]>
Commit | Line | Data |
---|---|---|
52826846 | 1 | .\" -*- nroff -*- |
90fc992e NB |
2 | ''' Copyright Neil Brown and others. |
3 | ''' This program is free software; you can redistribute it and/or modify | |
4 | ''' it under the terms of the GNU General Public License as published by | |
5 | ''' the Free Software Foundation; either version 2 of the License, or | |
6 | ''' (at your option) any later version. | |
7 | ''' See file COPYING in distribution for details. | |
e003092c | 8 | .TH MDADM 8 "" v2.6.1 |
52826846 | 9 | .SH NAME |
9a9dab36 | 10 | mdadm \- manage MD devices |
cd29a5c8 NB |
11 | .I aka |
12 | Linux Software Raid. | |
13 | ||
52826846 NB |
14 | .SH SYNOPSIS |
15 | ||
e0d19036 | 16 | .BI mdadm " [mode] <raiddevice> [options] <component-devices>" |
52826846 | 17 | |
2ae555c3 | 18 | .SH DESCRIPTION |
52826846 | 19 | RAID devices are virtual devices created from two or more |
cd29a5c8 | 20 | real block devices. This allows multiple devices (typically disk |
35cc5be4 | 21 | drives or partitions thereof) to be combined into a single device to |
cd29a5c8 | 22 | hold (for example) a single filesystem. |
2d465520 | 23 | Some RAID levels include redundancy and so can survive some degree of |
cd29a5c8 NB |
24 | device failure. |
25 | ||
2d465520 NB |
26 | Linux Software RAID devices are implemented through the md (Multiple |
27 | Devices) device driver. | |
cd29a5c8 NB |
28 | |
29 | Currently, Linux supports | |
30 | .B LINEAR | |
31 | md devices, | |
32 | .B RAID0 | |
33 | (striping), | |
34 | .B RAID1 | |
35 | (mirroring), | |
d013a55e NB |
36 | .BR RAID4 , |
37 | .BR RAID5 , | |
98c6faba | 38 | .BR RAID6 , |
1a7dfc35 | 39 | .BR RAID10 , |
b5e64645 | 40 | .BR MULTIPATH , |
cd29a5c8 | 41 | and |
b5e64645 | 42 | .BR FAULTY . |
d013a55e | 43 | |
a9d69660 NB |
44 | .B MULTIPATH |
45 | is not a Software RAID mechanism, but does involve | |
d013a55e NB |
46 | multiple devices. For |
47 | .B MULTIPATH | |
48 | each device is a path to one common physical storage device. | |
49 | ||
a9d69660 NB |
50 | .B FAULTY |
51 | is also not true RAID, and it only involves one device. It | |
b5e64645 | 52 | provides a layer over a true device that can be used to inject faults. |
52826846 | 53 | |
a9d69660 NB |
54 | '''.B mdadm |
55 | '''is a program that can be used to create, manage, and monitor | |
56 | '''MD devices. As | |
57 | '''such it provides a similar set of functionality to the | |
58 | '''.B raidtools | |
59 | '''packages. | |
60 | '''The key differences between | |
61 | '''.B mdadm | |
62 | '''and | |
63 | '''.B raidtools | |
64 | '''are: | |
65 | '''.IP \(bu 4 | |
66 | '''.B mdadm | |
67 | '''is a single program and not a collection of programs. | |
68 | '''.IP \(bu 4 | |
69 | '''.B mdadm | |
70 | '''can perform (almost) all of its functions without having a | |
71 | '''configuration file and does not use one by default. Also | |
72 | '''.B mdadm | |
73 | '''helps with management of the configuration | |
74 | '''file. | |
75 | '''.IP \(bu 4 | |
76 | '''.B mdadm | |
77 | '''can provide information about your arrays (through Query, Detail, and Examine) | |
78 | '''that | |
79 | '''.B raidtools | |
80 | '''cannot. | |
81 | '''.P | |
82 | '''.I mdadm | |
83 | '''does not use | |
84 | '''.IR /etc/raidtab , | |
85 | '''the | |
86 | '''.B raidtools | |
87 | '''configuration file, at all. It has a different configuration file | |
98b24a2a | 88 | '''with a different format and a different purpose. |
52826846 NB |
89 | |
90 | .SH MODES | |
8382f19b | 91 | mdadm has several major modes of operation: |
cd29a5c8 NB |
92 | .TP |
93 | .B Assemble | |
94 | Assemble the parts of a previously created | |
52826846 | 95 | array into an active array. Components can be explicitly given |
2ae555c3 | 96 | or can be searched for. |
9a9dab36 | 97 | .B mdadm |
cd29a5c8 NB |
98 | checks that the components |
99 | do form a bona fide array, and can, on request, fiddle superblock | |
100 | information so as to assemble a faulty array. | |
101 | ||
102 | .TP | |
103 | .B Build | |
a9d69660 NB |
104 | Build an array that doesn't have per-device superblocks. For these |
105 | sorts of arrays, | |
106 | .I mdadm | |
107 | cannot differentiate between initial creation and subsequent assembly | |
108 | of an array. It also cannot perform any checks that appropriate | |
109 | devices have been requested. Because of this, the | |
110 | .B Build | |
111 | mode should only be used together with a complete understanding of | |
112 | what you are doing. | |
cd29a5c8 NB |
113 | |
114 | .TP | |
115 | .B Create | |
116 | Create a new array with per-device superblocks. | |
117 | '''It can progress | |
118 | '''in several step create-add-add-run or it can all happen with one command. | |
119 | ||
cd29a5c8 NB |
120 | .TP |
121 | .B "Follow or Monitor" | |
5787fa49 | 122 | Monitor one or more md devices and act on any state changes. This is |
1a7dfc35 | 123 | only meaningful for raid1, 4, 5, 6, 10 or multipath arrays as |
98c6faba NB |
124 | only these have interesting state. raid0 or linear never have |
125 | missing, spare, or failed drives, so there is nothing to monitor. | |
5787fa49 | 126 | |
dd0781e5 NB |
127 | .TP |
128 | .B "Grow" | |
129 | Grow (or shrink) an array, or otherwise reshape it in some way. | |
130 | Currently supported growth options including changing the active size | |
2ae555c3 | 131 | of component devices in RAID level 1/4/5/6 and changing the number of |
00be0b12 | 132 | active devices in RAID1/5/6. |
cd29a5c8 | 133 | |
8382f19b NB |
134 | .TP |
135 | .B "Incremental Assembly" | |
136 | Add a single device to an appropriate array. If the addition of the | |
137 | device makes the array runnable, the array will be started. | |
138 | This provides a convenient interface to a | |
139 | .I hot-plug | |
140 | system. As each device is detected, | |
141 | .I mdadm | |
142 | has a chance to include it in some array as appropriate. | |
143 | ||
2ae555c3 NB |
144 | .TP |
145 | .B Manage | |
146 | This is for doing things to specific components of an array such as | |
147 | adding new spares and removing faulty devices. | |
148 | ||
149 | .TP | |
150 | .B Misc | |
151 | This is an 'everything else' mode that supports operations on active | |
152 | arrays, operations on component devices such as erasing old superblocks, and | |
153 | information gathering operations. | |
154 | '''This mode allows operations on independent devices such as examine MD | |
155 | '''superblocks, erasing old superblocks and stopping active arrays. | |
156 | ||
52826846 NB |
157 | .SH OPTIONS |
158 | ||
2ae555c3 | 159 | .SH Options for selecting a mode are: |
52826846 | 160 | |
cd29a5c8 NB |
161 | .TP |
162 | .BR -A ", " --assemble | |
2d465520 | 163 | Assemble a pre-existing array. |
52826846 | 164 | |
cd29a5c8 NB |
165 | .TP |
166 | .BR -B ", " --build | |
167 | Build a legacy array without superblocks. | |
52826846 | 168 | |
cd29a5c8 NB |
169 | .TP |
170 | .BR -C ", " --create | |
171 | Create a new array. | |
52826846 | 172 | |
cd29a5c8 NB |
173 | .TP |
174 | .BR -F ", " --follow ", " --monitor | |
175 | Select | |
176 | .B Monitor | |
177 | mode. | |
52826846 | 178 | |
dd0781e5 NB |
179 | .TP |
180 | .BR -G ", " --grow | |
181 | Change the size or shape of an active array. | |
8382f19b NB |
182 | |
183 | .TP | |
184 | .BE -I ", " --incremental | |
185 | Add a single device into an appropriate array, and possibly start the array. | |
186 | ||
2ae555c3 NB |
187 | .P |
188 | If a device is given before any options, or if the first option is | |
189 | .BR --add , | |
190 | .BR --fail , | |
191 | or | |
192 | .BR --remove , | |
193 | then the MANAGE mode is assume. | |
194 | Anything other than these will cause the | |
195 | .B Misc | |
196 | mode to be assumed. | |
dd0781e5 | 197 | |
2ae555c3 | 198 | .SH Options that are not mode-specific are: |
e793c2e5 | 199 | |
cd29a5c8 NB |
200 | .TP |
201 | .BR -h ", " --help | |
a9d69660 NB |
202 | Display general help message or, after one of the above options, a |
203 | mode specific help message. | |
56eedc1a NB |
204 | |
205 | .TP | |
206 | .B --help-options | |
207 | Display more detailed help about command line parsing and some commonly | |
208 | used options. | |
52826846 | 209 | |
cd29a5c8 NB |
210 | .TP |
211 | .BR -V ", " --version | |
9a9dab36 | 212 | Print version information for mdadm. |
52826846 | 213 | |
cd29a5c8 NB |
214 | .TP |
215 | .BR -v ", " --verbose | |
22892d56 NB |
216 | Be more verbose about what is happening. This can be used twice to be |
217 | extra-verbose. | |
a9d69660 | 218 | The extra verbosity currently only affects |
22892d56 NB |
219 | .B --detail --scan |
220 | and | |
221 | .BR "--examine --scan" . | |
52826846 | 222 | |
dab6685f NB |
223 | .TP |
224 | .BR -q ", " --quiet | |
225 | Avoid printing purely informative messages. With this, | |
226 | .B mdadm | |
227 | will be silent unless there is something really important to report. | |
228 | ||
cd29a5c8 NB |
229 | .TP |
230 | .BR -b ", " --brief | |
231 | Be less verbose. This is used with | |
232 | .B --detail | |
233 | and | |
234 | .BR --examine . | |
22892d56 NB |
235 | Using |
236 | .B --brief | |
237 | with | |
238 | .B --verbose | |
239 | gives an intermediate level of verbosity. | |
52826846 | 240 | |
e0d19036 NB |
241 | .TP |
242 | .BR -f ", " --force | |
243 | Be more forceful about certain operations. See the various modes of | |
244 | the exact meaning of this option in different contexts. | |
245 | ||
246 | .TP | |
247 | .BR -c ", " --config= | |
2ae555c3 NB |
248 | Specify the config file. Default is to use |
249 | .BR /etc/mdadm.conf , | |
250 | or if that is missing, then | |
251 | .BR /etc/mdadm/mdadm.conf . | |
5787fa49 NB |
252 | If the config file given is |
253 | .B partitions | |
254 | then nothing will be read, but | |
255 | .I mdadm | |
256 | will act as though the config file contained exactly | |
257 | .B "DEVICE partitions" | |
258 | and will read | |
259 | .B /proc/partitions | |
260 | to find a list of devices to scan. | |
d013a55e NB |
261 | If the word |
262 | .B none | |
263 | is given for the config file, then | |
264 | .I mdadm | |
265 | will act as though the config file were empty. | |
e0d19036 NB |
266 | |
267 | .TP | |
268 | .BR -s ", " --scan | |
269 | scan config file or | |
270 | .B /proc/mdstat | |
271 | for missing information. | |
272 | In general, this option gives | |
273 | .B mdadm | |
274 | permission to get any missing information, like component devices, | |
275 | array devices, array identities, and alert destination from the | |
276 | configuration file: | |
277 | .BR /etc/mdadm.conf . | |
278 | One exception is MISC mode when using | |
279 | .B --detail | |
280 | or | |
281 | .B --stop | |
282 | in which case | |
283 | .B --scan | |
284 | says to get a list of array devices from | |
285 | .BR /proc/mdstat . | |
286 | ||
570c0542 NB |
287 | .TP |
288 | .B -e ", " --metadata= | |
289 | Declare the style of superblock (raid metadata) to be used. The | |
53e8b987 PS |
290 | default is 0.90 for |
291 | .BR --create , | |
292 | and to guess for other operations. | |
2790ffe3 GB |
293 | The default can be overridden by setting the |
294 | .B metadata | |
295 | value for the | |
296 | .B CREATE | |
297 | keyword in | |
298 | .BR mdadm.conf . | |
570c0542 NB |
299 | |
300 | Options are: | |
301 | .RS | |
302 | .IP "0, 0.90, default" | |
303 | Use the original 0.90 format superblock. This format limits arrays to | |
304 | 28 componenet devices and limits component devices of levels 1 and | |
305 | greater to 2 terabytes. | |
306 | .IP "1, 1.0, 1.1, 1.2" | |
307 | Use the new version-1 format superblock. This has few restrictions. | |
308 | The different subversion store the superblock at different locations | |
309 | on the device, either at the end (for 1.0), at the start (for 1.1) or | |
310 | 4K from the start (for 1.2). | |
311 | .RE | |
312 | ||
41a3b72a NB |
313 | .TP |
314 | .B --homehost= | |
35cc5be4 | 315 | This will override any |
41a3b72a NB |
316 | .B HOMEHOST |
317 | setting in the config file and provides the identify of the host which | |
318 | should be considered the home for any arrays. | |
319 | ||
320 | When creating an array, the | |
321 | .B homehost | |
322 | will be recorded in the superblock. For version-1 superblocks, it will | |
323 | be prefixed to the array name. For version-0.90 superblocks part of | |
324 | the SHA1 hash of the hostname will be stored in the later half of the | |
325 | UUID. | |
326 | ||
327 | When reporting information about an array, any array which is tagged | |
328 | for the given homehost will be reported as such. | |
329 | ||
330 | When using Auto-Assemble, only arrays tagged for the given homehost | |
331 | will be assembled. | |
332 | ||
2ae555c3 NB |
333 | .SH For create, build, or grow: |
334 | ||
335 | .TP | |
336 | .BR -n ", " --raid-devices= | |
337 | Specify the number of active devices in the array. This, plus the | |
338 | number of spare devices (see below) must equal the number of | |
339 | .I component-devices | |
340 | (including "\fBmissing\fP" devices) | |
341 | that are listed on the command line for | |
342 | .BR --create . | |
343 | Setting a value of 1 is probably | |
344 | a mistake and so requires that | |
345 | .B --force | |
346 | be specified first. A value of 1 will then be allowed for linear, | |
347 | multipath, raid0 and raid1. It is never allowed for raid4 or raid5. | |
348 | .br | |
349 | This number can only be changed using | |
350 | .B --grow | |
00be0b12 NB |
351 | for RAID1, RAID5 and RAID6 arrays, and only on kernels which provide |
352 | necessary support. | |
2ae555c3 NB |
353 | |
354 | .TP | |
355 | .BR -x ", " --spare-devices= | |
356 | Specify the number of spare (eXtra) devices in the initial array. | |
357 | Spares can also be added | |
358 | and removed later. The number of component devices listed | |
359 | on the command line must equal the number of raid devices plus the | |
360 | number of spare devices. | |
361 | ||
362 | ||
363 | .TP | |
364 | .BR -z ", " --size= | |
365 | Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6. | |
366 | This must be a multiple of the chunk size, and must leave about 128Kb | |
367 | of space at the end of the drive for the RAID superblock. | |
368 | If this is not specified | |
369 | (as it normally is not) the smallest drive (or partition) sets the | |
370 | size, though if there is a variance among the drives of greater than 1%, a warning is | |
371 | issued. | |
372 | ||
373 | This value can be set with | |
374 | .B --grow | |
375 | for RAID level 1/4/5/6. If the array was created with a size smaller | |
376 | than the currently active drives, the extra space can be accessed | |
377 | using | |
378 | .BR --grow . | |
379 | The size can be given as | |
380 | .B max | |
381 | which means to choose the largest size that fits on all current drives. | |
52826846 | 382 | |
cd29a5c8 NB |
383 | .TP |
384 | .BR -c ", " --chunk= | |
385 | Specify chunk size of kibibytes. The default is 64. | |
52826846 | 386 | |
cd29a5c8 NB |
387 | .TP |
388 | .BR --rounding= | |
389 | Specify rounding factor for linear array (==chunk size) | |
52826846 | 390 | |
cd29a5c8 NB |
391 | .TP |
392 | .BR -l ", " --level= | |
aa88f531 | 393 | Set raid level. When used with |
53e8b987 | 394 | .BR --create , |
98c6faba | 395 | options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4, |
2ae555c3 | 396 | raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty. Obviously some of these are synonymous. |
aa88f531 NB |
397 | |
398 | When used with | |
53e8b987 | 399 | .BR --build , |
a9d69660 | 400 | only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid. |
52826846 | 401 | |
2ae555c3 | 402 | Not yet supported with |
53e8b987 | 403 | .BR --grow . |
2ae555c3 | 404 | |
cd29a5c8 | 405 | .TP |
1a7dfc35 NB |
406 | .BR -p ", " --layout= |
407 | This option configures the fine details of data layout for raid5, | |
408 | and raid10 arrays, and controls the failure modes for | |
409 | .IR faulty . | |
410 | ||
411 | The layout of the raid5 parity block can be one of | |
53e8b987 PS |
412 | .BR left-asymmetric , |
413 | .BR left-symmetric , | |
414 | .BR right-asymmetric , | |
415 | .BR right-symmetric , | |
416 | .BR la ", " ra ", " ls ", " rs . | |
417 | The default is | |
418 | .BR left-symmetric . | |
52826846 | 419 | |
1a7dfc35 NB |
420 | When setting the failure mode for |
421 | .I faulty | |
422 | the options are: | |
53e8b987 PS |
423 | .BR write-transient ", " wt , |
424 | .BR read-transient ", " rt , | |
425 | .BR write-persistent ", " wp , | |
426 | .BR read-persistent ", " rp , | |
427 | .BR write-all , | |
428 | .BR read-fixable ", " rf , | |
429 | .BR clear ", " flush ", " none . | |
b5e64645 NB |
430 | |
431 | Each mode can be followed by a number which is used as a period | |
432 | between fault generation. Without a number, the fault is generated | |
433 | once on the first relevant request. With a number, the fault will be | |
434 | generated after that many request, and will continue to be generated | |
435 | every time the period elapses. | |
436 | ||
437 | Multiple failure modes can be current simultaneously by using the | |
53e8b987 PS |
438 | .B --grow |
439 | option to set subsequent failure modes. | |
b5e64645 NB |
440 | |
441 | "clear" or "none" will remove any pending or periodic failure modes, | |
2ae555c3 | 442 | and "flush" will clear any persistent faults. |
b5e64645 | 443 | |
53e8b987 PS |
444 | To set the parity with |
445 | .BR --grow , | |
446 | the level of the array ("faulty") | |
b5e64645 NB |
447 | must be specified before the fault mode is specified. |
448 | ||
b578481c | 449 | Finally, the layout options for RAID10 are one of 'n', 'o' or 'p' followed |
1a7dfc35 NB |
450 | by a small number. The default is 'n2'. |
451 | ||
452 | .I n | |
b578481c NB |
453 | signals 'near' copies. Multiple copies of one data block are at |
454 | similar offsets in different devices. | |
455 | ||
456 | .I o | |
457 | signals 'offset' copies. Rather than the chunks being duplicated | |
458 | within a stripe, whole stripes are duplicated but are rotated by one | |
459 | device so duplicate blocks are on different devices. Thus subsequent | |
460 | copies of a block are in the next drive, and are one chunk further | |
461 | down. | |
462 | ||
1a7dfc35 NB |
463 | .I f |
464 | signals 'far' copies | |
465 | (multiple copies have very different offsets). See md(4) for more | |
466 | detail about 'near' and 'far'. | |
467 | ||
468 | The number is the number of copies of each datablock. 2 is normal, 3 | |
469 | can be useful. This number can be at most equal to the number of | |
470 | devices in the array. It does not need to divide evenly into that | |
471 | number (e.g. it is perfectly legal to have an 'n2' layout for an array | |
472 | with an odd number of devices). | |
473 | ||
cd29a5c8 | 474 | .TP |
1a7dfc35 | 475 | .BR --parity= |
53e8b987 PS |
476 | same as |
477 | .B --layout | |
478 | (thus explaining the p of | |
479 | .BR -p ). | |
52826846 | 480 | |
e793c2e5 NB |
481 | .TP |
482 | .BR -b ", " --bitmap= | |
483 | Specify a file to store a write-intent bitmap in. The file should not | |
53e8b987 PS |
484 | exist unless |
485 | .B --force | |
486 | is also given. The same file should be provided | |
2ae555c3 NB |
487 | when assembling the array. If the word |
488 | .B internal | |
489 | is given, then the bitmap is stored with the metadata on the array, | |
490 | and so is replicated on all devices. If the word | |
491 | .B none | |
492 | is given with | |
493 | .B --grow | |
494 | mode, then any bitmap that is present is removed. | |
e793c2e5 | 495 | |
2ae555c3 NB |
496 | To help catch typing errors, the filename must contain at least one |
497 | slash ('/') if it is a real file (not 'internal' or 'none'). | |
498 | ||
499 | Note: external bitmaps are only known to work on ext2 and ext3. | |
500 | Storing bitmap files on other filesystems may result in serious problems. | |
e793c2e5 | 501 | |
cd29a5c8 | 502 | .TP |
2ae555c3 NB |
503 | .BR --bitmap-chunk= |
504 | Set the chunksize of the bitmap. Each bit corresponds to that many | |
1bfdbe01 NB |
505 | Kilobytes of storage. |
506 | When using a file based bitmap, the default is to use the smallest | |
507 | size that is atleast 4 and requires no more than 2^21 chunks. | |
2ae555c3 NB |
508 | When using an |
509 | .B internal | |
510 | bitmap, the chunksize is automatically determined to make best use of | |
511 | available space. | |
5787fa49 | 512 | |
cd29a5c8 NB |
513 | |
514 | .TP | |
2ae555c3 NB |
515 | .BR -W ", " --write-mostly |
516 | subsequent devices lists in a | |
517 | .BR --build , | |
518 | .BR --create , | |
519 | or | |
520 | .B --add | |
521 | command will be flagged as 'write-mostly'. This is valid for RAID1 | |
522 | only and means that the 'md' driver will avoid reading from these | |
523 | devices if at all possible. This can be useful if mirroring over a | |
524 | slow link. | |
52826846 | 525 | |
2ae555c3 NB |
526 | .TP |
527 | .BR --write-behind= | |
528 | Specify that write-behind mode should be enabled (valid for RAID1 | |
529 | only). If an argument is specified, it will set the maximum number | |
530 | of outstanding writes allowed. The default value is 256. | |
531 | A write-intent bitmap is required in order to use write-behind | |
532 | mode, and write-behind is only attempted on drives marked as | |
533 | .IR write-mostly . | |
dd0781e5 NB |
534 | |
535 | .TP | |
536 | .BR --assume-clean | |
537 | Tell | |
538 | .I mdadm | |
47d79ef8 NB |
539 | that the array pre-existed and is known to be clean. It can be useful |
540 | when trying to recover from a major failure as you can be sure that no | |
541 | data will be affected unless you actually write to the array. It can | |
542 | also be used when creating a RAID1 or RAID10 if you want to avoid the | |
b3f1c093 | 543 | initial resync, however this practice \(em while normally safe \(em is not |
47d79ef8 | 544 | recommended. Use this ony if you really know what you are doing. |
dd0781e5 | 545 | |
2ae555c3 NB |
546 | .TP |
547 | .BR --backup-file= | |
53e8b987 PS |
548 | This is needed when |
549 | .B --grow | |
550 | is used to increase the number of | |
2ae555c3 NB |
551 | raid-devices in a RAID5 if there are no spare devices available. |
552 | See the section below on RAID_DEVICE CHANGES. The file should be | |
553 | stored on a separate device, not on the raid array being reshaped. | |
554 | ||
947fd4dd NB |
555 | .TP |
556 | .BR -N ", " --name= | |
557 | Set a | |
558 | .B name | |
559 | for the array. This is currently only effective when creating an | |
560 | array with a version-1 superblock. The name is a simple textual | |
561 | string that can be used to identify array components when assembling. | |
562 | ||
dd0781e5 NB |
563 | .TP |
564 | .BR -R ", " --run | |
565 | Insist that | |
566 | .I mdadm | |
567 | run the array, even if some of the components | |
568 | appear to be active in another array or filesystem. Normally | |
569 | .I mdadm | |
570 | will ask for confirmation before including such components in an | |
571 | array. This option causes that question to be suppressed. | |
572 | ||
573 | .TP | |
574 | .BR -f ", " --force | |
575 | Insist that | |
576 | .I mdadm | |
577 | accept the geometry and layout specified without question. Normally | |
578 | .I mdadm | |
579 | will not allow creation of an array with only one device, and will try | |
580 | to create a raid5 array with one missing drive (as this makes the | |
581 | initial resync work faster). With | |
582 | .BR --force , | |
583 | .I mdadm | |
584 | will not try to be so clever. | |
585 | ||
586 | .TP | |
587 | .BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}" | |
48f7b27a NB |
588 | Instruct mdadm to create the device file if needed, possibly allocating |
589 | an unused minor number. "md" causes a non-partitionable array | |
dd0781e5 | 590 | to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and |
2ae555c3 | 591 | later) to be used. "yes" requires the named md device to have |
f9c25f1d | 592 | a 'standard' format, and the type and minor number will be determined |
48f7b27a NB |
593 | from this. See DEVICE NAMES below. |
594 | ||
a9d69660 | 595 | The argument can also come immediately after |
dd0781e5 NB |
596 | "-a". e.g. "-ap". |
597 | ||
53e8b987 PS |
598 | If |
599 | .B --auto | |
600 | is not given on the command line or in the config file, then | |
75723446 NB |
601 | the default will be |
602 | .BR --auto=yes . | |
603 | ||
1337546d | 604 | If |
53e8b987 | 605 | .B --scan |
1337546d NB |
606 | is also given, then any |
607 | .I auto= | |
35cc5be4 | 608 | entries in the config file will override the |
53e8b987 | 609 | .B --auto |
1337546d NB |
610 | instruction given on the command line. |
611 | ||
dd0781e5 NB |
612 | For partitionable arrays, |
613 | .I mdadm | |
614 | will create the device file for the whole array and for the first 4 | |
615 | partitions. A different number of partitions can be specified at the | |
616 | end of this option (e.g. | |
617 | .BR --auto=p7 ). | |
2ae555c3 | 618 | If the device name ends with a digit, the partition names add a 'p', |
48f7b27a | 619 | and a number, e.g. "/dev/home1p3". If there is no |
dd0781e5 NB |
620 | trailing digit, then the partition names just have a number added, |
621 | e.g. "/dev/scratch3". | |
622 | ||
48f7b27a NB |
623 | If the md device name is in a 'standard' format as described in DEVICE |
624 | NAMES, then it will be created, if necessary, with the appropriate | |
625 | number based on that name. If the device name is not in one of these | |
a9d69660 | 626 | formats, then a unused minor number will be allocated. The minor |
48f7b27a NB |
627 | number will be considered unused if there is no active array for that |
628 | number, and there is no entry in /dev for that number and with a | |
629 | non-standard name. | |
630 | ||
38098016 NB |
631 | .TP |
632 | .BR --symlink = no | |
633 | Normally when | |
634 | .B --auto | |
635 | causes | |
636 | .I mdadm | |
637 | to create devices in | |
638 | .B /dev/md/ | |
639 | it will also create symlinks from | |
640 | .B /dev/ | |
641 | with names starting with | |
642 | .B md | |
643 | or | |
644 | .BR md_ . | |
645 | Use | |
646 | .B --symlink=no | |
647 | to suppress this, or | |
648 | .B --symlink=yes | |
649 | to enforce this even if it is suppressing | |
650 | .IR mdadm.conf . | |
651 | ||
652 | ||
52826846 NB |
653 | .SH For assemble: |
654 | ||
cd29a5c8 NB |
655 | .TP |
656 | .BR -u ", " --uuid= | |
657 | uuid of array to assemble. Devices which don't have this uuid are | |
658 | excluded | |
659 | ||
660 | .TP | |
661 | .BR -m ", " --super-minor= | |
662 | Minor number of device that array was created for. Devices which | |
663 | don't have this minor number are excluded. If you create an array as | |
2d465520 | 664 | /dev/md1, then all superblocks will contain the minor number 1, even if |
cd29a5c8 NB |
665 | the array is later assembled as /dev/md2. |
666 | ||
d013a55e NB |
667 | Giving the literal word "dev" for |
668 | .B --super-minor | |
669 | will cause | |
670 | .I mdadm | |
671 | to use the minor number of the md device that is being assembled. | |
672 | e.g. when assembling | |
673 | .BR /dev/md0 , | |
674 | .M --super-minor=dev | |
675 | will look for super blocks with a minor number of 0. | |
676 | ||
947fd4dd NB |
677 | .TP |
678 | .BR -N ", " --name= | |
679 | Specify the name of the array to assemble. This must be the name | |
624920bb NB |
680 | that was specified when creating the array. It must either match |
681 | then name stored in the superblock exactly, or it must match | |
41a3b72a | 682 | with the current |
624920bb NB |
683 | .I homehost |
684 | is added to the start of the given name. | |
947fd4dd | 685 | |
cd29a5c8 NB |
686 | .TP |
687 | .BR -f ", " --force | |
52826846 NB |
688 | Assemble the array even if some superblocks appear out-of-date |
689 | ||
cd29a5c8 NB |
690 | .TP |
691 | .BR -R ", " --run | |
b8a8ccf9 NB |
692 | Attempt to start the array even if fewer drives were given than were |
693 | present last time the array was active. Normally if not all the | |
694 | expected drives are found and | |
cd29a5c8 NB |
695 | .B --scan |
696 | is not used, then the array will be assembled but not started. | |
697 | With | |
698 | .B --run | |
699 | an attempt will be made to start it anyway. | |
52826846 | 700 | |
b8a8ccf9 NB |
701 | .TP |
702 | .B --no-degraded | |
703 | This is the reverse of | |
704 | .B --run | |
705 | in that it inhibits the started if array unless all expected drives | |
706 | are present. This is only needed with | |
707 | .B --scan | |
708 | and can be used if you physical connections to devices are | |
709 | not as reliable as you would like. | |
710 | ||
dd0781e5 NB |
711 | .TP |
712 | .BR -a ", " "--auto{=no,yes,md,mdp,part}" | |
713 | See this option under Create and Build options. | |
714 | ||
e793c2e5 NB |
715 | .TP |
716 | .BR -b ", " --bitmap= | |
2ae555c3 NB |
717 | Specify the bitmap file that was given when the array was created. If |
718 | an array has an | |
719 | .B internal | |
720 | bitmap, there is no need to specify this when assembling the array. | |
721 | ||
722 | .TP | |
723 | .BR --backup-file= | |
724 | If | |
725 | .B --backup-file | |
726 | was used to grow the number of raid-devices in a RAID5, and the system | |
727 | crashed during the critical section, then the same | |
728 | .B --backup-file | |
53e8b987 PS |
729 | must be presented to |
730 | .B --assemble | |
731 | to allow possibly corrupted data to be restored. | |
e793c2e5 | 732 | |
5787fa49 NB |
733 | .TP |
734 | .BR -U ", " --update= | |
735 | Update the superblock on each device while assembling the array. The | |
feb716e9 NB |
736 | argument given to this flag can be one of |
737 | .BR sparc2.2 , | |
738 | .BR summaries , | |
7d99579f | 739 | .BR uuid , |
c4f12c13 | 740 | .BR name , |
0237e0ca | 741 | .BR homehost , |
e5329c37 | 742 | .BR resync , |
586ed405 | 743 | .BR byteorder , |
bee8ec56 | 744 | .BR devicesize , |
5787fa49 NB |
745 | or |
746 | .BR super-minor . | |
747 | ||
748 | The | |
749 | .B sparc2.2 | |
7d99579f | 750 | option will adjust the superblock of an array what was created on a Sparc |
5787fa49 NB |
751 | machine running a patched 2.2 Linux kernel. This kernel got the |
752 | alignment of part of the superblock wrong. You can use the | |
753 | .B "--examine --sparc2.2" | |
754 | option to | |
755 | .I mdadm | |
756 | to see what effect this would have. | |
757 | ||
758 | The | |
759 | .B super-minor | |
760 | option will update the | |
2ae555c3 | 761 | .B "preferred minor" |
5787fa49 | 762 | field on each superblock to match the minor number of the array being |
45c073c9 NB |
763 | assembled. |
764 | This can be useful if | |
765 | .B --examine | |
766 | reports a different "Preferred Minor" to | |
767 | .BR --detail . | |
768 | In some cases this update will be performed automatically | |
769 | by the kernel driver. In particular the update happens automatically | |
770 | at the first write to an array with redundancy (RAID level 1 or | |
771 | greater) on a 2.6 (or later) kernel. | |
5787fa49 | 772 | |
7d99579f NB |
773 | The |
774 | .B uuid | |
775 | option will change the uuid of the array. If a UUID is given with the | |
53e8b987 PS |
776 | .B --uuid |
777 | option that UUID will be used as a new UUID and will | |
7d99579f NB |
778 | .B NOT |
779 | be used to help identify the devices in the array. | |
53e8b987 PS |
780 | If no |
781 | .B --uuid | |
782 | is given, a random UUID is chosen. | |
7d99579f | 783 | |
c4f12c13 NB |
784 | The |
785 | .B name | |
786 | option will change the | |
787 | .I name | |
788 | of the array as stored in the superblock. This is only supported for | |
789 | version-1 superblocks. | |
790 | ||
0237e0ca NB |
791 | The |
792 | .B homehost | |
793 | option will change the | |
794 | .I homehost | |
795 | as recorded in the superblock. For version-0 superblocks, this is the | |
796 | same as updating the UUID. | |
797 | For version-1 superblocks, this involves updating the name. | |
798 | ||
e5329c37 NB |
799 | The |
800 | .B resync | |
801 | option will cause the array to be marked | |
802 | .I dirty | |
803 | meaning that any redundancy in the array (e.g. parity for raid5, | |
804 | copies for raid1) may be incorrect. This will cause the raid system | |
805 | to perform a "resync" pass to make sure that all redundant information | |
806 | is correct. | |
807 | ||
586ed405 NB |
808 | The |
809 | .B byteorder | |
810 | option allows arrays to be moved between machines with different | |
811 | byte-order. | |
2ae555c3 | 812 | When assembling such an array for the first time after a move, giving |
586ed405 NB |
813 | .B "--update=byteorder" |
814 | will cause | |
815 | .I mdadm | |
816 | to expect superblocks to have their byteorder reversed, and will | |
817 | correct that order before assembling the array. This is only valid | |
2ae555c3 | 818 | with original (Version 0.90) superblocks. |
586ed405 | 819 | |
feb716e9 NB |
820 | The |
821 | .B summaries | |
822 | option will correct the summaries in the superblock. That is the | |
823 | counts of total, working, active, failed, and spare devices. | |
5787fa49 | 824 | |
bee8ec56 NB |
825 | The |
826 | .B devicesize | |
827 | will rarely be of use. It applies to version 1.1 and 1.2 metadata | |
828 | only (where the metadata is at the start of the device) and is only | |
829 | useful when the component device has changed size (typically become | |
830 | larger). The version 1 metadata records the amount of the device that | |
831 | can be used to store data, so if a device in a version 1.1 or 1.2 | |
832 | array becomes larger, the metadata will still be visible, but the | |
833 | extra space will not. In this case it might be useful to assemble the | |
834 | array with | |
835 | .BR --update=devicesize . | |
836 | This will cause | |
837 | .I mdadm | |
838 | to determine the maximum usable amount of space on each device and | |
839 | update the relevant field in the metadata. | |
840 | ||
41a3b72a NB |
841 | .TP |
842 | .B --auto-update-homehost | |
843 | This flag is only meaning with auto-assembly (see discussion below). | |
844 | In that situation, if no suitable arrays are found for this homehost, | |
845 | .I mdadm | |
846 | will recan for any arrays at all and will assemble them and update the | |
847 | homehost to match the current host. | |
848 | ||
e0d19036 | 849 | .SH For Manage mode: |
52826846 | 850 | |
cd29a5c8 NB |
851 | .TP |
852 | .BR -a ", " --add | |
2ae555c3 | 853 | hot-add listed devices. |
52826846 | 854 | |
fe80f49b NB |
855 | .TP |
856 | .BR --re-add | |
2ae555c3 | 857 | re-add a device that was recently removed from an array. |
fe80f49b | 858 | |
cd29a5c8 NB |
859 | .TP |
860 | .BR -r ", " --remove | |
2d465520 | 861 | remove listed devices. They must not be active. i.e. they should |
cd29a5c8 | 862 | be failed or spare devices. |
52826846 | 863 | |
cd29a5c8 NB |
864 | .TP |
865 | .BR -f ", " --fail | |
866 | mark listed devices as faulty. | |
52826846 | 867 | |
cd29a5c8 NB |
868 | .TP |
869 | .BR --set-faulty | |
53e8b987 PS |
870 | same as |
871 | .BR --fail . | |
52826846 | 872 | |
2ae555c3 NB |
873 | .P |
874 | Each of these options require that the first device list is the array | |
875 | to be acted upon and the remainder are component devices to be added, | |
876 | removed, or marked as fault. Several different operations can be | |
877 | specified for different devices, e.g. | |
878 | .in +5 | |
879 | mdadm /dev/md0 --add /dev/sda1 --fail /dev/sdb1 --remove /dev/sdb1 | |
880 | .in -5 | |
881 | Each operation applies to all devices listed until the next | |
882 | operations. | |
883 | ||
884 | If an array is using a write-intent bitmap, then devices which have | |
885 | been removed can be re-added in a way that avoids a full | |
886 | reconstruction but instead just updated the blocks that have changed | |
887 | since the device was removed. For arrays with persistent metadata | |
888 | (superblocks) this is done automatically. For arrays created with | |
889 | .B --build | |
890 | mdadm needs to be told that this device we removed recently with | |
53e8b987 | 891 | .BR --re-add . |
2ae555c3 NB |
892 | |
893 | Devices can only be removed from an array if they are not in active | |
894 | use. i.e. that must be spares or failed devices. To remove an active | |
895 | device, it must be marked as | |
896 | .B faulty | |
897 | first. | |
898 | ||
899 | .SH For Misc mode: | |
900 | ||
901 | .TP | |
902 | .BR -Q ", " --query | |
903 | Examine a device to see | |
904 | (1) if it is an md device and (2) if it is a component of an md | |
905 | array. | |
906 | Information about what is discovered is presented. | |
907 | ||
908 | .TP | |
909 | .BR -D ", " --detail | |
910 | Print detail of one or more md devices. | |
5787fa49 | 911 | |
2ae555c3 NB |
912 | .TP |
913 | .BR -E ", " --examine | |
914 | Print content of md superblock on device(s). | |
5787fa49 NB |
915 | .TP |
916 | .B --sparc2.2 | |
a9d69660 | 917 | If an array was created on a 2.2 Linux kernel patched with RAID |
5787fa49 NB |
918 | support, the superblock will have been created incorrectly, or at |
919 | least incompatibly with 2.4 and later kernels. Using the | |
920 | .B --sparc2.2 | |
921 | flag with | |
922 | .B --examine | |
923 | will fix the superblock before displaying it. If this appears to do | |
924 | the right thing, then the array can be successfully assembled using | |
925 | .BR "--assemble --update=sparc2.2" . | |
926 | ||
2ae555c3 NB |
927 | .TP |
928 | .BR -X ", " --examine-bitmap | |
929 | Report information about a bitmap file. | |
e0d19036 | 930 | |
cd29a5c8 NB |
931 | .TP |
932 | .BR -R ", " --run | |
933 | start a partially built array. | |
52826846 | 934 | |
cd29a5c8 NB |
935 | .TP |
936 | .BR -S ", " --stop | |
937 | deactivate array, releasing all resources. | |
52826846 | 938 | |
cd29a5c8 NB |
939 | .TP |
940 | .BR -o ", " --readonly | |
941 | mark array as readonly. | |
52826846 | 942 | |
cd29a5c8 NB |
943 | .TP |
944 | .BR -w ", " --readwrite | |
945 | mark array as readwrite. | |
52826846 | 946 | |
e0d19036 NB |
947 | .TP |
948 | .B --zero-superblock | |
949 | If the device contains a valid md superblock, the block is | |
35cc5be4 | 950 | overwritten with zeros. With |
53e8b987 | 951 | .B --force |
35cc5be4 | 952 | the block where the superblock would be is overwritten even if it |
e0d19036 | 953 | doesn't appear to be valid. |
52826846 | 954 | |
feb716e9 NB |
955 | .TP |
956 | .BR -t ", " --test | |
957 | When used with | |
958 | .BR --detail , | |
959 | the exit status of | |
960 | .I mdadm | |
961 | is set to reflect the status of the device. | |
962 | ||
b90c0e9a NB |
963 | .TP |
964 | .BR -W ", " --wait | |
965 | For each md device given, wait for any resync, recovery, or reshape | |
966 | activity to finish before returning. | |
967 | .I mdadm | |
968 | will return with success if it actually waited for every device | |
969 | listed, otherwise it will return failure. | |
970 | ||
8382f19b NB |
971 | .SH For Incremental Assembly mode: |
972 | .TP | |
973 | .BR --rebuild-map ", " -r | |
974 | Rebuild the map file | |
975 | .RB ( /var/run/mdadm/map ) | |
976 | that | |
977 | .I mdadm | |
978 | uses to help track which arrays are currently being assembled. | |
979 | ||
980 | .TP | |
981 | .BR --run ", " -R | |
982 | Run any array assembled as soon as a minimal number of devices are | |
983 | available, rather than waiting until all expected devices are present. | |
984 | ||
985 | .TP | |
986 | .BR --scan ", " -s | |
987 | Only meaningful with | |
988 | .B -R | |
989 | this will scan the | |
990 | .B map | |
991 | file for arrays that are being incrementally assembled and will try to | |
992 | start any that are not already started. If any such array is listed | |
993 | in | |
994 | .B mdadm.conf | |
995 | as requiring an external bitmap, that bitmap will be attached first. | |
996 | ||
e0d19036 NB |
997 | .SH For Monitor mode: |
998 | .TP | |
999 | .BR -m ", " --mail | |
1000 | Give a mail address to send alerts to. | |
1001 | ||
1002 | .TP | |
1003 | .BR -p ", " --program ", " --alert | |
1004 | Give a program to be run whenever an event is detected. | |
1005 | ||
773135f5 NB |
1006 | .TP |
1007 | .BR -y ", " --syslog | |
1008 | Cause all events to be reported through 'syslog'. The messages have | |
1009 | facility of 'daemon' and varying priorities. | |
1010 | ||
e0d19036 NB |
1011 | .TP |
1012 | .BR -d ", " --delay | |
1013 | Give a delay in seconds. | |
1014 | .B mdadm | |
1015 | polls the md arrays and then waits this many seconds before polling | |
1016 | again. The default is 60 seconds. | |
1017 | ||
d013a55e NB |
1018 | .TP |
1019 | .BR -f ", " --daemonise | |
1020 | Tell | |
1021 | .B mdadm | |
1022 | to run as a background daemon if it decides to monitor anything. This | |
1023 | causes it to fork and run in the child, and to disconnect form the | |
1024 | terminal. The process id of the child is written to stdout. | |
1025 | This is useful with | |
1026 | .B --scan | |
1027 | which will only continue monitoring if a mail address or alert program | |
1028 | is found in the config file. | |
1029 | ||
b5e64645 NB |
1030 | .TP |
1031 | .BR -i ", " --pid-file | |
1032 | When | |
1033 | .B mdadm | |
1034 | is running in daemon mode, write the pid of the daemon process to | |
1035 | the specified file, instead of printing it on standard output. | |
1036 | ||
aa88f531 NB |
1037 | .TP |
1038 | .BR -1 ", " --oneshot | |
1039 | Check arrays only once. This will generate | |
1040 | .B NewArray | |
1041 | events and more significantly | |
1042 | .B DegradedArray | |
a9d69660 NB |
1043 | and |
1044 | .B SparesMissing | |
aa88f531 NB |
1045 | events. Running |
1046 | .in +5 | |
1047 | .B " mdadm --monitor --scan -1" | |
1048 | .in -5 | |
1049 | from a cron script will ensure regular notification of any degraded arrays. | |
1050 | ||
98c6faba NB |
1051 | .TP |
1052 | .BR -t ", " --test | |
1053 | Generate a | |
1054 | .B TestMessage | |
1055 | alert for every array found at startup. This alert gets mailed and | |
1056 | passed to the alert program. This can be used for testing that alert | |
a9d69660 | 1057 | message do get through successfully. |
98c6faba | 1058 | |
e0d19036 | 1059 | .SH ASSEMBLE MODE |
52826846 | 1060 | |
cd29a5c8 NB |
1061 | .HP 12 |
1062 | Usage: | |
9a9dab36 | 1063 | .B mdadm --assemble |
5787fa49 NB |
1064 | .I md-device options-and-component-devices... |
1065 | .HP 12 | |
1066 | Usage: | |
1067 | .B mdadm --assemble --scan | |
1068 | .I md-devices-and-options... | |
cd29a5c8 NB |
1069 | .HP 12 |
1070 | Usage: | |
9a9dab36 | 1071 | .B mdadm --assemble --scan |
cd29a5c8 | 1072 | .I options... |
52826846 | 1073 | |
cd29a5c8 | 1074 | .PP |
52826846 | 1075 | This usage assembles one or more raid arrays from pre-existing components. |
9a9dab36 | 1076 | For each array, mdadm needs to know the md device, the identity of the |
e0d19036 | 1077 | array, and a number of component-devices. These can be found in a number of ways. |
52826846 | 1078 | |
5787fa49 NB |
1079 | In the first usage example (without the |
1080 | .BR --scan ) | |
1081 | the first device given is the md device. | |
1082 | In the second usage example, all devices listed are treated as md | |
1083 | devices and assembly is attempted. | |
1084 | In the third (where no devices are listed) all md devices that are | |
1085 | listed in the configuration file are assembled. | |
52826846 | 1086 | |
d013a55e NB |
1087 | If precisely one device is listed, but |
1088 | .B --scan | |
dd0781e5 | 1089 | is not given, then |
d013a55e NB |
1090 | .I mdadm |
1091 | acts as though | |
1092 | .B --scan | |
1093 | was given and identify information is extracted from the configuration file. | |
1094 | ||
2ae555c3 | 1095 | The identity can be given with the |
52826846 | 1096 | .B --uuid |
cd29a5c8 NB |
1097 | option, with the |
1098 | .B --super-minor | |
5787fa49 | 1099 | option, can be found in the config file, or will be taken from the |
e0d19036 | 1100 | super block on the first component-device listed on the command line. |
52826846 | 1101 | |
2ae555c3 | 1102 | Devices can be given on the |
52826846 | 1103 | .B --assemble |
5787fa49 NB |
1104 | command line or in the config file. Only devices which have an md |
1105 | superblock which contains the right identity will be considered for | |
1106 | any array. | |
52826846 | 1107 | |
2ae555c3 | 1108 | The config file is only used if explicitly named with |
52826846 | 1109 | .B --config |
d013a55e | 1110 | or requested with (a possibly implicit) |
53e8b987 | 1111 | .BR --scan . |
52826846 | 1112 | In the later case, |
9a9dab36 | 1113 | .B /etc/mdadm.conf |
52826846 NB |
1114 | is used. |
1115 | ||
2ae555c3 | 1116 | If |
52826846 | 1117 | .B --scan |
cd29a5c8 NB |
1118 | is not given, then the config file will only be used to find the |
1119 | identity of md arrays. | |
52826846 | 1120 | |
2d465520 | 1121 | Normally the array will be started after it is assembled. However if |
cd29a5c8 | 1122 | .B --scan |
2d465520 | 1123 | is not given and insufficient drives were listed to start a complete |
cd29a5c8 NB |
1124 | (non-degraded) array, then the array is not started (to guard against |
1125 | usage errors). To insist that the array be started in this case (as | |
1a7dfc35 | 1126 | may work for RAID1, 4, 5, 6, or 10), give the |
cd29a5c8 NB |
1127 | .B --run |
1128 | flag. | |
52826846 | 1129 | |
75723446 NB |
1130 | If the md device does not exist, then it will be created providing the |
1131 | intent is clear. i.e. the name must be in a standard form, or the | |
53e8b987 | 1132 | .B --auto |
75723446 NB |
1133 | option must be given to clarify how and whether the device should be |
1134 | created. | |
dd0781e5 NB |
1135 | |
1136 | This can be useful for handling partitioned devices (which don't have | |
b3f1c093 | 1137 | a stable device number \(em it can change after a reboot) and when using |
dd0781e5 NB |
1138 | "udev" to manage your |
1139 | .B /dev | |
1140 | tree (udev cannot handle md devices because of the unusual device | |
1141 | initialisation conventions). | |
1142 | ||
1143 | If the option to "auto" is "mdp" or "part" or (on the command line | |
1144 | only) "p", then mdadm will create a partitionable array, using the | |
2ae555c3 | 1145 | first free one that is not in use, and does not already have an entry |
dd0781e5 NB |
1146 | in /dev (apart from numeric /dev/md* entries). |
1147 | ||
1148 | If the option to "auto" is "yes" or "md" or (on the command line) | |
1149 | nothing, then mdadm will create a traditional, non-partitionable md | |
1150 | array. | |
1151 | ||
1152 | It is expected that the "auto" functionality will be used to create | |
1153 | device entries with meaningful names such as "/dev/md/home" or | |
1154 | "/dev/md/root", rather than names based on the numerical array number. | |
1155 | ||
1156 | When using this option to create a partitionable array, the device | |
1157 | files for the first 4 partitions are also created. If a different | |
1158 | number is required it can be simply appended to the auto option. | |
1159 | e.g. "auto=part8". Partition names are created by appending a digit | |
a9d69660 | 1160 | string to the device name, with an intervening "p" if the device name |
dd0781e5 NB |
1161 | ends with a digit. |
1162 | ||
1163 | The | |
1164 | .B --auto | |
1165 | option is also available in Build and Create modes. As those modes do | |
1166 | not use a config file, the "auto=" config option does not apply to | |
1167 | these modes. | |
52826846 | 1168 | |
41a3b72a NB |
1169 | .SS Auto Assembly |
1170 | When | |
1171 | .B --assemble | |
1172 | is used with | |
1173 | .B --scan | |
1174 | and no devices are listed, | |
1175 | .I mdadm | |
1176 | will first attempt to assemble all the arrays listed in the config | |
1177 | file. | |
1178 | ||
1179 | If a | |
1180 | .B homehost | |
1181 | has been specified (either in the config file or on the command line), | |
1182 | .I mdadm | |
1183 | will look further for possible arrays and will try to assemble | |
1184 | anything that it finds which is tagged as belonging to the given | |
1185 | homehost. This is the only situation where | |
1186 | .I mdadm | |
1187 | will assemble arrays without being given specific device name or | |
1188 | identify information for the array. | |
1189 | ||
1190 | If | |
1191 | .I mdadm | |
1192 | finds a consistent set of devices that look like they should comprise | |
1193 | an array, and if the superblock is tagged as belonging to the given | |
1194 | home host, it will automatically choose a device name and try to | |
1195 | assemble the array. If the array uses version-0.90 metadata, then the | |
1196 | .B minor | |
1197 | number as recorded in the superblock is used to create a name in | |
1198 | .B /dev/md/ | |
1199 | so for example | |
1200 | .BR /dev/md/3 . | |
1201 | If the array uses version-1 metadata, then the | |
1202 | .B name | |
1203 | from the superblock is used to similarly create a name in | |
1204 | .BR /dev/md . | |
1205 | The name will have any 'host' prefix stripped first. | |
1206 | ||
1207 | If | |
1208 | .I mdadm | |
1209 | cannot find any array for the given host at all, and if | |
1210 | .B --auto-update-homehost | |
1211 | is given, then | |
1212 | .I mdadm | |
1213 | will search again for any array (not just an array created for this | |
1214 | host) and will assemble each assuming | |
53e8b987 | 1215 | .BR --update=homehost . |
41a3b72a NB |
1216 | This will change the host tag in the superblock so that on the next run, |
1217 | these arrays will be found without the second pass. The intention of | |
1218 | this feature is to support transitioning a set of md arrays to using | |
1219 | homehost tagging. | |
1220 | ||
1221 | The reason for requiring arrays to be tagged with the homehost for | |
1222 | auto assembly is to guard against problems that can arise when moving | |
1223 | devices from one host to another. | |
1224 | ||
cd29a5c8 | 1225 | .SH BUILD MODE |
52826846 | 1226 | |
cd29a5c8 NB |
1227 | .HP 12 |
1228 | Usage: | |
9a9dab36 | 1229 | .B mdadm --build |
cd29a5c8 NB |
1230 | .I device |
1231 | .BI --chunk= X | |
1232 | .BI --level= Y | |
b83d95f3 | 1233 | .BI --raid-devices= Z |
cd29a5c8 NB |
1234 | .I devices |
1235 | ||
1236 | .PP | |
2ae555c3 | 1237 | This usage is similar to |
cd29a5c8 | 1238 | .BR --create . |
a9d69660 | 1239 | The difference is that it creates an array without a superblock. With |
cd29a5c8 | 1240 | these arrays there is no difference between initially creating the array and |
52826846 NB |
1241 | subsequently assembling the array, except that hopefully there is useful |
1242 | data there in the second case. | |
1243 | ||
a9d69660 NB |
1244 | The level may raid0, linear, multipath, or faulty, or one of their |
1245 | synonyms. All devices must be listed and the array will be started | |
1246 | once complete. | |
cd29a5c8 NB |
1247 | |
1248 | .SH CREATE MODE | |
1249 | ||
1250 | .HP 12 | |
1251 | Usage: | |
9a9dab36 | 1252 | .B mdadm --create |
cd29a5c8 NB |
1253 | .I device |
1254 | .BI --chunk= X | |
1255 | .BI --level= Y | |
1256 | .br | |
b83d95f3 | 1257 | .BI --raid-devices= Z |
cd29a5c8 NB |
1258 | .I devices |
1259 | ||
1260 | .PP | |
1261 | This usage will initialise a new md array, associate some devices with | |
1262 | it, and activate the array. | |
1263 | ||
a9d69660 | 1264 | If the |
dd0781e5 NB |
1265 | .B --auto |
1266 | option is given (as described in more detail in the section on | |
1267 | Assemble mode), then the md device will be created with a suitable | |
1268 | device number if necessary. | |
1269 | ||
cd29a5c8 | 1270 | As devices are added, they are checked to see if they contain raid |
2d465520 | 1271 | superblocks or filesystems. They are also checked to see if the variance in |
cd29a5c8 NB |
1272 | device size exceeds 1%. |
1273 | ||
1274 | If any discrepancy is found, the array will not automatically be run, though | |
2ae555c3 | 1275 | the presence of a |
cd29a5c8 NB |
1276 | .B --run |
1277 | can override this caution. | |
1278 | ||
2d465520 | 1279 | To create a "degraded" array in which some devices are missing, simply |
d013a55e | 1280 | give the word "\fBmissing\fP" |
2d465520 NB |
1281 | in place of a device name. This will cause |
1282 | .B mdadm | |
1283 | to leave the corresponding slot in the array empty. | |
1284 | For a RAID4 or RAID5 array at most one slot can be | |
98c6faba | 1285 | "\fBmissing\fP"; for a RAID6 array at most two slots. |
2d465520 NB |
1286 | For a RAID1 array, only one real device needs to be given. All of the |
1287 | others can be | |
d013a55e | 1288 | "\fBmissing\fP". |
2d465520 | 1289 | |
feb716e9 NB |
1290 | When creating a RAID5 array, |
1291 | .B mdadm | |
1292 | will automatically create a degraded array with an extra spare drive. | |
1293 | This is because building the spare into a degraded array is in general faster than resyncing | |
1294 | the parity on a non-degraded, but not clean, array. This feature can | |
35cc5be4 | 1295 | be overridden with the |
53e8b987 | 1296 | .B --force |
feb716e9 NB |
1297 | option. |
1298 | ||
41a3b72a NB |
1299 | When creating an array with version-1 metadata a name for the host is |
1300 | required. | |
1301 | If this is not given with the | |
1302 | .B --name | |
1303 | option, | |
1304 | .I mdadm | |
1305 | will chose a name based on the last component of the name of the | |
1306 | device being created. So if | |
1307 | .B /dev/md3 | |
1308 | is being created, then the name | |
1309 | .B 3 | |
1310 | will be chosen. | |
1311 | If | |
1312 | .B /dev/md/home | |
1313 | is being created, then the name | |
1314 | .B home | |
1315 | will be used. | |
1316 | ||
3d3dd91e NB |
1317 | A new array will normally get a randomly assigned 128bit UUID which is |
1318 | very likely to be unique. If you have a specific need, you can choose | |
1319 | a UUID for the array by giving the | |
1320 | .B --uuid= | |
1321 | option. Be warned that creating two arrays with the same UUID is a | |
1322 | recipe for disaster. Also, using | |
1323 | .B --uuid= | |
1324 | when creating a v0.90 array will silently override any | |
1325 | .B --homehost= | |
1326 | setting. | |
2ae555c3 | 1327 | '''If the |
cd29a5c8 | 1328 | '''.B --size |
e0d19036 | 1329 | '''option is given, it is not necessary to list any component-devices in this command. |
cd29a5c8 | 1330 | '''They can be added later, before a |
2ae555c3 NB |
1331 | '''.B --run. |
1332 | '''If no | |
cd29a5c8 NB |
1333 | '''.B --size |
1334 | '''is given, the apparent size of the smallest drive given is used. | |
1335 | ||
53e8b987 PS |
1336 | The General Management options that are valid with |
1337 | .B --create | |
1338 | are: | |
cd29a5c8 NB |
1339 | .TP |
1340 | .B --run | |
dd0781e5 | 1341 | insist on running the array even if some devices look like they might |
cd29a5c8 NB |
1342 | be in use. |
1343 | ||
1344 | .TP | |
1345 | .B --readonly | |
b3f1c093 | 1346 | start the array readonly \(em not supported yet. |
52826846 | 1347 | |
2ae555c3 | 1348 | |
e0d19036 | 1349 | .SH MANAGE MODE |
cd29a5c8 NB |
1350 | .HP 12 |
1351 | Usage: | |
e0d19036 NB |
1352 | .B mdadm |
1353 | .I device | |
1354 | .I options... devices... | |
cd29a5c8 NB |
1355 | .PP |
1356 | ||
e0d19036 NB |
1357 | This usage will allow individual devices in an array to be failed, |
1358 | removed or added. It is possible to perform multiple operations with | |
1359 | on command. For example: | |
1360 | .br | |
5787fa49 | 1361 | .B " mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1" |
e0d19036 NB |
1362 | .br |
1363 | will firstly mark | |
1364 | .B /dev/hda1 | |
1365 | as faulty in | |
1366 | .B /dev/md0 | |
1367 | and will then remove it from the array and finally add it back | |
2d465520 | 1368 | in as a spare. However only one md array can be affected by a single |
2ae555c3 | 1369 | command. |
e0d19036 NB |
1370 | |
1371 | .SH MISC MODE | |
1372 | .HP 12 | |
1373 | Usage: | |
9a9dab36 | 1374 | .B mdadm |
e0d19036 NB |
1375 | .I options ... |
1376 | .I devices ... | |
1377 | .PP | |
cd29a5c8 | 1378 | |
b5e64645 | 1379 | MISC mode includes a number of distinct operations that |
e0d19036 NB |
1380 | operate on distinct devices. The operations are: |
1381 | .TP | |
1382 | --query | |
1383 | The device is examined to see if it is | |
1384 | (1) an active md array, or | |
1385 | (2) a component of an md array. | |
1386 | The information discovered is reported. | |
1387 | ||
1388 | .TP | |
1389 | --detail | |
2d465520 NB |
1390 | The device should be an active md device. |
1391 | .B mdadm | |
1392 | will display a detailed description of the array. | |
cd29a5c8 | 1393 | .B --brief |
2d465520 NB |
1394 | or |
1395 | .B --scan | |
1396 | will cause the output to be less detailed and the format to be | |
e0d19036 | 1397 | suitable for inclusion in |
9a9dab36 | 1398 | .BR /etc/mdadm.conf . |
feb716e9 NB |
1399 | The exit status of |
1400 | .I mdadm | |
1401 | will normally be 0 unless | |
1402 | .I mdadm | |
1403 | failed to get useful information about the device(s). However if the | |
1404 | .B --test | |
1405 | option is given, then the exit status will be: | |
1406 | .RS | |
1407 | .TP | |
1408 | 0 | |
1409 | The array is functioning normally. | |
1410 | .TP | |
1411 | 1 | |
1412 | The array has at least one failed device. | |
1413 | .TP | |
1414 | 2 | |
1415 | The array has multiple failed devices and hence is unusable (raid4 or | |
1416 | raid5). | |
1417 | .TP | |
1418 | 4 | |
1419 | There was an error while trying to get information about the device. | |
1420 | .RE | |
cd29a5c8 | 1421 | |
e0d19036 NB |
1422 | .TP |
1423 | --examine | |
2d465520 NB |
1424 | The device should be a component of an md array. |
1425 | .B mdadm | |
1426 | will read the md superblock of the device and display the contents. | |
e0d19036 NB |
1427 | If |
1428 | .B --brief | |
1429 | is given, or | |
1430 | .B --scan | |
1431 | then multiple devices that are components of the one array | |
1432 | are grouped together and reported in a single entry suitable | |
1433 | for inclusion in | |
1434 | .BR /etc/mdadm.conf . | |
1435 | ||
2d465520 | 1436 | Having |
e0d19036 NB |
1437 | .B --scan |
1438 | without listing any devices will cause all devices listed in the | |
1439 | config file to be examined. | |
1440 | ||
1441 | .TP | |
1442 | --stop | |
98c6faba NB |
1443 | The devices should be active md arrays which will be deactivated, as |
1444 | long as they are not currently in use. | |
e0d19036 NB |
1445 | |
1446 | .TP | |
1447 | --run | |
1448 | This will fully activate a partially assembled md array. | |
1449 | ||
1450 | .TP | |
1451 | --readonly | |
1452 | This will mark an active array as read-only, providing that it is | |
1453 | not currently being used. | |
1454 | ||
1455 | .TP | |
1456 | --readwrite | |
1457 | This will change a | |
1458 | .B readonly | |
1459 | array back to being read/write. | |
1460 | ||
2d465520 NB |
1461 | .TP |
1462 | --scan | |
1463 | For all operations except | |
1464 | .BR --examine , | |
1465 | .B --scan | |
1466 | will cause the operation to be applied to all arrays listed in | |
1467 | .BR /proc/mdstat . | |
1468 | For | |
1469 | .BR --examine, | |
1470 | .B --scan | |
1471 | causes all devices listed in the config file to be examined. | |
1472 | ||
1473 | ||
e0d19036 NB |
1474 | .SH MONITOR MODE |
1475 | ||
cd29a5c8 NB |
1476 | .HP 12 |
1477 | Usage: | |
e0d19036 NB |
1478 | .B mdadm --monitor |
1479 | .I options... devices... | |
1480 | ||
cd29a5c8 | 1481 | .PP |
e0d19036 NB |
1482 | This usage causes |
1483 | .B mdadm | |
1484 | to periodically poll a number of md arrays and to report on any events | |
1485 | noticed. | |
1486 | .B mdadm | |
1487 | will never exit once it decides that there are arrays to be checked, | |
1488 | so it should normally be run in the background. | |
1489 | ||
2d465520 NB |
1490 | As well as reporting events, |
1491 | .B mdadm | |
1492 | may move a spare drive from one array to another if they are in the | |
1493 | same | |
1494 | .B spare-group | |
a9d69660 | 1495 | and if the destination array has a failed drive but no spares. |
2d465520 | 1496 | |
e0d19036 NB |
1497 | If any devices are listed on the command line, |
1498 | .B mdadm | |
1499 | will only monitor those devices. Otherwise all arrays listed in the | |
1500 | configuration file will be monitored. Further, if | |
1501 | .B --scan | |
1502 | is given, then any other md devices that appear in | |
1503 | .B /proc/mdstat | |
1504 | will also be monitored. | |
1505 | ||
1506 | The result of monitoring the arrays is the generation of events. | |
bd526cee | 1507 | These events are passed to a separate program (if specified) and may |
2d465520 | 1508 | be mailed to a given E-mail address. |
e0d19036 | 1509 | |
bd526cee | 1510 | When passing event to program, the program is run once for each event |
2ae555c3 | 1511 | and is given 2 or 3 command-line arguments. The first is the |
bd526cee NB |
1512 | name of the event (see below). The second is the name of the |
1513 | md device which is affected, and the third is the name of a related | |
1514 | device if relevant, such as a component device that has failed. | |
cd29a5c8 NB |
1515 | |
1516 | If | |
1517 | .B --scan | |
e0d19036 NB |
1518 | is given, then a program or an E-mail address must be specified on the |
1519 | command line or in the config file. If neither are available, then | |
1520 | .B mdadm | |
1521 | will not monitor anything. | |
1522 | Without | |
cd29a5c8 | 1523 | .B --scan |
e0d19036 | 1524 | .B mdadm |
2d465520 | 1525 | will continue monitoring as long as something was found to monitor. If |
e0d19036 NB |
1526 | no program or email is given, then each event is reported to |
1527 | .BR stdout . | |
cd29a5c8 | 1528 | |
e0d19036 NB |
1529 | The different events are: |
1530 | ||
1531 | .RS 4 | |
1532 | .TP | |
1533 | .B DeviceDisappeared | |
2d465520 | 1534 | An md array which previously was configured appears to no longer be |
773135f5 | 1535 | configured. (syslog priority: Critical) |
e0d19036 | 1536 | |
b8f72a62 NB |
1537 | If |
1538 | .I mdadm | |
1539 | was told to monitor an array which is RAID0 or Linear, then it will | |
1540 | report | |
1541 | .B DeviceDisappeared | |
1542 | with the extra information | |
1543 | .BR Wrong-Level . | |
1544 | This is because RAID0 and Linear do not support the device-failed, | |
1545 | hot-spare and resync operations which are monitored. | |
1546 | ||
e0d19036 NB |
1547 | .TP |
1548 | .B RebuildStarted | |
773135f5 | 1549 | An md array started reconstruction. (syslog priority: Warning) |
e0d19036 NB |
1550 | |
1551 | .TP | |
1552 | .BI Rebuild NN | |
1553 | Where | |
1554 | .I NN | |
1555 | is 20, 40, 60, or 80, this indicates that rebuild has passed that many | |
773135f5 | 1556 | percentage of the total. (syslog priority: Warning) |
e0d19036 | 1557 | |
98c6faba NB |
1558 | .TP |
1559 | .B RebuildFinished | |
1560 | An md array that was rebuilding, isn't any more, either because it | |
773135f5 | 1561 | finished normally or was aborted. (syslog priority: Warning) |
98c6faba | 1562 | |
e0d19036 NB |
1563 | .TP |
1564 | .B Fail | |
773135f5 NB |
1565 | An active component device of an array has been marked as |
1566 | faulty. (syslog priority: Critical) | |
e0d19036 NB |
1567 | |
1568 | .TP | |
1569 | .B FailSpare | |
1570 | A spare component device which was being rebuilt to replace a faulty | |
773135f5 | 1571 | device has failed. (syslog priority: Critial) |
e0d19036 NB |
1572 | |
1573 | .TP | |
1574 | .B SpareActive | |
1575 | A spare component device which was being rebuilt to replace a faulty | |
98b24a2a | 1576 | device has been successfully rebuilt and has been made active. |
773135f5 | 1577 | (syslog priority: Info) |
e0d19036 NB |
1578 | |
1579 | .TP | |
1580 | .B NewArray | |
1581 | A new md array has been detected in the | |
1582 | .B /proc/mdstat | |
773135f5 | 1583 | file. (syslog priority: Info) |
e0d19036 | 1584 | |
aa88f531 NB |
1585 | .TP |
1586 | .B DegradedArray | |
1587 | A newly noticed array appears to be degraded. This message is not | |
1588 | generated when | |
1589 | .I mdadm | |
1590 | notices a drive failure which causes degradation, but only when | |
1591 | .I mdadm | |
1592 | notices that an array is degraded when it first sees the array. | |
773135f5 | 1593 | (syslog priority: Critial) |
aa88f531 | 1594 | |
e0d19036 NB |
1595 | .TP |
1596 | .B MoveSpare | |
1597 | A spare drive has been moved from one array in a | |
1598 | .B spare-group | |
1599 | to another to allow a failed drive to be replaced. | |
773135f5 | 1600 | (syslog priority: Info) |
e0d19036 | 1601 | |
b8f72a62 NB |
1602 | .TP |
1603 | .B SparesMissing | |
1604 | If | |
1605 | .I mdadm | |
1606 | has been told, via the config file, that an array should have a certain | |
1607 | number of spare devices, and | |
1608 | .I mdadm | |
1609 | detects that it has fewer that this number when it first sees the | |
1610 | array, it will report a | |
1611 | .B SparesMissing | |
1612 | message. | |
d1732eeb | 1613 | (syslog priority: Warning) |
b8f72a62 | 1614 | |
98c6faba NB |
1615 | .TP |
1616 | .B TestMessage | |
1617 | An array was found at startup, and the | |
1618 | .B --test | |
1619 | flag was given. | |
773135f5 | 1620 | (syslog priority: Info) |
e0d19036 NB |
1621 | .RE |
1622 | ||
1623 | Only | |
98c6faba NB |
1624 | .B Fail , |
1625 | .B FailSpare , | |
1626 | .B DegradedArray , | |
d1732eeb | 1627 | .B SparesMissing , |
e0d19036 | 1628 | and |
98c6faba | 1629 | .B TestMessage |
e0d19036 NB |
1630 | cause Email to be sent. All events cause the program to be run. |
1631 | The program is run with two or three arguments, they being the event | |
1632 | name, the array device and possibly a second device. | |
1633 | ||
1634 | Each event has an associated array device (e.g. | |
1635 | .BR /dev/md1 ) | |
1636 | and possibly a second device. For | |
1637 | .BR Fail , | |
1638 | .BR FailSpare , | |
1639 | and | |
1640 | .B SpareActive | |
1641 | the second device is the relevant component device. | |
1642 | For | |
1643 | .B MoveSpare | |
1644 | the second device is the array that the spare was moved from. | |
1645 | ||
1646 | For | |
1647 | .B mdadm | |
1648 | to move spares from one array to another, the different arrays need to | |
1649 | be labelled with the same | |
1650 | .B spare-group | |
1651 | in the configuration file. The | |
1652 | .B spare-group | |
1653 | name can be any string. It is only necessary that different spare | |
2d465520 | 1654 | groups use different names. |
e0d19036 NB |
1655 | |
1656 | When | |
9a9dab36 | 1657 | .B mdadm |
e0d19036 NB |
1658 | detects that an array which is in a spare group has fewer active |
1659 | devices than necessary for the complete array, and has no spare | |
1660 | devices, it will look for another array in the same spare group that | |
1661 | has a full complement of working drive and a spare. It will then | |
1662 | attempt to remove the spare from the second drive and add it to the | |
1663 | first. | |
1664 | If the removal succeeds but the adding fails, then it is added back to | |
1665 | the original array. | |
1666 | ||
dd0781e5 NB |
1667 | .SH GROW MODE |
1668 | The GROW mode is used for changing the size or shape of an active | |
1669 | array. | |
1670 | For this to work, the kernel must support the necessary change. | |
2ae555c3 | 1671 | Various types of growth are being added during 2.6 development, |
dd0781e5 NB |
1672 | including restructuring a raid5 array to have more active devices. |
1673 | ||
dfd4d8ee NB |
1674 | Currently the only support available is to |
1675 | .IP \(bu 4 | |
1676 | change the "size" attribute | |
1677 | for RAID1, RAID5 and RAID6. | |
1678 | .IP \(bu 4 | |
00be0b12 | 1679 | increase the "raid-disks" attribute of RAID1, RAID5, and RAID6. |
dfd4d8ee | 1680 | .IP \(bu 4 |
2ae555c3 NB |
1681 | add a write-intent bitmap to any array which support these bitmaps, or |
1682 | remove a write-intent bitmap from such an array. | |
dfd4d8ee | 1683 | .PP |
dd0781e5 | 1684 | |
2ae555c3 | 1685 | .SS SIZE CHANGES |
fe80f49b | 1686 | Normally when an array is built the "size" it taken from the smallest |
dd0781e5 NB |
1687 | of the drives. If all the small drives in an arrays are, one at a |
1688 | time, removed and replaced with larger drives, then you could have an | |
1689 | array of large drives with only a small amount used. In this | |
1690 | situation, changing the "size" with "GROW" mode will allow the extra | |
1691 | space to start being used. If the size is increased in this way, a | |
1692 | "resync" process will start to make sure the new parts of the array | |
1693 | are synchronised. | |
1694 | ||
1695 | Note that when an array changes size, any filesystem that may be | |
1696 | stored in the array will not automatically grow to use the space. The | |
1697 | filesystem will need to be explicitly told to use the extra space. | |
1698 | ||
2ae555c3 NB |
1699 | .SS RAID-DEVICES CHANGES |
1700 | ||
dd0781e5 NB |
1701 | A RAID1 array can work with any number of devices from 1 upwards |
1702 | (though 1 is not very useful). There may be times which you want to | |
1703 | increase or decrease the number of active devices. Note that this is | |
1704 | different to hot-add or hot-remove which changes the number of | |
1705 | inactive devices. | |
1706 | ||
1707 | When reducing the number of devices in a RAID1 array, the slots which | |
1708 | are to be removed from the array must already be vacant. That is, the | |
1709 | devices that which were in those slots must be failed and removed. | |
1710 | ||
1711 | When the number of devices is increased, any hot spares that are | |
a9d69660 | 1712 | present will be activated immediately. |
dd0781e5 | 1713 | |
2ae555c3 NB |
1714 | Increasing the number of active devices in a RAID5 is much more |
1715 | effort. Every block in the array will need to be read and written | |
1716 | back to a new location. From 2.6.17, the Linux Kernel is able to do | |
1717 | this safely, including restart and interrupted "reshape". | |
1718 | ||
1719 | When relocating the first few stripes on a raid5, it is not possible | |
1720 | to keep the data on disk completely consistent and crash-proof. To | |
1721 | provide the required safety, mdadm disables writes to the array while | |
1722 | this "critical section" is reshaped, and takes a backup of the data | |
1723 | that is in that section. This backup is normally stored in any spare | |
1724 | devices that the array has, however it can also be stored in a | |
1725 | separate file specified with the | |
1726 | .B --backup-file | |
1727 | option. If this option is used, and the system does crash during the | |
1728 | critical period, the same file must be passed to | |
1729 | .B --assemble | |
1730 | to restore the backup and reassemble the array. | |
1731 | ||
1732 | .SS BITMAP CHANGES | |
1733 | ||
1734 | A write-intent bitmap can be added to, or removed from, an active | |
1735 | array. Either internal bitmaps, or bitmaps stored in a separate file | |
fe80f49b NB |
1736 | can be added. Note that if you add a bitmap stored in a file which is |
1737 | in a filesystem that is on the raid array being affected, the system | |
1738 | will deadlock. The bitmap must be on a separate filesystem. | |
1739 | ||
8382f19b NB |
1740 | .SH INCREMENTAL MODE |
1741 | ||
1742 | .HP 12 | |
1743 | Usage: | |
1744 | .B mdadm --incremental | |
1745 | .RB [ --run ] | |
1746 | .RB [ --quiet ] | |
1747 | .I component-device | |
1748 | .HP 12 | |
1749 | Usage: | |
1750 | .B mdadm --incremental --rebuild | |
1751 | .HP 12 | |
1752 | Usage: | |
1753 | .B mdadm --incremental --run --scan | |
1754 | ||
1755 | ||
1756 | .PP | |
1757 | This mode is designed to be used in conjunction with a device | |
1758 | discovery system. As devices are found in a system, they can be | |
1759 | passed to | |
1760 | .B "mdadm --incremental" | |
1761 | to be conditionally added to an appropriate array. | |
1762 | ||
1763 | .I mdadm | |
1764 | performs a number of tests to determine if the device is part of an | |
1765 | array, and which array is should be part of. If an appropriate array | |
1766 | is found, or can be created, | |
1767 | .I mdadm | |
1768 | adds the device to the array and conditionally starts the array. | |
1769 | ||
1770 | Note that | |
1771 | .I mdadm | |
1772 | will only add devices to an array which were previously working | |
1773 | (active or spare) parts of that array. It does not currently support | |
1774 | automatic inclusion of a new drive as a spare in some array. | |
1775 | ||
1776 | .B "mdadm --incremental" | |
1777 | requires a bug present in all kernels through 2.6.19, to be fixed. | |
1778 | Hopefully this will be fixed in 2.6.20. Alternately apply the patch | |
1779 | which is included with the mdadm source distribution. If | |
1780 | .I mdadm | |
1781 | detects that this bug is present, it will abort any attempt to use | |
1782 | .BR --incremental . | |
1783 | ||
1784 | The tests that | |
1785 | .I mdadm | |
1786 | makes are as follow: | |
1787 | .IP + | |
1788 | Is the device permitted by | |
1789 | .BR mdadm.conf ? | |
1790 | That is, is it listed in a | |
1791 | .B DEVICES | |
1792 | line in that file. If | |
1793 | .B DEVICES | |
1794 | is absent then the default it to allow any device. Similar if | |
1795 | .B DEVICES | |
1796 | contains the special word | |
1797 | .B partitions | |
1798 | then any device is allowed. Otherwise the device name given to | |
1799 | .I mdadm | |
1800 | must match one of the names or patterns in a | |
1801 | .B DEVICES | |
1802 | line. | |
1803 | ||
1804 | .IP + | |
1805 | Does the device have a valid md superblock. If a specific metadata | |
1806 | version is request with | |
1807 | .B --metadata | |
1808 | or | |
1809 | .B -e | |
1810 | then only that style of metadata is accepted, otherwise | |
1811 | .I mdadm | |
1812 | finds any known version of metadata. If no | |
1813 | .I md | |
1814 | metadata is found, the device is rejected. | |
1815 | ||
1816 | .IP + | |
1817 | Does the metadata match an expected array? | |
1818 | The metadata can match in two ways. Either there is an array listed | |
1819 | in | |
1820 | .B mdadm.conf | |
1821 | which identifies the array (either by UUID, by name, by device list, | |
1822 | or by minor-number), the array was created with a | |
1823 | .B homehost | |
1824 | specified, and that | |
1825 | .B homehost | |
1826 | matches that which is given in | |
1827 | .B mdadm.conf | |
1828 | or on the command line. | |
1829 | If | |
1830 | .I mdadm | |
1831 | is not able to positively identify the array as belonging to the | |
1832 | current host, the device will be rejected. | |
1833 | ||
1834 | .IP + | |
1835 | .I mdadm | |
1836 | keeps a list of arrays that is has partly assembled in | |
1837 | .B /var/run/mdadm/map | |
1838 | (or | |
1839 | .B /var/run/mdadm.map | |
1840 | if the directory doesn't exist). If no array exists which matches | |
1841 | the metadata on the new device, | |
1842 | .I mdadm | |
1843 | must choose a device name and unit number. It does this based on any | |
1844 | name given in | |
1845 | .B mdadm.conf | |
1846 | or any name information stored in the metadata. If this name | |
1847 | suggests a unit number, that number will be used, otherwise a free | |
1848 | unit number will be chosen. Normally | |
1849 | .I mdadm | |
1850 | will prefer to create a partitionable array, however if the | |
1851 | .B CREATE | |
1852 | line in | |
1853 | .B mdadm.conf | |
1854 | suggests that a non-partitionable array is preferred, that will be | |
1855 | honoured. | |
1856 | ||
1857 | .IP + | |
1858 | Once an appropriate array is found or created and the device is added, | |
1859 | .I mdadm | |
1860 | must decide if the array is ready to be started. It will | |
1861 | normally compare the number of available (non-spare) devices to the | |
1862 | number of devices that the metadata suggests need to be active. If | |
1863 | there are at least that many, the array will be started. This means | |
1864 | that if any devices are missing the array will not be restarted. | |
1865 | ||
1866 | As an alternative, | |
1867 | .B --run | |
1868 | may be passed to | |
1869 | .B mdadm | |
1870 | in which case the array will be run as soon as there are enough | |
1871 | devices present for the data to be accessible. For a raid1, that | |
1872 | means one device will start the array. For a clean raid5, the array | |
1873 | will be started as soon as all but one drive is present. | |
1874 | ||
1875 | Note that neither of these approaches is really ideal. If it is can | |
1876 | be known that all device discovery has completed, then | |
1877 | .br | |
1878 | .B " mdadm -IRs" | |
1879 | .br | |
1880 | can be run which will try to start all arrays that are being | |
1881 | incrementally assembled. They are started in "read-auto" mode in | |
1882 | which they are read-only until the first write request. This means | |
1883 | that no metadata updates are made and no attempt at resync or recovery | |
1884 | happens. Further devices that are found before the first write can | |
1885 | still be added safely. | |
1886 | ||
2d465520 NB |
1887 | .SH EXAMPLES |
1888 | ||
5787fa49 | 1889 | .B " mdadm --query /dev/name-of-device" |
2d465520 | 1890 | .br |
5787fa49 NB |
1891 | This will find out if a given device is a raid array, or is part of |
1892 | one, and will provide brief information about the device. | |
2d465520 | 1893 | |
5787fa49 | 1894 | .B " mdadm --assemble --scan" |
2d465520 | 1895 | .br |
2ae555c3 | 1896 | This will assemble and start all arrays listed in the standard config file |
5787fa49 | 1897 | file. This command will typically go in a system startup file. |
2d465520 | 1898 | |
2d465520 | 1899 | .B " mdadm --stop --scan" |
5787fa49 NB |
1900 | .br |
1901 | This will shut down all array that can be shut down (i.e. are not | |
19f8b8fc | 1902 | currently in use). This will typically go in a system shutdown script. |
2d465520 | 1903 | |
5787fa49 | 1904 | .B " mdadm --follow --scan --delay=120" |
2d465520 | 1905 | .br |
5787fa49 NB |
1906 | If (and only if) there is an Email address or program given in the |
1907 | standard config file, then | |
1908 | monitor the status of all arrays listed in that file by | |
1909 | polling them ever 2 minutes. | |
2d465520 | 1910 | |
5787fa49 | 1911 | .B " mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[ac]1" |
2d465520 | 1912 | .br |
5787fa49 | 1913 | Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1. |
2d465520 | 1914 | |
2d465520 NB |
1915 | .br |
1916 | .B " echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > mdadm.conf" | |
1917 | .br | |
1918 | .B " mdadm --detail --scan >> mdadm.conf" | |
1919 | .br | |
5787fa49 NB |
1920 | This will create a prototype config file that describes currently |
1921 | active arrays that are known to be made from partitions of IDE or SCSI drives. | |
2d465520 NB |
1922 | This file should be reviewed before being used as it may |
1923 | contain unwanted detail. | |
1924 | ||
2d465520 NB |
1925 | .B " echo 'DEVICE /dev/hd[a-z] /dev/sd*[a-z]' > mdadm.conf" |
1926 | .br | |
5787fa49 NB |
1927 | .B " mdadm --examine --scan --config=mdadm.conf >> mdadm.conf" |
1928 | .ber | |
2ae555c3 | 1929 | This will find what arrays could be assembled from existing IDE and |
5787fa49 NB |
1930 | SCSI whole drives (not partitions) and store the information is the |
1931 | format of a config file. | |
2d465520 NB |
1932 | This file is very likely to contain unwanted detail, particularly |
1933 | the | |
1934 | .B devices= | |
5787fa49 NB |
1935 | entries. It should be reviewed and edited before being used as an |
1936 | actual config file. | |
2d465520 | 1937 | |
5787fa49 | 1938 | .B " mdadm --examine --brief --scan --config=partitions" |
2d465520 | 1939 | .br |
5787fa49 NB |
1940 | .B " mdadm -Ebsc partitions" |
1941 | .br | |
1942 | Create a list of devices by reading | |
1943 | .BR /proc/partitions , | |
1944 | scan these for RAID superblocks, and printout a brief listing of all | |
1945 | that was found. | |
2d465520 | 1946 | |
5787fa49 | 1947 | .B " mdadm -Ac partitions -m 0 /dev/md0" |
2d465520 | 1948 | .br |
5787fa49 NB |
1949 | Scan all partitions and devices listed in |
1950 | .BR /proc/partitions | |
1951 | and assemble | |
1952 | .B /dev/md0 | |
1953 | out of all such devices with a RAID superblock with a minor number of 0. | |
2d465520 | 1954 | |
d013a55e NB |
1955 | .B " mdadm --monitor --scan --daemonise > /var/run/mdadm" |
1956 | .br | |
1957 | If config file contains a mail address or alert program, run mdadm in | |
1958 | the background in monitor mode monitoring all md devices. Also write | |
1959 | pid of mdadm daemon to | |
1960 | .BR /var/run/mdadm . | |
1961 | ||
8382f19b NB |
1962 | .B " mdadm -Iq /dev/somedevice" |
1963 | .br | |
1964 | Try to incorporate newly discovered device into some array as | |
1965 | appropriate. | |
1966 | ||
1967 | .B " mdadm --incremental --rebuild --run --scan" | |
1968 | .br | |
1969 | Rebuild the array map from any current arrays, and then start any that | |
1970 | can be started. | |
1971 | ||
5787fa49 | 1972 | .B " mdadm --create --help" |
2d465520 | 1973 | .br |
2ae555c3 | 1974 | Provide help about the Create mode. |
2d465520 | 1975 | |
5787fa49 NB |
1976 | .B " mdadm --config --help" |
1977 | .br | |
1978 | Provide help about the format of the config file. | |
2d465520 | 1979 | |
5787fa49 NB |
1980 | .B " mdadm --help" |
1981 | .br | |
1982 | Provide general help. | |
cd29a5c8 | 1983 | |
cd29a5c8 NB |
1984 | |
1985 | .SH FILES | |
1986 | ||
1987 | .SS /proc/mdstat | |
1988 | ||
2ae555c3 NB |
1989 | If you're using the |
1990 | .B /proc | |
cd29a5c8 NB |
1991 | filesystem, |
1992 | .B /proc/mdstat | |
2d465520 NB |
1993 | lists all active md devices with information about them. |
1994 | .B mdadm | |
1995 | uses this to find arrays when | |
1996 | .B --scan | |
1997 | is given in Misc mode, and to monitor array reconstruction | |
1998 | on Monitor mode. | |
1999 | ||
cd29a5c8 | 2000 | |
9a9dab36 | 2001 | .SS /etc/mdadm.conf |
cd29a5c8 | 2002 | |
11a3e71d NB |
2003 | The config file lists which devices may be scanned to see if |
2004 | they contain MD super block, and gives identifying information | |
2005 | (e.g. UUID) about known MD arrays. See | |
2006 | .BR mdadm.conf (5) | |
2007 | for more details. | |
cd29a5c8 | 2008 | |
8382f19b NB |
2009 | .SS /var/run/mdadm/map |
2010 | When | |
53e8b987 | 2011 | .B --incremental |
8382f19b NB |
2012 | mode is used. this file gets a list of arrays currently being created. |
2013 | If | |
2014 | .B /var/run/mdadm | |
2015 | does not exist as a directory, then | |
2016 | .B /var/run/mdadm.map | |
2017 | is used instead. | |
2018 | ||
48f7b27a NB |
2019 | .SH DEVICE NAMES |
2020 | ||
2021 | While entries in the /dev directory can have any format you like, | |
2022 | .I mdadm | |
2023 | has an understanding of 'standard' formats which it uses to guide its | |
2024 | behaviour when creating device files via the | |
53e8b987 | 2025 | .B --auto |
48f7b27a NB |
2026 | option. |
2027 | ||
2028 | The standard names for non-partitioned arrays (the only sort of md | |
2029 | array available in 2.4 and earlier) either of | |
2030 | .IP | |
2031 | /dev/mdNN | |
2032 | .br | |
2033 | /dev/md/NN | |
2034 | .PP | |
2035 | where NN is a number. | |
2036 | The standard names for partitionable arrays (as available from 2.6 | |
2037 | onwards) is one of | |
2038 | .IP | |
2039 | /dev/md/dNN | |
2040 | .br | |
2041 | /dev/md_dNN | |
2042 | .PP | |
2043 | Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2". | |
52826846 | 2044 | |
2d465520 NB |
2045 | .SH NOTE |
2046 | .B mdadm | |
2047 | was previously known as | |
2048 | .BR mdctl . | |
a9d69660 NB |
2049 | .P |
2050 | .B mdadm | |
2051 | is completely separate from the | |
2052 | .B raidtools | |
2053 | package, and does not use the | |
2054 | .I /etc/raidtab | |
2055 | configuration file at all. | |
2056 | ||
52826846 | 2057 | .SH SEE ALSO |
cd29a5c8 NB |
2058 | For information on the various levels of |
2059 | RAID, check out: | |
2060 | ||
2061 | .IP | |
2062 | .UR http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/ | |
2063 | http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/ | |
2064 | .UE | |
a9d69660 NB |
2065 | '''.PP |
2066 | '''for new releases of the RAID driver check out: | |
2067 | ''' | |
2068 | '''.IP | |
2069 | '''.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2070 | '''ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2071 | '''.UE | |
2072 | '''.PP | |
2073 | '''or | |
2074 | '''.IP | |
2075 | '''.UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2076 | '''http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2077 | '''.UE | |
cd29a5c8 | 2078 | .PP |
2ae555c3 | 2079 | The latest version of |
a9d69660 NB |
2080 | .I mdadm |
2081 | should always be available from | |
cd29a5c8 | 2082 | .IP |
a9d69660 NB |
2083 | .UR http://www.kernel.org/pub/linux/utils/raid/mdadm/ |
2084 | http://www.kernel.org/pub/linux/utils/raid/mdadm/ | |
cd29a5c8 NB |
2085 | .UE |
2086 | .PP | |
a9d69660 NB |
2087 | .IR mdadm.conf (5), |
2088 | .IR md (4). | |
56eb10c0 | 2089 | .PP |
52826846 NB |
2090 | .IR raidtab (5), |
2091 | .IR raid0run (8), | |
2092 | .IR raidstop (8), | |
a9d69660 | 2093 | .IR mkraid (8). |