655string to the device name, with an intervening "_p" if the device name
656ends with a digit.
657
658The
659.B --auto
660option is also available in Build and Create modes. As those modes do
661not use a config file, the "auto=" config option does not apply to
662these modes.
52826846 663
cd29a5c8 664.SH BUILD MODE
52826846 665
cd29a5c8
NB
666.HP 12
667Usage:
9a9dab36 668.B mdadm --build
cd29a5c8
NB
669.I device
670.BI --chunk= X
671.BI --level= Y
b83d95f3 672.BI --raid-devices= Z
cd29a5c8
NB
673.I devices
674
675.PP
52826846 676This usage is similar to
cd29a5c8 677.BR --create .
52826846 678The difference is that it creates a legacy array without a superblock. With
cd29a5c8 679these arrays there is no difference between initially creating the array and
52826846
NB
680subsequently assembling the array, except that hopefully there is useful
681data there in the second case.
682
cd29a5c8
NB
683The level may only be 0, raid0, or linear. All devices must be listed
684and the array will be started once complete.
685
686.SH CREATE MODE
687
688.HP 12
689Usage:
9a9dab36 690.B mdadm --create
cd29a5c8
NB
691.I device
692.BI --chunk= X
693.BI --level= Y
694.br
b83d95f3 695.BI --raid-devices= Z
cd29a5c8
NB
696.I devices
697
698.PP
699This usage will initialise a new md array, associate some devices with
700it, and activate the array.
701
dd0781e5
NB
702This the
703.B --auto
704option is given (as described in more detail in the section on
705Assemble mode), then the md device will be created with a suitable
706device number if necessary.
707
cd29a5c8 708As devices are added, they are checked to see if they contain raid
2d465520 709superblocks or filesystems. They are also checked to see if the variance in
cd29a5c8
NB
710device size exceeds 1%.
711
712If any discrepancy is found, the array will not automatically be run, though
713the presence of a
714.B --run
715can override this caution.
716
2d465520 717To create a "degraded" array in which some devices are missing, simply
d013a55e 718give the word "\fBmissing\fP"
2d465520
NB
719in place of a device name. This will cause
720.B mdadm
721to leave the corresponding slot in the array empty.
722For a RAID4 or RAID5 array at most one slot can be
98c6faba 723"\fBmissing\fP"; for a RAID6 array at most two slots.
2d465520
NB
724For a RAID1 array, only one real device needs to be given. All of the
725others can be
d013a55e 726"\fBmissing\fP".
2d465520 727
feb716e9
NB
728When creating a RAID5 array,
729.B mdadm
730will automatically create a degraded array with an extra spare drive.
731This is because building the spare into a degraded array is in general faster than resyncing
732the parity on a non-degraded, but not clean, array. This feature can
733be over-ridden with the
734-I --force
735option.
736
cd29a5c8
NB
737'''If the
738'''.B --size
e0d19036 739'''option is given, it is not necessary to list any component-devices in this command.
cd29a5c8
NB
740'''They can be added later, before a
741'''.B --run.
742'''If no
743'''.B --size
744'''is given, the apparent size of the smallest drive given is used.
745
746The General Management options that are valid with --create are:
747.TP
748.B --run
dd0781e5 749insist on running the array even if some devices look like they might
cd29a5c8
NB
750be in use.
751
752.TP
753.B --readonly
754start the array readonly - not supported yet.
52826846 755
e0d19036 756.SH MANAGE MODE
cd29a5c8
NB
757.HP 12
758Usage:
e0d19036
NB
759.B mdadm
760.I device
761.I options... devices...
cd29a5c8
NB
762.PP
763
e0d19036
NB
764This usage will allow individual devices in an array to be failed,
765removed or added. It is possible to perform multiple operations with
766on command. For example:
767.br
5787fa49 768.B " mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1"
e0d19036
NB
769.br
770will firstly mark
771.B /dev/hda1
772as faulty in
773.B /dev/md0
774and will then remove it from the array and finally add it back
2d465520 775in as a spare. However only one md array can be affected by a single
e0d19036
NB
776command.
777
778.SH MISC MODE
779.HP 12
780Usage:
9a9dab36 781.B mdadm
e0d19036
NB
782.I options ...
783.I devices ...
784.PP
cd29a5c8 785
e0d19036
NB
786MISC mode includes a number if distinct operations that
787operate on distinct devices. The operations are:
788.TP
789--query
790The device is examined to see if it is
791(1) an active md array, or
792(2) a component of an md array.
793The information discovered is reported.
794
795.TP
796--detail
2d465520
NB
797The device should be an active md device.
798.B mdadm
799will display a detailed description of the array.
cd29a5c8 800.B --brief
2d465520
NB
801or
802.B --scan
803will cause the output to be less detailed and the format to be
e0d19036 804suitable for inclusion in
9a9dab36 805.BR /etc/mdadm.conf .
feb716e9
NB
806The exit status of
807.I mdadm
808will normally be 0 unless
809.I mdadm
810failed to get useful information about the device(s). However if the
811.B --test
812option is given, then the exit status will be:
813.RS
814.TP
8150
816The array is functioning normally.
817.TP
8181
819The array has at least one failed device.
820.TP
8212
822The array has multiple failed devices and hence is unusable (raid4 or
823raid5).
824.TP
8254
826There was an error while trying to get information about the device.
827.RE
cd29a5c8 828
e0d19036
NB
829.TP
830--examine
2d465520
NB
831The device should be a component of an md array.
832.B mdadm
833will read the md superblock of the device and display the contents.
e0d19036
NB
834If
835.B --brief
836is given, or
837.B --scan
838then multiple devices that are components of the one array
839are grouped together and reported in a single entry suitable
840for inclusion in
841.BR /etc/mdadm.conf .
842
2d465520 843Having
e0d19036
NB
844.B --scan
845without listing any devices will cause all devices listed in the
846config file to be examined.
847
848.TP
849--stop
98c6faba
NB
850The devices should be active md arrays which will be deactivated, as
851long as they are not currently in use.
e0d19036
NB
852
853.TP
854--run
855This will fully activate a partially assembled md array.
856
857.TP
858--readonly
859This will mark an active array as read-only, providing that it is
860not currently being used.
861
862.TP
863--readwrite
864This will change a
865.B readonly
866array back to being read/write.
867
2d465520
NB
868.TP
869--scan
870For all operations except
871.BR --examine ,
872.B --scan
873will cause the operation to be applied to all arrays listed in
874.BR /proc/mdstat .
875For
876.BR --examine,
877.B --scan
878causes all devices listed in the config file to be examined.
879
880
e0d19036
NB
881.SH MONITOR MODE
882
cd29a5c8
NB
883.HP 12
884Usage:
e0d19036
NB
885.B mdadm --monitor
886.I options... devices...
887
cd29a5c8 888.PP
e0d19036
NB
889This usage causes
890.B mdadm
891to periodically poll a number of md arrays and to report on any events
892noticed.
893.B mdadm
894will never exit once it decides that there are arrays to be checked,
895so it should normally be run in the background.
896
2d465520
NB
897As well as reporting events,
898.B mdadm
899may move a spare drive from one array to another if they are in the
900same
901.B spare-group
902and if the destination array has a failed drive but not spares.
903
e0d19036
NB
904If any devices are listed on the command line,
905.B mdadm
906will only monitor those devices. Otherwise all arrays listed in the
907configuration file will be monitored. Further, if
908.B --scan
909is given, then any other md devices that appear in
910.B /proc/mdstat
911will also be monitored.
912
913The result of monitoring the arrays is the generation of events.
bd526cee 914These events are passed to a separate program (if specified) and may
2d465520 915be mailed to a given E-mail address.
e0d19036 916
bd526cee
NB
917When passing event to program, the program is run once for each event
918and is given 2 or 3 command-line arguements. The first is the
919name of the event (see below). The second is the name of the
920md device which is affected, and the third is the name of a related
921device if relevant, such as a component device that has failed.
cd29a5c8
NB
922
923If
924.B --scan
e0d19036
NB
925is given, then a program or an E-mail address must be specified on the
926command line or in the config file. If neither are available, then
927.B mdadm
928will not monitor anything.
929Without
cd29a5c8 930.B --scan
e0d19036 931.B mdadm
2d465520 932will continue monitoring as long as something was found to monitor. If
e0d19036
NB
933no program or email is given, then each event is reported to
934.BR stdout .
cd29a5c8 935
e0d19036
NB
936The different events are:
937
938.RS 4
939.TP
940.B DeviceDisappeared
2d465520 941An md array which previously was configured appears to no longer be
e0d19036
NB
942configured.
943
944.TP
945.B RebuildStarted
946An md array started reconstruction.
947
948.TP
949.BI Rebuild NN
950Where
951.I NN
952is 20, 40, 60, or 80, this indicates that rebuild has passed that many
953percentage of the total.
954
98c6faba
NB
955.TP
956.B RebuildFinished
957An md array that was rebuilding, isn't any more, either because it
958finished normally or was aborted.
959
e0d19036
NB
960.TP
961.B Fail
962An active component device of an array has been marked as faulty.
963
964.TP
965.B FailSpare
966A spare component device which was being rebuilt to replace a faulty
967device has failed.
968
969.TP
970.B SpareActive
971A spare component device which was being rebuilt to replace a faulty
972device as been successfully rebuild and has been made active.
973
974.TP
975.B NewArray
976A new md array has been detected in the
977.B /proc/mdstat
978file.
979
aa88f531
NB
980.TP
981.B DegradedArray
982A newly noticed array appears to be degraded. This message is not
983generated when
984.I mdadm
985notices a drive failure which causes degradation, but only when
986.I mdadm
987notices that an array is degraded when it first sees the array.
988
e0d19036
NB
989.TP
990.B MoveSpare
991A spare drive has been moved from one array in a
992.B spare-group
993to another to allow a failed drive to be replaced.
994
98c6faba
NB
995.TP
996.B TestMessage
997An array was found at startup, and the
998.B --test
999flag was given.
e0d19036
NB
1000.RE
1001
1002Only
98c6faba
NB
1003.B Fail ,
1004.B FailSpare ,
1005.B DegradedArray ,
e0d19036 1006and
98c6faba 1007.B TestMessage
e0d19036
NB
1008cause Email to be sent. All events cause the program to be run.
1009The program is run with two or three arguments, they being the event
1010name, the array device and possibly a second device.
1011
1012Each event has an associated array device (e.g.
1013.BR /dev/md1 )
1014and possibly a second device. For
1015.BR Fail ,
1016.BR FailSpare ,
1017and
1018.B SpareActive
1019the second device is the relevant component device.
1020For
1021.B MoveSpare
1022the second device is the array that the spare was moved from.
1023
1024For
1025.B mdadm
1026to move spares from one array to another, the different arrays need to
1027be labelled with the same
1028.B spare-group
1029in the configuration file. The
1030.B spare-group
1031name can be any string. It is only necessary that different spare
2d465520 1032groups use different names.
e0d19036
NB
1033
1034When
9a9dab36 1035.B mdadm
e0d19036
NB
1036detects that an array which is in a spare group has fewer active
1037devices than necessary for the complete array, and has no spare
1038devices, it will look for another array in the same spare group that
1039has a full complement of working drive and a spare. It will then
1040attempt to remove the spare from the second drive and add it to the
1041first.
1042If the removal succeeds but the adding fails, then it is added back to
1043the original array.
1044
dd0781e5
NB
1045.SH GROW MODE
1046The GROW mode is used for changing the size or shape of an active
1047array.
1048For this to work, the kernel must support the necessary change.
1049Various types of growth may be added during 2.6 development, possibly
1050including restructuring a raid5 array to have more active devices.
1051
1052Currently the only support available is to change the "size" attribute
1053for arrays with redundancy, and the raid-disks attribute of RAID1
1054arrays.
1055
1056Normally when an array is build the "size" it taken from the smallest
1057of the drives. If all the small drives in an arrays are, one at a
1058time, removed and replaced with larger drives, then you could have an
1059array of large drives with only a small amount used. In this
1060situation, changing the "size" with "GROW" mode will allow the extra
1061space to start being used. If the size is increased in this way, a
1062"resync" process will start to make sure the new parts of the array
1063are synchronised.
1064
1065Note that when an array changes size, any filesystem that may be
1066stored in the array will not automatically grow to use the space. The
1067filesystem will need to be explicitly told to use the extra space.
1068
1069A RAID1 array can work with any number of devices from 1 upwards
1070(though 1 is not very useful). There may be times which you want to
1071increase or decrease the number of active devices. Note that this is
1072different to hot-add or hot-remove which changes the number of
1073inactive devices.
1074
1075When reducing the number of devices in a RAID1 array, the slots which
1076are to be removed from the array must already be vacant. That is, the
1077devices that which were in those slots must be failed and removed.
1078
1079When the number of devices is increased, any hot spares that are
1080present may be activated immediately.
1081
2d465520
NB
1082.SH EXAMPLES
1083
5787fa49 1084.B " mdadm --query /dev/name-of-device"
2d465520 1085.br
5787fa49
NB
1086This will find out if a given device is a raid array, or is part of
1087one, and will provide brief information about the device.
2d465520 1088
5787fa49 1089.B " mdadm --assemble --scan"
2d465520 1090.br
5787fa49
NB
1091This will assemble and start all arrays listed in the standard confile
1092file. This command will typically go in a system startup file.
2d465520 1093
2d465520 1094.B " mdadm --stop --scan"
5787fa49
NB
1095.br
1096This will shut down all array that can be shut down (i.e. are not
1097currently in used). This will typically going in a system shutdown script.
2d465520 1098
5787fa49 1099.B " mdadm --follow --scan --delay=120"
2d465520 1100.br
5787fa49
NB
1101If (and only if) there is an Email address or program given in the
1102standard config file, then
1103monitor the status of all arrays listed in that file by
1104polling them ever 2 minutes.
2d465520 1105
5787fa49 1106.B " mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[ac]1"
2d465520 1107.br
5787fa49 1108Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
2d465520 1109
2d465520
NB
1110.br
1111.B " echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > mdadm.conf"
1112.br
1113.B " mdadm --detail --scan >> mdadm.conf"
1114.br
5787fa49
NB
1115This will create a prototype config file that describes currently
1116active arrays that are known to be made from partitions of IDE or SCSI drives.
2d465520
NB
1117This file should be reviewed before being used as it may
1118contain unwanted detail.
1119
2d465520
NB
1120.B " echo 'DEVICE /dev/hd[a-z] /dev/sd*[a-z]' > mdadm.conf"
1121.br
5787fa49
NB
1122.B " mdadm --examine --scan --config=mdadm.conf >> mdadm.conf"
1123.ber
1124This will find what arrays could be assembled from existign IDE and
1125SCSI whole drives (not partitions) and store the information is the
1126format of a config file.
2d465520
NB
1127This file is very likely to contain unwanted detail, particularly
1128the
1129.B devices=
5787fa49
NB
1130entries. It should be reviewed and edited before being used as an
1131actual config file.
2d465520 1132
5787fa49 1133.B " mdadm --examine --brief --scan --config=partitions"
2d465520 1134.br
5787fa49
NB
1135.B " mdadm -Ebsc partitions"
1136.br
1137Create a list of devices by reading
1138.BR /proc/partitions ,
1139scan these for RAID superblocks, and printout a brief listing of all
1140that was found.
2d465520 1141
5787fa49 1142.B " mdadm -Ac partitions -m 0 /dev/md0"
2d465520 1143.br
5787fa49
NB
1144Scan all partitions and devices listed in
1145.BR /proc/partitions
1146and assemble
1147.B /dev/md0
1148out of all such devices with a RAID superblock with a minor number of 0.
2d465520 1149
d013a55e
NB
1150.B " mdadm --monitor --scan --daemonise > /var/run/mdadm"
1151.br
1152If config file contains a mail address or alert program, run mdadm in
1153the background in monitor mode monitoring all md devices. Also write
1154pid of mdadm daemon to
1155.BR /var/run/mdadm .
1156
5787fa49 1157.B " mdadm --create --help"
2d465520 1158.br
5787fa49 1159Providew help about the Create mode.
2d465520 1160
5787fa49
NB
1161.B " mdadm --config --help"
1162.br
1163Provide help about the format of the config file.
2d465520 1164
5787fa49
NB
1165.B " mdadm --help"
1166.br
1167Provide general help.
cd29a5c8 1168
cd29a5c8
NB
1169
1170.SH FILES
1171
1172.SS /proc/mdstat
1173
1174If you're using the
1175.B /proc
1176filesystem,
1177.B /proc/mdstat
2d465520
NB
1178lists all active md devices with information about them.
1179.B mdadm
1180uses this to find arrays when
1181.B --scan
1182is given in Misc mode, and to monitor array reconstruction
1183on Monitor mode.
1184
cd29a5c8 1185
9a9dab36 1186.SS /etc/mdadm.conf
cd29a5c8 1187
11a3e71d
NB
1188The config file lists which devices may be scanned to see if
1189they contain MD super block, and gives identifying information
1190(e.g. UUID) about known MD arrays. See
1191.BR mdadm.conf (5)
1192for more details.
cd29a5c8 1193
52826846 1194
2d465520
NB
1195.SH NOTE
1196.B mdadm
1197was previously known as
1198.BR mdctl .
1199
52826846 1200.SH SEE ALSO
cd29a5c8
NB
1201For information on the various levels of
1202RAID, check out:
1203
1204.IP
1205.UR http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
1206http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/
1207.UE
1208.PP
1209for new releases of the RAID driver check out:
1210
1211.IP
1212.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
1213ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
1214.UE
1215.PP
1216or
1217.IP
1218.UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
1219http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
1220.URk
1221.PP
56eb10c0
NB
1222.BR mdadm.conf (5),
1223.BR md (4).
1224.PP
52826846
NB
1225.IR raidtab (5),
1226.IR raid0run (8),
1227.IR raidstop (8),
1228.IR mkraid (8)