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1 | .\" -*- nroff -*- | |
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. | |
8 | .TH MDADM 8 "" v2.6.5 | |
9 | .SH NAME | |
10 | mdadm \- manage MD devices | |
11 | .I aka | |
12 | Linux Software RAID | |
13 | ||
14 | .SH SYNOPSIS | |
15 | ||
16 | .BI mdadm " [mode] <raiddevice> [options] <component-devices>" | |
17 | ||
18 | .SH DESCRIPTION | |
19 | RAID devices are virtual devices created from two or more | |
20 | real block devices. This allows multiple devices (typically disk | |
21 | drives or partitions thereof) to be combined into a single device to | |
22 | hold (for example) a single filesystem. | |
23 | Some RAID levels include redundancy and so can survive some degree of | |
24 | device failure. | |
25 | ||
26 | Linux Software RAID devices are implemented through the md (Multiple | |
27 | Devices) device driver. | |
28 | ||
29 | Currently, Linux supports | |
30 | .B LINEAR | |
31 | md devices, | |
32 | .B RAID0 | |
33 | (striping), | |
34 | .B RAID1 | |
35 | (mirroring), | |
36 | .BR RAID4 , | |
37 | .BR RAID5 , | |
38 | .BR RAID6 , | |
39 | .BR RAID10 , | |
40 | .BR MULTIPATH , | |
41 | and | |
42 | .BR FAULTY . | |
43 | ||
44 | .B MULTIPATH | |
45 | is not a Software RAID mechanism, but does involve | |
46 | multiple devices: | |
47 | each device is a path to one common physical storage device. | |
48 | ||
49 | .B FAULTY | |
50 | is also not true RAID, and it only involves one device. It | |
51 | provides a layer over a true device that can be used to inject faults. | |
52 | ||
53 | .\".B mdadm | |
54 | .\"is a program that can be used to create, manage, and monitor | |
55 | .\"MD devices. As | |
56 | .\"such it provides a similar set of functionality to the | |
57 | .\".B raidtools | |
58 | .\"packages. | |
59 | .\"The key differences between | |
60 | .\".B mdadm | |
61 | .\"and | |
62 | .\".B raidtools | |
63 | .\"are: | |
64 | .\".IP \(bu 4 | |
65 | .\".B mdadm | |
66 | .\"is a single program and not a collection of programs. | |
67 | .\".IP \(bu 4 | |
68 | .\".B mdadm | |
69 | .\"can perform (almost) all of its functions without having a | |
70 | .\"configuration file and does not use one by default. Also | |
71 | .\".B mdadm | |
72 | .\"helps with management of the configuration | |
73 | .\"file. | |
74 | .\".IP \(bu 4 | |
75 | .\".B mdadm | |
76 | .\"can provide information about your arrays (through Query, Detail, and Examine) | |
77 | .\"that | |
78 | .\".B raidtools | |
79 | .\"cannot. | |
80 | .\".P | |
81 | .\".I mdadm | |
82 | .\"does not use | |
83 | .\".IR /etc/raidtab , | |
84 | .\"the | |
85 | .\".B raidtools | |
86 | .\"configuration file, at all. It has a different configuration file | |
87 | .\"with a different format and a different purpose. | |
88 | ||
89 | .SH MODES | |
90 | mdadm has several major modes of operation: | |
91 | .TP | |
92 | .B Assemble | |
93 | Assemble the components of a previously created | |
94 | array into an active array. Components can be explicitly given | |
95 | or can be searched for. | |
96 | .B mdadm | |
97 | checks that the components | |
98 | do form a bona fide array, and can, on request, fiddle superblock | |
99 | information so as to assemble a faulty array. | |
100 | ||
101 | .TP | |
102 | .B Build | |
103 | Build an array that doesn't have per-device superblocks. For these | |
104 | sorts of arrays, | |
105 | .I mdadm | |
106 | cannot differentiate between initial creation and subsequent assembly | |
107 | of an array. It also cannot perform any checks that appropriate | |
108 | components have been requested. Because of this, the | |
109 | .B Build | |
110 | mode should only be used together with a complete understanding of | |
111 | what you are doing. | |
112 | ||
113 | .TP | |
114 | .B Create | |
115 | Create a new array with per-device superblocks. | |
116 | .\"It can progress | |
117 | .\"in several step create-add-add-run or it can all happen with one command. | |
118 | ||
119 | .TP | |
120 | .B "Follow or Monitor" | |
121 | Monitor one or more md devices and act on any state changes. This is | |
122 | only meaningful for raid1, 4, 5, 6, 10 or multipath arrays, as | |
123 | only these have interesting state. raid0 or linear never have | |
124 | missing, spare, or failed drives, so there is nothing to monitor. | |
125 | ||
126 | .TP | |
127 | .B "Grow" | |
128 | Grow (or shrink) an array, or otherwise reshape it in some way. | |
129 | Currently supported growth options including changing the active size | |
130 | of component devices and changing the number of active devices in RAID | |
131 | levels 1/4/5/6, as well as adding or removing a write-intent bitmap. | |
132 | ||
133 | .TP | |
134 | .B "Incremental Assembly" | |
135 | Add a single device to an appropriate array. If the addition of the | |
136 | device makes the array runnable, the array will be started. | |
137 | This provides a convenient interface to a | |
138 | .I hot-plug | |
139 | system. As each device is detected, | |
140 | .I mdadm | |
141 | has a chance to include it in some array as appropriate. | |
142 | ||
143 | .TP | |
144 | .B Manage | |
145 | This is for doing things to specific components of an array such as | |
146 | adding new spares and removing faulty devices. | |
147 | ||
148 | .TP | |
149 | .B Misc | |
150 | This is an 'everything else' mode that supports operations on active | |
151 | arrays, operations on component devices such as erasing old superblocks, and | |
152 | information gathering operations. | |
153 | .\"This mode allows operations on independent devices such as examine MD | |
154 | .\"superblocks, erasing old superblocks and stopping active arrays. | |
155 | ||
156 | .TP | |
157 | .B Auto-detect | |
158 | This mode does not act on a specific device or array, but rather it | |
159 | requests the Linux Kernel to activate any auto-detected arrays. | |
160 | .SH OPTIONS | |
161 | ||
162 | .SH Options for selecting a mode are: | |
163 | ||
164 | .TP | |
165 | .BR \-A ", " \-\-assemble | |
166 | Assemble a pre-existing array. | |
167 | ||
168 | .TP | |
169 | .BR \-B ", " \-\-build | |
170 | Build a legacy array without superblocks. | |
171 | ||
172 | .TP | |
173 | .BR \-C ", " \-\-create | |
174 | Create a new array. | |
175 | ||
176 | .TP | |
177 | .BR \-F ", " \-\-follow ", " \-\-monitor | |
178 | Select | |
179 | .B Monitor | |
180 | mode. | |
181 | ||
182 | .TP | |
183 | .BR \-G ", " \-\-grow | |
184 | Change the size or shape of an active array. | |
185 | ||
186 | .TP | |
187 | .BR \-I ", " \-\-incremental | |
188 | Add a single device into an appropriate array, and possibly start the array. | |
189 | ||
190 | .TP | |
191 | .B \-\-auto-detect | |
192 | Request that the kernel starts any auto-detected arrays. This can only | |
193 | work if | |
194 | .I md | |
195 | is compiled into the kernel \(em not if it is a module. | |
196 | Arrays can be auto-detected by the kernel if all the components are in | |
197 | primary MS-DOS partitions with partition type | |
198 | .BR FD . | |
199 | In-kernel autodetect is not recommended for new installations. Using | |
200 | .I mdadm | |
201 | to detect and assemble arrays \(em possibly in an | |
202 | .I initrd | |
203 | \(em is substantially more flexible and should be preferred. | |
204 | ||
205 | .P | |
206 | If a device is given before any options, or if the first option is | |
207 | .BR \-\-add , | |
208 | .BR \-\-fail , | |
209 | or | |
210 | .BR \-\-remove , | |
211 | then the MANAGE mode is assume. | |
212 | Anything other than these will cause the | |
213 | .B Misc | |
214 | mode to be assumed. | |
215 | ||
216 | .SH Options that are not mode-specific are: | |
217 | ||
218 | .TP | |
219 | .BR \-h ", " \-\-help | |
220 | Display general help message or, after one of the above options, a | |
221 | mode-specific help message. | |
222 | ||
223 | .TP | |
224 | .B \-\-help\-options | |
225 | Display more detailed help about command line parsing and some commonly | |
226 | used options. | |
227 | ||
228 | .TP | |
229 | .BR \-V ", " \-\-version | |
230 | Print version information for mdadm. | |
231 | ||
232 | .TP | |
233 | .BR \-v ", " \-\-verbose | |
234 | Be more verbose about what is happening. This can be used twice to be | |
235 | extra-verbose. | |
236 | The extra verbosity currently only affects | |
237 | .B \-\-detail \-\-scan | |
238 | and | |
239 | .BR "\-\-examine \-\-scan" . | |
240 | ||
241 | .TP | |
242 | .BR \-q ", " \-\-quiet | |
243 | Avoid printing purely informative messages. With this, | |
244 | .B mdadm | |
245 | will be silent unless there is something really important to report. | |
246 | ||
247 | .TP | |
248 | .BR \-b ", " \-\-brief | |
249 | Be less verbose. This is used with | |
250 | .B \-\-detail | |
251 | and | |
252 | .BR \-\-examine . | |
253 | Using | |
254 | .B \-\-brief | |
255 | with | |
256 | .B \-\-verbose | |
257 | gives an intermediate level of verbosity. | |
258 | ||
259 | .TP | |
260 | .BR \-f ", " \-\-force | |
261 | Be more forceful about certain operations. See the various modes for | |
262 | the exact meaning of this option in different contexts. | |
263 | ||
264 | .TP | |
265 | .BR \-c ", " \-\-config= | |
266 | Specify the config file. Default is to use | |
267 | .BR /etc/mdadm.conf , | |
268 | or if that is missing then | |
269 | .BR /etc/mdadm/mdadm.conf . | |
270 | If the config file given is | |
271 | .B "partitions" | |
272 | then nothing will be read, but | |
273 | .I mdadm | |
274 | will act as though the config file contained exactly | |
275 | .B "DEVICE partitions" | |
276 | and will read | |
277 | .B /proc/partitions | |
278 | to find a list of devices to scan. | |
279 | If the word | |
280 | .B "none" | |
281 | is given for the config file, then | |
282 | .I mdadm | |
283 | will act as though the config file were empty. | |
284 | ||
285 | .TP | |
286 | .BR \-s ", " \-\-scan | |
287 | Scan config file or | |
288 | .B /proc/mdstat | |
289 | for missing information. | |
290 | In general, this option gives | |
291 | .B mdadm | |
292 | permission to get any missing information (like component devices, | |
293 | array devices, array identities, and alert destination) from the | |
294 | configuration file (see previous option); | |
295 | one exception is MISC mode when using | |
296 | .B \-\-detail | |
297 | or | |
298 | .B \-\-stop, | |
299 | in which case | |
300 | .B \-\-scan | |
301 | says to get a list of array devices from | |
302 | .BR /proc/mdstat . | |
303 | ||
304 | .TP | |
305 | .B \-e ", " \-\-metadata= | |
306 | Declare the style of superblock (raid metadata) to be used. The | |
307 | default is 0.90 for | |
308 | .BR \-\-create , | |
309 | and to guess for other operations. | |
310 | The default can be overridden by setting the | |
311 | .B metadata | |
312 | value for the | |
313 | .B CREATE | |
314 | keyword in | |
315 | .BR mdadm.conf . | |
316 | ||
317 | Options are: | |
318 | .RS | |
319 | .IP "0, 0.90, default" | |
320 | Use the original 0.90 format superblock. This format limits arrays to | |
321 | 28 component devices and limits component devices of levels 1 and | |
322 | greater to 2 terabytes. | |
323 | .IP "1, 1.0, 1.1, 1.2" | |
324 | Use the new version-1 format superblock. This has few restrictions. | |
325 | The different sub-versions store the superblock at different locations | |
326 | on the device, either at the end (for 1.0), at the start (for 1.1) or | |
327 | 4K from the start (for 1.2). | |
328 | .RE | |
329 | ||
330 | .TP | |
331 | .B \-\-homehost= | |
332 | This will override any | |
333 | .B HOMEHOST | |
334 | setting in the config file and provides the identity of the host which | |
335 | should be considered the home for any arrays. | |
336 | ||
337 | When creating an array, the | |
338 | .B homehost | |
339 | will be recorded in the superblock. For version-1 superblocks, it will | |
340 | be prefixed to the array name. For version-0.90 superblocks, part of | |
341 | the SHA1 hash of the hostname will be stored in the later half of the | |
342 | UUID. | |
343 | ||
344 | When reporting information about an array, any array which is tagged | |
345 | for the given homehost will be reported as such. | |
346 | ||
347 | When using Auto-Assemble, only arrays tagged for the given homehost | |
348 | will be assembled. | |
349 | ||
350 | .SH For create, build, or grow: | |
351 | ||
352 | .TP | |
353 | .BR \-n ", " \-\-raid\-devices= | |
354 | Specify the number of active devices in the array. This, plus the | |
355 | number of spare devices (see below) must equal the number of | |
356 | .I component-devices | |
357 | (including "\fBmissing\fP" devices) | |
358 | that are listed on the command line for | |
359 | .BR \-\-create . | |
360 | Setting a value of 1 is probably | |
361 | a mistake and so requires that | |
362 | .B \-\-force | |
363 | be specified first. A value of 1 will then be allowed for linear, | |
364 | multipath, raid0 and raid1. It is never allowed for raid4 or raid5. | |
365 | .br | |
366 | This number can only be changed using | |
367 | .B \-\-grow | |
368 | for RAID1, RAID5 and RAID6 arrays, and only on kernels which provide | |
369 | necessary support. | |
370 | ||
371 | .TP | |
372 | .BR \-x ", " \-\-spare\-devices= | |
373 | Specify the number of spare (eXtra) devices in the initial array. | |
374 | Spares can also be added | |
375 | and removed later. The number of component devices listed | |
376 | on the command line must equal the number of raid devices plus the | |
377 | number of spare devices. | |
378 | ||
379 | ||
380 | .TP | |
381 | .BR \-z ", " \-\-size= | |
382 | Amount (in Kibibytes) of space to use from each drive in RAID level 1/4/5/6. | |
383 | This must be a multiple of the chunk size, and must leave about 128Kb | |
384 | of space at the end of the drive for the RAID superblock. | |
385 | If this is not specified | |
386 | (as it normally is not) the smallest drive (or partition) sets the | |
387 | size, though if there is a variance among the drives of greater than 1%, a warning is | |
388 | issued. | |
389 | ||
390 | This value can be set with | |
391 | .B \-\-grow | |
392 | for RAID level 1/4/5/6. If the array was created with a size smaller | |
393 | than the currently active drives, the extra space can be accessed | |
394 | using | |
395 | .BR \-\-grow . | |
396 | The size can be given as | |
397 | .B max | |
398 | which means to choose the largest size that fits on all current drives. | |
399 | ||
400 | .TP | |
401 | .BR \-c ", " \-\-chunk= | |
402 | Specify chunk size of kibibytes. The default is 64. | |
403 | ||
404 | .TP | |
405 | .BR \-\-rounding= | |
406 | Specify rounding factor for linear array (==chunk size) | |
407 | ||
408 | .TP | |
409 | .BR \-l ", " \-\-level= | |
410 | Set raid level. When used with | |
411 | .BR \-\-create , | |
412 | options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4, | |
413 | raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty. Obviously some of these are synonymous. | |
414 | ||
415 | When used with | |
416 | .BR \-\-build , | |
417 | only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid. | |
418 | ||
419 | Not yet supported with | |
420 | .BR \-\-grow . | |
421 | ||
422 | .TP | |
423 | .BR \-p ", " \-\-layout= | |
424 | This option configures the fine details of data layout for raid5, | |
425 | and raid10 arrays, and controls the failure modes for | |
426 | .IR faulty . | |
427 | ||
428 | The layout of the raid5 parity block can be one of | |
429 | .BR left\-asymmetric , | |
430 | .BR left\-symmetric , | |
431 | .BR right\-asymmetric , | |
432 | .BR right\-symmetric , | |
433 | .BR la ", " ra ", " ls ", " rs . | |
434 | The default is | |
435 | .BR left\-symmetric . | |
436 | ||
437 | When setting the failure mode for level | |
438 | .I faulty, | |
439 | the options are: | |
440 | .BR write\-transient ", " wt , | |
441 | .BR read\-transient ", " rt , | |
442 | .BR write\-persistent ", " wp , | |
443 | .BR read\-persistent ", " rp , | |
444 | .BR write\-all , | |
445 | .BR read\-fixable ", " rf , | |
446 | .BR clear ", " flush ", " none . | |
447 | ||
448 | Each failure mode can be followed by a number, which is used as a period | |
449 | between fault generation. Without a number, the fault is generated | |
450 | once on the first relevant request. With a number, the fault will be | |
451 | generated after that many requests, and will continue to be generated | |
452 | every time the period elapses. | |
453 | ||
454 | Multiple failure modes can be current simultaneously by using the | |
455 | .B \-\-grow | |
456 | option to set subsequent failure modes. | |
457 | ||
458 | "clear" or "none" will remove any pending or periodic failure modes, | |
459 | and "flush" will clear any persistent faults. | |
460 | ||
461 | To set the parity with | |
462 | .BR \-\-grow , | |
463 | the level of the array ("faulty") | |
464 | must be specified before the fault mode is specified. | |
465 | ||
466 | Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed | |
467 | by a small number. The default is 'n2'. The supported options are: | |
468 | ||
469 | .I 'n' | |
470 | signals 'near' copies. Multiple copies of one data block are at | |
471 | similar offsets in different devices. | |
472 | ||
473 | .I 'o' | |
474 | signals 'offset' copies. Rather than the chunks being duplicated | |
475 | within a stripe, whole stripes are duplicated but are rotated by one | |
476 | device so duplicate blocks are on different devices. Thus subsequent | |
477 | copies of a block are in the next drive, and are one chunk further | |
478 | down. | |
479 | ||
480 | .I 'f' | |
481 | signals 'far' copies | |
482 | (multiple copies have very different offsets). | |
483 | See md(4) for more detail about 'near' and 'far'. | |
484 | ||
485 | The number is the number of copies of each datablock. 2 is normal, 3 | |
486 | can be useful. This number can be at most equal to the number of | |
487 | devices in the array. It does not need to divide evenly into that | |
488 | number (e.g. it is perfectly legal to have an 'n2' layout for an array | |
489 | with an odd number of devices). | |
490 | ||
491 | .TP | |
492 | .BR \-\-parity= | |
493 | same as | |
494 | .B \-\-layout | |
495 | (thus explaining the p of | |
496 | .BR \-p ). | |
497 | ||
498 | .TP | |
499 | .BR \-b ", " \-\-bitmap= | |
500 | Specify a file to store a write-intent bitmap in. The file should not | |
501 | exist unless | |
502 | .B \-\-force | |
503 | is also given. The same file should be provided | |
504 | when assembling the array. If the word | |
505 | .B "internal" | |
506 | is given, then the bitmap is stored with the metadata on the array, | |
507 | and so is replicated on all devices. If the word | |
508 | .B "none" | |
509 | is given with | |
510 | .B \-\-grow | |
511 | mode, then any bitmap that is present is removed. | |
512 | ||
513 | To help catch typing errors, the filename must contain at least one | |
514 | slash ('/') if it is a real file (not 'internal' or 'none'). | |
515 | ||
516 | Note: external bitmaps are only known to work on ext2 and ext3. | |
517 | Storing bitmap files on other filesystems may result in serious problems. | |
518 | ||
519 | .TP | |
520 | .BR \-\-bitmap\-chunk= | |
521 | Set the chunksize of the bitmap. Each bit corresponds to that many | |
522 | Kilobytes of storage. | |
523 | When using a file based bitmap, the default is to use the smallest | |
524 | size that is at-least 4 and requires no more than 2^21 chunks. | |
525 | When using an | |
526 | .B internal | |
527 | bitmap, the chunksize is automatically determined to make best use of | |
528 | available space. | |
529 | ||
530 | ||
531 | .TP | |
532 | .BR \-W ", " \-\-write\-mostly | |
533 | subsequent devices lists in a | |
534 | .BR \-\-build , | |
535 | .BR \-\-create , | |
536 | or | |
537 | .B \-\-add | |
538 | command will be flagged as 'write-mostly'. This is valid for RAID1 | |
539 | only and means that the 'md' driver will avoid reading from these | |
540 | devices if at all possible. This can be useful if mirroring over a | |
541 | slow link. | |
542 | ||
543 | .TP | |
544 | .BR \-\-write\-behind= | |
545 | Specify that write-behind mode should be enabled (valid for RAID1 | |
546 | only). If an argument is specified, it will set the maximum number | |
547 | of outstanding writes allowed. The default value is 256. | |
548 | A write-intent bitmap is required in order to use write-behind | |
549 | mode, and write-behind is only attempted on drives marked as | |
550 | .IR write-mostly . | |
551 | ||
552 | .TP | |
553 | .BR \-\-assume\-clean | |
554 | Tell | |
555 | .I mdadm | |
556 | that the array pre-existed and is known to be clean. It can be useful | |
557 | when trying to recover from a major failure as you can be sure that no | |
558 | data will be affected unless you actually write to the array. It can | |
559 | also be used when creating a RAID1 or RAID10 if you want to avoid the | |
560 | initial resync, however this practice \(em while normally safe \(em is not | |
561 | recommended. Use this only if you really know what you are doing. | |
562 | ||
563 | .TP | |
564 | .BR \-\-backup\-file= | |
565 | This is needed when | |
566 | .B \-\-grow | |
567 | is used to increase the number of | |
568 | raid-devices in a RAID5 if there are no spare devices available. | |
569 | See the section below on RAID_DEVICE CHANGES. The file should be | |
570 | stored on a separate device, not on the raid array being reshaped. | |
571 | ||
572 | .TP | |
573 | .BR \-N ", " \-\-name= | |
574 | Set a | |
575 | .B name | |
576 | for the array. This is currently only effective when creating an | |
577 | array with a version-1 superblock. The name is a simple textual | |
578 | string that can be used to identify array components when assembling. | |
579 | ||
580 | .TP | |
581 | .BR \-R ", " \-\-run | |
582 | Insist that | |
583 | .I mdadm | |
584 | run the array, even if some of the components | |
585 | appear to be active in another array or filesystem. Normally | |
586 | .I mdadm | |
587 | will ask for confirmation before including such components in an | |
588 | array. This option causes that question to be suppressed. | |
589 | ||
590 | .TP | |
591 | .BR \-f ", " \-\-force | |
592 | Insist that | |
593 | .I mdadm | |
594 | accept the geometry and layout specified without question. Normally | |
595 | .I mdadm | |
596 | will not allow creation of an array with only one device, and will try | |
597 | to create a raid5 array with one missing drive (as this makes the | |
598 | initial resync work faster). With | |
599 | .BR \-\-force , | |
600 | .I mdadm | |
601 | will not try to be so clever. | |
602 | ||
603 | .TP | |
604 | .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part,p}{NN}" | |
605 | Instruct mdadm to create the device file if needed, possibly allocating | |
606 | an unused minor number. "md" causes a non-partitionable array | |
607 | to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and | |
608 | later) to be used. "yes" requires the named md device to have | |
609 | a 'standard' format, and the type and minor number will be determined | |
610 | from this. See DEVICE NAMES below. | |
611 | ||
612 | The argument can also come immediately after | |
613 | "\-a". e.g. "\-ap". | |
614 | ||
615 | If | |
616 | .B \-\-auto | |
617 | is not given on the command line or in the config file, then | |
618 | the default will be | |
619 | .BR \-\-auto=yes . | |
620 | ||
621 | If | |
622 | .B \-\-scan | |
623 | is also given, then any | |
624 | .I auto= | |
625 | entries in the config file will override the | |
626 | .B \-\-auto | |
627 | instruction given on the command line. | |
628 | ||
629 | For partitionable arrays, | |
630 | .I mdadm | |
631 | will create the device file for the whole array and for the first 4 | |
632 | partitions. A different number of partitions can be specified at the | |
633 | end of this option (e.g. | |
634 | .BR \-\-auto=p7 ). | |
635 | If the device name ends with a digit, the partition names add a 'p', | |
636 | and a number, e.g. "/dev/home1p3". If there is no | |
637 | trailing digit, then the partition names just have a number added, | |
638 | e.g. "/dev/scratch3". | |
639 | ||
640 | If the md device name is in a 'standard' format as described in DEVICE | |
641 | NAMES, then it will be created, if necessary, with the appropriate | |
642 | number based on that name. If the device name is not in one of these | |
643 | formats, then a unused minor number will be allocated. The minor | |
644 | number will be considered unused if there is no active array for that | |
645 | number, and there is no entry in /dev for that number and with a | |
646 | non-standard name. | |
647 | ||
648 | .TP | |
649 | .BR \-\-symlink = no | |
650 | Normally when | |
651 | .B \-\-auto | |
652 | causes | |
653 | .I mdadm | |
654 | to create devices in | |
655 | .B /dev/md/ | |
656 | it will also create symlinks from | |
657 | .B /dev/ | |
658 | with names starting with | |
659 | .B md | |
660 | or | |
661 | .BR md_ . | |
662 | Use | |
663 | .B \-\-symlink=no | |
664 | to suppress this, or | |
665 | .B \-\-symlink=yes | |
666 | to enforce this even if it is suppressing | |
667 | .IR mdadm.conf . | |
668 | ||
669 | ||
670 | .SH For assemble: | |
671 | ||
672 | .TP | |
673 | .BR \-u ", " \-\-uuid= | |
674 | uuid of array to assemble. Devices which don't have this uuid are | |
675 | excluded | |
676 | ||
677 | .TP | |
678 | .BR \-m ", " \-\-super\-minor= | |
679 | Minor number of device that array was created for. Devices which | |
680 | don't have this minor number are excluded. If you create an array as | |
681 | /dev/md1, then all superblocks will contain the minor number 1, even if | |
682 | the array is later assembled as /dev/md2. | |
683 | ||
684 | Giving the literal word "dev" for | |
685 | .B \-\-super\-minor | |
686 | will cause | |
687 | .I mdadm | |
688 | to use the minor number of the md device that is being assembled. | |
689 | e.g. when assembling | |
690 | .BR /dev/md0 , | |
691 | .M \-\-super\-minor=dev | |
692 | will look for super blocks with a minor number of 0. | |
693 | ||
694 | .TP | |
695 | .BR \-N ", " \-\-name= | |
696 | Specify the name of the array to assemble. This must be the name | |
697 | that was specified when creating the array. It must either match | |
698 | the name stored in the superblock exactly, or it must match | |
699 | with the current | |
700 | .I homehost | |
701 | prefixed to the start of the given name. | |
702 | ||
703 | .TP | |
704 | .BR \-f ", " \-\-force | |
705 | Assemble the array even if some superblocks appear out-of-date | |
706 | ||
707 | .TP | |
708 | .BR \-R ", " \-\-run | |
709 | Attempt to start the array even if fewer drives were given than were | |
710 | present last time the array was active. Normally if not all the | |
711 | expected drives are found and | |
712 | .B \-\-scan | |
713 | is not used, then the array will be assembled but not started. | |
714 | With | |
715 | .B \-\-run | |
716 | an attempt will be made to start it anyway. | |
717 | ||
718 | .TP | |
719 | .B \-\-no\-degraded | |
720 | This is the reverse of | |
721 | .B \-\-run | |
722 | in that it inhibits the startup of array unless all expected drives | |
723 | are present. This is only needed with | |
724 | .B \-\-scan, | |
725 | and can be used if the physical connections to devices are | |
726 | not as reliable as you would like. | |
727 | ||
728 | .TP | |
729 | .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}" | |
730 | See this option under Create and Build options. | |
731 | ||
732 | .TP | |
733 | .BR \-b ", " \-\-bitmap= | |
734 | Specify the bitmap file that was given when the array was created. If | |
735 | an array has an | |
736 | .B internal | |
737 | bitmap, there is no need to specify this when assembling the array. | |
738 | ||
739 | .TP | |
740 | .BR \-\-backup\-file= | |
741 | If | |
742 | .B \-\-backup\-file | |
743 | was used to grow the number of raid-devices in a RAID5, and the system | |
744 | crashed during the critical section, then the same | |
745 | .B \-\-backup\-file | |
746 | must be presented to | |
747 | .B \-\-assemble | |
748 | to allow possibly corrupted data to be restored. | |
749 | ||
750 | .TP | |
751 | .BR \-U ", " \-\-update= | |
752 | Update the superblock on each device while assembling the array. The | |
753 | argument given to this flag can be one of | |
754 | .BR sparc2.2 , | |
755 | .BR summaries , | |
756 | .BR uuid , | |
757 | .BR name , | |
758 | .BR homehost , | |
759 | .BR resync , | |
760 | .BR byteorder , | |
761 | .BR devicesize , | |
762 | or | |
763 | .BR super\-minor . | |
764 | ||
765 | The | |
766 | .B sparc2.2 | |
767 | option will adjust the superblock of an array what was created on a Sparc | |
768 | machine running a patched 2.2 Linux kernel. This kernel got the | |
769 | alignment of part of the superblock wrong. You can use the | |
770 | .B "\-\-examine \-\-sparc2.2" | |
771 | option to | |
772 | .I mdadm | |
773 | to see what effect this would have. | |
774 | ||
775 | The | |
776 | .B super\-minor | |
777 | option will update the | |
778 | .B "preferred minor" | |
779 | field on each superblock to match the minor number of the array being | |
780 | assembled. | |
781 | This can be useful if | |
782 | .B \-\-examine | |
783 | reports a different "Preferred Minor" to | |
784 | .BR \-\-detail . | |
785 | In some cases this update will be performed automatically | |
786 | by the kernel driver. In particular the update happens automatically | |
787 | at the first write to an array with redundancy (RAID level 1 or | |
788 | greater) on a 2.6 (or later) kernel. | |
789 | ||
790 | The | |
791 | .B uuid | |
792 | option will change the uuid of the array. If a UUID is given with the | |
793 | .B \-\-uuid | |
794 | option that UUID will be used as a new UUID and will | |
795 | .B NOT | |
796 | be used to help identify the devices in the array. | |
797 | If no | |
798 | .B \-\-uuid | |
799 | is given, a random UUID is chosen. | |
800 | ||
801 | The | |
802 | .B name | |
803 | option will change the | |
804 | .I name | |
805 | of the array as stored in the superblock. This is only supported for | |
806 | version-1 superblocks. | |
807 | ||
808 | The | |
809 | .B homehost | |
810 | option will change the | |
811 | .I homehost | |
812 | as recorded in the superblock. For version-0 superblocks, this is the | |
813 | same as updating the UUID. | |
814 | For version-1 superblocks, this involves updating the name. | |
815 | ||
816 | The | |
817 | .B resync | |
818 | option will cause the array to be marked | |
819 | .I dirty | |
820 | meaning that any redundancy in the array (e.g. parity for raid5, | |
821 | copies for raid1) may be incorrect. This will cause the raid system | |
822 | to perform a "resync" pass to make sure that all redundant information | |
823 | is correct. | |
824 | ||
825 | The | |
826 | .B byteorder | |
827 | option allows arrays to be moved between machines with different | |
828 | byte-order. | |
829 | When assembling such an array for the first time after a move, giving | |
830 | .B "\-\-update=byteorder" | |
831 | will cause | |
832 | .I mdadm | |
833 | to expect superblocks to have their byteorder reversed, and will | |
834 | correct that order before assembling the array. This is only valid | |
835 | with original (Version 0.90) superblocks. | |
836 | ||
837 | The | |
838 | .B summaries | |
839 | option will correct the summaries in the superblock. That is the | |
840 | counts of total, working, active, failed, and spare devices. | |
841 | ||
842 | The | |
843 | .B devicesize | |
844 | will rarely be of use. It applies to version 1.1 and 1.2 metadata | |
845 | only (where the metadata is at the start of the device) and is only | |
846 | useful when the component device has changed size (typically become | |
847 | larger). The version 1 metadata records the amount of the device that | |
848 | can be used to store data, so if a device in a version 1.1 or 1.2 | |
849 | array becomes larger, the metadata will still be visible, but the | |
850 | extra space will not. In this case it might be useful to assemble the | |
851 | array with | |
852 | .BR \-\-update=devicesize . | |
853 | This will cause | |
854 | .I mdadm | |
855 | to determine the maximum usable amount of space on each device and | |
856 | update the relevant field in the metadata. | |
857 | ||
858 | .TP | |
859 | .B \-\-auto\-update\-homehost | |
860 | This flag is only meaningful with auto-assembly (see discussion below). | |
861 | In that situation, if no suitable arrays are found for this homehost, | |
862 | .I mdadm | |
863 | will rescan for any arrays at all and will assemble them and update the | |
864 | homehost to match the current host. | |
865 | ||
866 | .SH For Manage mode: | |
867 | ||
868 | .TP | |
869 | .BR \-a ", " \-\-add | |
870 | hot-add listed devices. | |
871 | ||
872 | .TP | |
873 | .BR \-\-re\-add | |
874 | re-add a device that was recently removed from an array. | |
875 | ||
876 | .TP | |
877 | .BR \-r ", " \-\-remove | |
878 | remove listed devices. They must not be active. i.e. they should | |
879 | be failed or spare devices. As well as the name of a device file | |
880 | (e.g. | |
881 | .BR /dev/sda1 ) | |
882 | the words | |
883 | .B failed | |
884 | and | |
885 | .B detached | |
886 | can be given to | |
887 | .BR \-\-remove . | |
888 | The first causes all failed device to be removed. The second causes | |
889 | any device which is no longer connected to the system (i.e an 'open' | |
890 | returns | |
891 | .BR ENXIO ) | |
892 | to be removed. This will only succeed for devices that are spares or | |
893 | have already been marked as failed. | |
894 | ||
895 | .TP | |
896 | .BR \-f ", " \-\-fail | |
897 | mark listed devices as faulty. | |
898 | As well as the name of a device file, the word | |
899 | .B detached | |
900 | can be given. This will cause any device that has been detached from | |
901 | the system to be marked as failed. It can then be removed. | |
902 | ||
903 | .TP | |
904 | .BR \-\-set\-faulty | |
905 | same as | |
906 | .BR \-\-fail . | |
907 | ||
908 | .P | |
909 | Each of these options require that the first device listed is the array | |
910 | to be acted upon, and the remainder are component devices to be added, | |
911 | removed, or marked as faulty. Several different operations can be | |
912 | specified for different devices, e.g. | |
913 | .in +5 | |
914 | mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1 | |
915 | .in -5 | |
916 | Each operation applies to all devices listed until the next | |
917 | operation. | |
918 | ||
919 | If an array is using a write-intent bitmap, then devices which have | |
920 | been removed can be re-added in a way that avoids a full | |
921 | reconstruction but instead just updates the blocks that have changed | |
922 | since the device was removed. For arrays with persistent metadata | |
923 | (superblocks) this is done automatically. For arrays created with | |
924 | .B \-\-build | |
925 | mdadm needs to be told that this device we removed recently with | |
926 | .BR \-\-re\-add . | |
927 | ||
928 | Devices can only be removed from an array if they are not in active | |
929 | use, i.e. that must be spares or failed devices. To remove an active | |
930 | device, it must first be marked as | |
931 | .B faulty. | |
932 | ||
933 | .SH For Misc mode: | |
934 | ||
935 | .TP | |
936 | .BR \-Q ", " \-\-query | |
937 | Examine a device to see | |
938 | (1) if it is an md device and (2) if it is a component of an md | |
939 | array. | |
940 | Information about what is discovered is presented. | |
941 | ||
942 | .TP | |
943 | .BR \-D ", " \-\-detail | |
944 | Print detail of one or more md devices. | |
945 | ||
946 | .TP | |
947 | .BR \-Y ", " \-\-export | |
948 | When used with | |
949 | .B \-\-detail | |
950 | or | |
951 | .BR \-\-examine , | |
952 | output will be formatted as | |
953 | .B key=value | |
954 | pairs for easy import into the environment. | |
955 | ||
956 | .TP | |
957 | .BR \-E ", " \-\-examine | |
958 | Print content of md superblock on device(s). | |
959 | .TP | |
960 | .B \-\-sparc2.2 | |
961 | If an array was created on a 2.2 Linux kernel patched with RAID | |
962 | support, the superblock will have been created incorrectly, or at | |
963 | least incompatibly with 2.4 and later kernels. Using the | |
964 | .B \-\-sparc2.2 | |
965 | flag with | |
966 | .B \-\-examine | |
967 | will fix the superblock before displaying it. If this appears to do | |
968 | the right thing, then the array can be successfully assembled using | |
969 | .BR "\-\-assemble \-\-update=sparc2.2" . | |
970 | ||
971 | .TP | |
972 | .BR \-X ", " \-\-examine\-bitmap | |
973 | Report information about a bitmap file. | |
974 | The argument is either an external bitmap file or an array component | |
975 | in case of an internal bitmap. | |
976 | ||
977 | .TP | |
978 | .BR \-R ", " \-\-run | |
979 | start a partially built array. | |
980 | ||
981 | .TP | |
982 | .BR \-S ", " \-\-stop | |
983 | deactivate array, releasing all resources. | |
984 | ||
985 | .TP | |
986 | .BR \-o ", " \-\-readonly | |
987 | mark array as readonly. | |
988 | ||
989 | .TP | |
990 | .BR \-w ", " \-\-readwrite | |
991 | mark array as readwrite. | |
992 | ||
993 | .TP | |
994 | .B \-\-zero\-superblock | |
995 | If the device contains a valid md superblock, the block is | |
996 | overwritten with zeros. With | |
997 | .B \-\-force | |
998 | the block where the superblock would be is overwritten even if it | |
999 | doesn't appear to be valid. | |
1000 | ||
1001 | .TP | |
1002 | .BR \-t ", " \-\-test | |
1003 | When used with | |
1004 | .BR \-\-detail , | |
1005 | the exit status of | |
1006 | .I mdadm | |
1007 | is set to reflect the status of the device. | |
1008 | ||
1009 | .TP | |
1010 | .BR \-W ", " \-\-wait | |
1011 | For each md device given, wait for any resync, recovery, or reshape | |
1012 | activity to finish before returning. | |
1013 | .I mdadm | |
1014 | will return with success if it actually waited for every device | |
1015 | listed, otherwise it will return failure. | |
1016 | ||
1017 | .SH For Incremental Assembly mode: | |
1018 | .TP | |
1019 | .BR \-\-rebuild\-map ", " \-r | |
1020 | Rebuild the map file | |
1021 | .RB ( /var/run/mdadm/map ) | |
1022 | that | |
1023 | .I mdadm | |
1024 | uses to help track which arrays are currently being assembled. | |
1025 | ||
1026 | .TP | |
1027 | .BR \-\-run ", " \-R | |
1028 | Run any array assembled as soon as a minimal number of devices are | |
1029 | available, rather than waiting until all expected devices are present. | |
1030 | ||
1031 | .TP | |
1032 | .BR \-\-scan ", " \-s | |
1033 | Only meaningful with | |
1034 | .B \-R | |
1035 | this will scan the | |
1036 | .B map | |
1037 | file for arrays that are being incrementally assembled and will try to | |
1038 | start any that are not already started. If any such array is listed | |
1039 | in | |
1040 | .B mdadm.conf | |
1041 | as requiring an external bitmap, that bitmap will be attached first. | |
1042 | ||
1043 | .SH For Monitor mode: | |
1044 | .TP | |
1045 | .BR \-m ", " \-\-mail | |
1046 | Give a mail address to send alerts to. | |
1047 | ||
1048 | .TP | |
1049 | .BR \-p ", " \-\-program ", " \-\-alert | |
1050 | Give a program to be run whenever an event is detected. | |
1051 | ||
1052 | .TP | |
1053 | .BR \-y ", " \-\-syslog | |
1054 | Cause all events to be reported through 'syslog'. The messages have | |
1055 | facility of 'daemon' and varying priorities. | |
1056 | ||
1057 | .TP | |
1058 | .BR \-d ", " \-\-delay | |
1059 | Give a delay in seconds. | |
1060 | .B mdadm | |
1061 | polls the md arrays and then waits this many seconds before polling | |
1062 | again. The default is 60 seconds. | |
1063 | ||
1064 | .TP | |
1065 | .BR \-f ", " \-\-daemonise | |
1066 | Tell | |
1067 | .B mdadm | |
1068 | to run as a background daemon if it decides to monitor anything. This | |
1069 | causes it to fork and run in the child, and to disconnect form the | |
1070 | terminal. The process id of the child is written to stdout. | |
1071 | This is useful with | |
1072 | .B \-\-scan | |
1073 | which will only continue monitoring if a mail address or alert program | |
1074 | is found in the config file. | |
1075 | ||
1076 | .TP | |
1077 | .BR \-i ", " \-\-pid\-file | |
1078 | When | |
1079 | .B mdadm | |
1080 | is running in daemon mode, write the pid of the daemon process to | |
1081 | the specified file, instead of printing it on standard output. | |
1082 | ||
1083 | .TP | |
1084 | .BR \-1 ", " \-\-oneshot | |
1085 | Check arrays only once. This will generate | |
1086 | .B NewArray | |
1087 | events and more significantly | |
1088 | .B DegradedArray | |
1089 | and | |
1090 | .B SparesMissing | |
1091 | events. Running | |
1092 | .in +5 | |
1093 | .B " mdadm \-\-monitor \-\-scan \-1" | |
1094 | .in -5 | |
1095 | from a cron script will ensure regular notification of any degraded arrays. | |
1096 | ||
1097 | .TP | |
1098 | .BR \-t ", " \-\-test | |
1099 | Generate a | |
1100 | .B TestMessage | |
1101 | alert for every array found at startup. This alert gets mailed and | |
1102 | passed to the alert program. This can be used for testing that alert | |
1103 | message do get through successfully. | |
1104 | ||
1105 | .SH ASSEMBLE MODE | |
1106 | ||
1107 | .HP 12 | |
1108 | Usage: | |
1109 | .B mdadm \-\-assemble | |
1110 | .I md-device options-and-component-devices... | |
1111 | .HP 12 | |
1112 | Usage: | |
1113 | .B mdadm \-\-assemble \-\-scan | |
1114 | .I md-devices-and-options... | |
1115 | .HP 12 | |
1116 | Usage: | |
1117 | .B mdadm \-\-assemble \-\-scan | |
1118 | .I options... | |
1119 | ||
1120 | .PP | |
1121 | This usage assembles one or more raid arrays from pre-existing components. | |
1122 | For each array, mdadm needs to know the md device, the identity of the | |
1123 | array, and a number of component-devices. These can be found in a number of ways. | |
1124 | ||
1125 | In the first usage example (without the | |
1126 | .BR \-\-scan ) | |
1127 | the first device given is the md device. | |
1128 | In the second usage example, all devices listed are treated as md | |
1129 | devices and assembly is attempted. | |
1130 | In the third (where no devices are listed) all md devices that are | |
1131 | listed in the configuration file are assembled. | |
1132 | ||
1133 | If precisely one device is listed, but | |
1134 | .B \-\-scan | |
1135 | is not given, then | |
1136 | .I mdadm | |
1137 | acts as though | |
1138 | .B \-\-scan | |
1139 | was given and identity information is extracted from the configuration file. | |
1140 | ||
1141 | The identity can be given with the | |
1142 | .B \-\-uuid | |
1143 | option, with the | |
1144 | .B \-\-super\-minor | |
1145 | option, will be taken from the md-device record in the config file, or | |
1146 | will be taken from the super block of the first component-device | |
1147 | listed on the command line. | |
1148 | ||
1149 | Devices can be given on the | |
1150 | .B \-\-assemble | |
1151 | command line or in the config file. Only devices which have an md | |
1152 | superblock which contains the right identity will be considered for | |
1153 | any array. | |
1154 | ||
1155 | The config file is only used if explicitly named with | |
1156 | .B \-\-config | |
1157 | or requested with (a possibly implicit) | |
1158 | .BR \-\-scan . | |
1159 | In the later case, | |
1160 | .B /etc/mdadm.conf | |
1161 | is used. | |
1162 | ||
1163 | If | |
1164 | .B \-\-scan | |
1165 | is not given, then the config file will only be used to find the | |
1166 | identity of md arrays. | |
1167 | ||
1168 | Normally the array will be started after it is assembled. However if | |
1169 | .B \-\-scan | |
1170 | is not given and insufficient drives were listed to start a complete | |
1171 | (non-degraded) array, then the array is not started (to guard against | |
1172 | usage errors). To insist that the array be started in this case (as | |
1173 | may work for RAID1, 4, 5, 6, or 10), give the | |
1174 | .B \-\-run | |
1175 | flag. | |
1176 | ||
1177 | If the md device does not exist, then it will be created providing the | |
1178 | intent is clear. i.e. the name must be in a standard form, or the | |
1179 | .B \-\-auto | |
1180 | option must be given to clarify how and whether the device should be | |
1181 | created. | |
1182 | This can be useful for handling partitioned devices (which don't have | |
1183 | a stable device number \(em it can change after a reboot) and when using | |
1184 | "udev" to manage your | |
1185 | .B /dev | |
1186 | tree (udev cannot handle md devices because of the unusual device | |
1187 | initialisation conventions). | |
1188 | ||
1189 | If the option to "auto" is "mdp" or "part" or (on the command line | |
1190 | only) "p", then mdadm will create a partitionable array, using the | |
1191 | first free one that is not in use and does not already have an entry | |
1192 | in /dev (apart from numeric /dev/md* entries). | |
1193 | ||
1194 | If the option to "auto" is "yes" or "md" or (on the command line) | |
1195 | nothing, then mdadm will create a traditional, non-partitionable md | |
1196 | array. | |
1197 | ||
1198 | It is expected that the "auto" functionality will be used to create | |
1199 | device entries with meaningful names such as "/dev/md/home" or | |
1200 | "/dev/md/root", rather than names based on the numerical array number. | |
1201 | ||
1202 | When using option "auto" to create a partitionable array, the device | |
1203 | files for the first 4 partitions are also created. If a different | |
1204 | number is required it can be simply appended to the auto option. | |
1205 | e.g. "auto=part8". Partition names are created by appending a digit | |
1206 | string to the device name, with an intervening "p" if the device name | |
1207 | ends with a digit. | |
1208 | ||
1209 | The | |
1210 | .B \-\-auto | |
1211 | option is also available in Build and Create modes. As those modes do | |
1212 | not use a config file, the "auto=" config option does not apply to | |
1213 | these modes. | |
1214 | ||
1215 | .SS Auto Assembly | |
1216 | When | |
1217 | .B \-\-assemble | |
1218 | is used with | |
1219 | .B \-\-scan | |
1220 | and no devices are listed, | |
1221 | .I mdadm | |
1222 | will first attempt to assemble all the arrays listed in the config | |
1223 | file. | |
1224 | ||
1225 | If a | |
1226 | .B homehost | |
1227 | has been specified (either in the config file or on the command line), | |
1228 | .I mdadm | |
1229 | will look further for possible arrays and will try to assemble | |
1230 | anything that it finds which is tagged as belonging to the given | |
1231 | homehost. This is the only situation where | |
1232 | .I mdadm | |
1233 | will assemble arrays without being given specific device name or | |
1234 | identity information for the array. | |
1235 | ||
1236 | If | |
1237 | .I mdadm | |
1238 | finds a consistent set of devices that look like they should comprise | |
1239 | an array, and if the superblock is tagged as belonging to the given | |
1240 | home host, it will automatically choose a device name and try to | |
1241 | assemble the array. If the array uses version-0.90 metadata, then the | |
1242 | .B minor | |
1243 | number as recorded in the superblock is used to create a name in | |
1244 | .B /dev/md/ | |
1245 | so for example | |
1246 | .BR /dev/md/3 . | |
1247 | If the array uses version-1 metadata, then the | |
1248 | .B name | |
1249 | from the superblock is used to similarly create a name in | |
1250 | .BR /dev/md | |
1251 | (the name will have any 'host' prefix stripped first). | |
1252 | ||
1253 | If | |
1254 | .I mdadm | |
1255 | cannot find any array for the given host at all, and if | |
1256 | .B \-\-auto\-update\-homehost | |
1257 | is given, then | |
1258 | .I mdadm | |
1259 | will search again for any array (not just an array created for this | |
1260 | host) and will assemble each assuming | |
1261 | .BR \-\-update=homehost . | |
1262 | This will change the host tag in the superblock so that on the next run, | |
1263 | these arrays will be found without the second pass. The intention of | |
1264 | this feature is to support transitioning a set of md arrays to using | |
1265 | homehost tagging. | |
1266 | ||
1267 | The reason for requiring arrays to be tagged with the homehost for | |
1268 | auto assembly is to guard against problems that can arise when moving | |
1269 | devices from one host to another. | |
1270 | ||
1271 | .SH BUILD MODE | |
1272 | ||
1273 | .HP 12 | |
1274 | Usage: | |
1275 | .B mdadm \-\-build | |
1276 | .I md-device | |
1277 | .BI \-\-chunk= X | |
1278 | .BI \-\-level= Y | |
1279 | .BI \-\-raid\-devices= Z | |
1280 | .I devices | |
1281 | ||
1282 | .PP | |
1283 | This usage is similar to | |
1284 | .BR \-\-create . | |
1285 | The difference is that it creates an array without a superblock. With | |
1286 | these arrays there is no difference between initially creating the array and | |
1287 | subsequently assembling the array, except that hopefully there is useful | |
1288 | data there in the second case. | |
1289 | ||
1290 | The level may raid0, linear, multipath, or faulty, or one of their | |
1291 | synonyms. All devices must be listed and the array will be started | |
1292 | once complete. | |
1293 | ||
1294 | .SH CREATE MODE | |
1295 | ||
1296 | .HP 12 | |
1297 | Usage: | |
1298 | .B mdadm \-\-create | |
1299 | .I md-device | |
1300 | .BI \-\-chunk= X | |
1301 | .BI \-\-level= Y | |
1302 | .br | |
1303 | .BI \-\-raid\-devices= Z | |
1304 | .I devices | |
1305 | ||
1306 | .PP | |
1307 | This usage will initialise a new md array, associate some devices with | |
1308 | it, and activate the array. | |
1309 | ||
1310 | If the | |
1311 | .B \-\-auto | |
1312 | option is given (as described in more detail in the section on | |
1313 | Assemble mode), then the md device will be created with a suitable | |
1314 | device number if necessary. | |
1315 | ||
1316 | As devices are added, they are checked to see if they contain raid | |
1317 | superblocks or filesystems. They are also checked to see if the variance in | |
1318 | device size exceeds 1%. | |
1319 | ||
1320 | If any discrepancy is found, the array will not automatically be run, though | |
1321 | the presence of a | |
1322 | .B \-\-run | |
1323 | can override this caution. | |
1324 | ||
1325 | To create a "degraded" array in which some devices are missing, simply | |
1326 | give the word "\fBmissing\fP" | |
1327 | in place of a device name. This will cause | |
1328 | .B mdadm | |
1329 | to leave the corresponding slot in the array empty. | |
1330 | For a RAID4 or RAID5 array at most one slot can be | |
1331 | "\fBmissing\fP"; for a RAID6 array at most two slots. | |
1332 | For a RAID1 array, only one real device needs to be given. All of the | |
1333 | others can be | |
1334 | "\fBmissing\fP". | |
1335 | ||
1336 | When creating a RAID5 array, | |
1337 | .B mdadm | |
1338 | will automatically create a degraded array with an extra spare drive. | |
1339 | This is because building the spare into a degraded array is in general faster than resyncing | |
1340 | the parity on a non-degraded, but not clean, array. This feature can | |
1341 | be overridden with the | |
1342 | .B \-\-force | |
1343 | option. | |
1344 | ||
1345 | When creating an array with version-1 metadata a name for the host is | |
1346 | required. | |
1347 | If this is not given with the | |
1348 | .B \-\-name | |
1349 | option, | |
1350 | .I mdadm | |
1351 | will chose a name based on the last component of the name of the | |
1352 | device being created. So if | |
1353 | .B /dev/md3 | |
1354 | is being created, then the name | |
1355 | .B 3 | |
1356 | will be chosen. | |
1357 | If | |
1358 | .B /dev/md/home | |
1359 | is being created, then the name | |
1360 | .B home | |
1361 | will be used. | |
1362 | ||
1363 | A new array will normally get a randomly assigned 128bit UUID which is | |
1364 | very likely to be unique. If you have a specific need, you can choose | |
1365 | a UUID for the array by giving the | |
1366 | .B \-\-uuid= | |
1367 | option. Be warned that creating two arrays with the same UUID is a | |
1368 | recipe for disaster. Also, using | |
1369 | .B \-\-uuid= | |
1370 | when creating a v0.90 array will silently override any | |
1371 | .B \-\-homehost= | |
1372 | setting. | |
1373 | .\"If the | |
1374 | .\".B \-\-size | |
1375 | .\"option is given, it is not necessary to list any component-devices in this command. | |
1376 | .\"They can be added later, before a | |
1377 | .\".B \-\-run. | |
1378 | .\"If no | |
1379 | .\".B \-\-size | |
1380 | .\"is given, the apparent size of the smallest drive given is used. | |
1381 | ||
1382 | The General Management options that are valid with | |
1383 | .B \-\-create | |
1384 | are: | |
1385 | .TP | |
1386 | .B \-\-run | |
1387 | insist on running the array even if some devices look like they might | |
1388 | be in use. | |
1389 | ||
1390 | .TP | |
1391 | .B \-\-readonly | |
1392 | start the array readonly \(em not supported yet. | |
1393 | ||
1394 | ||
1395 | .SH MANAGE MODE | |
1396 | .HP 12 | |
1397 | Usage: | |
1398 | .B mdadm | |
1399 | .I device | |
1400 | .I options... devices... | |
1401 | .PP | |
1402 | ||
1403 | This usage will allow individual devices in an array to be failed, | |
1404 | removed or added. It is possible to perform multiple operations with | |
1405 | on command. For example: | |
1406 | .br | |
1407 | .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1" | |
1408 | .br | |
1409 | will firstly mark | |
1410 | .B /dev/hda1 | |
1411 | as faulty in | |
1412 | .B /dev/md0 | |
1413 | and will then remove it from the array and finally add it back | |
1414 | in as a spare. However only one md array can be affected by a single | |
1415 | command. | |
1416 | ||
1417 | .SH MISC MODE | |
1418 | .HP 12 | |
1419 | Usage: | |
1420 | .B mdadm | |
1421 | .I options ... | |
1422 | .I devices ... | |
1423 | .PP | |
1424 | ||
1425 | MISC mode includes a number of distinct operations that | |
1426 | operate on distinct devices. The operations are: | |
1427 | .TP | |
1428 | .B \-\-query | |
1429 | The device is examined to see if it is | |
1430 | (1) an active md array, or | |
1431 | (2) a component of an md array. | |
1432 | The information discovered is reported. | |
1433 | ||
1434 | .TP | |
1435 | .B \-\-detail | |
1436 | The device should be an active md device. | |
1437 | .B mdadm | |
1438 | will display a detailed description of the array. | |
1439 | .B \-\-brief | |
1440 | or | |
1441 | .B \-\-scan | |
1442 | will cause the output to be less detailed and the format to be | |
1443 | suitable for inclusion in | |
1444 | .BR /etc/mdadm.conf . | |
1445 | The exit status of | |
1446 | .I mdadm | |
1447 | will normally be 0 unless | |
1448 | .I mdadm | |
1449 | failed to get useful information about the device(s); however, if the | |
1450 | .B \-\-test | |
1451 | option is given, then the exit status will be: | |
1452 | .RS | |
1453 | .TP | |
1454 | 0 | |
1455 | The array is functioning normally. | |
1456 | .TP | |
1457 | 1 | |
1458 | The array has at least one failed device. | |
1459 | .TP | |
1460 | 2 | |
1461 | The array has multiple failed devices such that it is unusable. | |
1462 | .TP | |
1463 | 4 | |
1464 | There was an error while trying to get information about the device. | |
1465 | .RE | |
1466 | ||
1467 | .TP | |
1468 | .B \-\-examine | |
1469 | The device should be a component of an md array. | |
1470 | .B mdadm | |
1471 | will read the md superblock of the device and display the contents. | |
1472 | If | |
1473 | .B \-\-brief | |
1474 | or | |
1475 | .B \-\-scan | |
1476 | is given, then multiple devices that are components of the one array | |
1477 | are grouped together and reported in a single entry suitable | |
1478 | for inclusion in | |
1479 | .BR /etc/mdadm.conf . | |
1480 | ||
1481 | Having | |
1482 | .B \-\-scan | |
1483 | without listing any devices will cause all devices listed in the | |
1484 | config file to be examined. | |
1485 | ||
1486 | .TP | |
1487 | .B \-\-stop | |
1488 | The devices should be active md arrays which will be deactivated, as | |
1489 | long as they are not currently in use. | |
1490 | ||
1491 | .TP | |
1492 | .B \-\-run | |
1493 | This will fully activate a partially assembled md array. | |
1494 | ||
1495 | .TP | |
1496 | .B \-\-readonly | |
1497 | This will mark an active array as read-only, providing that it is | |
1498 | not currently being used. | |
1499 | ||
1500 | .TP | |
1501 | .B \-\-readwrite | |
1502 | This will change a | |
1503 | .B readonly | |
1504 | array back to being read/write. | |
1505 | ||
1506 | .TP | |
1507 | .B \-\-scan | |
1508 | For all operations except | |
1509 | .BR \-\-examine , | |
1510 | .B \-\-scan | |
1511 | will cause the operation to be applied to all arrays listed in | |
1512 | .BR /proc/mdstat . | |
1513 | For | |
1514 | .BR \-\-examine, | |
1515 | .B \-\-scan | |
1516 | causes all devices listed in the config file to be examined. | |
1517 | ||
1518 | ||
1519 | .SH MONITOR MODE | |
1520 | ||
1521 | .HP 12 | |
1522 | Usage: | |
1523 | .B mdadm \-\-monitor | |
1524 | .I options... devices... | |
1525 | ||
1526 | .PP | |
1527 | This usage causes | |
1528 | .B mdadm | |
1529 | to periodically poll a number of md arrays and to report on any events | |
1530 | noticed. | |
1531 | .B mdadm | |
1532 | will never exit once it decides that there are arrays to be checked, | |
1533 | so it should normally be run in the background. | |
1534 | ||
1535 | As well as reporting events, | |
1536 | .B mdadm | |
1537 | may move a spare drive from one array to another if they are in the | |
1538 | same | |
1539 | .B spare-group | |
1540 | and if the destination array has a failed drive but no spares. | |
1541 | ||
1542 | If any devices are listed on the command line, | |
1543 | .B mdadm | |
1544 | will only monitor those devices. Otherwise all arrays listed in the | |
1545 | configuration file will be monitored. Further, if | |
1546 | .B \-\-scan | |
1547 | is given, then any other md devices that appear in | |
1548 | .B /proc/mdstat | |
1549 | will also be monitored. | |
1550 | ||
1551 | The result of monitoring the arrays is the generation of events. | |
1552 | These events are passed to a separate program (if specified) and may | |
1553 | be mailed to a given E-mail address. | |
1554 | ||
1555 | When passing events to a program, the program is run once for each event, | |
1556 | and is given 2 or 3 command-line arguments: the first is the | |
1557 | name of the event (see below), the second is the name of the | |
1558 | md device which is affected, and the third is the name of a related | |
1559 | device if relevant (such as a component device that has failed). | |
1560 | ||
1561 | If | |
1562 | .B \-\-scan | |
1563 | is given, then a program or an E-mail address must be specified on the | |
1564 | command line or in the config file. If neither are available, then | |
1565 | .B mdadm | |
1566 | will not monitor anything. | |
1567 | Without | |
1568 | .B \-\-scan, | |
1569 | .B mdadm | |
1570 | will continue monitoring as long as something was found to monitor. If | |
1571 | no program or email is given, then each event is reported to | |
1572 | .BR stdout . | |
1573 | ||
1574 | The different events are: | |
1575 | ||
1576 | .RS 4 | |
1577 | .TP | |
1578 | .B DeviceDisappeared | |
1579 | An md array which previously was configured appears to no longer be | |
1580 | configured. (syslog priority: Critical) | |
1581 | ||
1582 | If | |
1583 | .I mdadm | |
1584 | was told to monitor an array which is RAID0 or Linear, then it will | |
1585 | report | |
1586 | .B DeviceDisappeared | |
1587 | with the extra information | |
1588 | .BR Wrong-Level . | |
1589 | This is because RAID0 and Linear do not support the device-failed, | |
1590 | hot-spare and resync operations which are monitored. | |
1591 | ||
1592 | .TP | |
1593 | .B RebuildStarted | |
1594 | An md array started reconstruction. (syslog priority: Warning) | |
1595 | ||
1596 | .TP | |
1597 | .BI Rebuild NN | |
1598 | Where | |
1599 | .I NN | |
1600 | is 20, 40, 60, or 80, this indicates that rebuild has passed that many | |
1601 | percentage of the total. (syslog priority: Warning) | |
1602 | ||
1603 | .TP | |
1604 | .B RebuildFinished | |
1605 | An md array that was rebuilding, isn't any more, either because it | |
1606 | finished normally or was aborted. (syslog priority: Warning) | |
1607 | ||
1608 | .TP | |
1609 | .B Fail | |
1610 | An active component device of an array has been marked as | |
1611 | faulty. (syslog priority: Critical) | |
1612 | ||
1613 | .TP | |
1614 | .B FailSpare | |
1615 | A spare component device which was being rebuilt to replace a faulty | |
1616 | device has failed. (syslog priority: Critical) | |
1617 | ||
1618 | .TP | |
1619 | .B SpareActive | |
1620 | A spare component device which was being rebuilt to replace a faulty | |
1621 | device has been successfully rebuilt and has been made active. | |
1622 | (syslog priority: Info) | |
1623 | ||
1624 | .TP | |
1625 | .B NewArray | |
1626 | A new md array has been detected in the | |
1627 | .B /proc/mdstat | |
1628 | file. (syslog priority: Info) | |
1629 | ||
1630 | .TP | |
1631 | .B DegradedArray | |
1632 | A newly noticed array appears to be degraded. This message is not | |
1633 | generated when | |
1634 | .I mdadm | |
1635 | notices a drive failure which causes degradation, but only when | |
1636 | .I mdadm | |
1637 | notices that an array is degraded when it first sees the array. | |
1638 | (syslog priority: Critical) | |
1639 | ||
1640 | .TP | |
1641 | .B MoveSpare | |
1642 | A spare drive has been moved from one array in a | |
1643 | .B spare-group | |
1644 | to another to allow a failed drive to be replaced. | |
1645 | (syslog priority: Info) | |
1646 | ||
1647 | .TP | |
1648 | .B SparesMissing | |
1649 | If | |
1650 | .I mdadm | |
1651 | has been told, via the config file, that an array should have a certain | |
1652 | number of spare devices, and | |
1653 | .I mdadm | |
1654 | detects that it has fewer than this number when it first sees the | |
1655 | array, it will report a | |
1656 | .B SparesMissing | |
1657 | message. | |
1658 | (syslog priority: Warning) | |
1659 | ||
1660 | .TP | |
1661 | .B TestMessage | |
1662 | An array was found at startup, and the | |
1663 | .B \-\-test | |
1664 | flag was given. | |
1665 | (syslog priority: Info) | |
1666 | .RE | |
1667 | ||
1668 | Only | |
1669 | .B Fail, | |
1670 | .B FailSpare, | |
1671 | .B DegradedArray, | |
1672 | .B SparesMissing | |
1673 | and | |
1674 | .B TestMessage | |
1675 | cause Email to be sent. All events cause the program to be run. | |
1676 | The program is run with two or three arguments: the event | |
1677 | name, the array device and possibly a second device. | |
1678 | ||
1679 | Each event has an associated array device (e.g. | |
1680 | .BR /dev/md1 ) | |
1681 | and possibly a second device. For | |
1682 | .BR Fail , | |
1683 | .BR FailSpare , | |
1684 | and | |
1685 | .B SpareActive | |
1686 | the second device is the relevant component device. | |
1687 | For | |
1688 | .B MoveSpare | |
1689 | the second device is the array that the spare was moved from. | |
1690 | ||
1691 | For | |
1692 | .B mdadm | |
1693 | to move spares from one array to another, the different arrays need to | |
1694 | be labeled with the same | |
1695 | .B spare-group | |
1696 | in the configuration file. The | |
1697 | .B spare-group | |
1698 | name can be any string; it is only necessary that different spare | |
1699 | groups use different names. | |
1700 | ||
1701 | When | |
1702 | .B mdadm | |
1703 | detects that an array in a spare group has fewer active | |
1704 | devices than necessary for the complete array, and has no spare | |
1705 | devices, it will look for another array in the same spare group that | |
1706 | has a full complement of working drive and a spare. It will then | |
1707 | attempt to remove the spare from the second drive and add it to the | |
1708 | first. | |
1709 | If the removal succeeds but the adding fails, then it is added back to | |
1710 | the original array. | |
1711 | ||
1712 | .SH GROW MODE | |
1713 | The GROW mode is used for changing the size or shape of an active | |
1714 | array. | |
1715 | For this to work, the kernel must support the necessary change. | |
1716 | Various types of growth are being added during 2.6 development, | |
1717 | including restructuring a raid5 array to have more active devices. | |
1718 | ||
1719 | Currently the only support available is to | |
1720 | .IP \(bu 4 | |
1721 | change the "size" attribute | |
1722 | for RAID1, RAID5 and RAID6. | |
1723 | .IP \(bu 4 | |
1724 | increase the "raid-disks" attribute of RAID1, RAID5, and RAID6. | |
1725 | .IP \(bu 4 | |
1726 | add a write-intent bitmap to any array which supports these bitmaps, or | |
1727 | remove a write-intent bitmap from such an array. | |
1728 | .PP | |
1729 | ||
1730 | .SS SIZE CHANGES | |
1731 | Normally when an array is built the "size" it taken from the smallest | |
1732 | of the drives. If all the small drives in an arrays are, one at a | |
1733 | time, removed and replaced with larger drives, then you could have an | |
1734 | array of large drives with only a small amount used. In this | |
1735 | situation, changing the "size" with "GROW" mode will allow the extra | |
1736 | space to start being used. If the size is increased in this way, a | |
1737 | "resync" process will start to make sure the new parts of the array | |
1738 | are synchronised. | |
1739 | ||
1740 | Note that when an array changes size, any filesystem that may be | |
1741 | stored in the array will not automatically grow to use the space. The | |
1742 | filesystem will need to be explicitly told to use the extra space. | |
1743 | ||
1744 | .SS RAID-DEVICES CHANGES | |
1745 | ||
1746 | A RAID1 array can work with any number of devices from 1 upwards | |
1747 | (though 1 is not very useful). There may be times which you want to | |
1748 | increase or decrease the number of active devices. Note that this is | |
1749 | different to hot-add or hot-remove which changes the number of | |
1750 | inactive devices. | |
1751 | ||
1752 | When reducing the number of devices in a RAID1 array, the slots which | |
1753 | are to be removed from the array must already be vacant. That is, the | |
1754 | devices which were in those slots must be failed and removed. | |
1755 | ||
1756 | When the number of devices is increased, any hot spares that are | |
1757 | present will be activated immediately. | |
1758 | ||
1759 | Increasing the number of active devices in a RAID5 is much more | |
1760 | effort. Every block in the array will need to be read and written | |
1761 | back to a new location. From 2.6.17, the Linux Kernel is able to do | |
1762 | this safely, including restart and interrupted "reshape". | |
1763 | ||
1764 | When relocating the first few stripes on a raid5, it is not possible | |
1765 | to keep the data on disk completely consistent and crash-proof. To | |
1766 | provide the required safety, mdadm disables writes to the array while | |
1767 | this "critical section" is reshaped, and takes a backup of the data | |
1768 | that is in that section. This backup is normally stored in any spare | |
1769 | devices that the array has, however it can also be stored in a | |
1770 | separate file specified with the | |
1771 | .B \-\-backup\-file | |
1772 | option. If this option is used, and the system does crash during the | |
1773 | critical period, the same file must be passed to | |
1774 | .B \-\-assemble | |
1775 | to restore the backup and reassemble the array. | |
1776 | ||
1777 | .SS BITMAP CHANGES | |
1778 | ||
1779 | A write-intent bitmap can be added to, or removed from, an active | |
1780 | array. Either internal bitmaps, or bitmaps stored in a separate file, | |
1781 | can be added. Note that if you add a bitmap stored in a file which is | |
1782 | in a filesystem that is on the raid array being affected, the system | |
1783 | will deadlock. The bitmap must be on a separate filesystem. | |
1784 | ||
1785 | .SH INCREMENTAL MODE | |
1786 | ||
1787 | .HP 12 | |
1788 | Usage: | |
1789 | .B mdadm \-\-incremental | |
1790 | .RB [ \-\-run ] | |
1791 | .RB [ \-\-quiet ] | |
1792 | .I component-device | |
1793 | .HP 12 | |
1794 | Usage: | |
1795 | .B mdadm \-\-incremental \-\-rebuild | |
1796 | .HP 12 | |
1797 | Usage: | |
1798 | .B mdadm \-\-incremental \-\-run \-\-scan | |
1799 | ||
1800 | ||
1801 | .PP | |
1802 | This mode is designed to be used in conjunction with a device | |
1803 | discovery system. As devices are found in a system, they can be | |
1804 | passed to | |
1805 | .B "mdadm \-\-incremental" | |
1806 | to be conditionally added to an appropriate array. | |
1807 | ||
1808 | .I mdadm | |
1809 | performs a number of tests to determine if the device is part of an | |
1810 | array, and which array it should be part of. If an appropriate array | |
1811 | is found, or can be created, | |
1812 | .I mdadm | |
1813 | adds the device to the array and conditionally starts the array. | |
1814 | ||
1815 | Note that | |
1816 | .I mdadm | |
1817 | will only add devices to an array which were previously working | |
1818 | (active or spare) parts of that array. It does not currently support | |
1819 | automatic inclusion of a new drive as a spare in some array. | |
1820 | ||
1821 | .B "mdadm \-\-incremental" | |
1822 | requires a bug-fix in all kernels through 2.6.19. | |
1823 | Hopefully, this will be fixed in 2.6.20; alternately, apply the patch | |
1824 | which is included with the mdadm source distribution. If | |
1825 | .I mdadm | |
1826 | detects that this bug is present, it will abort any attempt to use | |
1827 | .BR \-\-incremental . | |
1828 | ||
1829 | The tests that | |
1830 | .I mdadm | |
1831 | makes are as follow: | |
1832 | .IP + | |
1833 | Is the device permitted by | |
1834 | .BR mdadm.conf ? | |
1835 | That is, is it listed in a | |
1836 | .B DEVICES | |
1837 | line in that file. If | |
1838 | .B DEVICES | |
1839 | is absent then the default it to allow any device. Similar if | |
1840 | .B DEVICES | |
1841 | contains the special word | |
1842 | .B partitions | |
1843 | then any device is allowed. Otherwise the device name given to | |
1844 | .I mdadm | |
1845 | must match one of the names or patterns in a | |
1846 | .B DEVICES | |
1847 | line. | |
1848 | ||
1849 | .IP + | |
1850 | Does the device have a valid md superblock. If a specific metadata | |
1851 | version is request with | |
1852 | .B \-\-metadata | |
1853 | or | |
1854 | .B \-e | |
1855 | then only that style of metadata is accepted, otherwise | |
1856 | .I mdadm | |
1857 | finds any known version of metadata. If no | |
1858 | .I md | |
1859 | metadata is found, the device is rejected. | |
1860 | ||
1861 | .IP + | |
1862 | Does the metadata match an expected array? | |
1863 | The metadata can match in two ways. Either there is an array listed | |
1864 | in | |
1865 | .B mdadm.conf | |
1866 | which identifies the array (either by UUID, by name, by device list, | |
1867 | or by minor-number), or the array was created with a | |
1868 | .B homehost | |
1869 | specified and that | |
1870 | .B homehost | |
1871 | matches the one in | |
1872 | .B mdadm.conf | |
1873 | or on the command line. | |
1874 | If | |
1875 | .I mdadm | |
1876 | is not able to positively identify the array as belonging to the | |
1877 | current host, the device will be rejected. | |
1878 | ||
1879 | .IP + | |
1880 | .I mdadm | |
1881 | keeps a list of arrays that it has partially assembled in | |
1882 | .B /var/run/mdadm/map | |
1883 | (or | |
1884 | .B /var/run/mdadm.map | |
1885 | if the directory doesn't exist). If no array exists which matches | |
1886 | the metadata on the new device, | |
1887 | .I mdadm | |
1888 | must choose a device name and unit number. It does this based on any | |
1889 | name given in | |
1890 | .B mdadm.conf | |
1891 | or any name information stored in the metadata. If this name | |
1892 | suggests a unit number, that number will be used, otherwise a free | |
1893 | unit number will be chosen. Normally | |
1894 | .I mdadm | |
1895 | will prefer to create a partitionable array, however if the | |
1896 | .B CREATE | |
1897 | line in | |
1898 | .B mdadm.conf | |
1899 | suggests that a non-partitionable array is preferred, that will be | |
1900 | honoured. | |
1901 | ||
1902 | .IP + | |
1903 | Once an appropriate array is found or created and the device is added, | |
1904 | .I mdadm | |
1905 | must decide if the array is ready to be started. It will | |
1906 | normally compare the number of available (non-spare) devices to the | |
1907 | number of devices that the metadata suggests need to be active. If | |
1908 | there are at least that many, the array will be started. This means | |
1909 | that if any devices are missing the array will not be restarted. | |
1910 | ||
1911 | As an alternative, | |
1912 | .B \-\-run | |
1913 | may be passed to | |
1914 | .B mdadm | |
1915 | in which case the array will be run as soon as there are enough | |
1916 | devices present for the data to be accessible. For a raid1, that | |
1917 | means one device will start the array. For a clean raid5, the array | |
1918 | will be started as soon as all but one drive is present. | |
1919 | ||
1920 | Note that neither of these approaches is really ideal. If it can | |
1921 | be known that all device discovery has completed, then | |
1922 | .br | |
1923 | .B " mdadm \-IRs" | |
1924 | .br | |
1925 | can be run which will try to start all arrays that are being | |
1926 | incrementally assembled. They are started in "read-auto" mode in | |
1927 | which they are read-only until the first write request. This means | |
1928 | that no metadata updates are made and no attempt at resync or recovery | |
1929 | happens. Further devices that are found before the first write can | |
1930 | still be added safely. | |
1931 | ||
1932 | .SH EXAMPLES | |
1933 | ||
1934 | .B " mdadm \-\-query /dev/name-of-device" | |
1935 | .br | |
1936 | This will find out if a given device is a raid array, or is part of | |
1937 | one, and will provide brief information about the device. | |
1938 | ||
1939 | .B " mdadm \-\-assemble \-\-scan" | |
1940 | .br | |
1941 | This will assemble and start all arrays listed in the standard config | |
1942 | file. This command will typically go in a system startup file. | |
1943 | ||
1944 | .B " mdadm \-\-stop \-\-scan" | |
1945 | .br | |
1946 | This will shut down all arrays that can be shut down (i.e. are not | |
1947 | currently in use). This will typically go in a system shutdown script. | |
1948 | ||
1949 | .B " mdadm \-\-follow \-\-scan \-\-delay=120" | |
1950 | .br | |
1951 | If (and only if) there is an Email address or program given in the | |
1952 | standard config file, then | |
1953 | monitor the status of all arrays listed in that file by | |
1954 | polling them ever 2 minutes. | |
1955 | ||
1956 | .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1" | |
1957 | .br | |
1958 | Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1. | |
1959 | ||
1960 | .br | |
1961 | .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf" | |
1962 | .br | |
1963 | .B " mdadm \-\-detail \-\-scan >> mdadm.conf" | |
1964 | .br | |
1965 | This will create a prototype config file that describes currently | |
1966 | active arrays that are known to be made from partitions of IDE or SCSI drives. | |
1967 | This file should be reviewed before being used as it may | |
1968 | contain unwanted detail. | |
1969 | ||
1970 | .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf" | |
1971 | .br | |
1972 | .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf" | |
1973 | .br | |
1974 | This will find arrays which could be assembled from existing IDE and | |
1975 | SCSI whole drives (not partitions), and store the information in the | |
1976 | format of a config file. | |
1977 | This file is very likely to contain unwanted detail, particularly | |
1978 | the | |
1979 | .B devices= | |
1980 | entries. It should be reviewed and edited before being used as an | |
1981 | actual config file. | |
1982 | ||
1983 | .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions" | |
1984 | .br | |
1985 | .B " mdadm \-Ebsc partitions" | |
1986 | .br | |
1987 | Create a list of devices by reading | |
1988 | .BR /proc/partitions , | |
1989 | scan these for RAID superblocks, and printout a brief listing of all | |
1990 | that were found. | |
1991 | ||
1992 | .B " mdadm \-Ac partitions \-m 0 /dev/md0" | |
1993 | .br | |
1994 | Scan all partitions and devices listed in | |
1995 | .BR /proc/partitions | |
1996 | and assemble | |
1997 | .B /dev/md0 | |
1998 | out of all such devices with a RAID superblock with a minor number of 0. | |
1999 | ||
2000 | .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /var/run/mdadm" | |
2001 | .br | |
2002 | If config file contains a mail address or alert program, run mdadm in | |
2003 | the background in monitor mode monitoring all md devices. Also write | |
2004 | pid of mdadm daemon to | |
2005 | .BR /var/run/mdadm . | |
2006 | ||
2007 | .B " mdadm \-Iq /dev/somedevice" | |
2008 | .br | |
2009 | Try to incorporate newly discovered device into some array as | |
2010 | appropriate. | |
2011 | ||
2012 | .B " mdadm \-\-incremental \-\-rebuild \-\-run \-\-scan" | |
2013 | .br | |
2014 | Rebuild the array map from any current arrays, and then start any that | |
2015 | can be started. | |
2016 | ||
2017 | .B " mdadm /dev/md4 --fail detached --remove detached" | |
2018 | .br | |
2019 | Any devices which are components of /dev/md4 will be marked as faulty | |
2020 | and then remove from the array. | |
2021 | ||
2022 | .B " mdadm \-\-create \-\-help" | |
2023 | .br | |
2024 | Provide help about the Create mode. | |
2025 | ||
2026 | .B " mdadm \-\-config \-\-help" | |
2027 | .br | |
2028 | Provide help about the format of the config file. | |
2029 | ||
2030 | .B " mdadm \-\-help" | |
2031 | .br | |
2032 | Provide general help. | |
2033 | ||
2034 | ||
2035 | .SH FILES | |
2036 | ||
2037 | .SS /proc/mdstat | |
2038 | ||
2039 | If you're using the | |
2040 | .B /proc | |
2041 | filesystem, | |
2042 | .B /proc/mdstat | |
2043 | lists all active md devices with information about them. | |
2044 | .B mdadm | |
2045 | uses this to find arrays when | |
2046 | .B \-\-scan | |
2047 | is given in Misc mode, and to monitor array reconstruction | |
2048 | on Monitor mode. | |
2049 | ||
2050 | ||
2051 | .SS /etc/mdadm.conf | |
2052 | ||
2053 | The config file lists which devices may be scanned to see if | |
2054 | they contain MD super block, and gives identifying information | |
2055 | (e.g. UUID) about known MD arrays. See | |
2056 | .BR mdadm.conf (5) | |
2057 | for more details. | |
2058 | ||
2059 | .SS /var/run/mdadm/map | |
2060 | When | |
2061 | .B \-\-incremental | |
2062 | mode is used, this file gets a list of arrays currently being created. | |
2063 | If | |
2064 | .B /var/run/mdadm | |
2065 | does not exist as a directory, then | |
2066 | .B /var/run/mdadm.map | |
2067 | is used instead. | |
2068 | ||
2069 | .SH DEVICE NAMES | |
2070 | ||
2071 | While entries in the /dev directory can have any format you like, | |
2072 | .I mdadm | |
2073 | has an understanding of 'standard' formats which it uses to guide its | |
2074 | behaviour when creating device files via the | |
2075 | .B \-\-auto | |
2076 | option. | |
2077 | ||
2078 | The standard names for non-partitioned arrays (the only sort of md | |
2079 | array available in 2.4 and earlier) are either of | |
2080 | .IP | |
2081 | /dev/mdNN | |
2082 | .br | |
2083 | /dev/md/NN | |
2084 | .PP | |
2085 | where NN is a number. | |
2086 | The standard names for partitionable arrays (as available from 2.6 | |
2087 | onwards) are either of | |
2088 | .IP | |
2089 | /dev/md/dNN | |
2090 | .br | |
2091 | /dev/md_dNN | |
2092 | .PP | |
2093 | Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2". | |
2094 | ||
2095 | .SH NOTE | |
2096 | .B mdadm | |
2097 | was previously known as | |
2098 | .BR mdctl . | |
2099 | .P | |
2100 | .B mdadm | |
2101 | is completely separate from the | |
2102 | .B raidtools | |
2103 | package, and does not use the | |
2104 | .I /etc/raidtab | |
2105 | configuration file at all. | |
2106 | ||
2107 | .SH SEE ALSO | |
2108 | For further information on MD and the various levels of | |
2109 | RAID, see: | |
2110 | ||
2111 | .IP | |
2112 | .UR http://unthought.net/Software-RAID.HOWTO/ | |
2113 | http://unthought.net/Software\-RAID.HOWTO/ | |
2114 | .UE | |
2115 | .IP | |
2116 | .UR http://linux-raid.osdl.org/ | |
2117 | http://linux\-raid.osdl.org/ | |
2118 | .UE | |
2119 | .\".PP | |
2120 | .\"for new releases of the RAID driver check out: | |
2121 | .\" | |
2122 | .\".IP | |
2123 | .\".UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2124 | .\"ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2125 | .\".UE | |
2126 | .\".PP | |
2127 | .\"or | |
2128 | .\".IP | |
2129 | .\".UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2130 | .\"http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2131 | .\".UE | |
2132 | .PP | |
2133 | The latest version of | |
2134 | .I mdadm | |
2135 | should always be available from | |
2136 | .IP | |
2137 | .UR http://www.kernel.org/pub/linux/utils/raid/mdadm/ | |
2138 | http://www.kernel.org/pub/linux/utils/raid/mdadm/ | |
2139 | .UE | |
2140 | .PP | |
2141 | .IR mdadm.conf (5), | |
2142 | .IR md (4). | |
2143 | .PP | |
2144 | .IR raidtab (5), | |
2145 | .IR raid0run (8), | |
2146 | .IR raidstop (8), | |
2147 | .IR mkraid (8). |