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- Committer: Dmitrijs Ledkovs
- Author(s): martin f. krafft
- Date: 2009-11-06 10:06:03 UTC
- mto: This revision was merged to the branch mainline in revision 55.
- Revision ID: dmitrijs.ledkovs@canonical.com-20091106100603-q9s0evnzd106mrzt
Tags: 3.0.3-2
* Bumped Standards-Version to 3.8.3 without having to make changes.
* Fixed init dependencies of mdadm daemon init.d script; thanks Petter
Reinholdtsen (closes: #541396).
* Switched source package to v3-quilt format.
* Fixed init dependencies of mdadm daemon init.d script; thanks Petter
Reinholdtsen (closes: #541396).
* Switched source package to v3-quilt format.
- files added:
- .pc
- .pc/contrib
- .pc/contrib/docs
- .pc/contrib/docs/jd-rebuilding-raid.diff
- .pc/contrib/docs/jd-rebuilding-raid.diff/docs
- .pc/contrib/docs/md.txt.diff
- .pc/contrib/docs/md.txt.diff/docs
- .pc/contrib/docs/raid5-vs-raid10.diff
- .pc/contrib/docs/raid5-vs-raid10.diff/docs
- .pc/contrib/docs/superblock_formats.diff
- .pc/contrib/docs/superblock_formats.diff/docs
- .pc/debian
- .pc/debian/conffile-location.diff
- .pc/fixes
- .pc/fixes/udev-blkid.diff
- debian/source
- docs
- files modified:
- Makefile
- debian/bugscript.in *
- debian/newdisk *
added
removed
.pc/debian/conffile-location.diff/mdadm.8
1
.\" -*- nroff -*-
2
.\" Copyright Neil Brown and others.
3
.\" This program is free software; you can redistribute it and/or modify
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.\" it under the terms of the GNU General Public License as published by
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.\" the Free Software Foundation; either version 2 of the License, or
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.\" (at your option) any later version.
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.\" See file COPYING in distribution for details.
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.TH MDADM 8 "" v3.0.3
9
.SH NAME
10
mdadm \- manage MD devices
11
.I aka
12
Linux Software RAID
13
14
.SH SYNOPSIS
15
16
.BI mdadm " [mode] <raiddevice> [options] <component-devices>"
17
18
.SH DESCRIPTION
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
24
device failure.
25
26
Linux Software RAID devices are implemented through the md (Multiple
27
Devices) device driver.
28
29
Currently, Linux supports
30
.B LINEAR
31
md devices,
32
.B RAID0
33
(striping),
34
.B RAID1
35
(mirroring),
36
.BR RAID4 ,
37
.BR RAID5 ,
38
.BR RAID6 ,
39
.BR RAID10 ,
40
.BR MULTIPATH ,
41
.BR FAULTY ,
42
and
43
.BR CONTAINER .
44
45
.B MULTIPATH
46
is not a Software RAID mechanism, but does involve
47
multiple devices:
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.
52
53
.B FAULTY
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.
56
57
.B CONTAINER
58
is different again. A
59
.B CONTAINER
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
67
second half.
68
69
With a
70
.BR CONTAINER ,
71
there is one set of metadata that describes all of
72
the arrays in the container. So when
73
.I mdadm
74
creates a
75
.B CONTAINER
76
device, the device just represents the metadata. Other normal arrays (RAID1
77
etc) can be created inside the container.
78
79
.SH MODES
80
mdadm has several major modes of operation:
81
.TP
82
.B Assemble
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.
86
.I mdadm
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.
90
91
.TP
92
.B Build
93
Build an array that doesn't have per-device metadata (superblocks). For these
94
sorts of arrays,
95
.I mdadm
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
99
.B Build
100
mode should only be used together with a complete understanding of
101
what you are doing.
102
103
.TP
104
.B Create
105
Create a new array with per-device metadata (superblocks).
106
Appropriate metadata is written to each device, and then the array
107
comprising those devices is activated. A 'resync' process is started
108
to make sure that the array is consistent (e.g. both sides of a mirror
109
contain the same data) but the content of the device is left otherwise
110
untouched.
111
The array can be used as soon as it has been created. There is no
112
need to wait for the initial resync to finish.
113
114
.TP
115
.B "Follow or Monitor"
116
Monitor one or more md devices and act on any state changes. This is
117
only meaningful for RAID1, 4, 5, 6, 10 or multipath arrays, as
118
only these have interesting state. RAID0 or Linear never have
119
missing, spare, or failed drives, so there is nothing to monitor.
120
121
.TP
122
.B "Grow"
123
Grow (or shrink) an array, or otherwise reshape it in some way.
124
Currently supported growth options including changing the active size
125
of component devices and changing the number of active devices in RAID
126
levels 1/4/5/6, as well as adding or removing a write-intent bitmap.
127
128
.TP
129
.B "Incremental Assembly"
130
Add a single device to an appropriate array. If the addition of the
131
device makes the array runnable, the array will be started.
132
This provides a convenient interface to a
133
.I hot-plug
134
system. As each device is detected,
135
.I mdadm
136
has a chance to include it in some array as appropriate.
137
138
If a
139
.B CONTAINER
140
is passed to
141
.I mdadm
142
in this mode, then any arrays within that container will be assembled
143
and started.
144
145
.TP
146
.B Manage
147
This is for doing things to specific components of an array such as
148
adding new spares and removing faulty devices.
149
150
.TP
151
.B Misc
152
This is an 'everything else' mode that supports operations on active
153
arrays, operations on component devices such as erasing old superblocks, and
154
information gathering operations.
155
.\"This mode allows operations on independent devices such as examine MD
156
.\"superblocks, erasing old superblocks and stopping active arrays.
157
158
.TP
159
.B Auto-detect
160
This mode does not act on a specific device or array, but rather it
161
requests the Linux Kernel to activate any auto-detected arrays.
162
.SH OPTIONS
163
164
.SH Options for selecting a mode are:
165
166
.TP
167
.BR \-A ", " \-\-assemble
168
Assemble a pre-existing array.
169
170
.TP
171
.BR \-B ", " \-\-build
172
Build a legacy array without superblocks.
173
174
.TP
175
.BR \-C ", " \-\-create
176
Create a new array.
177
178
.TP
179
.BR \-F ", " \-\-follow ", " \-\-monitor
180
Select
181
.B Monitor
182
mode.
183
184
.TP
185
.BR \-G ", " \-\-grow
186
Change the size or shape of an active array.
187
188
.TP
189
.BR \-I ", " \-\-incremental
190
Add a single device into an appropriate array, and possibly start the array.
191
192
.TP
193
.B \-\-auto-detect
194
Request that the kernel starts any auto-detected arrays. This can only
195
work if
196
.I md
197
is compiled into the kernel \(em not if it is a module.
198
Arrays can be auto-detected by the kernel if all the components are in
199
primary MS-DOS partitions with partition type
200
.BR FD ,
201
and all use v0.90 metadata.
202
In-kernel autodetect is not recommended for new installations. Using
203
.I mdadm
204
to detect and assemble arrays \(em possibly in an
205
.I initrd
206
\(em is substantially more flexible and should be preferred.
207
208
.P
209
If a device is given before any options, or if the first option is
210
.BR \-\-add ,
211
.BR \-\-fail ,
212
or
213
.BR \-\-remove ,
214
then the MANAGE mode is assumed.
215
Anything other than these will cause the
216
.B Misc
217
mode to be assumed.
218
219
.SH Options that are not mode-specific are:
220
221
.TP
222
.BR \-h ", " \-\-help
223
Display general help message or, after one of the above options, a
224
mode-specific help message.
225
226
.TP
227
.B \-\-help\-options
228
Display more detailed help about command line parsing and some commonly
229
used options.
230
231
.TP
232
.BR \-V ", " \-\-version
233
Print version information for mdadm.
234
235
.TP
236
.BR \-v ", " \-\-verbose
237
Be more verbose about what is happening. This can be used twice to be
238
extra-verbose.
239
The extra verbosity currently only affects
240
.B \-\-detail \-\-scan
241
and
242
.BR "\-\-examine \-\-scan" .
243
244
.TP
245
.BR \-q ", " \-\-quiet
246
Avoid printing purely informative messages. With this,
247
.I mdadm
248
will be silent unless there is something really important to report.
249
250
.TP
251
.BR \-b ", " \-\-brief
252
Be less verbose. This is used with
253
.B \-\-detail
254
and
255
.BR \-\-examine .
256
Using
257
.B \-\-brief
258
with
259
.B \-\-verbose
260
gives an intermediate level of verbosity.
261
262
.TP
263
.BR \-f ", " \-\-force
264
Be more forceful about certain operations. See the various modes for
265
the exact meaning of this option in different contexts.
266
267
.TP
268
.BR \-c ", " \-\-config=
269
Specify the config file. Default is to use
270
.BR /etc/mdadm.conf ,
271
or if that is missing then
272
.BR /etc/mdadm/mdadm.conf .
273
If the config file given is
274
.B "partitions"
275
then nothing will be read, but
276
.I mdadm
277
will act as though the config file contained exactly
278
.B "DEVICE partitions containers"
279
and will read
280
.B /proc/partitions
281
to find a list of devices to scan, and
282
.B /proc/mdstat
283
to find a list of containers to examine.
284
If the word
285
.B "none"
286
is given for the config file, then
287
.I mdadm
288
will act as though the config file were empty.
289
290
.TP
291
.BR \-s ", " \-\-scan
292
Scan config file or
293
.B /proc/mdstat
294
for missing information.
295
In general, this option gives
296
.I mdadm
297
permission to get any missing information (like component devices,
298
array devices, array identities, and alert destination) from the
299
configuration file (see previous option);
300
one exception is MISC mode when using
301
.B \-\-detail
302
or
303
.B \-\-stop,
304
in which case
305
.B \-\-scan
306
says to get a list of array devices from
307
.BR /proc/mdstat .
308
309
.TP
310
.BR \-e ", " \-\-metadata=
311
Declare the style of RAID metadata (superblock) to be used. The
312
default is 0.90 for
313
.BR \-\-create ,
314
and to guess for other operations.
315
The default can be overridden by setting the
316
.B metadata
317
value for the
318
.B CREATE
319
keyword in
320
.BR mdadm.conf .
321
322
Options are:
323
.RS
324
.IP "0, 0.90, default"
325
Use the original 0.90 format superblock. This format limits arrays to
326
28 component devices and limits component devices of levels 1 and
327
greater to 2 terabytes.
328
.IP "1, 1.0, 1.1, 1.2"
329
Use the new version-1 format superblock. This has few restrictions.
330
The different sub-versions store the superblock at different locations
331
on the device, either at the end (for 1.0), at the start (for 1.1) or
332
4K from the start (for 1.2).
333
.IP ddf
334
Use the "Industry Standard" DDF (Disk Data Format) format defined by
335
SNIA.
336
When creating a DDF array a
337
.B CONTAINER
338
will be created, and normal arrays can be created in that container.
339
.IP imsm
340
Use the Intel(R) Matrix Storage Manager metadata format. This creates a
341
.B CONTAINER
342
which is managed in a similar manner to DDF, and is supported by an
343
option-rom on some platforms:
344
.IP
345
.B http://www.intel.com/design/chipsets/matrixstorage_sb.htm
346
.PP
347
.RE
348
349
.TP
350
.B \-\-homehost=
351
This will override any
352
.B HOMEHOST
353
setting in the config file and provides the identity of the host which
354
should be considered the home for any arrays.
355
356
When creating an array, the
357
.B homehost
358
will be recorded in the metadata. For version-1 superblocks, it will
359
be prefixed to the array name. For version-0.90 superblocks, part of
360
the SHA1 hash of the hostname will be stored in the later half of the
361
UUID.
362
363
When reporting information about an array, any array which is tagged
364
for the given homehost will be reported as such.
365
366
When using Auto-Assemble, only arrays tagged for the given homehost
367
will be allowed to use 'local' names (i.e. not ending in '_' followed
368
by a digit string). See below under
369
.BR "Auto Assembly" .
370
371
.SH For create, build, or grow:
372
373
.TP
374
.BR \-n ", " \-\-raid\-devices=
375
Specify the number of active devices in the array. This, plus the
376
number of spare devices (see below) must equal the number of
377
.I component-devices
378
(including "\fBmissing\fP" devices)
379
that are listed on the command line for
380
.BR \-\-create .
381
Setting a value of 1 is probably
382
a mistake and so requires that
383
.B \-\-force
384
be specified first. A value of 1 will then be allowed for linear,
385
multipath, RAID0 and RAID1. It is never allowed for RAID4, RAID5 or RAID6.
386
.br
387
This number can only be changed using
388
.B \-\-grow
389
for RAID1, RAID4, RAID5 and RAID6 arrays, and only on kernels which provide
390
the necessary support.
391
392
.TP
393
.BR \-x ", " \-\-spare\-devices=
394
Specify the number of spare (eXtra) devices in the initial array.
395
Spares can also be added
396
and removed later. The number of component devices listed
397
on the command line must equal the number of RAID devices plus the
398
number of spare devices.
399
400
.TP
401
.BR \-z ", " \-\-size=
402
Amount (in Kibibytes) of space to use from each drive in RAID levels 1/4/5/6.
403
This must be a multiple of the chunk size, and must leave about 128Kb
404
of space at the end of the drive for the RAID superblock.
405
If this is not specified
406
(as it normally is not) the smallest drive (or partition) sets the
407
size, though if there is a variance among the drives of greater than 1%, a warning is
408
issued.
409
410
This value can be set with
411
.B \-\-grow
412
for RAID level 1/4/5/6. If the array was created with a size smaller
413
than the currently active drives, the extra space can be accessed
414
using
415
.BR \-\-grow .
416
The size can be given as
417
.B max
418
which means to choose the largest size that fits on all current drives.
419
420
This value can not be used with
421
.B CONTAINER
422
metadata such as DDF and IMSM.
423
424
.TP
425
.BR \-c ", " \-\-chunk=
426
Specify chunk size of kibibytes. The default is 64.
427
This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
428
429
.TP
430
.BR \-\-rounding=
431
Specify rounding factor for a Linear array. The size of each
432
component will be rounded down to a multiple of this size.
433
This is a synonym for
434
.B \-\-chunk
435
but highlights the different meaning for Linear as compared to other
436
RAID levels.
437
438
.TP
439
.BR \-l ", " \-\-level=
440
Set RAID level. When used with
441
.BR \-\-create ,
442
options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
443
raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
444
Obviously some of these are synonymous.
445
446
When a
447
.B CONTAINER
448
metadata type is requested, only the
449
.B container
450
level is permitted, and it does not need to be explicitly given.
451
452
When used with
453
.BR \-\-build ,
454
only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
455
456
Not yet supported with
457
.BR \-\-grow .
458
459
.TP
460
.BR \-p ", " \-\-layout=
461
This option configures the fine details of data layout for RAID5, RAID6,
462
and RAID10 arrays, and controls the failure modes for
463
.IR faulty .
464
465
The layout of the RAID5 parity block can be one of
466
.BR left\-asymmetric ,
467
.BR left\-symmetric ,
468
.BR right\-asymmetric ,
469
.BR right\-symmetric ,
470
.BR la ", " ra ", " ls ", " rs .
471
The default is
472
.BR left\-symmetric .
473
474
It is also possibly to cause RAID5 to use a RAID4-like layout by
475
choosing
476
.BR parity\-first ,
477
or
478
.BR parity\-last .
479
480
Finally for RAID5 there are DDF\-compatible layouts,
481
.BR ddf\-zero\-restart ,
482
.BR ddf\-N\-restart ,
483
and
484
.BR ddf\-N\-continue .
485
486
These same layouts are available for RAID6. There are also 4 layouts
487
that will provide an intermediate stage for converting between RAID5
488
and RAID6. These provide a layout which is identical to the
489
corresponding RAID5 layout on the first N\-1 devices, and has the 'Q'
490
syndrome (the second 'parity' block used by RAID6) on the last device.
491
These layouts are:
492
.BR left\-symmetric\-6 ,
493
.BR right\-symmetric\-6 ,
494
.BR left\-asymmetric\-6 ,
495
.BR right\-asymmetric\-6 ,
496
and
497
.BR pairty\-first\-6 .
498
499
When setting the failure mode for level
500
.I faulty,
501
the options are:
502
.BR write\-transient ", " wt ,
503
.BR read\-transient ", " rt ,
504
.BR write\-persistent ", " wp ,
505
.BR read\-persistent ", " rp ,
506
.BR write\-all ,
507
.BR read\-fixable ", " rf ,
508
.BR clear ", " flush ", " none .
509
510
Each failure mode can be followed by a number, which is used as a period
511
between fault generation. Without a number, the fault is generated
512
once on the first relevant request. With a number, the fault will be
513
generated after that many requests, and will continue to be generated
514
every time the period elapses.
515
516
Multiple failure modes can be current simultaneously by using the
517
.B \-\-grow
518
option to set subsequent failure modes.
519
520
"clear" or "none" will remove any pending or periodic failure modes,
521
and "flush" will clear any persistent faults.
522
523
To set the parity with
524
.BR \-\-grow ,
525
the level of the array ("faulty")
526
must be specified before the fault mode is specified.
527
528
Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
529
by a small number. The default is 'n2'. The supported options are:
530
531
.I 'n'
532
signals 'near' copies. Multiple copies of one data block are at
533
similar offsets in different devices.
534
535
.I 'o'
536
signals 'offset' copies. Rather than the chunks being duplicated
537
within a stripe, whole stripes are duplicated but are rotated by one
538
device so duplicate blocks are on different devices. Thus subsequent
539
copies of a block are in the next drive, and are one chunk further
540
down.
541
542
.I 'f'
543
signals 'far' copies
544
(multiple copies have very different offsets).
545
See md(4) for more detail about 'near', 'offset', and 'far'.
546
547
The number is the number of copies of each datablock. 2 is normal, 3
548
can be useful. This number can be at most equal to the number of
549
devices in the array. It does not need to divide evenly into that
550
number (e.g. it is perfectly legal to have an 'n2' layout for an array
551
with an odd number of devices).
552
553
.TP
554
.BR \-\-parity=
555
same as
556
.B \-\-layout
557
(thus explaining the p of
558
.BR \-p ).
559
560
.TP
561
.BR \-b ", " \-\-bitmap=
562
Specify a file to store a write-intent bitmap in. The file should not
563
exist unless
564
.B \-\-force
565
is also given. The same file should be provided
566
when assembling the array. If the word
567
.B "internal"
568
is given, then the bitmap is stored with the metadata on the array,
569
and so is replicated on all devices. If the word
570
.B "none"
571
is given with
572
.B \-\-grow
573
mode, then any bitmap that is present is removed.
574
575
To help catch typing errors, the filename must contain at least one
576
slash ('/') if it is a real file (not 'internal' or 'none').
577
578
Note: external bitmaps are only known to work on ext2 and ext3.
579
Storing bitmap files on other filesystems may result in serious problems.
580
581
.TP
582
.BR \-\-bitmap\-chunk=
583
Set the chunksize of the bitmap. Each bit corresponds to that many
584
Kilobytes of storage.
585
When using a file based bitmap, the default is to use the smallest
586
size that is at-least 4 and requires no more than 2^21 chunks.
587
When using an
588
.B internal
589
bitmap, the chunksize is automatically determined to make best use of
590
available space.
591
592
.TP
593
.BR \-W ", " \-\-write\-mostly
594
subsequent devices listed in a
595
.BR \-\-build ,
596
.BR \-\-create ,
597
or
598
.B \-\-add
599
command will be flagged as 'write-mostly'. This is valid for RAID1
600
only and means that the 'md' driver will avoid reading from these
601
devices if at all possible. This can be useful if mirroring over a
602
slow link.
603
604
.TP
605
.BR \-\-write\-behind=
606
Specify that write-behind mode should be enabled (valid for RAID1
607
only). If an argument is specified, it will set the maximum number
608
of outstanding writes allowed. The default value is 256.
609
A write-intent bitmap is required in order to use write-behind
610
mode, and write-behind is only attempted on drives marked as
611
.IR write-mostly .
612
613
.TP
614
.BR \-\-assume\-clean
615
Tell
616
.I mdadm
617
that the array pre-existed and is known to be clean. It can be useful
618
when trying to recover from a major failure as you can be sure that no
619
data will be affected unless you actually write to the array. It can
620
also be used when creating a RAID1 or RAID10 if you want to avoid the
621
initial resync, however this practice \(em while normally safe \(em is not
622
recommended. Use this only if you really know what you are doing.
623
624
.TP
625
.BR \-\-backup\-file=
626
This is needed when
627
.B \-\-grow
628
is used to increase the number of
629
raid-devices in a RAID5 if there are no spare devices available.
630
See the GROW MODE section below on RAID\-DEVICES CHANGES. The file
631
should be stored on a separate device, not on the RAID array being
632
reshaped.
633
634
.TP
635
.BR \-N ", " \-\-name=
636
Set a
637
.B name
638
for the array. This is currently only effective when creating an
639
array with a version-1 superblock, or an array in a DDF container.
640
The name is a simple textual string that can be used to identify array
641
components when assembling. If name is needed but not specified, it
642
is taken from the basename of the device that is being created.
643
e.g. when creating
644
.I /dev/md/home
645
the
646
.B name
647
will default to
648
.IR home .
649
650
.TP
651
.BR \-R ", " \-\-run
652
Insist that
653
.I mdadm
654
run the array, even if some of the components
655
appear to be active in another array or filesystem. Normally
656
.I mdadm
657
will ask for confirmation before including such components in an
658
array. This option causes that question to be suppressed.
659
660
.TP
661
.BR \-f ", " \-\-force
662
Insist that
663
.I mdadm
664
accept the geometry and layout specified without question. Normally
665
.I mdadm
666
will not allow creation of an array with only one device, and will try
667
to create a RAID5 array with one missing drive (as this makes the
668
initial resync work faster). With
669
.BR \-\-force ,
670
.I mdadm
671
will not try to be so clever.
672
673
.TP
674
.BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
675
Instruct mdadm how to create the device file if needed, possibly allocating
676
an unused minor number. "md" causes a non-partitionable array
677
to be used (though since Linux 2.6.28, these array devices are in fact
678
partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
679
later) to be used. "yes" requires the named md device to have
680
a 'standard' format, and the type and minor number will be determined
681
from this. With mdadm 3.0, device creation is normally left up to
682
.I udev
683
so this option is unlikely to be needed.
684
See DEVICE NAMES below.
685
686
The argument can also come immediately after
687
"\-a". e.g. "\-ap".
688
689
If
690
.B \-\-auto
691
is not given on the command line or in the config file, then
692
the default will be
693
.BR \-\-auto=yes .
694
695
If
696
.B \-\-scan
697
is also given, then any
698
.I auto=
699
entries in the config file will override the
700
.B \-\-auto
701
instruction given on the command line.
702
703
For partitionable arrays,
704
.I mdadm
705
will create the device file for the whole array and for the first 4
706
partitions. A different number of partitions can be specified at the
707
end of this option (e.g.
708
.BR \-\-auto=p7 ).
709
If the device name ends with a digit, the partition names add a 'p',
710
and a number, e.g.
711
.IR /dev/md/home1p3 .
712
If there is no trailing digit, then the partition names just have a
713
number added, e.g.
714
.IR /dev/md/scratch3 .
715
716
If the md device name is in a 'standard' format as described in DEVICE
717
NAMES, then it will be created, if necessary, with the appropriate
718
device number based on that name. If the device name is not in one of these
719
formats, then a unused device number will be allocated. The device
720
number will be considered unused if there is no active array for that
721
number, and there is no entry in /dev for that number and with a
722
non-standard name. Names that are not in 'standard' format are only
723
allowed in "/dev/md/".
724
725
.\".TP
726
.\".BR \-\-symlink = no
727
.\"Normally when
728
.\".B \-\-auto
729
.\"causes
730
.\".I mdadm
731
.\"to create devices in
732
.\".B /dev/md/
733
.\"it will also create symlinks from
734
.\".B /dev/
735
.\"with names starting with
736
.\".B md
737
.\"or
738
.\".BR md_ .
739
.\"Use
740
.\".B \-\-symlink=no
741
.\"to suppress this, or
742
.\".B \-\-symlink=yes
743
.\"to enforce this even if it is suppressing
744
.\".IR mdadm.conf .
745
.\"
746
747
.SH For assemble:
748
749
.TP
750
.BR \-u ", " \-\-uuid=
751
uuid of array to assemble. Devices which don't have this uuid are
752
excluded
753
754
.TP
755
.BR \-m ", " \-\-super\-minor=
756
Minor number of device that array was created for. Devices which
757
don't have this minor number are excluded. If you create an array as
758
/dev/md1, then all superblocks will contain the minor number 1, even if
759
the array is later assembled as /dev/md2.
760
761
Giving the literal word "dev" for
762
.B \-\-super\-minor
763
will cause
764
.I mdadm
765
to use the minor number of the md device that is being assembled.
766
e.g. when assembling
767
.BR /dev/md0 ,
768
.B \-\-super\-minor=dev
769
will look for super blocks with a minor number of 0.
770
771
.B \-\-super\-minor
772
is only relevant for v0.90 metadata, and should not normally be used.
773
Using
774
.B \-\-uuid
775
is much safer.
776
777
.TP
778
.BR \-N ", " \-\-name=
779
Specify the name of the array to assemble. This must be the name
780
that was specified when creating the array. It must either match
781
the name stored in the superblock exactly, or it must match
782
with the current
783
.I homehost
784
prefixed to the start of the given name.
785
786
.TP
787
.BR \-f ", " \-\-force
788
Assemble the array even if the metadata on some devices appears to be
789
out-of-date. If
790
.I mdadm
791
cannot find enough working devices to start the array, but can find
792
some devices that are recorded as having failed, then it will mark
793
those devices as working so that the array can be started.
794
An array which requires
795
.B \-\-force
796
to be started may contain data corruption. Use it carefully.
797
798
.TP
799
.BR \-R ", " \-\-run
800
Attempt to start the array even if fewer drives were given than were
801
present last time the array was active. Normally if not all the
802
expected drives are found and
803
.B \-\-scan
804
is not used, then the array will be assembled but not started.
805
With
806
.B \-\-run
807
an attempt will be made to start it anyway.
808
809
.TP
810
.B \-\-no\-degraded
811
This is the reverse of
812
.B \-\-run
813
in that it inhibits the startup of array unless all expected drives
814
are present. This is only needed with
815
.B \-\-scan,
816
and can be used if the physical connections to devices are
817
not as reliable as you would like.
818
819
.TP
820
.BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
821
See this option under Create and Build options.
822
823
.TP
824
.BR \-b ", " \-\-bitmap=
825
Specify the bitmap file that was given when the array was created. If
826
an array has an
827
.B internal
828
bitmap, there is no need to specify this when assembling the array.
829
830
.TP
831
.BR \-\-backup\-file=
832
If
833
.B \-\-backup\-file
834
was used to grow the number of raid-devices in a RAID5, and the system
835
crashed during the critical section, then the same
836
.B \-\-backup\-file
837
must be presented to
838
.B \-\-assemble
839
to allow possibly corrupted data to be restored.
840
841
.TP
842
.BR \-U ", " \-\-update=
843
Update the superblock on each device while assembling the array. The
844
argument given to this flag can be one of
845
.BR sparc2.2 ,
846
.BR summaries ,
847
.BR uuid ,
848
.BR name ,
849
.BR homehost ,
850
.BR resync ,
851
.BR byteorder ,
852
.BR devicesize ,
853
or
854
.BR super\-minor .
855
856
The
857
.B sparc2.2
858
option will adjust the superblock of an array what was created on a Sparc
859
machine running a patched 2.2 Linux kernel. This kernel got the
860
alignment of part of the superblock wrong. You can use the
861
.B "\-\-examine \-\-sparc2.2"
862
option to
863
.I mdadm
864
to see what effect this would have.
865
866
The
867
.B super\-minor
868
option will update the
869
.B "preferred minor"
870
field on each superblock to match the minor number of the array being
871
assembled.
872
This can be useful if
873
.B \-\-examine
874
reports a different "Preferred Minor" to
875
.BR \-\-detail .
876
In some cases this update will be performed automatically
877
by the kernel driver. In particular the update happens automatically
878
at the first write to an array with redundancy (RAID level 1 or
879
greater) on a 2.6 (or later) kernel.
880
881
The
882
.B uuid
883
option will change the uuid of the array. If a UUID is given with the
884
.B \-\-uuid
885
option that UUID will be used as a new UUID and will
886
.B NOT
887
be used to help identify the devices in the array.
888
If no
889
.B \-\-uuid
890
is given, a random UUID is chosen.
891
892
The
893
.B name
894
option will change the
895
.I name
896
of the array as stored in the superblock. This is only supported for
897
version-1 superblocks.
898
899
The
900
.B homehost
901
option will change the
902
.I homehost
903
as recorded in the superblock. For version-0 superblocks, this is the
904
same as updating the UUID.
905
For version-1 superblocks, this involves updating the name.
906
907
The
908
.B resync
909
option will cause the array to be marked
910
.I dirty
911
meaning that any redundancy in the array (e.g. parity for RAID5,
912
copies for RAID1) may be incorrect. This will cause the RAID system
913
to perform a "resync" pass to make sure that all redundant information
914
is correct.
915
916
The
917
.B byteorder
918
option allows arrays to be moved between machines with different
919
byte-order.
920
When assembling such an array for the first time after a move, giving
921
.B "\-\-update=byteorder"
922
will cause
923
.I mdadm
924
to expect superblocks to have their byteorder reversed, and will
925
correct that order before assembling the array. This is only valid
926
with original (Version 0.90) superblocks.
927
928
The
929
.B summaries
930
option will correct the summaries in the superblock. That is the
931
counts of total, working, active, failed, and spare devices.
932
933
The
934
.B devicesize
935
will rarely be of use. It applies to version 1.1 and 1.2 metadata
936
only (where the metadata is at the start of the device) and is only
937
useful when the component device has changed size (typically become
938
larger). The version 1 metadata records the amount of the device that
939
can be used to store data, so if a device in a version 1.1 or 1.2
940
array becomes larger, the metadata will still be visible, but the
941
extra space will not. In this case it might be useful to assemble the
942
array with
943
.BR \-\-update=devicesize .
944
This will cause
945
.I mdadm
946
to determine the maximum usable amount of space on each device and
947
update the relevant field in the metadata.
948
949
.ig XX
950
.TP
951
.B \-\-auto\-update\-homehost
952
This flag is only meaningful with auto-assembly (see discussion below).
953
In that situation, if no suitable arrays are found for this homehost,
954
.I mdadm
955
will rescan for any arrays at all and will assemble them and update the
956
homehost to match the current host.
957
.XX
958
959
.SH For Manage mode:
960
961
.TP
962
.BR \-a ", " \-\-add
963
hot-add listed devices. For arrays with redundancy, the listed
964
devices become available as spares. If the array is degraded, it will
965
immediately start recovering data on to one of these spares.
966
967
.TP
968
.BR \-\-re\-add
969
re-add a device that was recently removed from an array. This is only
970
needed for arrays that have be built (i.e. with
971
.BR --build ).
972
For created arrays, devices are always re-added if that is possible.
973
When re-adding a device, if nothing has changed on the array since the
974
device was removed, no recovery is performed. Also, if the array has
975
a write-intent bitmap, then the recovery performed after a re-add will
976
be limited to those blocks which, according to the bitmap, might have
977
changed since the device was removed.
978
979
.TP
980
.BR \-r ", " \-\-remove
981
remove listed devices. They must not be active. i.e. they should
982
be failed or spare devices. As well as the name of a device file
983
(e.g.
984
.BR /dev/sda1 )
985
the words
986
.B failed
987
and
988
.B detached
989
can be given to
990
.BR \-\-remove .
991
The first causes all failed device to be removed. The second causes
992
any device which is no longer connected to the system (i.e an 'open'
993
returns
994
.BR ENXIO )
995
to be removed. This will only succeed for devices that are spares or
996
have already been marked as failed.
997
998
.TP
999
.BR \-f ", " \-\-fail
1000
mark listed devices as faulty.
1001
As well as the name of a device file, the word
1002
.B detached
1003
can be given. This will cause any device that has been detached from
1004
the system to be marked as failed. It can then be removed.
1005
1006
.TP
1007
.BR \-\-set\-faulty
1008
same as
1009
.BR \-\-fail .
1010
1011
.TP
1012
.BR \-\-write\-mostly
1013
Subsequent devices that are added or re-added will have the 'write-mostly'
1014
flag set. This is only valid for RAID1 and means that the 'md' driver
1015
will avoid reading from these devices if possible.
1016
.TP
1017
.BR \-\-readwrite
1018
Subsequent devices that are added or re-added will have the 'write-mostly'
1019
flag cleared.
1020
1021
.P
1022
Each of these options requires that the first device listed is the array
1023
to be acted upon, and the remainder are component devices to be added,
1024
removed, marked as faulty, etc. Several different operations can be
1025
specified for different devices, e.g.
1026
.in +5
1027
mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1028
.in -5
1029
Each operation applies to all devices listed until the next
1030
operation.
1031
1032
If an array is using a write-intent bitmap, then devices which have
1033
been removed can be re-added in a way that avoids a full
1034
reconstruction but instead just updates the blocks that have changed
1035
since the device was removed. For arrays with persistent metadata
1036
(superblocks) this is done automatically. For arrays created with
1037
.B \-\-build
1038
mdadm needs to be told that this device we removed recently with
1039
.BR \-\-re\-add .
1040
1041
Devices can only be removed from an array if they are not in active
1042
use, i.e. that must be spares or failed devices. To remove an active
1043
device, it must first be marked as
1044
.B faulty.
1045
1046
.SH For Misc mode:
1047
1048
.TP
1049
.BR \-Q ", " \-\-query
1050
Examine a device to see
1051
(1) if it is an md device and (2) if it is a component of an md
1052
array.
1053
Information about what is discovered is presented.
1054
1055
.TP
1056
.BR \-D ", " \-\-detail
1057
Print details of one or more md devices.
1058
1059
.TP
1060
.BR \-\-detail\-platform
1061
Print details of the platform's RAID capabilities (firmware / hardware
1062
topology) for a given metadata format.
1063
1064
.TP
1065
.BR \-Y ", " \-\-export
1066
When used with
1067
.B \-\-detail
1068
or
1069
.BR \-\-examine ,
1070
output will be formatted as
1071
.B key=value
1072
pairs for easy import into the environment.
1073
1074
.TP
1075
.BR \-E ", " \-\-examine
1076
Print contents of the metadata stored on the named device(s).
1077
Note the contrast between
1078
.B \-\-examine
1079
and
1080
.BR \-\-detail .
1081
.B \-\-examine
1082
applies to devices which are components of an array, while
1083
.B \-\-detail
1084
applies to a whole array which is currently active.
1085
.TP
1086
.B \-\-sparc2.2
1087
If an array was created on a SPARC machine with a 2.2 Linux kernel
1088
patched with RAID support, the superblock will have been created
1089
incorrectly, or at least incompatibly with 2.4 and later kernels.
1090
Using the
1091
.B \-\-sparc2.2
1092
flag with
1093
.B \-\-examine
1094
will fix the superblock before displaying it. If this appears to do
1095
the right thing, then the array can be successfully assembled using
1096
.BR "\-\-assemble \-\-update=sparc2.2" .
1097
1098
.TP
1099
.BR \-X ", " \-\-examine\-bitmap
1100
Report information about a bitmap file.
1101
The argument is either an external bitmap file or an array component
1102
in case of an internal bitmap. Note that running this on an array
1103
device (e.g.
1104
.BR /dev/md0 )
1105
does not report the bitmap for that array.
1106
1107
.TP
1108
.BR \-R ", " \-\-run
1109
start a partially assembled array. If
1110
.B \-\-assemble
1111
did not find enough devices to fully start the array, it might leaving
1112
it partially assembled. If you wish, you can then use
1113
.B \-\-run
1114
to start the array in degraded mode.
1115
1116
.TP
1117
.BR \-S ", " \-\-stop
1118
deactivate array, releasing all resources.
1119
1120
.TP
1121
.BR \-o ", " \-\-readonly
1122
mark array as readonly.
1123
1124
.TP
1125
.BR \-w ", " \-\-readwrite
1126
mark array as readwrite.
1127
1128
.TP
1129
.B \-\-zero\-superblock
1130
If the device contains a valid md superblock, the block is
1131
overwritten with zeros. With
1132
.B \-\-force
1133
the block where the superblock would be is overwritten even if it
1134
doesn't appear to be valid.
1135
1136
.TP
1137
.BR \-t ", " \-\-test
1138
When used with
1139
.BR \-\-detail ,
1140
the exit status of
1141
.I mdadm
1142
is set to reflect the status of the device. See below in
1143
.B MISC MODE
1144
for details.
1145
1146
.TP
1147
.BR \-W ", " \-\-wait
1148
For each md device given, wait for any resync, recovery, or reshape
1149
activity to finish before returning.
1150
.I mdadm
1151
will return with success if it actually waited for every device
1152
listed, otherwise it will return failure.
1153
1154
.TP
1155
.BR \-\-wait\-clean
1156
For each md device given, or each device in /proc/mdstat if
1157
.B \-\-scan
1158
is given, arrange for the array to be marked clean as soon as possible.
1159
Also, quiesce resync so that the monitor for external metadata arrays
1160
(mdmon) has an opportunity to checkpoint the resync position.
1161
.I mdadm
1162
will return with success if the array uses external metadata and we
1163
successfully waited. For native arrays this returns immediately as the
1164
kernel handles both dirty-clean transitions and resync checkpointing in
1165
the kernel at shutdown. No action is taken if safe-mode handling is
1166
disabled.
1167
1168
.SH For Incremental Assembly mode:
1169
.TP
1170
.BR \-\-rebuild\-map ", " \-r
1171
Rebuild the map file
1172
.RB ( /var/run/mdadm/map )
1173
that
1174
.I mdadm
1175
uses to help track which arrays are currently being assembled.
1176
1177
.TP
1178
.BR \-\-run ", " \-R
1179
Run any array assembled as soon as a minimal number of devices are
1180
available, rather than waiting until all expected devices are present.
1181
1182
.TP
1183
.B \-\-no\-degraded
1184
This allows the hot-plug system to prevent arrays from running when it knows
1185
that more disks may arrive later in the discovery process.
1186
1187
.TP
1188
.BR \-\-scan ", " \-s
1189
Only meaningful with
1190
.B \-R
1191
this will scan the
1192
.B map
1193
file for arrays that are being incrementally assembled and will try to
1194
start any that are not already started. If any such array is listed
1195
in
1196
.B mdadm.conf
1197
as requiring an external bitmap, that bitmap will be attached first.
1198
1199
.SH For Monitor mode:
1200
.TP
1201
.BR \-m ", " \-\-mail
1202
Give a mail address to send alerts to.
1203
1204
.TP
1205
.BR \-p ", " \-\-program ", " \-\-alert
1206
Give a program to be run whenever an event is detected.
1207
1208
.TP
1209
.BR \-y ", " \-\-syslog
1210
Cause all events to be reported through 'syslog'. The messages have
1211
facility of 'daemon' and varying priorities.
1212
1213
.TP
1214
.BR \-d ", " \-\-delay
1215
Give a delay in seconds.
1216
.I mdadm
1217
polls the md arrays and then waits this many seconds before polling
1218
again. The default is 60 seconds. Since 2.6.16, there is no need to
1219
reduce this as the kernel alerts
1220
.I mdadm
1221
immediately when there is any change.
1222
1223
.TP
1224
.BR \-r ", " \-\-increment
1225
Give a percentage increment.
1226
.I mdadm
1227
will generate RebuildNN events with the given percentage increment.
1228
1229
.TP
1230
.BR \-f ", " \-\-daemonise
1231
Tell
1232
.I mdadm
1233
to run as a background daemon if it decides to monitor anything. This
1234
causes it to fork and run in the child, and to disconnect from the
1235
terminal. The process id of the child is written to stdout.
1236
This is useful with
1237
.B \-\-scan
1238
which will only continue monitoring if a mail address or alert program
1239
is found in the config file.
1240
1241
.TP
1242
.BR \-i ", " \-\-pid\-file
1243
When
1244
.I mdadm
1245
is running in daemon mode, write the pid of the daemon process to
1246
the specified file, instead of printing it on standard output.
1247
1248
.TP
1249
.BR \-1 ", " \-\-oneshot
1250
Check arrays only once. This will generate
1251
.B NewArray
1252
events and more significantly
1253
.B DegradedArray
1254
and
1255
.B SparesMissing
1256
events. Running
1257
.in +5
1258
.B " mdadm \-\-monitor \-\-scan \-1"
1259
.in -5
1260
from a cron script will ensure regular notification of any degraded arrays.
1261
1262
.TP
1263
.BR \-t ", " \-\-test
1264
Generate a
1265
.B TestMessage
1266
alert for every array found at startup. This alert gets mailed and
1267
passed to the alert program. This can be used for testing that alert
1268
message do get through successfully.
1269
1270
.SH ASSEMBLE MODE
1271
1272
.HP 12
1273
Usage:
1274
.B mdadm \-\-assemble
1275
.I md-device options-and-component-devices...
1276
.HP 12
1277
Usage:
1278
.B mdadm \-\-assemble \-\-scan
1279
.I md-devices-and-options...
1280
.HP 12
1281
Usage:
1282
.B mdadm \-\-assemble \-\-scan
1283
.I options...
1284
1285
.PP
1286
This usage assembles one or more RAID arrays from pre-existing components.
1287
For each array, mdadm needs to know the md device, the identity of the
1288
array, and a number of component-devices. These can be found in a number of ways.
1289
1290
In the first usage example (without the
1291
.BR \-\-scan )
1292
the first device given is the md device.
1293
In the second usage example, all devices listed are treated as md
1294
devices and assembly is attempted.
1295
In the third (where no devices are listed) all md devices that are
1296
listed in the configuration file are assembled. If not arrays are
1297
described by the configuration file, then any arrays that
1298
can be found on unused devices will be assembled.
1299
1300
If precisely one device is listed, but
1301
.B \-\-scan
1302
is not given, then
1303
.I mdadm
1304
acts as though
1305
.B \-\-scan
1306
was given and identity information is extracted from the configuration file.
1307
1308
The identity can be given with the
1309
.B \-\-uuid
1310
option, the
1311
.B \-\-name
1312
option, or the
1313
.B \-\-super\-minor
1314
option, will be taken from the md-device record in the config file, or
1315
will be taken from the super block of the first component-device
1316
listed on the command line.
1317
1318
Devices can be given on the
1319
.B \-\-assemble
1320
command line or in the config file. Only devices which have an md
1321
superblock which contains the right identity will be considered for
1322
any array.
1323
1324
The config file is only used if explicitly named with
1325
.B \-\-config
1326
or requested with (a possibly implicit)
1327
.BR \-\-scan .
1328
In the later case,
1329
.B /etc/mdadm.conf
1330
or
1331
.B /etc/mdadm/mdadm.conf
1332
is used.
1333
1334
If
1335
.B \-\-scan
1336
is not given, then the config file will only be used to find the
1337
identity of md arrays.
1338
1339
Normally the array will be started after it is assembled. However if
1340
.B \-\-scan
1341
is not given and not all expected drives were listed, then the array
1342
is not started (to guard against usage errors). To insist that the
1343
array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1344
give the
1345
.B \-\-run
1346
flag.
1347
1348
If
1349
.I udev
1350
is active,
1351
.I mdadm
1352
does not create any entries in
1353
.B /dev
1354
but leaves that to
1355
.IR udev .
1356
It does record information in
1357
.B /var/run/mdadm/map
1358
which will allow
1359
.I udev
1360
to choose the correct name.
1361
1362
If
1363
.I mdadm
1364
detects that udev is not configured, it will create the devices in
1365
.B /dev
1366
itself.
1367
1368
In Linux kernels prior to version 2.6.28 there were two distinctly
1369
different types of md devices that could be created: one that could be
1370
partitioned using standard partitioning tools and one that could not.
1371
Since 2.6.28 that distinction is no longer relevant as both type of
1372
devices can be partitioned.
1373
.I mdadm
1374
will normally create the type that originally could not be partitioned
1375
as it has a well defined major number (9).
1376
1377
Prior to 2.6.28, it is important that mdadm chooses the correct type
1378
of array device to use. This can be controlled with the
1379
.B \-\-auto
1380
option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1381
to use a partitionable device rather than the default.
1382
1383
In the no-udev case, the value given to
1384
.B \-\-auto
1385
can be suffixed by a number. This tells
1386
.I mdadm
1387
to create that number of partition devices rather than the default of 4.
1388
1389
The value given to
1390
.B \-\-auto
1391
can also be given in the configuration file as a word starting
1392
.B auto=
1393
on the ARRAY line for the relevant array.
1394
1395
.SS Auto Assembly
1396
When
1397
.B \-\-assemble
1398
is used with
1399
.B \-\-scan
1400
and no devices are listed,
1401
.I mdadm
1402
will first attempt to assemble all the arrays listed in the config
1403
file.
1404
1405
In no array at listed in the config (other than those marked
1406
.BR <ignore> )
1407
it will look through the available devices for possible arrays and
1408
will try to assemble anything that it finds. Arrays which are tagged
1409
as belonging to the given homehost will be assembled and started
1410
normally. Arrays which do not obviously belong to this host are given
1411
names that are expected not to conflict with anything local, and are
1412
started "read-auto" so that nothing is written to any device until the
1413
array is written to. i.e. automatic resync etc is delayed.
1414
1415
If
1416
.I mdadm
1417
finds a consistent set of devices that look like they should comprise
1418
an array, and if the superblock is tagged as belonging to the given
1419
home host, it will automatically choose a device name and try to
1420
assemble the array. If the array uses version-0.90 metadata, then the
1421
.B minor
1422
number as recorded in the superblock is used to create a name in
1423
.B /dev/md/
1424
so for example
1425
.BR /dev/md/3 .
1426
If the array uses version-1 metadata, then the
1427
.B name
1428
from the superblock is used to similarly create a name in
1429
.B /dev/md/
1430
(the name will have any 'host' prefix stripped first).
1431
1432
.ig XX
1433
If
1434
.I mdadm
1435
cannot find any array for the given host at all, and if
1436
.B \-\-auto\-update\-homehost
1437
is given, then
1438
.I mdadm
1439
will search again for any array (not just an array created for this
1440
host) and will assemble each assuming
1441
.BR \-\-update=homehost .
1442
This will change the host tag in the superblock so that on the next run,
1443
these arrays will be found without the second pass. The intention of
1444
this feature is to support transitioning a set of md arrays to using
1445
homehost tagging.
1446
1447
The reason for requiring arrays to be tagged with the homehost for
1448
auto assembly is to guard against problems that can arise when moving
1449
devices from one host to another.
1450
.XX
1451
1452
.SH BUILD MODE
1453
1454
.HP 12
1455
Usage:
1456
.B mdadm \-\-build
1457
.I md-device
1458
.BI \-\-chunk= X
1459
.BI \-\-level= Y
1460
.BI \-\-raid\-devices= Z
1461
.I devices
1462
1463
.PP
1464
This usage is similar to
1465
.BR \-\-create .
1466
The difference is that it creates an array without a superblock. With
1467
these arrays there is no difference between initially creating the array and
1468
subsequently assembling the array, except that hopefully there is useful
1469
data there in the second case.
1470
1471
The level may raid0, linear, raid1, raid10, multipath, or faulty, or
1472
one of their synonyms. All devices must be listed and the array will
1473
be started once complete. It will often be appropriate to use
1474
.B \-\-assume\-clean
1475
with levels raid1 or raid10.
1476
1477
.SH CREATE MODE
1478
1479
.HP 12
1480
Usage:
1481
.B mdadm \-\-create
1482
.I md-device
1483
.BI \-\-chunk= X
1484
.BI \-\-level= Y
1485
.br
1486
.BI \-\-raid\-devices= Z
1487
.I devices
1488
1489
.PP
1490
This usage will initialise a new md array, associate some devices with
1491
it, and activate the array.
1492
1493
The named device will normally not exist when
1494
.I "mdadm \-\-create"
1495
is run, but will be created by
1496
.I udev
1497
once the array becomes active.
1498
1499
As devices are added, they are checked to see if they contain RAID
1500
superblocks or filesystems. They are also checked to see if the variance in
1501
device size exceeds 1%.
1502
1503
If any discrepancy is found, the array will not automatically be run, though
1504
the presence of a
1505
.B \-\-run
1506
can override this caution.
1507
1508
To create a "degraded" array in which some devices are missing, simply
1509
give the word "\fBmissing\fP"
1510
in place of a device name. This will cause
1511
.I mdadm
1512
to leave the corresponding slot in the array empty.
1513
For a RAID4 or RAID5 array at most one slot can be
1514
"\fBmissing\fP"; for a RAID6 array at most two slots.
1515
For a RAID1 array, only one real device needs to be given. All of the
1516
others can be
1517
"\fBmissing\fP".
1518
1519
When creating a RAID5 array,
1520
.I mdadm
1521
will automatically create a degraded array with an extra spare drive.
1522
This is because building the spare into a degraded array is in general
1523
faster than resyncing the parity on a non-degraded, but not clean,
1524
array. This feature can be overridden with the
1525
.B \-\-force
1526
option.
1527
1528
When creating an array with version-1 metadata a name for the array is
1529
required.
1530
If this is not given with the
1531
.B \-\-name
1532
option,
1533
.I mdadm
1534
will choose a name based on the last component of the name of the
1535
device being created. So if
1536
.B /dev/md3
1537
is being created, then the name
1538
.B 3
1539
will be chosen.
1540
If
1541
.B /dev/md/home
1542
is being created, then the name
1543
.B home
1544
will be used.
1545
1546
When creating a partition based array, using
1547
.I mdadm
1548
with version-1.x metadata, the partition type should be set to
1549
.B 0xDA
1550
(non fs-data). This type selection allows for greater precision since
1551
using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
1552
might create problems in the event of array recovery through a live cdrom.
1553
1554
A new array will normally get a randomly assigned 128bit UUID which is
1555
very likely to be unique. If you have a specific need, you can choose
1556
a UUID for the array by giving the
1557
.B \-\-uuid=
1558
option. Be warned that creating two arrays with the same UUID is a
1559
recipe for disaster. Also, using
1560
.B \-\-uuid=
1561
when creating a v0.90 array will silently override any
1562
.B \-\-homehost=
1563
setting.
1564
.\"If the
1565
.\".B \-\-size
1566
.\"option is given, it is not necessary to list any component-devices in this command.
1567
.\"They can be added later, before a
1568
.\".B \-\-run.
1569
.\"If no
1570
.\".B \-\-size
1571
.\"is given, the apparent size of the smallest drive given is used.
1572
1573
When creating an array within a
1574
.B CONTAINER
1575
.I mdadm
1576
can be given either the list of devices to use, or simply the name of
1577
the container. The former case gives control over which devices in
1578
the container will be used for the array. The latter case allows
1579
.I mdadm
1580
to automatically choose which devices to use based on how much spare
1581
space is available.
1582
1583
The General Management options that are valid with
1584
.B \-\-create
1585
are:
1586
.TP
1587
.B \-\-run
1588
insist on running the array even if some devices look like they might
1589
be in use.
1590
1591
.TP
1592
.B \-\-readonly
1593
start the array readonly \(em not supported yet.
1594
1595
.SH MANAGE MODE
1596
.HP 12
1597
Usage:
1598
.B mdadm
1599
.I device
1600
.I options... devices...
1601
.PP
1602
1603
This usage will allow individual devices in an array to be failed,
1604
removed or added. It is possible to perform multiple operations with
1605
on command. For example:
1606
.br
1607
.B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
1608
.br
1609
will firstly mark
1610
.B /dev/hda1
1611
as faulty in
1612
.B /dev/md0
1613
and will then remove it from the array and finally add it back
1614
in as a spare. However only one md array can be affected by a single
1615
command.
1616
1617
When a device is added to an active array, mdadm checks to see if it
1618
has metadata on it which suggests that it was recently a member of the
1619
array. If it does, it tried to "re-add" the device. If there have
1620
been no changes since the device was removed, or if the array has a
1621
write-intent bitmap which has recorded whatever changes there were,
1622
then the device will immediately become a full member of the array and
1623
those differences recorded in the bitmap will be resolved.
1624
1625
.SH MISC MODE
1626
.HP 12
1627
Usage:
1628
.B mdadm
1629
.I options ...
1630
.I devices ...
1631
.PP
1632
1633
MISC mode includes a number of distinct operations that
1634
operate on distinct devices. The operations are:
1635
.TP
1636
.B \-\-query
1637
The device is examined to see if it is
1638
(1) an active md array, or
1639
(2) a component of an md array.
1640
The information discovered is reported.
1641
1642
.TP
1643
.B \-\-detail
1644
The device should be an active md device.
1645
.B mdadm
1646
will display a detailed description of the array.
1647
.B \-\-brief
1648
or
1649
.B \-\-scan
1650
will cause the output to be less detailed and the format to be
1651
suitable for inclusion in
1652
.BR /etc/mdadm.conf .
1653
The exit status of
1654
.I mdadm
1655
will normally be 0 unless
1656
.I mdadm
1657
failed to get useful information about the device(s); however, if the
1658
.B \-\-test
1659
option is given, then the exit status will be:
1660
.RS
1661
.TP
1662
0
1663
The array is functioning normally.
1664
.TP
1665
1
1666
The array has at least one failed device.
1667
.TP
1668
2
1669
The array has multiple failed devices such that it is unusable.
1670
.TP
1671
4
1672
There was an error while trying to get information about the device.
1673
.RE
1674
1675
.TP
1676
.B \-\-detail\-platform
1677
Print detail of the platform's RAID capabilities (firmware / hardware
1678
topology). If the metadata is specified with
1679
.B \-e
1680
or
1681
.B \-\-metadata=
1682
then the return status will be:
1683
.RS
1684
.TP
1685
0
1686
metadata successfully enumerated its platform components on this system
1687
.TP
1688
1
1689
metadata is platform independent
1690
.TP
1691
2
1692
metadata failed to find its platform components on this system
1693
.RE
1694
1695
.TP
1696
.B \-\-examine
1697
The device should be a component of an md array.
1698
.I mdadm
1699
will read the md superblock of the device and display the contents.
1700
If
1701
.B \-\-brief
1702
or
1703
.B \-\-scan
1704
is given, then multiple devices that are components of the one array
1705
are grouped together and reported in a single entry suitable
1706
for inclusion in
1707
.BR /etc/mdadm.conf .
1708
1709
Having
1710
.B \-\-scan
1711
without listing any devices will cause all devices listed in the
1712
config file to be examined.
1713
1714
.TP
1715
.B \-\-stop
1716
The devices should be active md arrays which will be deactivated, as
1717
long as they are not currently in use.
1718
1719
.TP
1720
.B \-\-run
1721
This will fully activate a partially assembled md array.
1722
1723
.TP
1724
.B \-\-readonly
1725
This will mark an active array as read-only, providing that it is
1726
not currently being used.
1727
1728
.TP
1729
.B \-\-readwrite
1730
This will change a
1731
.B readonly
1732
array back to being read/write.
1733
1734
.TP
1735
.B \-\-scan
1736
For all operations except
1737
.BR \-\-examine ,
1738
.B \-\-scan
1739
will cause the operation to be applied to all arrays listed in
1740
.BR /proc/mdstat .
1741
For
1742
.BR \-\-examine,
1743
.B \-\-scan
1744
causes all devices listed in the config file to be examined.
1745
1746
.SH MONITOR MODE
1747
1748
.HP 12
1749
Usage:
1750
.B mdadm \-\-monitor
1751
.I options... devices...
1752
1753
.PP
1754
This usage causes
1755
.I mdadm
1756
to periodically poll a number of md arrays and to report on any events
1757
noticed.
1758
.I mdadm
1759
will never exit once it decides that there are arrays to be checked,
1760
so it should normally be run in the background.
1761
1762
As well as reporting events,
1763
.I mdadm
1764
may move a spare drive from one array to another if they are in the
1765
same
1766
.B spare-group
1767
and if the destination array has a failed drive but no spares.
1768
1769
If any devices are listed on the command line,
1770
.I mdadm
1771
will only monitor those devices. Otherwise all arrays listed in the
1772
configuration file will be monitored. Further, if
1773
.B \-\-scan
1774
is given, then any other md devices that appear in
1775
.B /proc/mdstat
1776
will also be monitored.
1777
1778
The result of monitoring the arrays is the generation of events.
1779
These events are passed to a separate program (if specified) and may
1780
be mailed to a given E-mail address.
1781
1782
When passing events to a program, the program is run once for each event,
1783
and is given 2 or 3 command-line arguments: the first is the
1784
name of the event (see below), the second is the name of the
1785
md device which is affected, and the third is the name of a related
1786
device if relevant (such as a component device that has failed).
1787
1788
If
1789
.B \-\-scan
1790
is given, then a program or an E-mail address must be specified on the
1791
command line or in the config file. If neither are available, then
1792
.I mdadm
1793
will not monitor anything.
1794
Without
1795
.B \-\-scan,
1796
.I mdadm
1797
will continue monitoring as long as something was found to monitor. If
1798
no program or email is given, then each event is reported to
1799
.BR stdout .
1800
1801
The different events are:
1802
1803
.RS 4
1804
.TP
1805
.B DeviceDisappeared
1806
An md array which previously was configured appears to no longer be
1807
configured. (syslog priority: Critical)
1808
1809
If
1810
.I mdadm
1811
was told to monitor an array which is RAID0 or Linear, then it will
1812
report
1813
.B DeviceDisappeared
1814
with the extra information
1815
.BR Wrong-Level .
1816
This is because RAID0 and Linear do not support the device-failed,
1817
hot-spare and resync operations which are monitored.
1818
1819
.TP
1820
.B RebuildStarted
1821
An md array started reconstruction. (syslog priority: Warning)
1822
1823
.TP
1824
.BI Rebuild NN
1825
Where
1826
.I NN
1827
is a two-digit number (ie. 05, 48). This indicates that rebuild
1828
has passed that many percent of the total. The events are generated
1829
with fixed increment since 0. Increment size may be specified with
1830
a commandline option (default is 20). (syslog priority: Warning)
1831
1832
.TP
1833
.B RebuildFinished
1834
An md array that was rebuilding, isn't any more, either because it
1835
finished normally or was aborted. (syslog priority: Warning)
1836
1837
.TP
1838
.B Fail
1839
An active component device of an array has been marked as
1840
faulty. (syslog priority: Critical)
1841
1842
.TP
1843
.B FailSpare
1844
A spare component device which was being rebuilt to replace a faulty
1845
device has failed. (syslog priority: Critical)
1846
1847
.TP
1848
.B SpareActive
1849
A spare component device which was being rebuilt to replace a faulty
1850
device has been successfully rebuilt and has been made active.
1851
(syslog priority: Info)
1852
1853
.TP
1854
.B NewArray
1855
A new md array has been detected in the
1856
.B /proc/mdstat
1857
file. (syslog priority: Info)
1858
1859
.TP
1860
.B DegradedArray
1861
A newly noticed array appears to be degraded. This message is not
1862
generated when
1863
.I mdadm
1864
notices a drive failure which causes degradation, but only when
1865
.I mdadm
1866
notices that an array is degraded when it first sees the array.
1867
(syslog priority: Critical)
1868
1869
.TP
1870
.B MoveSpare
1871
A spare drive has been moved from one array in a
1872
.B spare-group
1873
to another to allow a failed drive to be replaced.
1874
(syslog priority: Info)
1875
1876
.TP
1877
.B SparesMissing
1878
If
1879
.I mdadm
1880
has been told, via the config file, that an array should have a certain
1881
number of spare devices, and
1882
.I mdadm
1883
detects that it has fewer than this number when it first sees the
1884
array, it will report a
1885
.B SparesMissing
1886
message.
1887
(syslog priority: Warning)
1888
1889
.TP
1890
.B TestMessage
1891
An array was found at startup, and the
1892
.B \-\-test
1893
flag was given.
1894
(syslog priority: Info)
1895
.RE
1896
1897
Only
1898
.B Fail,
1899
.B FailSpare,
1900
.B DegradedArray,
1901
.B SparesMissing
1902
and
1903
.B TestMessage
1904
cause Email to be sent. All events cause the program to be run.
1905
The program is run with two or three arguments: the event
1906
name, the array device and possibly a second device.
1907
1908
Each event has an associated array device (e.g.
1909
.BR /dev/md1 )
1910
and possibly a second device. For
1911
.BR Fail ,
1912
.BR FailSpare ,
1913
and
1914
.B SpareActive
1915
the second device is the relevant component device.
1916
For
1917
.B MoveSpare
1918
the second device is the array that the spare was moved from.
1919
1920
For
1921
.I mdadm
1922
to move spares from one array to another, the different arrays need to
1923
be labeled with the same
1924
.B spare-group
1925
in the configuration file. The
1926
.B spare-group
1927
name can be any string; it is only necessary that different spare
1928
groups use different names.
1929
1930
When
1931
.I mdadm
1932
detects that an array in a spare group has fewer active
1933
devices than necessary for the complete array, and has no spare
1934
devices, it will look for another array in the same spare group that
1935
has a full complement of working drive and a spare. It will then
1936
attempt to remove the spare from the second drive and add it to the
1937
first.
1938
If the removal succeeds but the adding fails, then it is added back to
1939
the original array.
1940
1941
.SH GROW MODE
1942
The GROW mode is used for changing the size or shape of an active
1943
array.
1944
For this to work, the kernel must support the necessary change.
1945
Various types of growth are being added during 2.6 development,
1946
including restructuring a RAID5 array to have more active devices.
1947
1948
Currently the only support available is to
1949
.IP \(bu 4
1950
change the "size" attribute
1951
for RAID1, RAID5 and RAID6.
1952
.IP \(bu 4
1953
increase the "raid\-devices" attribute of RAID1, RAID5, and RAID6.
1954
.IP \(bu 4
1955
add a write-intent bitmap to any array which supports these bitmaps, or
1956
remove a write-intent bitmap from such an array.
1957
.PP
1958
1959
GROW mode is not currently supported for
1960
.B CONTAINERS
1961
or arrays inside containers.
1962
1963
.SS SIZE CHANGES
1964
Normally when an array is built the "size" it taken from the smallest
1965
of the drives. If all the small drives in an arrays are, one at a
1966
time, removed and replaced with larger drives, then you could have an
1967
array of large drives with only a small amount used. In this
1968
situation, changing the "size" with "GROW" mode will allow the extra
1969
space to start being used. If the size is increased in this way, a
1970
"resync" process will start to make sure the new parts of the array
1971
are synchronised.
1972
1973
Note that when an array changes size, any filesystem that may be
1974
stored in the array will not automatically grow to use the space. The
1975
filesystem will need to be explicitly told to use the extra space.
1976
1977
Also the size of an array cannot be changed while it has an active
1978
bitmap. If an array has a bitmap, it must be removed before the size
1979
can be changed. Once the change it complete a new bitmap can be created.
1980
1981
.SS RAID\-DEVICES CHANGES
1982
1983
A RAID1 array can work with any number of devices from 1 upwards
1984
(though 1 is not very useful). There may be times which you want to
1985
increase or decrease the number of active devices. Note that this is
1986
different to hot-add or hot-remove which changes the number of
1987
inactive devices.
1988
1989
When reducing the number of devices in a RAID1 array, the slots which
1990
are to be removed from the array must already be vacant. That is, the
1991
devices which were in those slots must be failed and removed.
1992
1993
When the number of devices is increased, any hot spares that are
1994
present will be activated immediately.
1995
1996
Increasing the number of active devices in a RAID5 is much more
1997
effort. Every block in the array will need to be read and written
1998
back to a new location. From 2.6.17, the Linux Kernel is able to do
1999
this safely, including restarting an interrupted "reshape".
2000
2001
When relocating the first few stripes on a RAID5, it is not possible
2002
to keep the data on disk completely consistent and crash-proof. To
2003
provide the required safety, mdadm disables writes to the array while
2004
this "critical section" is reshaped, and takes a backup of the data
2005
that is in that section. This backup is normally stored in any spare
2006
devices that the array has, however it can also be stored in a
2007
separate file specified with the
2008
.B \-\-backup\-file
2009
option. If this option is used, and the system does crash during the
2010
critical period, the same file must be passed to
2011
.B \-\-assemble
2012
to restore the backup and reassemble the array.
2013
2014
.SS BITMAP CHANGES
2015
2016
A write-intent bitmap can be added to, or removed from, an active
2017
array. Either internal bitmaps, or bitmaps stored in a separate file,
2018
can be added. Note that if you add a bitmap stored in a file which is
2019
in a filesystem that is on the RAID array being affected, the system
2020
will deadlock. The bitmap must be on a separate filesystem.
2021
2022
.SH INCREMENTAL MODE
2023
2024
.HP 12
2025
Usage:
2026
.B mdadm \-\-incremental
2027
.RB [ \-\-run ]
2028
.RB [ \-\-quiet ]
2029
.I component-device
2030
.HP 12
2031
Usage:
2032
.B mdadm \-\-incremental \-\-rebuild
2033
.HP 12
2034
Usage:
2035
.B mdadm \-\-incremental \-\-run \-\-scan
2036
2037
.PP
2038
This mode is designed to be used in conjunction with a device
2039
discovery system. As devices are found in a system, they can be
2040
passed to
2041
.B "mdadm \-\-incremental"
2042
to be conditionally added to an appropriate array.
2043
2044
If the device passed is a
2045
.B CONTAINER
2046
device created by a previous call to
2047
.IR mdadm ,
2048
then rather than trying to add that device to an array, all the arrays
2049
described by the metadata of the container will be started.
2050
2051
.I mdadm
2052
performs a number of tests to determine if the device is part of an
2053
array, and which array it should be part of. If an appropriate array
2054
is found, or can be created,
2055
.I mdadm
2056
adds the device to the array and conditionally starts the array.
2057
2058
Note that
2059
.I mdadm
2060
will only add devices to an array which were previously working
2061
(active or spare) parts of that array. It does not currently support
2062
automatic inclusion of a new drive as a spare in some array.
2063
2064
The tests that
2065
.I mdadm
2066
makes are as follow:
2067
.IP +
2068
Is the device permitted by
2069
.BR mdadm.conf ?
2070
That is, is it listed in a
2071
.B DEVICES
2072
line in that file. If
2073
.B DEVICES
2074
is absent then the default it to allow any device. Similar if
2075
.B DEVICES
2076
contains the special word
2077
.B partitions
2078
then any device is allowed. Otherwise the device name given to
2079
.I mdadm
2080
must match one of the names or patterns in a
2081
.B DEVICES
2082
line.
2083
2084
.IP +
2085
Does the device have a valid md superblock. If a specific metadata
2086
version is request with
2087
.B \-\-metadata
2088
or
2089
.B \-e
2090
then only that style of metadata is accepted, otherwise
2091
.I mdadm
2092
finds any known version of metadata. If no
2093
.I md
2094
metadata is found, the device is rejected.
2095
2096
.ig XX
2097
.IP +
2098
Does the metadata match an expected array?
2099
The metadata can match in two ways. Either there is an array listed
2100
in
2101
.B mdadm.conf
2102
which identifies the array (either by UUID, by name, by device list,
2103
or by minor-number), or the array was created with a
2104
.B homehost
2105
specified and that
2106
.B homehost
2107
matches the one in
2108
.B mdadm.conf
2109
or on the command line.
2110
If
2111
.I mdadm
2112
is not able to positively identify the array as belonging to the
2113
current host, the device will be rejected.
2114
.XX
2115
2116
.I mdadm
2117
keeps a list of arrays that it has partially assembled in
2118
.B /var/run/mdadm/map
2119
(or
2120
.B /var/run/mdadm.map
2121
if the directory doesn't exist. Or maybe even
2122
.BR /dev/.mdadm.map ).
2123
If no array exists which matches
2124
the metadata on the new device,
2125
.I mdadm
2126
must choose a device name and unit number. It does this based on any
2127
name given in
2128
.B mdadm.conf
2129
or any name information stored in the metadata. If this name
2130
suggests a unit number, that number will be used, otherwise a free
2131
unit number will be chosen. Normally
2132
.I mdadm
2133
will prefer to create a partitionable array, however if the
2134
.B CREATE
2135
line in
2136
.B mdadm.conf
2137
suggests that a non-partitionable array is preferred, that will be
2138
honoured.
2139
2140
If the array is not found in the config file and its metadata does not
2141
identify it as belonging to the "homehost", then
2142
.I mdadm
2143
will choose a name for the array which is certain not to conflict with
2144
any array which does belong to this host. It does this be adding an
2145
underscore and a small number to the name preferred by the metadata.
2146
2147
Once an appropriate array is found or created and the device is added,
2148
.I mdadm
2149
must decide if the array is ready to be started. It will
2150
normally compare the number of available (non-spare) devices to the
2151
number of devices that the metadata suggests need to be active. If
2152
there are at least that many, the array will be started. This means
2153
that if any devices are missing the array will not be restarted.
2154
2155
As an alternative,
2156
.B \-\-run
2157
may be passed to
2158
.I mdadm
2159
in which case the array will be run as soon as there are enough
2160
devices present for the data to be accessible. For a RAID1, that
2161
means one device will start the array. For a clean RAID5, the array
2162
will be started as soon as all but one drive is present.
2163
2164
Note that neither of these approaches is really ideal. If it can
2165
be known that all device discovery has completed, then
2166
.br
2167
.B " mdadm \-IRs"
2168
.br
2169
can be run which will try to start all arrays that are being
2170
incrementally assembled. They are started in "read-auto" mode in
2171
which they are read-only until the first write request. This means
2172
that no metadata updates are made and no attempt at resync or recovery
2173
happens. Further devices that are found before the first write can
2174
still be added safely.
2175
2176
.SH ENVIRONMENT
2177
This section describes environment variables that affect how mdadm
2178
operates.
2179
2180
.TP
2181
.B MDADM_NO_MDMON
2182
Setting this value to 1 will prevent mdadm from automatically launching
2183
mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2184
2185
.TP
2186
.B MDADM_NO_UDEV
2187
Normally,
2188
.I mdadm
2189
does not create any device nodes in /dev, but leaves that task to
2190
.IR udev .
2191
If
2192
.I udev
2193
appears not to be configured, or if this environment variable is set
2194
to '1', the
2195
.I mdadm
2196
will create and devices that are needed.
2197
2198
.SH EXAMPLES
2199
2200
.B " mdadm \-\-query /dev/name-of-device"
2201
.br
2202
This will find out if a given device is a RAID array, or is part of
2203
one, and will provide brief information about the device.
2204
2205
.B " mdadm \-\-assemble \-\-scan"
2206
.br
2207
This will assemble and start all arrays listed in the standard config
2208
file. This command will typically go in a system startup file.
2209
2210
.B " mdadm \-\-stop \-\-scan"
2211
.br
2212
This will shut down all arrays that can be shut down (i.e. are not
2213
currently in use). This will typically go in a system shutdown script.
2214
2215
.B " mdadm \-\-follow \-\-scan \-\-delay=120"
2216
.br
2217
If (and only if) there is an Email address or program given in the
2218
standard config file, then
2219
monitor the status of all arrays listed in that file by
2220
polling them ever 2 minutes.
2221
2222
.B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
2223
.br
2224
Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
2225
2226
.br
2227
.B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
2228
.br
2229
.B " mdadm \-\-detail \-\-scan >> mdadm.conf"
2230
.br
2231
This will create a prototype config file that describes currently
2232
active arrays that are known to be made from partitions of IDE or SCSI drives.
2233
This file should be reviewed before being used as it may
2234
contain unwanted detail.
2235
2236
.B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
2237
.br
2238
.B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
2239
.br
2240
This will find arrays which could be assembled from existing IDE and
2241
SCSI whole drives (not partitions), and store the information in the
2242
format of a config file.
2243
This file is very likely to contain unwanted detail, particularly
2244
the
2245
.B devices=
2246
entries. It should be reviewed and edited before being used as an
2247
actual config file.
2248
2249
.B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
2250
.br
2251
.B " mdadm \-Ebsc partitions"
2252
.br
2253
Create a list of devices by reading
2254
.BR /proc/partitions ,
2255
scan these for RAID superblocks, and printout a brief listing of all
2256
that were found.
2257
2258
.B " mdadm \-Ac partitions \-m 0 /dev/md0"
2259
.br
2260
Scan all partitions and devices listed in
2261
.BR /proc/partitions
2262
and assemble
2263
.B /dev/md0
2264
out of all such devices with a RAID superblock with a minor number of 0.
2265
2266
.B " mdadm \-\-monitor \-\-scan \-\-daemonise > /var/run/mdadm"
2267
.br
2268
If config file contains a mail address or alert program, run mdadm in
2269
the background in monitor mode monitoring all md devices. Also write
2270
pid of mdadm daemon to
2271
.BR /var/run/mdadm .
2272
2273
.B " mdadm \-Iq /dev/somedevice"
2274
.br
2275
Try to incorporate newly discovered device into some array as
2276
appropriate.
2277
2278
.B " mdadm \-\-incremental \-\-rebuild \-\-run \-\-scan"
2279
.br
2280
Rebuild the array map from any current arrays, and then start any that
2281
can be started.
2282
2283
.B " mdadm /dev/md4 --fail detached --remove detached"
2284
.br
2285
Any devices which are components of /dev/md4 will be marked as faulty
2286
and then remove from the array.
2287
2288
.B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
2289
.br
2290
Create a DDF array over 6 devices.
2291
2292
.B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
2293
.br
2294
Create a RAID5 array over any 3 devices in the given DDF set. Use
2295
only 30 gigabytes of each device.
2296
2297
.B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
2298
.br
2299
Assemble a pre-exist ddf array.
2300
2301
.B " mdadm -I /dev/md/ddf1"
2302
.br
2303
Assemble all arrays contained in the ddf array, assigning names as
2304
appropriate.
2305
2306
.B " mdadm \-\-create \-\-help"
2307
.br
2308
Provide help about the Create mode.
2309
2310
.B " mdadm \-\-config \-\-help"
2311
.br
2312
Provide help about the format of the config file.
2313
2314
.B " mdadm \-\-help"
2315
.br
2316
Provide general help.
2317
2318
.SH FILES
2319
2320
.SS /proc/mdstat
2321
2322
If you're using the
2323
.B /proc
2324
filesystem,
2325
.B /proc/mdstat
2326
lists all active md devices with information about them.
2327
.I mdadm
2328
uses this to find arrays when
2329
.B \-\-scan
2330
is given in Misc mode, and to monitor array reconstruction
2331
on Monitor mode.
2332
2333
.SS /etc/mdadm.conf
2334
2335
The config file lists which devices may be scanned to see if
2336
they contain MD super block, and gives identifying information
2337
(e.g. UUID) about known MD arrays. See
2338
.BR mdadm.conf (5)
2339
for more details.
2340
2341
.SS /var/run/mdadm/map
2342
When
2343
.B \-\-incremental
2344
mode is used, this file gets a list of arrays currently being created.
2345
If
2346
.B /var/run/mdadm
2347
does not exist as a directory, then
2348
.B /var/run/mdadm.map
2349
is used instead. If
2350
.B /var/run
2351
is not available (as may be the case during early boot),
2352
.B /dev/.mdadm.map
2353
is used on the basis that
2354
.B /dev
2355
is usually available very early in boot.
2356
2357
.SH DEVICE NAMES
2358
2359
.I mdadm
2360
understand two sorts of names for array devices.
2361
2362
The first is the so-called 'standard' format name, which matches the
2363
names used by the kernel and which appear in
2364
.IR /proc/mdstat .
2365
2366
The second sort can be freely chosen, but must reside in
2367
.IR /dev/md/ .
2368
When giving a device name to
2369
.I mdadm
2370
to create or assemble an array, either full path name such as
2371
.I /dev/md0
2372
or
2373
.I /dev/md/home
2374
can be given, or just the suffix of the second sort of name, such as
2375
.I home
2376
can be given.
2377
2378
When
2379
.I mdadm
2380
chooses device names during auto-assembly or incremental assembly, it
2381
will sometimes add a small sequence number to the end of the name to
2382
avoid conflicted between multiple arrays that have the same name. If
2383
.I mdadm
2384
can reasonably determine that the array really is meant for this host,
2385
either by a hostname in the metadata, or by the presence of the array
2386
in /etc/mdadm.conf, then it will leave off the suffix if possible.
2387
Also if the homehost is specified as
2388
.B <ignore>
2389
.I mdadm
2390
will only use a suffix if a different array of the same name already
2391
exists or is listed in the config file.
2392
2393
The standard names for non-partitioned arrays (the only sort of md
2394
array available in 2.4 and earlier) are of the form
2395
.IP
2396
/dev/mdNN
2397
.PP
2398
where NN is a number.
2399
The standard names for partitionable arrays (as available from 2.6
2400
onwards) are of the form
2401
.IP
2402
/dev/md_dNN
2403
.PP
2404
Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
2405
.PP
2406
From kernel version, 2.6.28 the "non-partitioned array" can actually
2407
be partitioned. So the "md_dNN" names are no longer needed, and
2408
partitions such as "/dev/mdNNpXX" are possible.
2409
2410
.SH NOTE
2411
.I mdadm
2412
was previously known as
2413
.IR mdctl .
2414
.P
2415
.I mdadm
2416
is completely separate from the
2417
.I raidtools
2418
package, and does not use the
2419
.I /etc/raidtab
2420
configuration file at all.
2421
2422
.SH SEE ALSO
2423
For further information on mdadm usage, MD and the various levels of
2424
RAID, see:
2425
.IP
2426
.B http://linux\-raid.osdl.org/
2427
.PP
2428
(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
2429
.\".PP
2430
.\"for new releases of the RAID driver check out:
2431
.\"
2432
.\".IP
2433
.\".UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2434
.\"ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2435
.\".UE
2436
.\".PP
2437
.\"or
2438
.\".IP
2439
.\".UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2440
.\"http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2441
.\".UE
2442
.PP
2443
The latest version of
2444
.I mdadm
2445
should always be available from
2446
.IP
2447
.B http://www.kernel.org/pub/linux/utils/raid/mdadm/
2448
.PP
2449
Related man pages:
2450
.PP
2451
.IR mdmon (8),
2452
.IR mdadm.conf (5),
2453
.IR md (4).
2454
.PP
2455
.IR raidtab (5),
2456
.IR raid0run (8),
2457
.IR raidstop (8),
2458
.IR mkraid (8).
Loggerhead is a web-based interface for Breezy
Version: 2.0.1