1
.\" Copyright Neil Brown and others.
2
.\" This program is free software; you can redistribute it and/or modify
3
.\" it under the terms of the GNU General Public License as published by
4
.\" the Free Software Foundation; either version 2 of the License, or
5
.\" (at your option) any later version.
6
.\" See file COPYING in distribution for details.
9
mdadm.conf \- configuration for management of Software RAID with mdadm
15
is a tool for creating, managing, and monitoring RAID devices using the
19
Some common tasks, such as assembling all arrays, can be simplified
20
by describing the devices and arrays in this configuration file.
23
The file should be seen as a collection of words separated by white
24
space (space, tab, or newline).
25
Any word that beings with a hash sign (#) starts a comment and that
26
word together with the remainder of the line is ignored.
28
Any line that starts with white space (space or tab) is treated as
29
though it were a continuation of the previous line.
31
Empty lines are ignored, but otherwise each (non continuation) line
32
must start with a keyword as listed below. The keywords are case
33
insensitive and can be abbreviated to 3 characters.
40
line lists the devices (whole devices or partitions) that might contain
41
a component of an MD array. When looking for the components of an
44
will scan these devices (or any devices listed on the command line).
48
line may contain a number of different devices (separated by spaces)
49
and each device name can contain wild cards as defined by
52
Also, there may be several device lines present in the file.
56
line can contain either or both of the words
64
to look for assembled CONTAINER arrays and included them as a source
65
for assembling further arrays.
73
and include all devices and partitions found therein.
75
does not use the names from
77
but only the major and minor device numbers. It scans
79
to find the name that matches the numbers.
81
If no DEVICE line is present, then "DEVICE partitions containers" is assumed.
85
DEVICE /dev/hda* /dev/hdc*
89
DEVICE /dev/disk/by-path/pci*
95
The ARRAY lines identify actual arrays. The second word on the line
96
may be the name of the device where the array is normally
101
If the name does not start with a slash
103
it is treated as being in
107
(complete with angle brackets) can be given in which case any array
108
which matches the rest of the line will never be automatically assembled.
109
If no device name is given,
111
will use various heuristics to determine an appropriate name.
113
Subsequent words identify the array, or identify the array as a member
114
of a group. If multiple identities are given,
115
then a component device must match ALL identities to be considered a
116
match. Each identity word has a tag, and equals sign, and some value.
121
The value should be a 128 bit uuid in hexadecimal, with punctuation
122
interspersed if desired. This must match the uuid stored in the
126
The value should be a simple textual name as was given to
128
when the array was created. This must match the name stored in the
129
superblock on a device for that device to be included in the array.
130
Not all superblock formats support names.
133
The value is an integer which indicates the minor number that was
134
stored in the superblock when the array was created. When an array is
135
created as /dev/mdX, then the minor number X is stored.
138
The value is a comma separated list of device names or device name
140
Only devices with names which match one entry in the list will be used
141
to assemble the array. Note that the devices
142
listed there must also be listed on a DEVICE line.
145
The value is a raid level. This is not normally used to
146
identify an array, but is supported so that the output of
148
.B "mdadm \-\-examine \-\-scan"
150
can be use directly in the configuration file.
153
The value is the number of devices in a complete active array. As with
155
this is mainly for compatibility with the output of
157
.BR "mdadm \-\-examine \-\-scan" .
161
The value is a number of spare devices to expect the array to have.
162
The sole use of this keyword and value is as follows:
164
will report an array if it is found to have fewer than this number of
173
The value is a textual name for a group of arrays. All arrays with
176
name are considered to be part of the same group. The significance of
177
a group of arrays is that
179
will, when monitoring the arrays, move a spare drive from one array in
180
a group to another array in that group if the first array had a failed
181
or missing drive but no spare.
185
This option is rarely needed with mdadm-3.0, particularly if use with
186
the Linux kernel v2.6.28 or later.
189
whether to use partitionable array or non-partitionable arrays and,
192
how many partition devices to create. From 2.6.28 all md array
193
devices are partitionable, hence this option is not needed.
195
The value of this option can be "yes" or "md" to indicate that a
196
traditional, non-partitionable md array should be created, or "mdp",
197
"part" or "partition" to indicate that a partitionable md array (only
198
available in linux 2.6 and later) should be used. This later set can
199
also have a number appended to indicate how many partitions to create
200
device files for, e.g.
206
The option specifies a file in which a write-intent bitmap should be
207
found. When assembling the array,
209
will provide this file to the
211
driver as the bitmap file. This has the same function as the
218
Specify the metadata format that the array has. This is mainly
219
recognised for comparability with the output of
224
Specify that this array is a member array of some container. The
225
value given can be either a path name in /dev, or a UUID of the
230
Specify that this array is a member array of some container. Each
231
type of container has some way to enumerate member arrays, often a
232
simple sequence number. The value identifies which member of a
233
container the array is. It will usually accompany a "container=" word.
240
line gives an E-mail address that alerts should be
245
mode (and was given the
247
option). There should only be one
249
line and it should have only one address.
256
line (which can only be abbreviated to at least 5 characters) gives an
257
address to appear in the "From" address for alert mails. This can be
258
useful if you want to explicitly set a domain, as the default from
259
address is "root" with no domain. All words on this line are
260
catenated with spaces to form the address.
262
Note that this value cannot be set via the
264
commandline. It is only settable via the config file.
270
line gives the name of a program to be run when
271
.B "mdadm \-\-monitor"
272
detects potentially interesting events on any of the arrays that it
273
is monitoring. This program gets run with two or three arguments, they
274
being the Event, the md device, and possibly the related component
277
There should only be one
279
line and it should be give only one program.
286
line gives default values to be used when creating arrays and device entries for
295
These can give user/group ids or names to use instead of system
296
defaults (root/wheel or root/disk).
299
An octal file mode such as 0660 can be given to override the default
303
This corresponds to the
310
\(em possibly followed by a number of partitions \(em to indicate how
311
missing device entries should be created.
315
The name of the metadata format to use if none is explicitly given.
316
This can be useful to impose a system-wide default of version-1 superblocks.
320
Normally when creating devices in
323
will create a matching symlink from
331
to suppress this symlink creation.
338
line gives a default value for the
340
option to mdadm. There should normally be only one other word on the line.
341
It should either be a host name, or one of the special words
349
.BR gethostname ( 2 )
350
systemcall is used to get the host name. This is the default.
354
is given, then a flag is set so that when arrays are being
355
auto-assembled the checking of the recorded
360
is given it is also possible to give an explicit name which will be
361
used when creating arrays. This is the only case when there can be
362
more that one other word on the
368
is given, then the default of using
369
.BR gethostname ( 2 )
370
is over-ridden and no homehost name is assumed.
372
When arrays are created, this host name will be stored in the
373
metadata. When arrays are assembled using auto-assembly, arrays which
374
do not record the correct homehost name in their metadata will be
375
assembled using a "foreign" name. A "foreign" name alway ends with a
376
digit string preceded by an underscore to differentiate it
377
from any possible local name. e.g.
383
A list of names of metadata format can be given, each preceded by a
384
plus or minus sign. Also the word
388
preceded by plus or minus sign.
394
is auto-assembling an array, either via
398
and it finds metadata of a given type, it checks that metadata type
399
against those listed in this line. The first match wins, where
402
If a match is found that was preceded by a plus sign, the auto
403
assembly is allowed. If the match was preceded by a minus sign, the
404
auto assembly is disallowed. If no match is found, the auto assembly
407
If the metadata indicates that the array was created for
411
appears before any other match, then the array is treated as a valid
412
candidate for auto-assembly.
414
This can be used to disable all auto-assembly (so that only arrays
415
explicitly listed in mdadm.conf or on the command line are assembled),
416
or to disable assembly of certain metadata types which might be
417
handled by other software. It can also be used to disable assembly of
418
all foreign arrays - normally such arrays are assembled but given a
419
non-deterministic name in
422
The known metadata types are
430
This is used to specify what automatic behavior is allowed on devices
431
newly appearing in the system and provides a way of marking spares that can
432
be moved to other arrays as well as the migration domains.
434
can be defined through
436
line by specifying a domain name for a number of paths from
437
.BR /dev/disk/by-path/ .
438
A device may belong to several domains. The domain of an array is a union
439
of domains of all devices in that array. A spare can be automatically
440
moved from one array to another if the set of the destination array's
444
of the new disk or if both arrays have the same
447
To update hot plug configuration it is necessary to execute
448
.B mdadm \-\-udev\-rules
449
command after changing the config file
451
Key words used in the
453
line and supported values are:
464
file glob matching anything from
474
include, re-add, spare, spare-same-slot, or force-spare
476
yes, no, or homehost.
481
item determines the automatic behavior allowed for devices matching the
485
in the same line. If a device matches several lines with different
487
then the most permissive will apply. The ordering of policy lines
488
is irrelevant to the end result.
491
allows adding a disk to an array if metadata on that disk matches that array
494
will include the device in the array if it appears to be a current member
495
or a member that was recently removed
498
as above and additionally: if the device is bare it can
499
become a spare if there is any array that it is a candidate for based
500
on domains and metadata.
503
as above and additionally if given slot was used by an array that went
504
degraded recently and the device plugged in has no metadata then it will
505
be automatically added to that array (or it's container)
508
as above and the disk will become a spare in remaining cases
512
DEVICE /dev/sd[bcdjkl]1
514
DEVICE /dev/hda1 /dev/hdb1
516
# /dev/md0 is known by its UUID.
518
ARRAY /dev/md0 UUID=3aaa0122:29827cfa:5331ad66:ca767371
520
# /dev/md1 contains all devices with a minor number of
522
# 1 in the superblock.
524
ARRAY /dev/md1 superminor=1
526
# /dev/md2 is made from precisely these two devices
528
ARRAY /dev/md2 devices=/dev/hda1,/dev/hdb1
530
# /dev/md4 and /dev/md5 are a spare-group and spares
532
# can be moved between them
534
ARRAY /dev/md4 uuid=b23f3c6d:aec43a9f:fd65db85:369432df
538
ARRAY /dev/md5 uuid=19464854:03f71b1b:e0df2edd:246cc977
542
# /dev/md/home is created if need to be a partitionable md array
544
# any spare device number is allocated.
546
ARRAY /dev/md/home UUID=9187a482:5dde19d9:eea3cc4a:d646ab8b
550
POLICY domain=domain1 metadata=imsm path=pci-0000:00:1f.2-scsi-*
554
POLICY domain=domain1 metadata=imsm path=pci-0000:04:00.0-scsi-[01]*
558
# One domain comprising of devices attached to specified paths is defined.
560
# Bare device matching first path will be made an imsm spare on hot plug.
562
# If more than one array is created on devices belonging to domain1 and
564
# one of them becomes degraded, then any imsm spare matching any path for
566
# given domain name can be migrated.
568
MAILADDR root@mydomain.tld
570
PROGRAM /usr/sbin/handle\-mdadm\-events
572
CREATE group=system mode=0640 auto=part\-8
576
AUTO +1.x homehost -all