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- Committer: Package Import Robot
- Author(s): Dmitrijs Ledkovs
- Date: 2012-06-15 15:31:59 UTC
- mfrom: (1.1.30 sid)
- Revision ID: package-import@ubuntu.com-20120615153159-9lp7jykbq7vua4bo
Tags: 3.2.5-1ubuntu1
* Merge from Debian testing. (LP: #920324) Remaining changes:
- Call checks in local-premount to avoid race condition with udev
and opening a degraded array.
- d/initramfs/mdadm-functions: Record in /run when boot-degraded
question has been asked so that it is only asked once
- pass --test to mdadm to enable result codes for degraded arrays.
- debian/control: we need udev and util-linux in the right version. We
also remove the build dependency from quilt and docbook-to-man as both
are not used in Ubuntus mdadm.
- debian/initramfs/hook: kept the Ubuntus version for handling the absence
of active raid arrays in <initramfs>/etc/mdadm/mdadm.conf
- debian/initramfs/script.local-top.DEBIAN, debian/mdadm-startall,
debian/mdadm.raid.DEBIAN: removed. udev does its job now instead.
- debian/mdadm-startall.sgml, debian/mdadm-startall.8: documentation of
unused startall script
- debian/mdadm.config, debian/mdadm.postinst - let udev do the handling
instead. Resolved merge conflict by keeping Ubuntu's version.
- debian/mdadm.postinst, debian/mdadm.config, initramfs/init-premount:
boot-degraded enablement; maintain udev starting of RAID devices;
init-premount hook script for the initramfs, to provide information at
boot
- debian/mkconf.in is the older mkconf. Kept the Ubuntu version.
- debian/rules: Kept Ubuntus version for installing apport hooks, not
installing un-used startall script.
- debian/install-rc, check.d/_numbers, check.d/root_on_raid: Ubuntu partman
installer changes
- debian/presubj: Dropped this unused bug reporting file. Instead use
source_mdadm.py act as an apport hook for bug handling.
- d/p/debian-changes-3.1.4-1+8efb9d1ubuntu4: mdadm udev rule
incrementally adds mdadm member when detected. Starting such an
array in degraded mode is possible by mdadm -IRs. Using mdadm
-ARs without stopping the array first does nothing when no
mdarray-unassociated device is available. Using mdadm -IRs to
start a previously partially assembled array through incremental
mode. Keeping the mdadm -ARs for assembling arrays which were for
some reason not assembled through incremental mode (i.e through
mdadm's udev rule).
* Additional Ubuntu changes:
- debian/initramfs/local-premount: add call wait_for_udev to wait a
little longer for RAID devices to appear (LP: #942106)
* Dropped Ubuntu changes:
- Build udeb with -O2 on ppc64, working around a link error. Builds
fine without it on debian.
- rename debian/mdadm.vol_id.udev to debian/mdadm.mdadm-blkid.udev so
that the rules file ends up with a more reasonable name. debian/rules
changes for adding ubuntu's udev rule corresponding to mdadm. As we
are now using 'upstream' udev rules see 3.2.3-2ubuntu2.
* Changes to Ubuntu changes:
- debian/source_mdadm.py: make apport hook python 2 and 3 compatible
(LP: #1013171).
* New upstream release closes this bugs:
- mdadm --detail --scan segfaults during update-initramfs (LP: #969384)
- Call checks in local-premount to avoid race condition with udev
and opening a degraded array.
- d/initramfs/mdadm-functions: Record in /run when boot-degraded
question has been asked so that it is only asked once
- pass --test to mdadm to enable result codes for degraded arrays.
- debian/control: we need udev and util-linux in the right version. We
also remove the build dependency from quilt and docbook-to-man as both
are not used in Ubuntus mdadm.
- debian/initramfs/hook: kept the Ubuntus version for handling the absence
of active raid arrays in <initramfs>/etc/mdadm/mdadm.conf
- debian/initramfs/script.local-top.DEBIAN, debian/mdadm-startall,
debian/mdadm.raid.DEBIAN: removed. udev does its job now instead.
- debian/mdadm-startall.sgml, debian/mdadm-startall.8: documentation of
unused startall script
- debian/mdadm.config, debian/mdadm.postinst - let udev do the handling
instead. Resolved merge conflict by keeping Ubuntu's version.
- debian/mdadm.postinst, debian/mdadm.config, initramfs/init-premount:
boot-degraded enablement; maintain udev starting of RAID devices;
init-premount hook script for the initramfs, to provide information at
boot
- debian/mkconf.in is the older mkconf. Kept the Ubuntu version.
- debian/rules: Kept Ubuntus version for installing apport hooks, not
installing un-used startall script.
- debian/install-rc, check.d/_numbers, check.d/root_on_raid: Ubuntu partman
installer changes
- debian/presubj: Dropped this unused bug reporting file. Instead use
source_mdadm.py act as an apport hook for bug handling.
- d/p/debian-changes-3.1.4-1+8efb9d1ubuntu4: mdadm udev rule
incrementally adds mdadm member when detected. Starting such an
array in degraded mode is possible by mdadm -IRs. Using mdadm
-ARs without stopping the array first does nothing when no
mdarray-unassociated device is available. Using mdadm -IRs to
start a previously partially assembled array through incremental
mode. Keeping the mdadm -ARs for assembling arrays which were for
some reason not assembled through incremental mode (i.e through
mdadm's udev rule).
* Additional Ubuntu changes:
- debian/initramfs/local-premount: add call wait_for_udev to wait a
little longer for RAID devices to appear (LP: #942106)
* Dropped Ubuntu changes:
- Build udeb with -O2 on ppc64, working around a link error. Builds
fine without it on debian.
- rename debian/mdadm.vol_id.udev to debian/mdadm.mdadm-blkid.udev so
that the rules file ends up with a more reasonable name. debian/rules
changes for adding ubuntu's udev rule corresponding to mdadm. As we
are now using 'upstream' udev rules see 3.2.3-2ubuntu2.
* Changes to Ubuntu changes:
- debian/source_mdadm.py: make apport hook python 2 and 3 compatible
(LP: #1013171).
* New upstream release closes this bugs:
- mdadm --detail --scan segfaults during update-initramfs (LP: #969384)
- files added:
- .pc/debian-conffile-location.diff
- .pc/debian-no-Werror.diff
- .pc/sha1-includes.diff
- files removed:
- .pc/debian
- .pc/debian/conffile-location.diff
- .pc/debian/no-Werror.diff
- debian/patches/debian
- files modified:
- .pc/applied-patches
added
removed
.pc/debian/conffile-location.diff/mdadm.8.in
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.
8
.TH MDADM 8 "" v3.2.3
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.SH NAME
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mdadm \- manage MD devices
11
.I aka
12
Linux Software RAID
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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.
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Some RAID levels include redundancy and so can survive some degree of
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device failure.
25
26
Linux Software RAID devices are implemented through the md (Multiple
27
Devices) device driver.
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29
Currently, Linux supports
30
.B LINEAR
31
md devices,
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.B RAID0
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(striping),
34
.B RAID1
35
(mirroring),
36
.BR RAID4 ,
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.BR RAID5 ,
38
.BR RAID6 ,
39
.BR RAID10 ,
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.BR MULTIPATH ,
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.BR FAULTY ,
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and
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.BR CONTAINER .
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45
.B MULTIPATH
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is not a Software RAID mechanism, but does involve
47
multiple devices:
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each device is a path to one common physical storage device.
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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.
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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
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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
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creates a
75
.B CONTAINER
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device, the device just represents the metadata. Other normal arrays (RAID1
77
etc) can be created inside the container.
78
79
.SH MODES
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mdadm has several major modes of operation:
81
.TP
82
.B Assemble
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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
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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
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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
126
Linear and RAID levels 0/1/4/5/6,
127
changing the RAID level between 0, 1, 5, and 6, and between 0 and 10,
128
changing the chunk size and layout for RAID 0,4,5,6, as well as adding or
129
removing a write-intent bitmap.
130
131
.TP
132
.B "Incremental Assembly"
133
Add a single device to an appropriate array. If the addition of the
134
device makes the array runnable, the array will be started.
135
This provides a convenient interface to a
136
.I hot-plug
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system. As each device is detected,
138
.I mdadm
139
has a chance to include it in some array as appropriate.
140
Optionally, when the
141
.I \-\-fail
142
flag is passed in we will remove the device from any active array
143
instead of adding it.
144
145
If a
146
.B CONTAINER
147
is passed to
148
.I mdadm
149
in this mode, then any arrays within that container will be assembled
150
and started.
151
152
.TP
153
.B Manage
154
This is for doing things to specific components of an array such as
155
adding new spares and removing faulty devices.
156
157
.TP
158
.B Misc
159
This is an 'everything else' mode that supports operations on active
160
arrays, operations on component devices such as erasing old superblocks, and
161
information gathering operations.
162
.\"This mode allows operations on independent devices such as examine MD
163
.\"superblocks, erasing old superblocks and stopping active arrays.
164
165
.TP
166
.B Auto-detect
167
This mode does not act on a specific device or array, but rather it
168
requests the Linux Kernel to activate any auto-detected arrays.
169
.SH OPTIONS
170
171
.SH Options for selecting a mode are:
172
173
.TP
174
.BR \-A ", " \-\-assemble
175
Assemble a pre-existing array.
176
177
.TP
178
.BR \-B ", " \-\-build
179
Build a legacy array without superblocks.
180
181
.TP
182
.BR \-C ", " \-\-create
183
Create a new array.
184
185
.TP
186
.BR \-F ", " \-\-follow ", " \-\-monitor
187
Select
188
.B Monitor
189
mode.
190
191
.TP
192
.BR \-G ", " \-\-grow
193
Change the size or shape of an active array.
194
195
.TP
196
.BR \-I ", " \-\-incremental
197
Add/remove a single device to/from an appropriate array, and possibly start the array.
198
199
.TP
200
.B \-\-auto-detect
201
Request that the kernel starts any auto-detected arrays. This can only
202
work if
203
.I md
204
is compiled into the kernel \(em not if it is a module.
205
Arrays can be auto-detected by the kernel if all the components are in
206
primary MS-DOS partitions with partition type
207
.BR FD ,
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and all use v0.90 metadata.
209
In-kernel autodetect is not recommended for new installations. Using
210
.I mdadm
211
to detect and assemble arrays \(em possibly in an
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.I initrd
213
\(em is substantially more flexible and should be preferred.
214
215
.P
216
If a device is given before any options, or if the first option is
217
.BR \-\-add ,
218
.BR \-\-fail ,
219
or
220
.BR \-\-remove ,
221
then the MANAGE mode is assumed.
222
Anything other than these will cause the
223
.B Misc
224
mode to be assumed.
225
226
.SH Options that are not mode-specific are:
227
228
.TP
229
.BR \-h ", " \-\-help
230
Display general help message or, after one of the above options, a
231
mode-specific help message.
232
233
.TP
234
.B \-\-help\-options
235
Display more detailed help about command line parsing and some commonly
236
used options.
237
238
.TP
239
.BR \-V ", " \-\-version
240
Print version information for mdadm.
241
242
.TP
243
.BR \-v ", " \-\-verbose
244
Be more verbose about what is happening. This can be used twice to be
245
extra-verbose.
246
The extra verbosity currently only affects
247
.B \-\-detail \-\-scan
248
and
249
.BR "\-\-examine \-\-scan" .
250
251
.TP
252
.BR \-q ", " \-\-quiet
253
Avoid printing purely informative messages. With this,
254
.I mdadm
255
will be silent unless there is something really important to report.
256
257
.TP
258
.BR \-f ", " \-\-force
259
Be more forceful about certain operations. See the various modes for
260
the exact meaning of this option in different contexts.
261
262
.TP
263
.BR \-c ", " \-\-config=
264
Specify the config file. Default is to use
265
.BR /etc/mdadm.conf ,
266
or if that is missing then
267
.BR /etc/mdadm/mdadm.conf .
268
If the config file given is
269
.B "partitions"
270
then nothing will be read, but
271
.I mdadm
272
will act as though the config file contained exactly
273
.B "DEVICE partitions containers"
274
and will read
275
.B /proc/partitions
276
to find a list of devices to scan, and
277
.B /proc/mdstat
278
to find a list of containers to examine.
279
If the word
280
.B "none"
281
is given for the config file, then
282
.I mdadm
283
will act as though the config file were empty.
284
285
.TP
286
.BR \-s ", " \-\-scan
287
Scan config file or
288
.B /proc/mdstat
289
for missing information.
290
In general, this option gives
291
.I mdadm
292
permission to get any missing information (like component devices,
293
array devices, array identities, and alert destination) from the
294
configuration file (see previous option);
295
one exception is MISC mode when using
296
.B \-\-detail
297
or
298
.B \-\-stop,
299
in which case
300
.B \-\-scan
301
says to get a list of array devices from
302
.BR /proc/mdstat .
303
304
.TP
305
.BR \-e ", " \-\-metadata=
306
Declare the style of RAID metadata (superblock) to be used. The
307
default is {DEFAULT_METADATA} for
308
.BR \-\-create ,
309
and to guess for other operations.
310
The default can be overridden by setting the
311
.B metadata
312
value for the
313
.B CREATE
314
keyword in
315
.BR mdadm.conf .
316
317
Options are:
318
.RS
319
.ie '{DEFAULT_METADATA}'0.90'
320
.IP "0, 0.90, default"
321
.el
322
.IP "0, 0.90"
323
..
324
Use the original 0.90 format superblock. This format limits arrays to
325
28 component devices and limits component devices of levels 1 and
326
greater to 2 terabytes. It is also possible for there to be confusion
327
about whether the superblock applies to a whole device or just the
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last partition, if that partition starts on a 64K boundary.
329
.ie '{DEFAULT_METADATA}'0.90'
330
.IP "1, 1.0, 1.1, 1.2"
331
.el
332
.IP "1, 1.0, 1.1, 1.2 default"
333
..
334
Use the new version-1 format superblock. This has fewer restrictions.
335
It can easily be moved between hosts with different endian-ness, and a
336
recovery operation can be checkpointed and restarted. The different
337
sub-versions store the superblock at different locations on the
338
device, either at the end (for 1.0), at the start (for 1.1) or 4K from
339
the start (for 1.2). "1" is equivalent to "1.2" (the commonly
340
preferred 1.x format).
341
'if '{DEFAULT_METADATA}'1.2' "default" is equivalent to "1.2".
342
.IP ddf
343
Use the "Industry Standard" DDF (Disk Data Format) format defined by
344
SNIA.
345
When creating a DDF array a
346
.B CONTAINER
347
will be created, and normal arrays can be created in that container.
348
.IP imsm
349
Use the Intel(R) Matrix Storage Manager metadata format. This creates a
350
.B CONTAINER
351
which is managed in a similar manner to DDF, and is supported by an
352
option-rom on some platforms:
353
.IP
354
.B http://www.intel.com/design/chipsets/matrixstorage_sb.htm
355
.PP
356
.RE
357
358
.TP
359
.B \-\-homehost=
360
This will override any
361
.B HOMEHOST
362
setting in the config file and provides the identity of the host which
363
should be considered the home for any arrays.
364
365
When creating an array, the
366
.B homehost
367
will be recorded in the metadata. For version-1 superblocks, it will
368
be prefixed to the array name. For version-0.90 superblocks, part of
369
the SHA1 hash of the hostname will be stored in the later half of the
370
UUID.
371
372
When reporting information about an array, any array which is tagged
373
for the given homehost will be reported as such.
374
375
When using Auto-Assemble, only arrays tagged for the given homehost
376
will be allowed to use 'local' names (i.e. not ending in '_' followed
377
by a digit string). See below under
378
.BR "Auto Assembly" .
379
380
.SH For create, build, or grow:
381
382
.TP
383
.BR \-n ", " \-\-raid\-devices=
384
Specify the number of active devices in the array. This, plus the
385
number of spare devices (see below) must equal the number of
386
.I component-devices
387
(including "\fBmissing\fP" devices)
388
that are listed on the command line for
389
.BR \-\-create .
390
Setting a value of 1 is probably
391
a mistake and so requires that
392
.B \-\-force
393
be specified first. A value of 1 will then be allowed for linear,
394
multipath, RAID0 and RAID1. It is never allowed for RAID4, RAID5 or RAID6.
395
.br
396
This number can only be changed using
397
.B \-\-grow
398
for RAID1, RAID4, RAID5 and RAID6 arrays, and only on kernels which provide
399
the necessary support.
400
401
.TP
402
.BR \-x ", " \-\-spare\-devices=
403
Specify the number of spare (eXtra) devices in the initial array.
404
Spares can also be added
405
and removed later. The number of component devices listed
406
on the command line must equal the number of RAID devices plus the
407
number of spare devices.
408
409
.TP
410
.BR \-z ", " \-\-size=
411
Amount (in Kibibytes) of space to use from each drive in RAID levels 1/4/5/6.
412
This must be a multiple of the chunk size, and must leave about 128Kb
413
of space at the end of the drive for the RAID superblock.
414
If this is not specified
415
(as it normally is not) the smallest drive (or partition) sets the
416
size, though if there is a variance among the drives of greater than 1%, a warning is
417
issued.
418
419
A suffix of 'M' or 'G' can be given to indicate Megabytes or
420
Gigabytes respectively.
421
422
Sometimes a replacement drive can be a little smaller than the
423
original drives though this should be minimised by IDEMA standards.
424
Such a replacement drive will be rejected by
425
.IR md .
426
To guard against this it can be useful to set the initial size
427
slightly smaller than the smaller device with the aim that it will
428
still be larger than any replacement.
429
430
This value can be set with
431
.B \-\-grow
432
for RAID level 1/4/5/6 though
433
.B CONTAINER
434
based arrays such as those with IMSM metadata may not be able to
435
support this.
436
If the array was created with a size smaller than the currently
437
active drives, the extra space can be accessed using
438
.BR \-\-grow .
439
The size can be given as
440
.B max
441
which means to choose the largest size that fits on all current drives.
442
443
Before reducing the size of the array (with
444
.BR "\-\-grow \-\-size=" )
445
you should make sure that space isn't needed. If the device holds a
446
filesystem, you would need to resize the filesystem to use less space.
447
448
After reducing the array size you should check that the data stored in
449
the device is still available. If the device holds a filesystem, then
450
an 'fsck' of the filesystem is a minimum requirement. If there are
451
problems the array can be made bigger again with no loss with another
452
.B "\-\-grow \-\-size="
453
command.
454
455
This value cannot be used when creating a
456
.B CONTAINER
457
such as with DDF and IMSM metadata, though it perfectly valid when
458
creating an array inside a container.
459
460
.TP
461
.BR \-Z ", " \-\-array\-size=
462
This is only meaningful with
463
.B \-\-grow
464
and its effect is not persistent: when the array is stopped and
465
restarted the default array size will be restored.
466
467
Setting the array-size causes the array to appear smaller to programs
468
that access the data. This is particularly needed before reshaping an
469
array so that it will be smaller. As the reshape is not reversible,
470
but setting the size with
471
.B \-\-array-size
472
is, it is required that the array size is reduced as appropriate
473
before the number of devices in the array is reduced.
474
475
Before reducing the size of the array you should make sure that space
476
isn't needed. If the device holds a filesystem, you would need to
477
resize the filesystem to use less space.
478
479
After reducing the array size you should check that the data stored in
480
the device is still available. If the device holds a filesystem, then
481
an 'fsck' of the filesystem is a minimum requirement. If there are
482
problems the array can be made bigger again with no loss with another
483
.B "\-\-grow \-\-array\-size="
484
command.
485
486
A suffix of 'M' or 'G' can be given to indicate Megabytes or
487
Gigabytes respectively.
488
A value of
489
.B max
490
restores the apparent size of the array to be whatever the real
491
amount of available space is.
492
493
.TP
494
.BR \-c ", " \-\-chunk=
495
Specify chunk size of kibibytes. The default when creating an
496
array is 512KB. To ensure compatibility with earlier versions, the
497
default when Building and array with no persistent metadata is 64KB.
498
This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10.
499
500
RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a power
501
of 2. In any case it must be a multiple of 4KB.
502
503
A suffix of 'M' or 'G' can be given to indicate Megabytes or
504
Gigabytes respectively.
505
506
.TP
507
.BR \-\-rounding=
508
Specify rounding factor for a Linear array. The size of each
509
component will be rounded down to a multiple of this size.
510
This is a synonym for
511
.B \-\-chunk
512
but highlights the different meaning for Linear as compared to other
513
RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in
514
use, and is 0K (i.e. no rounding) in later kernels.
515
516
.TP
517
.BR \-l ", " \-\-level=
518
Set RAID level. When used with
519
.BR \-\-create ,
520
options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4,
521
raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container.
522
Obviously some of these are synonymous.
523
524
When a
525
.B CONTAINER
526
metadata type is requested, only the
527
.B container
528
level is permitted, and it does not need to be explicitly given.
529
530
When used with
531
.BR \-\-build ,
532
only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid.
533
534
Can be used with
535
.B \-\-grow
536
to change the RAID level in some cases. See LEVEL CHANGES below.
537
538
.TP
539
.BR \-p ", " \-\-layout=
540
This option configures the fine details of data layout for RAID5, RAID6,
541
and RAID10 arrays, and controls the failure modes for
542
.IR faulty .
543
544
The layout of the RAID5 parity block can be one of
545
.BR left\-asymmetric ,
546
.BR left\-symmetric ,
547
.BR right\-asymmetric ,
548
.BR right\-symmetric ,
549
.BR la ", " ra ", " ls ", " rs .
550
The default is
551
.BR left\-symmetric .
552
553
It is also possible to cause RAID5 to use a RAID4-like layout by
554
choosing
555
.BR parity\-first ,
556
or
557
.BR parity\-last .
558
559
Finally for RAID5 there are DDF\-compatible layouts,
560
.BR ddf\-zero\-restart ,
561
.BR ddf\-N\-restart ,
562
and
563
.BR ddf\-N\-continue .
564
565
These same layouts are available for RAID6. There are also 4 layouts
566
that will provide an intermediate stage for converting between RAID5
567
and RAID6. These provide a layout which is identical to the
568
corresponding RAID5 layout on the first N\-1 devices, and has the 'Q'
569
syndrome (the second 'parity' block used by RAID6) on the last device.
570
These layouts are:
571
.BR left\-symmetric\-6 ,
572
.BR right\-symmetric\-6 ,
573
.BR left\-asymmetric\-6 ,
574
.BR right\-asymmetric\-6 ,
575
and
576
.BR parity\-first\-6 .
577
578
When setting the failure mode for level
579
.I faulty,
580
the options are:
581
.BR write\-transient ", " wt ,
582
.BR read\-transient ", " rt ,
583
.BR write\-persistent ", " wp ,
584
.BR read\-persistent ", " rp ,
585
.BR write\-all ,
586
.BR read\-fixable ", " rf ,
587
.BR clear ", " flush ", " none .
588
589
Each failure mode can be followed by a number, which is used as a period
590
between fault generation. Without a number, the fault is generated
591
once on the first relevant request. With a number, the fault will be
592
generated after that many requests, and will continue to be generated
593
every time the period elapses.
594
595
Multiple failure modes can be current simultaneously by using the
596
.B \-\-grow
597
option to set subsequent failure modes.
598
599
"clear" or "none" will remove any pending or periodic failure modes,
600
and "flush" will clear any persistent faults.
601
602
Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed
603
by a small number. The default is 'n2'. The supported options are:
604
605
.I 'n'
606
signals 'near' copies. Multiple copies of one data block are at
607
similar offsets in different devices.
608
609
.I 'o'
610
signals 'offset' copies. Rather than the chunks being duplicated
611
within a stripe, whole stripes are duplicated but are rotated by one
612
device so duplicate blocks are on different devices. Thus subsequent
613
copies of a block are in the next drive, and are one chunk further
614
down.
615
616
.I 'f'
617
signals 'far' copies
618
(multiple copies have very different offsets).
619
See md(4) for more detail about 'near', 'offset', and 'far'.
620
621
The number is the number of copies of each datablock. 2 is normal, 3
622
can be useful. This number can be at most equal to the number of
623
devices in the array. It does not need to divide evenly into that
624
number (e.g. it is perfectly legal to have an 'n2' layout for an array
625
with an odd number of devices).
626
627
When an array is converted between RAID5 and RAID6 an intermediate
628
RAID6 layout is used in which the second parity block (Q) is always on
629
the last device. To convert a RAID5 to RAID6 and leave it in this new
630
layout (which does not require re-striping) use
631
.BR \-\-layout=preserve .
632
This will try to avoid any restriping.
633
634
The converse of this is
635
.B \-\-layout=normalise
636
which will change a non-standard RAID6 layout into a more standard
637
arrangement.
638
639
.TP
640
.BR \-\-parity=
641
same as
642
.B \-\-layout
643
(thus explaining the p of
644
.BR \-p ).
645
646
.TP
647
.BR \-b ", " \-\-bitmap=
648
Specify a file to store a write-intent bitmap in. The file should not
649
exist unless
650
.B \-\-force
651
is also given. The same file should be provided
652
when assembling the array. If the word
653
.B "internal"
654
is given, then the bitmap is stored with the metadata on the array,
655
and so is replicated on all devices. If the word
656
.B "none"
657
is given with
658
.B \-\-grow
659
mode, then any bitmap that is present is removed.
660
661
To help catch typing errors, the filename must contain at least one
662
slash ('/') if it is a real file (not 'internal' or 'none').
663
664
Note: external bitmaps are only known to work on ext2 and ext3.
665
Storing bitmap files on other filesystems may result in serious problems.
666
667
.TP
668
.BR \-\-bitmap\-chunk=
669
Set the chunksize of the bitmap. Each bit corresponds to that many
670
Kilobytes of storage.
671
When using a file based bitmap, the default is to use the smallest
672
size that is at-least 4 and requires no more than 2^21 chunks.
673
When using an
674
.B internal
675
bitmap, the chunksize defaults to 64Meg, or larger if necessary to
676
fit the bitmap into the available space.
677
678
A suffix of 'M' or 'G' can be given to indicate Megabytes or
679
Gigabytes respectively.
680
681
.TP
682
.BR \-W ", " \-\-write\-mostly
683
subsequent devices listed in a
684
.BR \-\-build ,
685
.BR \-\-create ,
686
or
687
.B \-\-add
688
command will be flagged as 'write-mostly'. This is valid for RAID1
689
only and means that the 'md' driver will avoid reading from these
690
devices if at all possible. This can be useful if mirroring over a
691
slow link.
692
693
.TP
694
.BR \-\-write\-behind=
695
Specify that write-behind mode should be enabled (valid for RAID1
696
only). If an argument is specified, it will set the maximum number
697
of outstanding writes allowed. The default value is 256.
698
A write-intent bitmap is required in order to use write-behind
699
mode, and write-behind is only attempted on drives marked as
700
.IR write-mostly .
701
702
.TP
703
.BR \-\-assume\-clean
704
Tell
705
.I mdadm
706
that the array pre-existed and is known to be clean. It can be useful
707
when trying to recover from a major failure as you can be sure that no
708
data will be affected unless you actually write to the array. It can
709
also be used when creating a RAID1 or RAID10 if you want to avoid the
710
initial resync, however this practice \(em while normally safe \(em is not
711
recommended. Use this only if you really know what you are doing.
712
.IP
713
When the devices that will be part of a new array were filled
714
with zeros before creation the operator knows the array is
715
actually clean. If that is the case, such as after running
716
badblocks, this argument can be used to tell mdadm the
717
facts the operator knows.
718
.IP
719
When an array is resized to a larger size with
720
.B "\-\-grow \-\-size="
721
the new space is normally resynced in that same way that the whole
722
array is resynced at creation. From Linux version 3.0,
723
.B \-\-assume\-clean
724
can be used with that command to avoid the automatic resync.
725
726
.TP
727
.BR \-\-backup\-file=
728
This is needed when
729
.B \-\-grow
730
is used to increase the number of raid-devices in a RAID5 or RAID6 if
731
there are no spare devices available, or to shrink, change RAID level
732
or layout. See the GROW MODE section below on RAID\-DEVICES CHANGES.
733
The file must be stored on a separate device, not on the RAID array
734
being reshaped.
735
736
.TP
737
.BR \-\-continue
738
This option is complementary to the
739
.B \-\-freeze-reshape
740
option for assembly. It is needed when
741
.B \-\-grow
742
operation is interrupted and it is not restarted automatically due to
743
.B \-\-freeze-reshape
744
usage during array assembly. This option is used together with
745
.BR \-G
746
, (
747
.BR \-\-grow
748
) command and device for a pending reshape to be continued.
749
All parameters required for reshape continuation will be read from array metadata.
750
If initial
751
.BR \-\-grow
752
command had required
753
.BR \-\-backup\-file=
754
option to be set, continuation option will require to have exactly the same
755
backup file given as well.
756
.IP
757
Any other parameter passed together with
758
.BR \-\-continue
759
option will be ignored.
760
761
.TP
762
.BR \-N ", " \-\-name=
763
Set a
764
.B name
765
for the array. This is currently only effective when creating an
766
array with a version-1 superblock, or an array in a DDF container.
767
The name is a simple textual string that can be used to identify array
768
components when assembling. If name is needed but not specified, it
769
is taken from the basename of the device that is being created.
770
e.g. when creating
771
.I /dev/md/home
772
the
773
.B name
774
will default to
775
.IR home .
776
777
.TP
778
.BR \-R ", " \-\-run
779
Insist that
780
.I mdadm
781
run the array, even if some of the components
782
appear to be active in another array or filesystem. Normally
783
.I mdadm
784
will ask for confirmation before including such components in an
785
array. This option causes that question to be suppressed.
786
787
.TP
788
.BR \-f ", " \-\-force
789
Insist that
790
.I mdadm
791
accept the geometry and layout specified without question. Normally
792
.I mdadm
793
will not allow creation of an array with only one device, and will try
794
to create a RAID5 array with one missing drive (as this makes the
795
initial resync work faster). With
796
.BR \-\-force ,
797
.I mdadm
798
will not try to be so clever.
799
800
.TP
801
.BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}"
802
Instruct mdadm how to create the device file if needed, possibly allocating
803
an unused minor number. "md" causes a non-partitionable array
804
to be used (though since Linux 2.6.28, these array devices are in fact
805
partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and
806
later) to be used. "yes" requires the named md device to have
807
a 'standard' format, and the type and minor number will be determined
808
from this. With mdadm 3.0, device creation is normally left up to
809
.I udev
810
so this option is unlikely to be needed.
811
See DEVICE NAMES below.
812
813
The argument can also come immediately after
814
"\-a". e.g. "\-ap".
815
816
If
817
.B \-\-auto
818
is not given on the command line or in the config file, then
819
the default will be
820
.BR \-\-auto=yes .
821
822
If
823
.B \-\-scan
824
is also given, then any
825
.I auto=
826
entries in the config file will override the
827
.B \-\-auto
828
instruction given on the command line.
829
830
For partitionable arrays,
831
.I mdadm
832
will create the device file for the whole array and for the first 4
833
partitions. A different number of partitions can be specified at the
834
end of this option (e.g.
835
.BR \-\-auto=p7 ).
836
If the device name ends with a digit, the partition names add a 'p',
837
and a number, e.g.
838
.IR /dev/md/home1p3 .
839
If there is no trailing digit, then the partition names just have a
840
number added, e.g.
841
.IR /dev/md/scratch3 .
842
843
If the md device name is in a 'standard' format as described in DEVICE
844
NAMES, then it will be created, if necessary, with the appropriate
845
device number based on that name. If the device name is not in one of these
846
formats, then a unused device number will be allocated. The device
847
number will be considered unused if there is no active array for that
848
number, and there is no entry in /dev for that number and with a
849
non-standard name. Names that are not in 'standard' format are only
850
allowed in "/dev/md/".
851
852
This is meaningful with
853
.B \-\-create
854
or
855
.BR \-\-build .
856
857
.ig XX
858
.\".TP
859
.\".BR \-\-symlink = no
860
.\"Normally when
861
.\".B \-\-auto
862
.\"causes
863
.\".I mdadm
864
.\"to create devices in
865
.\".B /dev/md/
866
.\"it will also create symlinks from
867
.\".B /dev/
868
.\"with names starting with
869
.\".B md
870
.\"or
871
.\".BR md_ .
872
.\"Use
873
.\".B \-\-symlink=no
874
.\"to suppress this, or
875
.\".B \-\-symlink=yes
876
.\"to enforce this even if it is suppressing
877
.\".IR mdadm.conf .
878
.\"
879
.XX
880
881
.TP
882
.BR \-a ", " "\-\-add"
883
This option can be used in Grow mode in two cases.
884
885
If the target array is a Linear array, then
886
.B \-\-add
887
can be used to add one or more devices to the array. They
888
are simply catenated on to the end of the array. Once added, the
889
devices cannot be removed.
890
891
If the
892
.B \-\-raid\-disks
893
option is being used to increase the number of devices in an array,
894
then
895
.B \-\-add
896
can be used to add some extra devices to be included in the array.
897
In most cases this is not needed as the extra devices can be added as
898
spares first, and then the number of raid-disks can be changed.
899
However for RAID0, it is not possible to add spares. So to increase
900
the number of devices in a RAID0, it is necessary to set the new
901
number of devices, and to add the new devices, in the same command.
902
903
.SH For assemble:
904
905
.TP
906
.BR \-u ", " \-\-uuid=
907
uuid of array to assemble. Devices which don't have this uuid are
908
excluded
909
910
.TP
911
.BR \-m ", " \-\-super\-minor=
912
Minor number of device that array was created for. Devices which
913
don't have this minor number are excluded. If you create an array as
914
/dev/md1, then all superblocks will contain the minor number 1, even if
915
the array is later assembled as /dev/md2.
916
917
Giving the literal word "dev" for
918
.B \-\-super\-minor
919
will cause
920
.I mdadm
921
to use the minor number of the md device that is being assembled.
922
e.g. when assembling
923
.BR /dev/md0 ,
924
.B \-\-super\-minor=dev
925
will look for super blocks with a minor number of 0.
926
927
.B \-\-super\-minor
928
is only relevant for v0.90 metadata, and should not normally be used.
929
Using
930
.B \-\-uuid
931
is much safer.
932
933
.TP
934
.BR \-N ", " \-\-name=
935
Specify the name of the array to assemble. This must be the name
936
that was specified when creating the array. It must either match
937
the name stored in the superblock exactly, or it must match
938
with the current
939
.I homehost
940
prefixed to the start of the given name.
941
942
.TP
943
.BR \-f ", " \-\-force
944
Assemble the array even if the metadata on some devices appears to be
945
out-of-date. If
946
.I mdadm
947
cannot find enough working devices to start the array, but can find
948
some devices that are recorded as having failed, then it will mark
949
those devices as working so that the array can be started.
950
An array which requires
951
.B \-\-force
952
to be started may contain data corruption. Use it carefully.
953
954
.TP
955
.BR \-R ", " \-\-run
956
Attempt to start the array even if fewer drives were given than were
957
present last time the array was active. Normally if not all the
958
expected drives are found and
959
.B \-\-scan
960
is not used, then the array will be assembled but not started.
961
With
962
.B \-\-run
963
an attempt will be made to start it anyway.
964
965
.TP
966
.B \-\-no\-degraded
967
This is the reverse of
968
.B \-\-run
969
in that it inhibits the startup of array unless all expected drives
970
are present. This is only needed with
971
.B \-\-scan,
972
and can be used if the physical connections to devices are
973
not as reliable as you would like.
974
975
.TP
976
.BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}"
977
See this option under Create and Build options.
978
979
.TP
980
.BR \-b ", " \-\-bitmap=
981
Specify the bitmap file that was given when the array was created. If
982
an array has an
983
.B internal
984
bitmap, there is no need to specify this when assembling the array.
985
986
.TP
987
.BR \-\-backup\-file=
988
If
989
.B \-\-backup\-file
990
was used while reshaping an array (e.g. changing number of devices or
991
chunk size) and the system crashed during the critical section, then the same
992
.B \-\-backup\-file
993
must be presented to
994
.B \-\-assemble
995
to allow possibly corrupted data to be restored, and the reshape
996
to be completed.
997
998
.TP
999
.BR \-\-invalid\-backup
1000
If the file needed for the above option is not available for any
1001
reason an empty file can be given together with this option to
1002
indicate that the backup file is invalid. In this case the data that
1003
was being rearranged at the time of the crash could be irrecoverably
1004
lost, but the rest of the array may still be recoverable. This option
1005
should only be used as a last resort if there is no way to recover the
1006
backup file.
1007
1008
1009
.TP
1010
.BR \-U ", " \-\-update=
1011
Update the superblock on each device while assembling the array. The
1012
argument given to this flag can be one of
1013
.BR sparc2.2 ,
1014
.BR summaries ,
1015
.BR uuid ,
1016
.BR name ,
1017
.BR homehost ,
1018
.BR resync ,
1019
.BR byteorder ,
1020
.BR devicesize ,
1021
.BR no\-bitmap ,
1022
or
1023
.BR super\-minor .
1024
1025
The
1026
.B sparc2.2
1027
option will adjust the superblock of an array what was created on a Sparc
1028
machine running a patched 2.2 Linux kernel. This kernel got the
1029
alignment of part of the superblock wrong. You can use the
1030
.B "\-\-examine \-\-sparc2.2"
1031
option to
1032
.I mdadm
1033
to see what effect this would have.
1034
1035
The
1036
.B super\-minor
1037
option will update the
1038
.B "preferred minor"
1039
field on each superblock to match the minor number of the array being
1040
assembled.
1041
This can be useful if
1042
.B \-\-examine
1043
reports a different "Preferred Minor" to
1044
.BR \-\-detail .
1045
In some cases this update will be performed automatically
1046
by the kernel driver. In particular the update happens automatically
1047
at the first write to an array with redundancy (RAID level 1 or
1048
greater) on a 2.6 (or later) kernel.
1049
1050
The
1051
.B uuid
1052
option will change the uuid of the array. If a UUID is given with the
1053
.B \-\-uuid
1054
option that UUID will be used as a new UUID and will
1055
.B NOT
1056
be used to help identify the devices in the array.
1057
If no
1058
.B \-\-uuid
1059
is given, a random UUID is chosen.
1060
1061
The
1062
.B name
1063
option will change the
1064
.I name
1065
of the array as stored in the superblock. This is only supported for
1066
version-1 superblocks.
1067
1068
The
1069
.B homehost
1070
option will change the
1071
.I homehost
1072
as recorded in the superblock. For version-0 superblocks, this is the
1073
same as updating the UUID.
1074
For version-1 superblocks, this involves updating the name.
1075
1076
The
1077
.B resync
1078
option will cause the array to be marked
1079
.I dirty
1080
meaning that any redundancy in the array (e.g. parity for RAID5,
1081
copies for RAID1) may be incorrect. This will cause the RAID system
1082
to perform a "resync" pass to make sure that all redundant information
1083
is correct.
1084
1085
The
1086
.B byteorder
1087
option allows arrays to be moved between machines with different
1088
byte-order.
1089
When assembling such an array for the first time after a move, giving
1090
.B "\-\-update=byteorder"
1091
will cause
1092
.I mdadm
1093
to expect superblocks to have their byteorder reversed, and will
1094
correct that order before assembling the array. This is only valid
1095
with original (Version 0.90) superblocks.
1096
1097
The
1098
.B summaries
1099
option will correct the summaries in the superblock. That is the
1100
counts of total, working, active, failed, and spare devices.
1101
1102
The
1103
.B devicesize
1104
option will rarely be of use. It applies to version 1.1 and 1.2 metadata
1105
only (where the metadata is at the start of the device) and is only
1106
useful when the component device has changed size (typically become
1107
larger). The version 1 metadata records the amount of the device that
1108
can be used to store data, so if a device in a version 1.1 or 1.2
1109
array becomes larger, the metadata will still be visible, but the
1110
extra space will not. In this case it might be useful to assemble the
1111
array with
1112
.BR \-\-update=devicesize .
1113
This will cause
1114
.I mdadm
1115
to determine the maximum usable amount of space on each device and
1116
update the relevant field in the metadata.
1117
1118
The
1119
.B no\-bitmap
1120
option can be used when an array has an internal bitmap which is
1121
corrupt in some way so that assembling the array normally fails. It
1122
will cause any internal bitmap to be ignored.
1123
1124
.TP
1125
.BR \-\-freeze\-reshape
1126
Option is intended to be used in start-up scripts during initrd boot phase.
1127
When array under reshape is assembled during initrd phase, this option
1128
stops reshape after reshape critical section is being restored. This happens
1129
before file system pivot operation and avoids loss of file system context.
1130
Losing file system context would cause reshape to be broken.
1131
1132
Reshape can be continued later using the
1133
.B \-\-continue
1134
option for the grow command.
1135
1136
.SH For Manage mode:
1137
1138
.TP
1139
.BR \-t ", " \-\-test
1140
Unless a more serious error occurred,
1141
.I mdadm
1142
will exit with a status of 2 if no changes were made to the array and
1143
0 if at least one change was made.
1144
This can be useful when an indirect specifier such as
1145
.BR missing ,
1146
.B detached
1147
or
1148
.B faulty
1149
is used in requesting an operation on the array.
1150
.B \-\-test
1151
will report failure if these specifiers didn't find any match.
1152
1153
.TP
1154
.BR \-a ", " \-\-add
1155
hot-add listed devices.
1156
If a device appears to have recently been part of the array
1157
(possibly it failed or was removed) the device is re\-added as describe
1158
in the next point.
1159
If that fails or the device was never part of the array, the device is
1160
added as a hot-spare.
1161
If the array is degraded, it will immediately start to rebuild data
1162
onto that spare.
1163
1164
Note that this and the following options are only meaningful on array
1165
with redundancy. They don't apply to RAID0 or Linear.
1166
1167
.TP
1168
.BR \-\-re\-add
1169
re\-add a device that was previous removed from an array.
1170
If the metadata on the device reports that it is a member of the
1171
array, and the slot that it used is still vacant, then the device will
1172
be added back to the array in the same position. This will normally
1173
cause the data for that device to be recovered. However based on the
1174
event count on the device, the recovery may only require sections that
1175
are flagged a write-intent bitmap to be recovered or may not require
1176
any recovery at all.
1177
1178
When used on an array that has no metadata (i.e. it was built with
1179
.BR \-\-build)
1180
it will be assumed that bitmap-based recovery is enough to make the
1181
device fully consistent with the array.
1182
1183
When
1184
.B \-\-re\-add
1185
can be accompanied by
1186
.BR \-\-update=devicesize .
1187
See the description of this option when used in Assemble mode for an
1188
explanation of its use.
1189
1190
If the device name given is
1191
.B missing
1192
then mdadm will try to find any device that looks like it should be
1193
part of the array but isn't and will try to re\-add all such devices.
1194
1195
.TP
1196
.BR \-r ", " \-\-remove
1197
remove listed devices. They must not be active. i.e. they should
1198
be failed or spare devices. As well as the name of a device file
1199
(e.g.
1200
.BR /dev/sda1 )
1201
the words
1202
.B failed
1203
and
1204
.B detached
1205
can be given to
1206
.BR \-\-remove .
1207
The first causes all failed device to be removed. The second causes
1208
any device which is no longer connected to the system (i.e an 'open'
1209
returns
1210
.BR ENXIO )
1211
to be removed. This will only succeed for devices that are spares or
1212
have already been marked as failed.
1213
1214
.TP
1215
.BR \-f ", " \-\-fail
1216
mark listed devices as faulty.
1217
As well as the name of a device file, the word
1218
.B detached
1219
can be given. This will cause any device that has been detached from
1220
the system to be marked as failed. It can then be removed.
1221
1222
.TP
1223
.BR \-\-set\-faulty
1224
same as
1225
.BR \-\-fail .
1226
1227
.TP
1228
.BR \-\-write\-mostly
1229
Subsequent devices that are added or re\-added will have the 'write-mostly'
1230
flag set. This is only valid for RAID1 and means that the 'md' driver
1231
will avoid reading from these devices if possible.
1232
.TP
1233
.BR \-\-readwrite
1234
Subsequent devices that are added or re\-added will have the 'write-mostly'
1235
flag cleared.
1236
1237
.P
1238
Each of these options requires that the first device listed is the array
1239
to be acted upon, and the remainder are component devices to be added,
1240
removed, marked as faulty, etc. Several different operations can be
1241
specified for different devices, e.g.
1242
.in +5
1243
mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1
1244
.in -5
1245
Each operation applies to all devices listed until the next
1246
operation.
1247
1248
If an array is using a write-intent bitmap, then devices which have
1249
been removed can be re\-added in a way that avoids a full
1250
reconstruction but instead just updates the blocks that have changed
1251
since the device was removed. For arrays with persistent metadata
1252
(superblocks) this is done automatically. For arrays created with
1253
.B \-\-build
1254
mdadm needs to be told that this device we removed recently with
1255
.BR \-\-re\-add .
1256
1257
Devices can only be removed from an array if they are not in active
1258
use, i.e. that must be spares or failed devices. To remove an active
1259
device, it must first be marked as
1260
.B faulty.
1261
1262
.SH For Misc mode:
1263
1264
.TP
1265
.BR \-Q ", " \-\-query
1266
Examine a device to see
1267
(1) if it is an md device and (2) if it is a component of an md
1268
array.
1269
Information about what is discovered is presented.
1270
1271
.TP
1272
.BR \-D ", " \-\-detail
1273
Print details of one or more md devices.
1274
1275
.TP
1276
.BR \-\-detail\-platform
1277
Print details of the platform's RAID capabilities (firmware / hardware
1278
topology) for a given metadata format.
1279
1280
.TP
1281
.BR \-Y ", " \-\-export
1282
When used with
1283
.B \-\-detail
1284
or
1285
.BR \-\-examine ,
1286
output will be formatted as
1287
.B key=value
1288
pairs for easy import into the environment.
1289
1290
.TP
1291
.BR \-E ", " \-\-examine
1292
Print contents of the metadata stored on the named device(s).
1293
Note the contrast between
1294
.B \-\-examine
1295
and
1296
.BR \-\-detail .
1297
.B \-\-examine
1298
applies to devices which are components of an array, while
1299
.B \-\-detail
1300
applies to a whole array which is currently active.
1301
.TP
1302
.B \-\-sparc2.2
1303
If an array was created on a SPARC machine with a 2.2 Linux kernel
1304
patched with RAID support, the superblock will have been created
1305
incorrectly, or at least incompatibly with 2.4 and later kernels.
1306
Using the
1307
.B \-\-sparc2.2
1308
flag with
1309
.B \-\-examine
1310
will fix the superblock before displaying it. If this appears to do
1311
the right thing, then the array can be successfully assembled using
1312
.BR "\-\-assemble \-\-update=sparc2.2" .
1313
1314
.TP
1315
.BR \-X ", " \-\-examine\-bitmap
1316
Report information about a bitmap file.
1317
The argument is either an external bitmap file or an array component
1318
in case of an internal bitmap. Note that running this on an array
1319
device (e.g.
1320
.BR /dev/md0 )
1321
does not report the bitmap for that array.
1322
1323
.TP
1324
.BR \-R ", " \-\-run
1325
start a partially assembled array. If
1326
.B \-\-assemble
1327
did not find enough devices to fully start the array, it might leaving
1328
it partially assembled. If you wish, you can then use
1329
.B \-\-run
1330
to start the array in degraded mode.
1331
1332
.TP
1333
.BR \-S ", " \-\-stop
1334
deactivate array, releasing all resources.
1335
1336
.TP
1337
.BR \-o ", " \-\-readonly
1338
mark array as readonly.
1339
1340
.TP
1341
.BR \-w ", " \-\-readwrite
1342
mark array as readwrite.
1343
1344
.TP
1345
.B \-\-zero\-superblock
1346
If the device contains a valid md superblock, the block is
1347
overwritten with zeros. With
1348
.B \-\-force
1349
the block where the superblock would be is overwritten even if it
1350
doesn't appear to be valid.
1351
1352
.TP
1353
.B \-\-kill\-subarray=
1354
If the device is a container and the argument to \-\-kill\-subarray
1355
specifies an inactive subarray in the container, then the subarray is
1356
deleted. Deleting all subarrays will leave an 'empty-container' or
1357
spare superblock on the drives. See \-\-zero\-superblock for completely
1358
removing a superblock. Note that some formats depend on the subarray
1359
index for generating a UUID, this command will fail if it would change
1360
the UUID of an active subarray.
1361
1362
.TP
1363
.B \-\-update\-subarray=
1364
If the device is a container and the argument to \-\-update\-subarray
1365
specifies a subarray in the container, then attempt to update the given
1366
superblock field in the subarray. See below in
1367
.B MISC MODE
1368
for details.
1369
1370
.TP
1371
.BR \-t ", " \-\-test
1372
When used with
1373
.BR \-\-detail ,
1374
the exit status of
1375
.I mdadm
1376
is set to reflect the status of the device. See below in
1377
.B MISC MODE
1378
for details.
1379
1380
.TP
1381
.BR \-W ", " \-\-wait
1382
For each md device given, wait for any resync, recovery, or reshape
1383
activity to finish before returning.
1384
.I mdadm
1385
will return with success if it actually waited for every device
1386
listed, otherwise it will return failure.
1387
1388
.TP
1389
.BR \-\-wait\-clean
1390
For each md device given, or each device in /proc/mdstat if
1391
.B \-\-scan
1392
is given, arrange for the array to be marked clean as soon as possible.
1393
.I mdadm
1394
will return with success if the array uses external metadata and we
1395
successfully waited. For native arrays this returns immediately as the
1396
kernel handles dirty-clean transitions at shutdown. No action is taken
1397
if safe-mode handling is disabled.
1398
1399
.SH For Incremental Assembly mode:
1400
.TP
1401
.BR \-\-rebuild\-map ", " \-r
1402
Rebuild the map file
1403
.RB ( /var/run/mdadm/map )
1404
that
1405
.I mdadm
1406
uses to help track which arrays are currently being assembled.
1407
1408
.TP
1409
.BR \-\-run ", " \-R
1410
Run any array assembled as soon as a minimal number of devices are
1411
available, rather than waiting until all expected devices are present.
1412
1413
.TP
1414
.BR \-\-scan ", " \-s
1415
Only meaningful with
1416
.B \-R
1417
this will scan the
1418
.B map
1419
file for arrays that are being incrementally assembled and will try to
1420
start any that are not already started. If any such array is listed
1421
in
1422
.B mdadm.conf
1423
as requiring an external bitmap, that bitmap will be attached first.
1424
1425
.TP
1426
.BR \-\-fail ", " \-f
1427
This allows the hot-plug system to remove devices that have fully disappeared
1428
from the kernel. It will first fail and then remove the device from any
1429
array it belongs to.
1430
The device name given should be a kernel device name such as "sda",
1431
not a name in
1432
.IR /dev .
1433
1434
.TP
1435
.BR \-\-path=
1436
Only used with \-\-fail. The 'path' given will be recorded so that if
1437
a new device appears at the same location it can be automatically
1438
added to the same array. This allows the failed device to be
1439
automatically replaced by a new device without metadata if it appears
1440
at specified path. This option is normally only set by a
1441
.I udev
1442
script.
1443
1444
.SH For Monitor mode:
1445
.TP
1446
.BR \-m ", " \-\-mail
1447
Give a mail address to send alerts to.
1448
1449
.TP
1450
.BR \-p ", " \-\-program ", " \-\-alert
1451
Give a program to be run whenever an event is detected.
1452
1453
.TP
1454
.BR \-y ", " \-\-syslog
1455
Cause all events to be reported through 'syslog'. The messages have
1456
facility of 'daemon' and varying priorities.
1457
1458
.TP
1459
.BR \-d ", " \-\-delay
1460
Give a delay in seconds.
1461
.I mdadm
1462
polls the md arrays and then waits this many seconds before polling
1463
again. The default is 60 seconds. Since 2.6.16, there is no need to
1464
reduce this as the kernel alerts
1465
.I mdadm
1466
immediately when there is any change.
1467
1468
.TP
1469
.BR \-r ", " \-\-increment
1470
Give a percentage increment.
1471
.I mdadm
1472
will generate RebuildNN events with the given percentage increment.
1473
1474
.TP
1475
.BR \-f ", " \-\-daemonise
1476
Tell
1477
.I mdadm
1478
to run as a background daemon if it decides to monitor anything. This
1479
causes it to fork and run in the child, and to disconnect from the
1480
terminal. The process id of the child is written to stdout.
1481
This is useful with
1482
.B \-\-scan
1483
which will only continue monitoring if a mail address or alert program
1484
is found in the config file.
1485
1486
.TP
1487
.BR \-i ", " \-\-pid\-file
1488
When
1489
.I mdadm
1490
is running in daemon mode, write the pid of the daemon process to
1491
the specified file, instead of printing it on standard output.
1492
1493
.TP
1494
.BR \-1 ", " \-\-oneshot
1495
Check arrays only once. This will generate
1496
.B NewArray
1497
events and more significantly
1498
.B DegradedArray
1499
and
1500
.B SparesMissing
1501
events. Running
1502
.in +5
1503
.B " mdadm \-\-monitor \-\-scan \-1"
1504
.in -5
1505
from a cron script will ensure regular notification of any degraded arrays.
1506
1507
.TP
1508
.BR \-t ", " \-\-test
1509
Generate a
1510
.B TestMessage
1511
alert for every array found at startup. This alert gets mailed and
1512
passed to the alert program. This can be used for testing that alert
1513
message do get through successfully.
1514
1515
.TP
1516
.BR \-\-no\-sharing
1517
This inhibits the functionality for moving spares between arrays.
1518
Only one monitoring process started with
1519
.B \-\-scan
1520
but without this flag is allowed, otherwise the two could interfere
1521
with each other.
1522
1523
.SH ASSEMBLE MODE
1524
1525
.HP 12
1526
Usage:
1527
.B mdadm \-\-assemble
1528
.I md-device options-and-component-devices...
1529
.HP 12
1530
Usage:
1531
.B mdadm \-\-assemble \-\-scan
1532
.I md-devices-and-options...
1533
.HP 12
1534
Usage:
1535
.B mdadm \-\-assemble \-\-scan
1536
.I options...
1537
1538
.PP
1539
This usage assembles one or more RAID arrays from pre-existing components.
1540
For each array, mdadm needs to know the md device, the identity of the
1541
array, and a number of component-devices. These can be found in a number of ways.
1542
1543
In the first usage example (without the
1544
.BR \-\-scan )
1545
the first device given is the md device.
1546
In the second usage example, all devices listed are treated as md
1547
devices and assembly is attempted.
1548
In the third (where no devices are listed) all md devices that are
1549
listed in the configuration file are assembled. If no arrays are
1550
described by the configuration file, then any arrays that
1551
can be found on unused devices will be assembled.
1552
1553
If precisely one device is listed, but
1554
.B \-\-scan
1555
is not given, then
1556
.I mdadm
1557
acts as though
1558
.B \-\-scan
1559
was given and identity information is extracted from the configuration file.
1560
1561
The identity can be given with the
1562
.B \-\-uuid
1563
option, the
1564
.B \-\-name
1565
option, or the
1566
.B \-\-super\-minor
1567
option, will be taken from the md-device record in the config file, or
1568
will be taken from the super block of the first component-device
1569
listed on the command line.
1570
1571
Devices can be given on the
1572
.B \-\-assemble
1573
command line or in the config file. Only devices which have an md
1574
superblock which contains the right identity will be considered for
1575
any array.
1576
1577
The config file is only used if explicitly named with
1578
.B \-\-config
1579
or requested with (a possibly implicit)
1580
.BR \-\-scan .
1581
In the later case,
1582
.B /etc/mdadm.conf
1583
or
1584
.B /etc/mdadm/mdadm.conf
1585
is used.
1586
1587
If
1588
.B \-\-scan
1589
is not given, then the config file will only be used to find the
1590
identity of md arrays.
1591
1592
Normally the array will be started after it is assembled. However if
1593
.B \-\-scan
1594
is not given and not all expected drives were listed, then the array
1595
is not started (to guard against usage errors). To insist that the
1596
array be started in this case (as may work for RAID1, 4, 5, 6, or 10),
1597
give the
1598
.B \-\-run
1599
flag.
1600
1601
If
1602
.I udev
1603
is active,
1604
.I mdadm
1605
does not create any entries in
1606
.B /dev
1607
but leaves that to
1608
.IR udev .
1609
It does record information in
1610
.B /var/run/mdadm/map
1611
which will allow
1612
.I udev
1613
to choose the correct name.
1614
1615
If
1616
.I mdadm
1617
detects that udev is not configured, it will create the devices in
1618
.B /dev
1619
itself.
1620
1621
In Linux kernels prior to version 2.6.28 there were two distinctly
1622
different types of md devices that could be created: one that could be
1623
partitioned using standard partitioning tools and one that could not.
1624
Since 2.6.28 that distinction is no longer relevant as both type of
1625
devices can be partitioned.
1626
.I mdadm
1627
will normally create the type that originally could not be partitioned
1628
as it has a well defined major number (9).
1629
1630
Prior to 2.6.28, it is important that mdadm chooses the correct type
1631
of array device to use. This can be controlled with the
1632
.B \-\-auto
1633
option. In particular, a value of "mdp" or "part" or "p" tells mdadm
1634
to use a partitionable device rather than the default.
1635
1636
In the no-udev case, the value given to
1637
.B \-\-auto
1638
can be suffixed by a number. This tells
1639
.I mdadm
1640
to create that number of partition devices rather than the default of 4.
1641
1642
The value given to
1643
.B \-\-auto
1644
can also be given in the configuration file as a word starting
1645
.B auto=
1646
on the ARRAY line for the relevant array.
1647
1648
.SS Auto Assembly
1649
When
1650
.B \-\-assemble
1651
is used with
1652
.B \-\-scan
1653
and no devices are listed,
1654
.I mdadm
1655
will first attempt to assemble all the arrays listed in the config
1656
file.
1657
1658
If no arrays are listed in the config (other than those marked
1659
.BR <ignore> )
1660
it will look through the available devices for possible arrays and
1661
will try to assemble anything that it finds. Arrays which are tagged
1662
as belonging to the given homehost will be assembled and started
1663
normally. Arrays which do not obviously belong to this host are given
1664
names that are expected not to conflict with anything local, and are
1665
started "read-auto" so that nothing is written to any device until the
1666
array is written to. i.e. automatic resync etc is delayed.
1667
1668
If
1669
.I mdadm
1670
finds a consistent set of devices that look like they should comprise
1671
an array, and if the superblock is tagged as belonging to the given
1672
home host, it will automatically choose a device name and try to
1673
assemble the array. If the array uses version-0.90 metadata, then the
1674
.B minor
1675
number as recorded in the superblock is used to create a name in
1676
.B /dev/md/
1677
so for example
1678
.BR /dev/md/3 .
1679
If the array uses version-1 metadata, then the
1680
.B name
1681
from the superblock is used to similarly create a name in
1682
.B /dev/md/
1683
(the name will have any 'host' prefix stripped first).
1684
1685
This behaviour can be modified by the
1686
.I AUTO
1687
line in the
1688
.I mdadm.conf
1689
configuration file. This line can indicate that specific metadata
1690
type should, or should not, be automatically assembled. If an array
1691
is found which is not listed in
1692
.I mdadm.conf
1693
and has a metadata format that is denied by the
1694
.I AUTO
1695
line, then it will not be assembled.
1696
The
1697
.I AUTO
1698
line can also request that all arrays identified as being for this
1699
homehost should be assembled regardless of their metadata type.
1700
See
1701
.IR mdadm.conf (5)
1702
for further details.
1703
1704
Note: Auto assembly cannot be used for assembling and activating some
1705
arrays which are undergoing reshape. In particular as the
1706
.B backup\-file
1707
cannot be given, any reshape which requires a backup-file to continue
1708
cannot be started by auto assembly. An array which is growing to more
1709
devices and has passed the critical section can be assembled using
1710
auto-assembly.
1711
1712
.SH BUILD MODE
1713
1714
.HP 12
1715
Usage:
1716
.B mdadm \-\-build
1717
.I md-device
1718
.BI \-\-chunk= X
1719
.BI \-\-level= Y
1720
.BI \-\-raid\-devices= Z
1721
.I devices
1722
1723
.PP
1724
This usage is similar to
1725
.BR \-\-create .
1726
The difference is that it creates an array without a superblock. With
1727
these arrays there is no difference between initially creating the array and
1728
subsequently assembling the array, except that hopefully there is useful
1729
data there in the second case.
1730
1731
The level may raid0, linear, raid1, raid10, multipath, or faulty, or
1732
one of their synonyms. All devices must be listed and the array will
1733
be started once complete. It will often be appropriate to use
1734
.B \-\-assume\-clean
1735
with levels raid1 or raid10.
1736
1737
.SH CREATE MODE
1738
1739
.HP 12
1740
Usage:
1741
.B mdadm \-\-create
1742
.I md-device
1743
.BI \-\-chunk= X
1744
.BI \-\-level= Y
1745
.br
1746
.BI \-\-raid\-devices= Z
1747
.I devices
1748
1749
.PP
1750
This usage will initialise a new md array, associate some devices with
1751
it, and activate the array.
1752
1753
The named device will normally not exist when
1754
.I "mdadm \-\-create"
1755
is run, but will be created by
1756
.I udev
1757
once the array becomes active.
1758
1759
As devices are added, they are checked to see if they contain RAID
1760
superblocks or filesystems. They are also checked to see if the variance in
1761
device size exceeds 1%.
1762
1763
If any discrepancy is found, the array will not automatically be run, though
1764
the presence of a
1765
.B \-\-run
1766
can override this caution.
1767
1768
To create a "degraded" array in which some devices are missing, simply
1769
give the word "\fBmissing\fP"
1770
in place of a device name. This will cause
1771
.I mdadm
1772
to leave the corresponding slot in the array empty.
1773
For a RAID4 or RAID5 array at most one slot can be
1774
"\fBmissing\fP"; for a RAID6 array at most two slots.
1775
For a RAID1 array, only one real device needs to be given. All of the
1776
others can be
1777
"\fBmissing\fP".
1778
1779
When creating a RAID5 array,
1780
.I mdadm
1781
will automatically create a degraded array with an extra spare drive.
1782
This is because building the spare into a degraded array is in general
1783
faster than resyncing the parity on a non-degraded, but not clean,
1784
array. This feature can be overridden with the
1785
.B \-\-force
1786
option.
1787
1788
When creating an array with version-1 metadata a name for the array is
1789
required.
1790
If this is not given with the
1791
.B \-\-name
1792
option,
1793
.I mdadm
1794
will choose a name based on the last component of the name of the
1795
device being created. So if
1796
.B /dev/md3
1797
is being created, then the name
1798
.B 3
1799
will be chosen.
1800
If
1801
.B /dev/md/home
1802
is being created, then the name
1803
.B home
1804
will be used.
1805
1806
When creating a partition based array, using
1807
.I mdadm
1808
with version-1.x metadata, the partition type should be set to
1809
.B 0xDA
1810
(non fs-data). This type selection allows for greater precision since
1811
using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)],
1812
might create problems in the event of array recovery through a live cdrom.
1813
1814
A new array will normally get a randomly assigned 128bit UUID which is
1815
very likely to be unique. If you have a specific need, you can choose
1816
a UUID for the array by giving the
1817
.B \-\-uuid=
1818
option. Be warned that creating two arrays with the same UUID is a
1819
recipe for disaster. Also, using
1820
.B \-\-uuid=
1821
when creating a v0.90 array will silently override any
1822
.B \-\-homehost=
1823
setting.
1824
.\"If the
1825
.\".B \-\-size
1826
.\"option is given, it is not necessary to list any component-devices in this command.
1827
.\"They can be added later, before a
1828
.\".B \-\-run.
1829
.\"If no
1830
.\".B \-\-size
1831
.\"is given, the apparent size of the smallest drive given is used.
1832
1833
When creating an array within a
1834
.B CONTAINER
1835
.I mdadm
1836
can be given either the list of devices to use, or simply the name of
1837
the container. The former case gives control over which devices in
1838
the container will be used for the array. The latter case allows
1839
.I mdadm
1840
to automatically choose which devices to use based on how much spare
1841
space is available.
1842
1843
The General Management options that are valid with
1844
.B \-\-create
1845
are:
1846
.TP
1847
.B \-\-run
1848
insist on running the array even if some devices look like they might
1849
be in use.
1850
1851
.TP
1852
.B \-\-readonly
1853
start the array readonly \(em not supported yet.
1854
1855
.SH MANAGE MODE
1856
.HP 12
1857
Usage:
1858
.B mdadm
1859
.I device
1860
.I options... devices...
1861
.PP
1862
1863
This usage will allow individual devices in an array to be failed,
1864
removed or added. It is possible to perform multiple operations with
1865
on command. For example:
1866
.br
1867
.B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1"
1868
.br
1869
will firstly mark
1870
.B /dev/hda1
1871
as faulty in
1872
.B /dev/md0
1873
and will then remove it from the array and finally add it back
1874
in as a spare. However only one md array can be affected by a single
1875
command.
1876
1877
When a device is added to an active array, mdadm checks to see if it
1878
has metadata on it which suggests that it was recently a member of the
1879
array. If it does, it tries to "re\-add" the device. If there have
1880
been no changes since the device was removed, or if the array has a
1881
write-intent bitmap which has recorded whatever changes there were,
1882
then the device will immediately become a full member of the array and
1883
those differences recorded in the bitmap will be resolved.
1884
1885
.SH MISC MODE
1886
.HP 12
1887
Usage:
1888
.B mdadm
1889
.I options ...
1890
.I devices ...
1891
.PP
1892
1893
MISC mode includes a number of distinct operations that
1894
operate on distinct devices. The operations are:
1895
.TP
1896
.B \-\-query
1897
The device is examined to see if it is
1898
(1) an active md array, or
1899
(2) a component of an md array.
1900
The information discovered is reported.
1901
1902
.TP
1903
.B \-\-detail
1904
The device should be an active md device.
1905
.B mdadm
1906
will display a detailed description of the array.
1907
.B \-\-brief
1908
or
1909
.B \-\-scan
1910
will cause the output to be less detailed and the format to be
1911
suitable for inclusion in
1912
.BR mdadm.conf .
1913
The exit status of
1914
.I mdadm
1915
will normally be 0 unless
1916
.I mdadm
1917
failed to get useful information about the device(s); however, if the
1918
.B \-\-test
1919
option is given, then the exit status will be:
1920
.RS
1921
.TP
1922
0
1923
The array is functioning normally.
1924
.TP
1925
1
1926
The array has at least one failed device.
1927
.TP
1928
2
1929
The array has multiple failed devices such that it is unusable.
1930
.TP
1931
4
1932
There was an error while trying to get information about the device.
1933
.RE
1934
1935
.TP
1936
.B \-\-detail\-platform
1937
Print detail of the platform's RAID capabilities (firmware / hardware
1938
topology). If the metadata is specified with
1939
.B \-e
1940
or
1941
.B \-\-metadata=
1942
then the return status will be:
1943
.RS
1944
.TP
1945
0
1946
metadata successfully enumerated its platform components on this system
1947
.TP
1948
1
1949
metadata is platform independent
1950
.TP
1951
2
1952
metadata failed to find its platform components on this system
1953
.RE
1954
1955
.TP
1956
.B \-\-update\-subarray=
1957
If the device is a container and the argument to \-\-update\-subarray
1958
specifies a subarray in the container, then attempt to update the given
1959
superblock field in the subarray. Similar to updating an array in
1960
"assemble" mode, the field to update is selected by
1961
.B \-U
1962
or
1963
.B \-\-update=
1964
option. Currently only
1965
.B name
1966
is supported.
1967
1968
The
1969
.B name
1970
option updates the subarray name in the metadata, it may not affect the
1971
device node name or the device node symlink until the subarray is
1972
re\-assembled. If updating
1973
.B name
1974
would change the UUID of an active subarray this operation is blocked,
1975
and the command will end in an error.
1976
1977
.TP
1978
.B \-\-examine
1979
The device should be a component of an md array.
1980
.I mdadm
1981
will read the md superblock of the device and display the contents.
1982
If
1983
.B \-\-brief
1984
or
1985
.B \-\-scan
1986
is given, then multiple devices that are components of the one array
1987
are grouped together and reported in a single entry suitable
1988
for inclusion in
1989
.BR mdadm.conf .
1990
1991
Having
1992
.B \-\-scan
1993
without listing any devices will cause all devices listed in the
1994
config file to be examined.
1995
1996
.TP
1997
.B \-\-stop
1998
The devices should be active md arrays which will be deactivated, as
1999
long as they are not currently in use.
2000
2001
.TP
2002
.B \-\-run
2003
This will fully activate a partially assembled md array.
2004
2005
.TP
2006
.B \-\-readonly
2007
This will mark an active array as read-only, providing that it is
2008
not currently being used.
2009
2010
.TP
2011
.B \-\-readwrite
2012
This will change a
2013
.B readonly
2014
array back to being read/write.
2015
2016
.TP
2017
.B \-\-scan
2018
For all operations except
2019
.BR \-\-examine ,
2020
.B \-\-scan
2021
will cause the operation to be applied to all arrays listed in
2022
.BR /proc/mdstat .
2023
For
2024
.BR \-\-examine,
2025
.B \-\-scan
2026
causes all devices listed in the config file to be examined.
2027
2028
.TP
2029
.BR \-b ", " \-\-brief
2030
Be less verbose. This is used with
2031
.B \-\-detail
2032
and
2033
.BR \-\-examine .
2034
Using
2035
.B \-\-brief
2036
with
2037
.B \-\-verbose
2038
gives an intermediate level of verbosity.
2039
2040
.SH MONITOR MODE
2041
2042
.HP 12
2043
Usage:
2044
.B mdadm \-\-monitor
2045
.I options... devices...
2046
2047
.PP
2048
This usage causes
2049
.I mdadm
2050
to periodically poll a number of md arrays and to report on any events
2051
noticed.
2052
.I mdadm
2053
will never exit once it decides that there are arrays to be checked,
2054
so it should normally be run in the background.
2055
2056
As well as reporting events,
2057
.I mdadm
2058
may move a spare drive from one array to another if they are in the
2059
same
2060
.B spare-group
2061
or
2062
.B domain
2063
and if the destination array has a failed drive but no spares.
2064
2065
If any devices are listed on the command line,
2066
.I mdadm
2067
will only monitor those devices. Otherwise all arrays listed in the
2068
configuration file will be monitored. Further, if
2069
.B \-\-scan
2070
is given, then any other md devices that appear in
2071
.B /proc/mdstat
2072
will also be monitored.
2073
2074
The result of monitoring the arrays is the generation of events.
2075
These events are passed to a separate program (if specified) and may
2076
be mailed to a given E-mail address.
2077
2078
When passing events to a program, the program is run once for each event,
2079
and is given 2 or 3 command-line arguments: the first is the
2080
name of the event (see below), the second is the name of the
2081
md device which is affected, and the third is the name of a related
2082
device if relevant (such as a component device that has failed).
2083
2084
If
2085
.B \-\-scan
2086
is given, then a program or an E-mail address must be specified on the
2087
command line or in the config file. If neither are available, then
2088
.I mdadm
2089
will not monitor anything.
2090
Without
2091
.B \-\-scan,
2092
.I mdadm
2093
will continue monitoring as long as something was found to monitor. If
2094
no program or email is given, then each event is reported to
2095
.BR stdout .
2096
2097
The different events are:
2098
2099
.RS 4
2100
.TP
2101
.B DeviceDisappeared
2102
An md array which previously was configured appears to no longer be
2103
configured. (syslog priority: Critical)
2104
2105
If
2106
.I mdadm
2107
was told to monitor an array which is RAID0 or Linear, then it will
2108
report
2109
.B DeviceDisappeared
2110
with the extra information
2111
.BR Wrong-Level .
2112
This is because RAID0 and Linear do not support the device-failed,
2113
hot-spare and resync operations which are monitored.
2114
2115
.TP
2116
.B RebuildStarted
2117
An md array started reconstruction. (syslog priority: Warning)
2118
2119
.TP
2120
.BI Rebuild NN
2121
Where
2122
.I NN
2123
is a two-digit number (ie. 05, 48). This indicates that rebuild
2124
has passed that many percent of the total. The events are generated
2125
with fixed increment since 0. Increment size may be specified with
2126
a commandline option (default is 20). (syslog priority: Warning)
2127
2128
.TP
2129
.B RebuildFinished
2130
An md array that was rebuilding, isn't any more, either because it
2131
finished normally or was aborted. (syslog priority: Warning)
2132
2133
.TP
2134
.B Fail
2135
An active component device of an array has been marked as
2136
faulty. (syslog priority: Critical)
2137
2138
.TP
2139
.B FailSpare
2140
A spare component device which was being rebuilt to replace a faulty
2141
device has failed. (syslog priority: Critical)
2142
2143
.TP
2144
.B SpareActive
2145
A spare component device which was being rebuilt to replace a faulty
2146
device has been successfully rebuilt and has been made active.
2147
(syslog priority: Info)
2148
2149
.TP
2150
.B NewArray
2151
A new md array has been detected in the
2152
.B /proc/mdstat
2153
file. (syslog priority: Info)
2154
2155
.TP
2156
.B DegradedArray
2157
A newly noticed array appears to be degraded. This message is not
2158
generated when
2159
.I mdadm
2160
notices a drive failure which causes degradation, but only when
2161
.I mdadm
2162
notices that an array is degraded when it first sees the array.
2163
(syslog priority: Critical)
2164
2165
.TP
2166
.B MoveSpare
2167
A spare drive has been moved from one array in a
2168
.B spare-group
2169
or
2170
.B domain
2171
to another to allow a failed drive to be replaced.
2172
(syslog priority: Info)
2173
2174
.TP
2175
.B SparesMissing
2176
If
2177
.I mdadm
2178
has been told, via the config file, that an array should have a certain
2179
number of spare devices, and
2180
.I mdadm
2181
detects that it has fewer than this number when it first sees the
2182
array, it will report a
2183
.B SparesMissing
2184
message.
2185
(syslog priority: Warning)
2186
2187
.TP
2188
.B TestMessage
2189
An array was found at startup, and the
2190
.B \-\-test
2191
flag was given.
2192
(syslog priority: Info)
2193
.RE
2194
2195
Only
2196
.B Fail,
2197
.B FailSpare,
2198
.B DegradedArray,
2199
.B SparesMissing
2200
and
2201
.B TestMessage
2202
cause Email to be sent. All events cause the program to be run.
2203
The program is run with two or three arguments: the event
2204
name, the array device and possibly a second device.
2205
2206
Each event has an associated array device (e.g.
2207
.BR /dev/md1 )
2208
and possibly a second device. For
2209
.BR Fail ,
2210
.BR FailSpare ,
2211
and
2212
.B SpareActive
2213
the second device is the relevant component device.
2214
For
2215
.B MoveSpare
2216
the second device is the array that the spare was moved from.
2217
2218
For
2219
.I mdadm
2220
to move spares from one array to another, the different arrays need to
2221
be labeled with the same
2222
.B spare-group
2223
or the spares must be allowed to migrate through matching POLICY domains
2224
in the configuration file. The
2225
.B spare-group
2226
name can be any string; it is only necessary that different spare
2227
groups use different names.
2228
2229
When
2230
.I mdadm
2231
detects that an array in a spare group has fewer active
2232
devices than necessary for the complete array, and has no spare
2233
devices, it will look for another array in the same spare group that
2234
has a full complement of working drive and a spare. It will then
2235
attempt to remove the spare from the second drive and add it to the
2236
first.
2237
If the removal succeeds but the adding fails, then it is added back to
2238
the original array.
2239
2240
If the spare group for a degraded array is not defined,
2241
.I mdadm
2242
will look at the rules of spare migration specified by POLICY lines in
2243
.B mdadm.conf
2244
and then follow similar steps as above if a matching spare is found.
2245
2246
.SH GROW MODE
2247
The GROW mode is used for changing the size or shape of an active
2248
array.
2249
For this to work, the kernel must support the necessary change.
2250
Various types of growth are being added during 2.6 development.
2251
2252
Currently the supported changes include
2253
.IP \(bu 4
2254
change the "size" attribute for RAID1, RAID4, RAID5 and RAID6.
2255
.IP \(bu 4
2256
increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4,
2257
RAID5, and RAID6.
2258
.IP \(bu 4
2259
change the chunk-size and layout of RAID0, RAID4, RAID5 and RAID6.
2260
.IP \(bu 4
2261
convert between RAID1 and RAID5, between RAID5 and RAID6, between
2262
RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode).
2263
.IP \(bu 4
2264
add a write-intent bitmap to any array which supports these bitmaps, or
2265
remove a write-intent bitmap from such an array.
2266
.PP
2267
2268
Using GROW on containers is currently supported only for Intel's IMSM
2269
container format. The number of devices in a container can be
2270
increased - which affects all arrays in the container - or an array
2271
in a container can be converted between levels where those levels are
2272
supported by the container, and the conversion is on of those listed
2273
above. Resizing arrays in an IMSM container with
2274
.B "--grow --size"
2275
is not yet supported.
2276
2277
Grow functionality (e.g. expand a number of raid devices) for Intel's
2278
IMSM container format has an experimental status. It is guarded by the
2279
.B MDADM_EXPERIMENTAL
2280
environment variable which must be set to '1' for a GROW command to
2281
succeed.
2282
This is for the following reasons:
2283
2284
.IP 1.
2285
Intel's native IMSM check-pointing is not fully tested yet.
2286
This can causes IMSM incompatibility during the grow process: an array
2287
which is growing cannot roam between Microsoft Windows(R) and Linux
2288
systems.
2289
2290
.IP 2.
2291
Interrupting a grow operation is not recommended, because it
2292
has not been fully tested for Intel's IMSM container format yet.
2293
2294
.PP
2295
Note: Intel's native checkpointing doesn't use
2296
.B --backup-file
2297
option and it is transparent for assembly feature.
2298
2299
.SS SIZE CHANGES
2300
Normally when an array is built the "size" is taken from the smallest
2301
of the drives. If all the small drives in an arrays are, one at a
2302
time, removed and replaced with larger drives, then you could have an
2303
array of large drives with only a small amount used. In this
2304
situation, changing the "size" with "GROW" mode will allow the extra
2305
space to start being used. If the size is increased in this way, a
2306
"resync" process will start to make sure the new parts of the array
2307
are synchronised.
2308
2309
Note that when an array changes size, any filesystem that may be
2310
stored in the array will not automatically grow or shrink to use or
2311
vacate the space. The
2312
filesystem will need to be explicitly told to use the extra space
2313
after growing, or to reduce its size
2314
.B prior
2315
to shrinking the array.
2316
2317
Also the size of an array cannot be changed while it has an active
2318
bitmap. If an array has a bitmap, it must be removed before the size
2319
can be changed. Once the change is complete a new bitmap can be created.
2320
2321
.SS RAID\-DEVICES CHANGES
2322
2323
A RAID1 array can work with any number of devices from 1 upwards
2324
(though 1 is not very useful). There may be times which you want to
2325
increase or decrease the number of active devices. Note that this is
2326
different to hot-add or hot-remove which changes the number of
2327
inactive devices.
2328
2329
When reducing the number of devices in a RAID1 array, the slots which
2330
are to be removed from the array must already be vacant. That is, the
2331
devices which were in those slots must be failed and removed.
2332
2333
When the number of devices is increased, any hot spares that are
2334
present will be activated immediately.
2335
2336
Changing the number of active devices in a RAID5 or RAID6 is much more
2337
effort. Every block in the array will need to be read and written
2338
back to a new location. From 2.6.17, the Linux Kernel is able to
2339
increase the number of devices in a RAID5 safely, including restarting
2340
an interrupted "reshape". From 2.6.31, the Linux Kernel is able to
2341
increase or decrease the number of devices in a RAID5 or RAID6.
2342
2343
From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4
2344
or RAID5.
2345
.I mdadm
2346
uses this functionality and the ability to add
2347
devices to a RAID4 to allow devices to be added to a RAID0. When
2348
requested to do this,
2349
.I mdadm
2350
will convert the RAID0 to a RAID4, add the necessary disks and make
2351
the reshape happen, and then convert the RAID4 back to RAID0.
2352
2353
When decreasing the number of devices, the size of the array will also
2354
decrease. If there was data in the array, it could get destroyed and
2355
this is not reversible, so you should firstly shrink the filesystem on
2356
the array to fit within the new size. To help prevent accidents,
2357
.I mdadm
2358
requires that the size of the array be decreased first with
2359
.BR "mdadm --grow --array-size" .
2360
This is a reversible change which simply makes the end of the array
2361
inaccessible. The integrity of any data can then be checked before
2362
the non-reversible reduction in the number of devices is request.
2363
2364
When relocating the first few stripes on a RAID5 or RAID6, it is not
2365
possible to keep the data on disk completely consistent and
2366
crash-proof. To provide the required safety, mdadm disables writes to
2367
the array while this "critical section" is reshaped, and takes a
2368
backup of the data that is in that section. For grows, this backup may be
2369
stored in any spare devices that the array has, however it can also be
2370
stored in a separate file specified with the
2371
.B \-\-backup\-file
2372
option, and is required to be specified for shrinks, RAID level
2373
changes and layout changes. If this option is used, and the system
2374
does crash during the critical period, the same file must be passed to
2375
.B \-\-assemble
2376
to restore the backup and reassemble the array. When shrinking rather
2377
than growing the array, the reshape is done from the end towards the
2378
beginning, so the "critical section" is at the end of the reshape.
2379
2380
.SS LEVEL CHANGES
2381
2382
Changing the RAID level of any array happens instantaneously. However
2383
in the RAID5 to RAID6 case this requires a non-standard layout of the
2384
RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is
2385
required before the change can be accomplished. So while the level
2386
change is instant, the accompanying layout change can take quite a
2387
long time. A
2388
.B \-\-backup\-file
2389
is required. If the array is not simultaneously being grown or
2390
shrunk, so that the array size will remain the same - for example,
2391
reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will
2392
be used not just for a "cricital section" but throughout the reshape
2393
operation, as described below under LAYOUT CHANGES.
2394
2395
.SS CHUNK-SIZE AND LAYOUT CHANGES
2396
2397
Changing the chunk-size of layout without also changing the number of
2398
devices as the same time will involve re-writing all blocks in-place.
2399
To ensure against data loss in the case of a crash, a
2400
.B --backup-file
2401
must be provided for these changes. Small sections of the array will
2402
be copied to the backup file while they are being rearranged. This
2403
means that all the data is copied twice, once to the backup and once
2404
to the new layout on the array, so this type of reshape will go very
2405
slowly.
2406
2407
If the reshape is interrupted for any reason, this backup file must be
2408
made available to
2409
.B "mdadm --assemble"
2410
so the array can be reassembled. Consequently the file cannot be
2411
stored on the device being reshaped.
2412
2413
2414
.SS BITMAP CHANGES
2415
2416
A write-intent bitmap can be added to, or removed from, an active
2417
array. Either internal bitmaps, or bitmaps stored in a separate file,
2418
can be added. Note that if you add a bitmap stored in a file which is
2419
in a filesystem that is on the RAID array being affected, the system
2420
will deadlock. The bitmap must be on a separate filesystem.
2421
2422
.SH INCREMENTAL MODE
2423
2424
.HP 12
2425
Usage:
2426
.B mdadm \-\-incremental
2427
.RB [ \-\-run ]
2428
.RB [ \-\-quiet ]
2429
.I component-device
2430
.HP 12
2431
Usage:
2432
.B mdadm \-\-incremental \-\-fail
2433
.I component-device
2434
.HP 12
2435
Usage:
2436
.B mdadm \-\-incremental \-\-rebuild\-map
2437
.HP 12
2438
Usage:
2439
.B mdadm \-\-incremental \-\-run \-\-scan
2440
2441
.PP
2442
This mode is designed to be used in conjunction with a device
2443
discovery system. As devices are found in a system, they can be
2444
passed to
2445
.B "mdadm \-\-incremental"
2446
to be conditionally added to an appropriate array.
2447
2448
Conversely, it can also be used with the
2449
.B \-\-fail
2450
flag to do just the opposite and find whatever array a particular device
2451
is part of and remove the device from that array.
2452
2453
If the device passed is a
2454
.B CONTAINER
2455
device created by a previous call to
2456
.IR mdadm ,
2457
then rather than trying to add that device to an array, all the arrays
2458
described by the metadata of the container will be started.
2459
2460
.I mdadm
2461
performs a number of tests to determine if the device is part of an
2462
array, and which array it should be part of. If an appropriate array
2463
is found, or can be created,
2464
.I mdadm
2465
adds the device to the array and conditionally starts the array.
2466
2467
Note that
2468
.I mdadm
2469
will normally only add devices to an array which were previously working
2470
(active or spare) parts of that array. The support for automatic
2471
inclusion of a new drive as a spare in some array requires
2472
a configuration through POLICY in config file.
2473
2474
The tests that
2475
.I mdadm
2476
makes are as follow:
2477
.IP +
2478
Is the device permitted by
2479
.BR mdadm.conf ?
2480
That is, is it listed in a
2481
.B DEVICES
2482
line in that file. If
2483
.B DEVICES
2484
is absent then the default it to allow any device. Similar if
2485
.B DEVICES
2486
contains the special word
2487
.B partitions
2488
then any device is allowed. Otherwise the device name given to
2489
.I mdadm
2490
must match one of the names or patterns in a
2491
.B DEVICES
2492
line.
2493
2494
.IP +
2495
Does the device have a valid md superblock? If a specific metadata
2496
version is requested with
2497
.B \-\-metadata
2498
or
2499
.B \-e
2500
then only that style of metadata is accepted, otherwise
2501
.I mdadm
2502
finds any known version of metadata. If no
2503
.I md
2504
metadata is found, the device may be still added to an array
2505
as a spare if POLICY allows.
2506
2507
.ig
2508
.IP +
2509
Does the metadata match an expected array?
2510
The metadata can match in two ways. Either there is an array listed
2511
in
2512
.B mdadm.conf
2513
which identifies the array (either by UUID, by name, by device list,
2514
or by minor-number), or the array was created with a
2515
.B homehost
2516
specified and that
2517
.B homehost
2518
matches the one in
2519
.B mdadm.conf
2520
or on the command line.
2521
If
2522
.I mdadm
2523
is not able to positively identify the array as belonging to the
2524
current host, the device will be rejected.
2525
..
2526
2527
.PP
2528
.I mdadm
2529
keeps a list of arrays that it has partially assembled in
2530
.B /var/run/mdadm/map
2531
(or
2532
.B /var/run/mdadm.map
2533
if the directory doesn't exist. Or maybe even
2534
.BR /dev/.mdadm.map ).
2535
If no array exists which matches
2536
the metadata on the new device,
2537
.I mdadm
2538
must choose a device name and unit number. It does this based on any
2539
name given in
2540
.B mdadm.conf
2541
or any name information stored in the metadata. If this name
2542
suggests a unit number, that number will be used, otherwise a free
2543
unit number will be chosen. Normally
2544
.I mdadm
2545
will prefer to create a partitionable array, however if the
2546
.B CREATE
2547
line in
2548
.B mdadm.conf
2549
suggests that a non-partitionable array is preferred, that will be
2550
honoured.
2551
2552
If the array is not found in the config file and its metadata does not
2553
identify it as belonging to the "homehost", then
2554
.I mdadm
2555
will choose a name for the array which is certain not to conflict with
2556
any array which does belong to this host. It does this be adding an
2557
underscore and a small number to the name preferred by the metadata.
2558
2559
Once an appropriate array is found or created and the device is added,
2560
.I mdadm
2561
must decide if the array is ready to be started. It will
2562
normally compare the number of available (non-spare) devices to the
2563
number of devices that the metadata suggests need to be active. If
2564
there are at least that many, the array will be started. This means
2565
that if any devices are missing the array will not be restarted.
2566
2567
As an alternative,
2568
.B \-\-run
2569
may be passed to
2570
.I mdadm
2571
in which case the array will be run as soon as there are enough
2572
devices present for the data to be accessible. For a RAID1, that
2573
means one device will start the array. For a clean RAID5, the array
2574
will be started as soon as all but one drive is present.
2575
2576
Note that neither of these approaches is really ideal. If it can
2577
be known that all device discovery has completed, then
2578
.br
2579
.B " mdadm \-IRs"
2580
.br
2581
can be run which will try to start all arrays that are being
2582
incrementally assembled. They are started in "read-auto" mode in
2583
which they are read-only until the first write request. This means
2584
that no metadata updates are made and no attempt at resync or recovery
2585
happens. Further devices that are found before the first write can
2586
still be added safely.
2587
2588
.SH ENVIRONMENT
2589
This section describes environment variables that affect how mdadm
2590
operates.
2591
2592
.TP
2593
.B MDADM_NO_MDMON
2594
Setting this value to 1 will prevent mdadm from automatically launching
2595
mdmon. This variable is intended primarily for debugging mdadm/mdmon.
2596
2597
.TP
2598
.B MDADM_NO_UDEV
2599
Normally,
2600
.I mdadm
2601
does not create any device nodes in /dev, but leaves that task to
2602
.IR udev .
2603
If
2604
.I udev
2605
appears not to be configured, or if this environment variable is set
2606
to '1', the
2607
.I mdadm
2608
will create and devices that are needed.
2609
2610
.SH EXAMPLES
2611
2612
.B " mdadm \-\-query /dev/name-of-device"
2613
.br
2614
This will find out if a given device is a RAID array, or is part of
2615
one, and will provide brief information about the device.
2616
2617
.B " mdadm \-\-assemble \-\-scan"
2618
.br
2619
This will assemble and start all arrays listed in the standard config
2620
file. This command will typically go in a system startup file.
2621
2622
.B " mdadm \-\-stop \-\-scan"
2623
.br
2624
This will shut down all arrays that can be shut down (i.e. are not
2625
currently in use). This will typically go in a system shutdown script.
2626
2627
.B " mdadm \-\-follow \-\-scan \-\-delay=120"
2628
.br
2629
If (and only if) there is an Email address or program given in the
2630
standard config file, then
2631
monitor the status of all arrays listed in that file by
2632
polling them ever 2 minutes.
2633
2634
.B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1"
2635
.br
2636
Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1.
2637
2638
.br
2639
.B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf"
2640
.br
2641
.B " mdadm \-\-detail \-\-scan >> mdadm.conf"
2642
.br
2643
This will create a prototype config file that describes currently
2644
active arrays that are known to be made from partitions of IDE or SCSI drives.
2645
This file should be reviewed before being used as it may
2646
contain unwanted detail.
2647
2648
.B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf"
2649
.br
2650
.B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf"
2651
.br
2652
This will find arrays which could be assembled from existing IDE and
2653
SCSI whole drives (not partitions), and store the information in the
2654
format of a config file.
2655
This file is very likely to contain unwanted detail, particularly
2656
the
2657
.B devices=
2658
entries. It should be reviewed and edited before being used as an
2659
actual config file.
2660
2661
.B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions"
2662
.br
2663
.B " mdadm \-Ebsc partitions"
2664
.br
2665
Create a list of devices by reading
2666
.BR /proc/partitions ,
2667
scan these for RAID superblocks, and printout a brief listing of all
2668
that were found.
2669
2670
.B " mdadm \-Ac partitions \-m 0 /dev/md0"
2671
.br
2672
Scan all partitions and devices listed in
2673
.BR /proc/partitions
2674
and assemble
2675
.B /dev/md0
2676
out of all such devices with a RAID superblock with a minor number of 0.
2677
2678
.B " mdadm \-\-monitor \-\-scan \-\-daemonise > /var/run/mdadm"
2679
.br
2680
If config file contains a mail address or alert program, run mdadm in
2681
the background in monitor mode monitoring all md devices. Also write
2682
pid of mdadm daemon to
2683
.BR /var/run/mdadm .
2684
2685
.B " mdadm \-Iq /dev/somedevice"
2686
.br
2687
Try to incorporate newly discovered device into some array as
2688
appropriate.
2689
2690
.B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan"
2691
.br
2692
Rebuild the array map from any current arrays, and then start any that
2693
can be started.
2694
2695
.B " mdadm /dev/md4 --fail detached --remove detached"
2696
.br
2697
Any devices which are components of /dev/md4 will be marked as faulty
2698
and then remove from the array.
2699
2700
.B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4"
2701
.br
2702
The array
2703
.B /dev/md4
2704
which is currently a RAID5 array will be converted to RAID6. There
2705
should normally already be a spare drive attached to the array as a
2706
RAID6 needs one more drive than a matching RAID5.
2707
2708
.B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]"
2709
.br
2710
Create a DDF array over 6 devices.
2711
2712
.B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf"
2713
.br
2714
Create a RAID5 array over any 3 devices in the given DDF set. Use
2715
only 30 gigabytes of each device.
2716
2717
.B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]"
2718
.br
2719
Assemble a pre-exist ddf array.
2720
2721
.B " mdadm -I /dev/md/ddf1"
2722
.br
2723
Assemble all arrays contained in the ddf array, assigning names as
2724
appropriate.
2725
2726
.B " mdadm \-\-create \-\-help"
2727
.br
2728
Provide help about the Create mode.
2729
2730
.B " mdadm \-\-config \-\-help"
2731
.br
2732
Provide help about the format of the config file.
2733
2734
.B " mdadm \-\-help"
2735
.br
2736
Provide general help.
2737
2738
.SH FILES
2739
2740
.SS /proc/mdstat
2741
2742
If you're using the
2743
.B /proc
2744
filesystem,
2745
.B /proc/mdstat
2746
lists all active md devices with information about them.
2747
.I mdadm
2748
uses this to find arrays when
2749
.B \-\-scan
2750
is given in Misc mode, and to monitor array reconstruction
2751
on Monitor mode.
2752
2753
.SS /etc/mdadm.conf
2754
2755
The config file lists which devices may be scanned to see if
2756
they contain MD super block, and gives identifying information
2757
(e.g. UUID) about known MD arrays. See
2758
.BR mdadm.conf (5)
2759
for more details.
2760
2761
.SS /var/run/mdadm/map
2762
When
2763
.B \-\-incremental
2764
mode is used, this file gets a list of arrays currently being created.
2765
If
2766
.B /var/run/mdadm
2767
does not exist as a directory, then
2768
.B /var/run/mdadm.map
2769
is used instead. If
2770
.B /var/run
2771
is not available (as may be the case during early boot),
2772
.B /dev/.mdadm.map
2773
is used on the basis that
2774
.B /dev
2775
is usually available very early in boot.
2776
2777
.SH DEVICE NAMES
2778
2779
.I mdadm
2780
understand two sorts of names for array devices.
2781
2782
The first is the so-called 'standard' format name, which matches the
2783
names used by the kernel and which appear in
2784
.IR /proc/mdstat .
2785
2786
The second sort can be freely chosen, but must reside in
2787
.IR /dev/md/ .
2788
When giving a device name to
2789
.I mdadm
2790
to create or assemble an array, either full path name such as
2791
.I /dev/md0
2792
or
2793
.I /dev/md/home
2794
can be given, or just the suffix of the second sort of name, such as
2795
.I home
2796
can be given.
2797
2798
When
2799
.I mdadm
2800
chooses device names during auto-assembly or incremental assembly, it
2801
will sometimes add a small sequence number to the end of the name to
2802
avoid conflicted between multiple arrays that have the same name. If
2803
.I mdadm
2804
can reasonably determine that the array really is meant for this host,
2805
either by a hostname in the metadata, or by the presence of the array
2806
in
2807
.BR mdadm.conf ,
2808
then it will leave off the suffix if possible.
2809
Also if the homehost is specified as
2810
.B <ignore>
2811
.I mdadm
2812
will only use a suffix if a different array of the same name already
2813
exists or is listed in the config file.
2814
2815
The standard names for non-partitioned arrays (the only sort of md
2816
array available in 2.4 and earlier) are of the form
2817
.IP
2818
/dev/mdNN
2819
.PP
2820
where NN is a number.
2821
The standard names for partitionable arrays (as available from 2.6
2822
onwards) are of the form
2823
.IP
2824
/dev/md_dNN
2825
.PP
2826
Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2".
2827
.PP
2828
From kernel version, 2.6.28 the "non-partitioned array" can actually
2829
be partitioned. So the "md_dNN" names are no longer needed, and
2830
partitions such as "/dev/mdNNpXX" are possible.
2831
2832
.SH NOTE
2833
.I mdadm
2834
was previously known as
2835
.IR mdctl .
2836
.P
2837
.I mdadm
2838
is completely separate from the
2839
.I raidtools
2840
package, and does not use the
2841
.I /etc/raidtab
2842
configuration file at all.
2843
2844
.SH SEE ALSO
2845
For further information on mdadm usage, MD and the various levels of
2846
RAID, see:
2847
.IP
2848
.B http://raid.wiki.kernel.org/
2849
.PP
2850
(based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO)
2851
.\".PP
2852
.\"for new releases of the RAID driver check out:
2853
.\"
2854
.\".IP
2855
.\".UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2856
.\"ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches
2857
.\".UE
2858
.\".PP
2859
.\"or
2860
.\".IP
2861
.\".UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2862
.\"http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/
2863
.\".UE
2864
.PP
2865
The latest version of
2866
.I mdadm
2867
should always be available from
2868
.IP
2869
.B http://www.kernel.org/pub/linux/utils/raid/mdadm/
2870
.PP
2871
Related man pages:
2872
.PP
2873
.IR mdmon (8),
2874
.IR mdadm.conf (5),
2875
.IR md (4).
2876
.PP
2877
.IR raidtab (5),
2878
.IR raid0run (8),
2879
.IR raidstop (8),
2880
.IR mkraid (8).
Loggerhead is a web-based interface for Breezy
Version: 2.0.1