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 Spaces can be included in a word using quotation characters. Either
31 or double quotes (\fB"\fP)
32 may be used. All the characters from one quotation character to
33 next identical character are protected and will not be used to
34 separate words to start new quoted strings. To include a single quote
35 it must be between double quotes. To include a double quote it must
36 be between single quotes.
38 Any line that starts with white space (space or tab) is treated as
39 though it were a continuation of the previous line.
41 Empty lines are ignored, but otherwise each (non continuation) line
42 must start with a keyword as listed below. The keywords are case
43 insensitive and can be abbreviated to 3 characters.
50 line lists the devices (whole devices or partitions) that might contain
51 a component of an MD array. When looking for the components of an
54 will scan these devices (or any devices listed on the command line).
58 line may contain a number of different devices (separated by spaces)
59 and each device name can contain wild cards as defined by
62 Also, there may be several device lines present in the file.
66 line can contain either or both of the words
74 to look for assembled CONTAINER arrays and included them as a source
75 for assembling further arrays.
83 and include all devices and partitions found therein.
85 does not use the names from
87 but only the major and minor device numbers. It scans
89 to find the name that matches the numbers.
91 If no DEVICE line is present, then "DEVICE partitions containers" is assumed.
95 DEVICE /dev/hda* /dev/hdc*
99 DEVICE /dev/disk/by-path/pci*
105 The ARRAY lines identify actual arrays. The second word on the line
106 may be the name of the device where the array is normally
111 If the name does not start with a slash
113 it is treated as being in
117 (complete with angle brackets) can be given in which case any array
118 which matches the rest of the line will never be automatically assembled.
119 If no device name is given,
121 will use various heuristics to determine an appropriate name.
123 Subsequent words identify the array, or identify the array as a member
124 of a group. If multiple identities are given,
125 then a component device must match ALL identities to be considered a
126 match. Each identity word has a tag, and equals sign, and some value.
131 The value should be a 128 bit uuid in hexadecimal, with punctuation
132 interspersed if desired. This must match the uuid stored in the
136 The value should be a simple textual name as was given to
138 when the array was created. This must match the name stored in the
139 superblock on a device for that device to be included in the array.
140 Not all superblock formats support names.
143 The value is an integer which indicates the minor number that was
144 stored in the superblock when the array was created. When an array is
145 created as /dev/mdX, then the minor number X is stored.
148 The value is a comma separated list of device names or device name
150 Only devices with names which match one entry in the list will be used
151 to assemble the array. Note that the devices
152 listed there must also be listed on a DEVICE line.
155 The value is a RAID level. This is not normally used to
156 identify an array, but is supported so that the output of
158 .B "mdadm \-\-examine \-\-scan"
160 can be use directly in the configuration file.
163 The value is the number of devices in a complete active array. As with
165 this is mainly for compatibility with the output of
167 .BR "mdadm \-\-examine \-\-scan" .
171 The value is a number of spare devices to expect the array to have.
172 The sole use of this keyword and value is as follows:
174 will report an array if it is found to have fewer than this number of
183 The value is a textual name for a group of arrays. All arrays with
186 name are considered to be part of the same group. The significance of
187 a group of arrays is that
189 will, when monitoring the arrays, move a spare drive from one array in
190 a group to another array in that group if the first array had a failed
191 or missing drive but no spare.
195 This option is rarely needed with mdadm-3.0, particularly if use with
196 the Linux kernel v2.6.28 or later.
199 whether to use partitionable array or non-partitionable arrays and,
202 how many partition devices to create. From 2.6.28 all md array
203 devices are partitionable, hence this option is not needed.
205 The value of this option can be "yes" or "md" to indicate that a
206 traditional, non-partitionable md array should be created, or "mdp",
207 "part" or "partition" to indicate that a partitionable md array (only
208 available in linux 2.6 and later) should be used. This later set can
209 also have a number appended to indicate how many partitions to create
210 device files for, e.g.
216 The option specifies a file in which a write-intent bitmap should be
217 found. When assembling the array,
219 will provide this file to the
221 driver as the bitmap file. This has the same function as the
228 Specify the metadata format that the array has. This is mainly
229 recognised for comparability with the output of
234 Specify that this array is a member array of some container. The
235 value given can be either a path name in /dev, or a UUID of the
240 Specify that this array is a member array of some container. Each
241 type of container has some way to enumerate member arrays, often a
242 simple sequence number. The value identifies which member of a
243 container the array is. It will usually accompany a "container=" word.
250 line gives an E-mail address that alerts should be
255 mode (and was given the
257 option). There should only be one
259 line and it should have only one address. Any subsequent addresses
260 are silently ignored.
266 line (which can only be abbreviated to at least 5 characters) gives an
267 address to appear in the "From" address for alert mails. This can be
268 useful if you want to explicitly set a domain, as the default from
269 address is "root" with no domain. All words on this line are
270 catenated with spaces to form the address.
272 Note that this value cannot be set via the
274 commandline. It is only settable via the config file.
280 line gives the name of a program to be run when
281 .B "mdadm \-\-monitor"
282 detects potentially interesting events on any of the arrays that it
283 is monitoring. This program gets run with two or three arguments, they
284 being the Event, the md device, and possibly the related component
287 There should only be one
289 line and it should be give only one program.
296 line gives default values to be used when creating arrays, new members
297 of arrays, and device entries for arrays.
305 These can give user/group ids or names to use instead of system
306 defaults (root/wheel or root/disk).
309 An octal file mode such as 0660 can be given to override the default
313 This corresponds to the
320 \(em possibly followed by a number of partitions \(em to indicate how
321 missing device entries should be created.
325 The name of the metadata format to use if none is explicitly given.
326 This can be useful to impose a system-wide default of version-1 superblocks.
330 Normally when creating devices in
333 will create a matching symlink from
341 to suppress this symlink creation.
345 Since Linux 2.6.29 it has been possible to create
347 devices with a name like
349 rather than just a number, like
352 will use the numeric alternative by default as other tools that interact
353 with md arrays may expect only numbers.
360 will use a name when appropriate.
363 is given, then non-numeric
365 device names will not be used even if the default changes in a future
373 will reserve space for a bad block list (bbl) on all devices
374 included in or added to any array that supports them. Setting
376 will prevent this, so newly added devices will not have a bad
384 line gives a default value for the
386 option to mdadm. There should normally be only one other word on the line.
387 It should either be a host name, or one of the special words
395 .BR gethostname ( 2 )
396 systemcall is used to get the host name. This is the default.
400 is given, then a flag is set so that when arrays are being
401 auto-assembled the checking of the recorded
406 is given it is also possible to give an explicit name which will be
407 used when creating arrays. This is the only case when there can be
408 more that one other word on the
410 line. If there are other words, or other
412 lines, they are silently ignored.
416 is given, then the default of using
417 .BR gethostname ( 2 )
418 is over-ridden and no homehost name is assumed.
420 When arrays are created, this host name will be stored in the
421 metadata. When arrays are assembled using auto-assembly, arrays which
422 do not record the correct homehost name in their metadata will be
423 assembled using a "foreign" name. A "foreign" name alway ends with a
424 digit string preceded by an underscore to differentiate it
425 from any possible local name. e.g.
431 A list of names of metadata format can be given, each preceded by a
432 plus or minus sign. Also the word
436 preceded by plus or minus sign.
442 is auto-assembling an array, either via
446 and it finds metadata of a given type, it checks that metadata type
447 against those listed in this line. The first match wins, where
450 If a match is found that was preceded by a plus sign, the auto
451 assembly is allowed. If the match was preceded by a minus sign, the
452 auto assembly is disallowed. If no match is found, the auto assembly
455 If the metadata indicates that the array was created for
459 appears before any other match, then the array is treated as a valid
460 candidate for auto-assembly.
462 This can be used to disable all auto-assembly (so that only arrays
463 explicitly listed in mdadm.conf or on the command line are assembled),
464 or to disable assembly of certain metadata types which might be
465 handled by other software. It can also be used to disable assembly of
466 all foreign arrays - normally such arrays are assembled but given a
467 non-deterministic name in
470 The known metadata types are
477 should be given at most once. Subsequent lines are silently ignored.
478 Thus an earlier config file in a config directory will over-ride
479 the setting in a later config file.
483 This is used to specify what automatic behavior is allowed on devices
484 newly appearing in the system and provides a way of marking spares that can
485 be moved to other arrays as well as the migration domains.
487 can be defined through
489 line by specifying a domain name for a number of paths from
490 .BR /dev/disk/by-path/ .
491 A device may belong to several domains. The domain of an array is a union
492 of domains of all devices in that array. A spare can be automatically
493 moved from one array to another if the set of the destination array's
497 of the new disk or if both arrays have the same
500 To update hot plug configuration it is necessary to execute
501 .B mdadm \-\-udev\-rules
502 command after changing the config file
504 Key words used in the
506 line and supported values are:
517 file glob matching anything from
527 include, re-add, spare, spare-same-slot, or force-spare
530 yes, no, or homehost.
535 item determines the automatic behavior allowed for devices matching the
539 in the same line. If a device matches several lines with different
541 then the most permissive will apply. The ordering of policy lines
542 is irrelevant to the end result.
545 allows adding a disk to an array if metadata on that disk matches that array
548 will include the device in the array if it appears to be a current member
549 or a member that was recently removed and the array has a
550 write-intent-bitmap to allow the
555 as above and additionally: if the device is bare it can
556 become a spare if there is any array that it is a candidate for based
557 on domains and metadata.
560 as above and additionally if given slot was used by an array that went
561 degraded recently and the device plugged in has no metadata then it will
562 be automatically added to that array (or it's container)
565 as above and the disk will become a spare in remaining cases
569 DEVICE /dev/sd[bcdjkl]1
571 DEVICE /dev/hda1 /dev/hdb1
573 # /dev/md0 is known by its UUID.
575 ARRAY /dev/md0 UUID=3aaa0122:29827cfa:5331ad66:ca767371
577 # /dev/md1 contains all devices with a minor number of
579 # 1 in the superblock.
581 ARRAY /dev/md1 superminor=1
583 # /dev/md2 is made from precisely these two devices
585 ARRAY /dev/md2 devices=/dev/hda1,/dev/hdb1
587 # /dev/md4 and /dev/md5 are a spare-group and spares
589 # can be moved between them
591 ARRAY /dev/md4 uuid=b23f3c6d:aec43a9f:fd65db85:369432df
595 ARRAY /dev/md5 uuid=19464854:03f71b1b:e0df2edd:246cc977
599 # /dev/md/home is created if need to be a partitionable md array
601 # any spare device number is allocated.
603 ARRAY /dev/md/home UUID=9187a482:5dde19d9:eea3cc4a:d646ab8b
607 # The name of this array contains a space.
609 ARRAY /dev/md9 name='Data Storage'
611 POLICY domain=domain1 metadata=imsm path=pci-0000:00:1f.2-scsi-*
615 POLICY domain=domain1 metadata=imsm path=pci-0000:04:00.0-scsi-[01]*
619 # One domain comprising of devices attached to specified paths is defined.
621 # Bare device matching first path will be made an imsm spare on hot plug.
623 # If more than one array is created on devices belonging to domain1 and
625 # one of them becomes degraded, then any imsm spare matching any path for
627 # given domain name can be migrated.
629 MAILADDR root@mydomain.tld
631 PROGRAM /usr/sbin/handle\-mdadm\-events
633 CREATE group=system mode=0640 auto=part\-8
637 AUTO +1.x homehost \-all
projects / thirdparty / mdadm.git / blob