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 of 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
473 include, re-add, spare, spare-same-slot, or force-spare
478 item determines the automatic behavior allowed for devices matching the
482 in the same line. If a device matches several lines with different
484 then the most permissive will apply. The ordering of policy lines
485 is irrelevant to the end result.
488 allows adding a disk to an array if metadata on that disk matches that array
491 will include the device in the array if it appears to be a current member
492 or a member that was recently removed
495 as above and additionally: if the device is bare it can
496 become a spare if there is any array that it is a candidate for based
497 on domains and metadata.
500 as above and additionally if given slot was used by an array that went
501 degraded recently and the device plugged in has no metadata then it will
502 be automatically added to that array (or it's container)
505 as above and the disk will become a spare in remaining cases
509 DEVICE /dev/sd[bcdjkl]1
511 DEVICE /dev/hda1 /dev/hdb1
513 # /dev/md0 is known by its UUID.
515 ARRAY /dev/md0 UUID=3aaa0122:29827cfa:5331ad66:ca767371
517 # /dev/md1 contains all devices with a minor number of
519 # 1 in the superblock.
521 ARRAY /dev/md1 superminor=1
523 # /dev/md2 is made from precisely these two devices
525 ARRAY /dev/md2 devices=/dev/hda1,/dev/hdb1
527 # /dev/md4 and /dev/md5 are a spare-group and spares
529 # can be moved between them
531 ARRAY /dev/md4 uuid=b23f3c6d:aec43a9f:fd65db85:369432df
535 ARRAY /dev/md5 uuid=19464854:03f71b1b:e0df2edd:246cc977
539 # /dev/md/home is created if need to be a partitionable md array
541 # any spare device number is allocated.
543 ARRAY /dev/md/home UUID=9187a482:5dde19d9:eea3cc4a:d646ab8b
547 POLICY domain=domain1 metadata=imsm path=pci-0000:00:1f.2-scsi-*
551 POLICY domain=domain1 metadata=imsm path=pci-0000:04:00.0-scsi-[01]*
555 # One domain comprising of devices attached to specified paths is defined.
557 # Bare device matching first path will be made an imsm spare on hot plug.
559 # If more than one array is created on devices belonging to domain1 and
561 # one of them becomes degraded, then any imsm spare matching any path for
563 # given domain name can be migrated.
565 MAILADDR root@mydomain.tld
567 PROGRAM /usr/sbin/handle\-mdadm\-events
569 CREATE group=system mode=0640 auto=part\-8
573 AUTO +1.x homehost -all
projects / thirdparty / mdadm.git / blob