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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.
7 .TH MDADM.CONF 5
8 .SH NAME
9 mdadm.conf \- configuration for management of Software RAID with mdadm
10 .SH SYNOPSIS
11 /etc/mdadm.conf
12 .SH DESCRIPTION
13 .PP
14 .B mdadm
15 is a tool for creating, managing, and monitoring RAID devices using the
16 .B md
17 driver in Linux.
18 .PP
19 Some common tasks, such as assembling all arrays, can be simplified
20 by describing the devices and arrays in this configuration file.
21
22 .SS SYNTAX
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.
27
28 Any line that starts with white space (space or tab) is treated as
29 though it were a continuation of the previous line.
30
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.
34
35 The keywords are:
36 .TP
37 .B DEVICE
38 A
39 .B device
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
42 array,
43 .B mdadm
44 will scan these devices (or any devices listed on the command line).
45
46 The
47 .B device
48 line may contain a number of different devices (separated by spaces)
49 and each device name can contain wild cards as defined by
50 .BR glob (7).
51
52 Also, there may be several device lines present in the file.
53
54 Alternatively, a
55 .B device
56 line can contain the word
57 .BR partitions .
58 This will cause
59 .I mdadm
60 to read
61 .I /proc/partitions
62 and include all devices and partitions found therein.
63 .I mdadm
64 does not use the names from
65 .I /proc/partitions
66 but only the major and minor device numbers. It scans
67 .I /dev
68 to find the name that matches the numbers.
69
70 If no DEVICE line is present, then "DEVICE partitions" is assumed.
71
72 For example:
73 .IP
74 DEVICE /dev/hda* /dev/hdc*
75 .br
76 DEV /dev/sd*
77 .br
78 DEVICE /dev/discs/disc*/disc
79 .br
80 DEVICE partitions
81
82 .TP
83 .B ARRAY
84 The ARRAY lines identify actual arrays. The second word on the line
85 should be the name of the device where the array is normally
86 assembled, such as
87 .BR /dev/md1 .
88 Subsequent words identify the array, or identify the array as a member
89 of a group. If multiple identities are given,
90 then a component device must match ALL identities to be considered a
91 match. Each identity word has a tag, and equals sign, and some value.
92 The tags are:
93
94 .RS 4
95 .TP
96 .B uuid=
97 The value should be a 128 bit uuid in hexadecimal, with punctuation
98 interspersed if desired. This must match the uuid stored in the
99 superblock.
100 .TP
101 .B name=
102 The value should be a simple textual name as was given to
103 .I mdadm
104 when the array was created. This must match the name stored in the
105 superblock on a device for that device to be included in the array.
106 Not all superblock formats support names.
107 .TP
108 .B super\-minor=
109 The value is an integer which indicates the minor number that was
110 stored in the superblock when the array was created. When an array is
111 created as /dev/mdX, then the minor number X is stored.
112 .TP
113 .B devices=
114 The value is a comma separated list of device names or device name
115 patterns.
116 Only devices with names which match one entry in the list will be used
117 to assemble the array. Note that the devices
118 listed there must also be listed on a DEVICE line.
119 .TP
120 .B level=
121 The value is a raid level. This is not normally used to
122 identify an array, but is supported so that the output of
123
124 .B "mdadm \-\-examine \-\-scan"
125
126 can be use directly in the configuration file.
127 .TP
128 .B num\-devices=
129 The value is the number of devices in a complete active array. As with
130 .B level=
131 this is mainly for compatibility with the output of
132
133 .BR "mdadm \-\-examine \-\-scan" .
134
135 .TP
136 .B spares=
137 The value is a number of spare devices to expect the array to have.
138 .B mdadm \-\-monitor
139 will report an array if it is found to have fewer than this number of
140 spares when
141 .B \-\-monitor
142 starts or when
143 .B \-\-oneshot
144 is used.
145
146 .TP
147 .B spare\-group=
148 The value is a textual name for a group of arrays. All arrays with
149 the same
150 .B spare\-group
151 name are considered to be part of the same group. The significance of
152 a group of arrays is that
153 .B mdadm
154 will, when monitoring the arrays, move a spare drive from one array in
155 a group to another array in that group if the first array had a failed
156 or missing drive but no spare.
157
158 .TP
159 .B auto=
160 This option declares to
161 .B mdadm
162 that it should try to create the device file of the array if it
163 doesn't already exist, or exists but with the wrong device number.
164
165 The value of this option can be "yes" or "md" to indicate that a
166 traditional, non-partitionable md array should be created, or "mdp",
167 "part" or "partition" to indicate that a partitionable md array (only
168 available in linux 2.6 and later) should be used. This later set can
169 also have a number appended to indicate how many partitions to create
170 device files for, e.g.
171 .BR auto=mdp5 .
172 The default is 4.
173
174 .TP
175 .B bitmap=
176 The option specifies a file in which a write-intent bitmap should be
177 found. When assembling the array,
178 .I mdadm
179 will provide this file to the
180 .B md
181 driver as the bitmap file. This has the same function as the
182 .B \-\-bitmap\-file
183 option to
184 .BR \-\-assemble .
185
186 .TP
187 .B metadata=
188 Specify the metadata format that the array has. This is mainly
189 recognised for comparability with the output of
190 .BR "mdadm \-Es" .
191
192 .RE
193
194 .TP
195 .B MAILADDR
196 The
197 .B mailaddr
198 line gives an E-mail address that alerts should be
199 sent to when
200 .M mdadm
201 is running in
202 .B \-\-monitor
203 mode (and was given the
204 .B \-\-scan
205 option). There should only be one
206 .B MAILADDR
207 line and it should have only one address.
208
209
210 .TP
211 .B MAILFROM
212 The
213 .B mailfrom
214 line (which can only be abbreviated to at least 5 characters) gives an
215 address to appear in the "From" address for alert mails. This can be
216 useful if you want to explicitly set a domain, as the default from
217 address is "root" with no domain. All words on this line are
218 catenated with spaces to form the address.
219
220 Note that this value cannot be set via the
221 .I mdadm
222 commandline. It is only settable via the config file.
223
224 .TP
225 .B PROGRAM
226 The
227 .B program
228 line gives the name of a program to be run when
229 .B "mdadm \-\-monitor"
230 detects potentially interesting events on any of the arrays that it
231 is monitoring. This program gets run with two or three arguments, they
232 being the Event, the md device, and possibly the related component
233 device.
234
235 There should only be one
236 .B program
237 line and it should be give only one program.
238
239
240 .TP
241 .B CREATE
242 The
243 .B create
244 line gives default values to be used when creating arrays and device entries for
245 arrays.
246 These include:
247
248 .RS 4
249 .TP
250 .B owner=
251 .TP
252 .B group=
253 These can give user/group ids or names to use instead of system
254 defaults (root/wheel or root/disk).
255 .TP
256 .B mode=
257 An octal file mode such as 0660 can be given to override the default
258 of 0600.
259 .TP
260 .B auto=
261 This corresponds to the
262 .B \-\-auto
263 flag to mdadm. Give
264 .BR yes ,
265 .BR md ,
266 .BR mdp ,
267 .B part
268 \(em possibly followed by a number of partitions \(em to indicate how
269 missing device entries should be created.
270
271 .TP
272 .B metadata=
273 The name of the metadata format to use if none is explicitly given.
274 This can be useful to impose a system-wide default of version-1 superblocks.
275
276 .TP
277 .B symlinks=no
278 Normally when creating devices in
279 .B /dev/md/
280 .I mdadm
281 will create a matching symlink from
282 .B /dev/
283 with a name starting
284 .B md
285 or
286 .BR md_ .
287 Give
288 .B symlinks=no
289 to suppress this symlink creation.
290 .RE
291
292
293 .SH EXAMPLE
294 DEVICE /dev/sd[bcdjkl]1
295 .br
296 DEVICE /dev/hda1 /dev/hdb1
297
298 # /dev/md0 is known by its UID.
299 .br
300 ARRAY /dev/md0 UUID=3aaa0122:29827cfa:5331ad66:ca767371
301 .br
302 # /dev/md1 contains all devices with a minor number of
303 .br
304 # 1 in the superblock.
305 .br
306 ARRAY /dev/md1 superminor=1
307 .br
308 # /dev/md2 is made from precisely these two devices
309 .br
310 ARRAY /dev/md2 devices=/dev/hda1,/dev/hdb1
311
312 # /dev/md4 and /dev/md5 are a spare-group and spares
313 .br
314 # can be moved between them
315 .br
316 ARRAY /dev/md4 uuid=b23f3c6d:aec43a9f:fd65db85:369432df
317 .br
318 spare\-group=group1
319 .br
320 ARRAY /dev/md5 uuid=19464854:03f71b1b:e0df2edd:246cc977
321 .br
322 spare\-group=group1
323 .br
324 # /dev/md/home is created if need to be a partitionable md array
325 .br
326 # any spare device number is allocated.
327 .br
328 ARRAY /dev/md/home UUID=9187a482:5dde19d9:eea3cc4a:d646ab8b
329 .br
330 auto=part
331
332 MAILADDR root@mydomain.tld
333 .br
334 PROGRAM /usr/sbin/handle\-mdadm\-events
335 .br
336 CREATE group=system mode=0640 auto=part\-8
337 .br
338 HOMEHOST <system>
339
340 .SH SEE ALSO
341 .BR mdadm (8),
342 .BR md (4).
343