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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 "" v3.0-devel2 | |
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 | .BR FAULTY , | |
42 | and | |
43 | .BR CONTAINER . | |
44 | ||
45 | .B MULTIPATH | |
46 | is not a Software RAID mechanism, but does involve | |
47 | multiple devices: | |
48 | each device is a path to one common physical storage device. | |
49 | ||
50 | .B FAULTY | |
51 | is also not true RAID, and it only involves one device. It | |
52 | provides a layer over a true device that can be used to inject faults. | |
53 | ||
54 | .B CONTAINER | |
55 | is different again. A | |
56 | .B CONTAINER | |
57 | is a collection of devices that are | |
58 | managed as a set. This is similar to the set of devices connected to | |
59 | a hardware RAID controller. The set of devices may contain a number | |
60 | of different RAID arrays each utilising some (or all) blocks from a | |
61 | number of the devices in the set. For example, two devices in a 5-device set | |
62 | might form a RAID1 used the whole devices. The remaining three might | |
63 | have a RAID5 over the first half of each device, and a RAID0 over the | |
64 | second half. | |
65 | ||
66 | With a | |
67 | .BR CONTAINER , | |
68 | there is one set of metadata that describes all of | |
69 | the arrays in the container. So when | |
70 | .I mdadm | |
71 | creates a | |
72 | .B CONTAINER | |
73 | device, it just represents the metadata. Other normal arrays (RAID1 | |
74 | etc) can be created inside that container. | |
75 | ||
76 | ||
77 | .\".I mdadm | |
78 | .\"is a program that can be used to create, manage, and monitor | |
79 | .\"MD devices. As | |
80 | .\"such it provides a similar set of functionality to the | |
81 | .\".B raidtools | |
82 | .\"packages. | |
83 | .\"The key differences between | |
84 | .\".I mdadm | |
85 | .\"and | |
86 | .\".B raidtools | |
87 | .\"are: | |
88 | .\".IP \(bu 4 | |
89 | .\".I mdadm | |
90 | .\"is a single program and not a collection of programs. | |
91 | .\".IP \(bu 4 | |
92 | .\".I mdadm | |
93 | .\"can perform (almost) all of its functions without having a | |
94 | .\"configuration file and does not use one by default. Also | |
95 | .\".I mdadm | |
96 | .\"helps with management of the configuration | |
97 | .\"file. | |
98 | .\".IP \(bu 4 | |
99 | .\".I mdadm | |
100 | .\"can provide information about your arrays (through Query, Detail, and Examine) | |
101 | .\"that | |
102 | .\".B raidtools | |
103 | .\"cannot. | |
104 | .\".P | |
105 | .\".I mdadm | |
106 | .\"does not use | |
107 | .\".IR /etc/raidtab , | |
108 | .\"the | |
109 | .\".B raidtools | |
110 | .\"configuration file, at all. It has a different configuration file | |
111 | .\"with a different format and a different purpose. | |
112 | ||
113 | .SH MODES | |
114 | mdadm has several major modes of operation: | |
115 | .TP | |
116 | .B Assemble | |
117 | Assemble the components of a previously created | |
118 | array into an active array. Components can be explicitly given | |
119 | or can be searched for. | |
120 | .I mdadm | |
121 | checks that the components | |
122 | do form a bona fide array, and can, on request, fiddle superblock | |
123 | information so as to assemble a faulty array. | |
124 | ||
125 | .TP | |
126 | .B Build | |
127 | Build an array that doesn't have per-device superblocks. For these | |
128 | sorts of arrays, | |
129 | .I mdadm | |
130 | cannot differentiate between initial creation and subsequent assembly | |
131 | of an array. It also cannot perform any checks that appropriate | |
132 | components have been requested. Because of this, the | |
133 | .B Build | |
134 | mode should only be used together with a complete understanding of | |
135 | what you are doing. | |
136 | ||
137 | .TP | |
138 | .B Create | |
139 | Create a new array with per-device superblocks. | |
140 | .\"It can progress | |
141 | .\"in several step create-add-add-run or it can all happen with one command. | |
142 | ||
143 | .TP | |
144 | .B "Follow or Monitor" | |
145 | Monitor one or more md devices and act on any state changes. This is | |
146 | only meaningful for raid1, 4, 5, 6, 10 or multipath arrays, as | |
147 | only these have interesting state. raid0 or linear never have | |
148 | missing, spare, or failed drives, so there is nothing to monitor. | |
149 | ||
150 | .TP | |
151 | .B "Grow" | |
152 | Grow (or shrink) an array, or otherwise reshape it in some way. | |
153 | Currently supported growth options including changing the active size | |
154 | of component devices and changing the number of active devices in RAID | |
155 | levels 1/4/5/6, as well as adding or removing a write-intent bitmap. | |
156 | ||
157 | .TP | |
158 | .B "Incremental Assembly" | |
159 | Add a single device to an appropriate array. If the addition of the | |
160 | device makes the array runnable, the array will be started. | |
161 | This provides a convenient interface to a | |
162 | .I hot-plug | |
163 | system. As each device is detected, | |
164 | .I mdadm | |
165 | has a chance to include it in some array as appropriate. | |
166 | .P | |
167 | If a | |
168 | .B CONTAINER | |
169 | is passed to | |
170 | .I mdadm | |
171 | in this mode, then any arrays within that container will be assembled | |
172 | and started. | |
173 | ||
174 | .TP | |
175 | .B Manage | |
176 | This is for doing things to specific components of an array such as | |
177 | adding new spares and removing faulty devices. | |
178 | ||
179 | .TP | |
180 | .B Misc | |
181 | This is an 'everything else' mode that supports operations on active | |
182 | arrays, operations on component devices such as erasing old superblocks, and | |
183 | information gathering operations. | |
184 | .\"This mode allows operations on independent devices such as examine MD | |
185 | .\"superblocks, erasing old superblocks and stopping active arrays. | |
186 | ||
187 | .TP | |
188 | .B Auto-detect | |
189 | This mode does not act on a specific device or array, but rather it | |
190 | requests the Linux Kernel to activate any auto-detected arrays. | |
191 | .SH OPTIONS | |
192 | ||
193 | .SH Options for selecting a mode are: | |
194 | ||
195 | .TP | |
196 | .BR \-A ", " \-\-assemble | |
197 | Assemble a pre-existing array. | |
198 | ||
199 | .TP | |
200 | .BR \-B ", " \-\-build | |
201 | Build a legacy array without superblocks. | |
202 | ||
203 | .TP | |
204 | .BR \-C ", " \-\-create | |
205 | Create a new array. | |
206 | ||
207 | .TP | |
208 | .BR \-F ", " \-\-follow ", " \-\-monitor | |
209 | Select | |
210 | .B Monitor | |
211 | mode. | |
212 | ||
213 | .TP | |
214 | .BR \-G ", " \-\-grow | |
215 | Change the size or shape of an active array. | |
216 | ||
217 | .TP | |
218 | .BR \-I ", " \-\-incremental | |
219 | Add a single device into an appropriate array, and possibly start the array. | |
220 | ||
221 | .TP | |
222 | .B \-\-auto-detect | |
223 | Request that the kernel starts any auto-detected arrays. This can only | |
224 | work if | |
225 | .I md | |
226 | is compiled into the kernel \(em not if it is a module. | |
227 | Arrays can be auto-detected by the kernel if all the components are in | |
228 | primary MS-DOS partitions with partition type | |
229 | .BR FD . | |
230 | In-kernel autodetect is not recommended for new installations. Using | |
231 | .I mdadm | |
232 | to detect and assemble arrays \(em possibly in an | |
233 | .I initrd | |
234 | \(em is substantially more flexible and should be preferred. | |
235 | ||
236 | .P | |
237 | If a device is given before any options, or if the first option is | |
238 | .BR \-\-add , | |
239 | .BR \-\-fail , | |
240 | or | |
241 | .BR \-\-remove , | |
242 | then the MANAGE mode is assume. | |
243 | Anything other than these will cause the | |
244 | .B Misc | |
245 | mode to be assumed. | |
246 | ||
247 | .SH Options that are not mode-specific are: | |
248 | ||
249 | .TP | |
250 | .BR \-h ", " \-\-help | |
251 | Display general help message or, after one of the above options, a | |
252 | mode-specific help message. | |
253 | ||
254 | .TP | |
255 | .B \-\-help\-options | |
256 | Display more detailed help about command line parsing and some commonly | |
257 | used options. | |
258 | ||
259 | .TP | |
260 | .BR \-V ", " \-\-version | |
261 | Print version information for mdadm. | |
262 | ||
263 | .TP | |
264 | .BR \-v ", " \-\-verbose | |
265 | Be more verbose about what is happening. This can be used twice to be | |
266 | extra-verbose. | |
267 | The extra verbosity currently only affects | |
268 | .B \-\-detail \-\-scan | |
269 | and | |
270 | .BR "\-\-examine \-\-scan" . | |
271 | ||
272 | .TP | |
273 | .BR \-q ", " \-\-quiet | |
274 | Avoid printing purely informative messages. With this, | |
275 | .I mdadm | |
276 | will be silent unless there is something really important to report. | |
277 | ||
278 | .TP | |
279 | .BR \-b ", " \-\-brief | |
280 | Be less verbose. This is used with | |
281 | .B \-\-detail | |
282 | and | |
283 | .BR \-\-examine . | |
284 | Using | |
285 | .B \-\-brief | |
286 | with | |
287 | .B \-\-verbose | |
288 | gives an intermediate level of verbosity. | |
289 | ||
290 | .TP | |
291 | .BR \-f ", " \-\-force | |
292 | Be more forceful about certain operations. See the various modes for | |
293 | the exact meaning of this option in different contexts. | |
294 | ||
295 | .TP | |
296 | .BR \-c ", " \-\-config= | |
297 | Specify the config file. Default is to use | |
298 | .BR /etc/mdadm.conf , | |
299 | or if that is missing then | |
300 | .BR /etc/mdadm/mdadm.conf . | |
301 | If the config file given is | |
302 | .B "partitions" | |
303 | then nothing will be read, but | |
304 | .I mdadm | |
305 | will act as though the config file contained exactly | |
306 | .B "DEVICE partitions containers" | |
307 | and will read | |
308 | .B /proc/partitions | |
309 | to find a list of devices to scan, and | |
310 | .B /proc/mdstat | |
311 | to find a list of containers to examine. | |
312 | If the word | |
313 | .B "none" | |
314 | is given for the config file, then | |
315 | .I mdadm | |
316 | will act as though the config file were empty. | |
317 | ||
318 | .TP | |
319 | .BR \-s ", " \-\-scan | |
320 | Scan config file or | |
321 | .B /proc/mdstat | |
322 | for missing information. | |
323 | In general, this option gives | |
324 | .I mdadm | |
325 | permission to get any missing information (like component devices, | |
326 | array devices, array identities, and alert destination) from the | |
327 | configuration file (see previous option); | |
328 | one exception is MISC mode when using | |
329 | .B \-\-detail | |
330 | or | |
331 | .B \-\-stop, | |
332 | in which case | |
333 | .B \-\-scan | |
334 | says to get a list of array devices from | |
335 | .BR /proc/mdstat . | |
336 | ||
337 | .TP | |
338 | .B \-e ", " \-\-metadata= | |
339 | Declare the style of superblock (raid metadata) to be used. The | |
340 | default is 0.90 for | |
341 | .BR \-\-create , | |
342 | and to guess for other operations. | |
343 | The default can be overridden by setting the | |
344 | .B metadata | |
345 | value for the | |
346 | .B CREATE | |
347 | keyword in | |
348 | .BR mdadm.conf . | |
349 | ||
350 | Options are: | |
351 | .RS | |
352 | .IP "0, 0.90, default" | |
353 | Use the original 0.90 format superblock. This format limits arrays to | |
354 | 28 component devices and limits component devices of levels 1 and | |
355 | greater to 2 terabytes. | |
356 | .IP "1, 1.0, 1.1, 1.2" | |
357 | Use the new version-1 format superblock. This has few restrictions. | |
358 | The different sub-versions store the superblock at different locations | |
359 | on the device, either at the end (for 1.0), at the start (for 1.1) or | |
360 | 4K from the start (for 1.2). | |
361 | .IP ddf | |
362 | Use the "Industry Standard" DDF (Disk Data Format) format. When | |
363 | creating a DDF array a | |
364 | .B CONTAINER | |
365 | will be created, and normal arrays can be created in that container. | |
366 | .IP imsm | |
367 | Use the Intel(R) Matrix Storage Manager metadata format. This creates a | |
368 | .B CONTAINER | |
369 | which is managed in a similar manner to DDF, and is supported by an | |
370 | option-rom on some platforms: | |
371 | .IP | |
372 | .B http://www.intel.com/design/chipsets/matrixstorage_sb.htm | |
373 | .PP | |
374 | .RE | |
375 | ||
376 | .TP | |
377 | .B \-\-homehost= | |
378 | This will override any | |
379 | .B HOMEHOST | |
380 | setting in the config file and provides the identity of the host which | |
381 | should be considered the home for any arrays. | |
382 | ||
383 | When creating an array, the | |
384 | .B homehost | |
385 | will be recorded in the superblock. For version-1 superblocks, it will | |
386 | be prefixed to the array name. For version-0.90 superblocks, part of | |
387 | the SHA1 hash of the hostname will be stored in the later half of the | |
388 | UUID. | |
389 | ||
390 | When reporting information about an array, any array which is tagged | |
391 | for the given homehost will be reported as such. | |
392 | ||
393 | When using Auto-Assemble, only arrays tagged for the given homehost | |
394 | will be assembled. | |
395 | ||
396 | .SH For create, build, or grow: | |
397 | ||
398 | .TP | |
399 | .BR \-n ", " \-\-raid\-devices= | |
400 | Specify the number of active devices in the array. This, plus the | |
401 | number of spare devices (see below) must equal the number of | |
402 | .I component-devices | |
403 | (including "\fBmissing\fP" devices) | |
404 | that are listed on the command line for | |
405 | .BR \-\-create . | |
406 | Setting a value of 1 is probably | |
407 | a mistake and so requires that | |
408 | .B \-\-force | |
409 | be specified first. A value of 1 will then be allowed for linear, | |
410 | multipath, raid0 and raid1. It is never allowed for raid4 or raid5. | |
411 | .br | |
412 | This number can only be changed using | |
413 | .B \-\-grow | |
414 | for RAID1, RAID5 and RAID6 arrays, and only on kernels which provide | |
415 | necessary support. | |
416 | ||
417 | .TP | |
418 | .BR \-x ", " \-\-spare\-devices= | |
419 | Specify the number of spare (eXtra) devices in the initial array. | |
420 | Spares can also be added | |
421 | and removed later. The number of component devices listed | |
422 | on the command line must equal the number of raid devices plus the | |
423 | number of spare devices. | |
424 | ||
425 | ||
426 | .TP | |
427 | .BR \-z ", " \-\-size= | |
428 | Amount (in Kibibytes) of space to use from each drive in RAID level 1/4/5/6. | |
429 | This must be a multiple of the chunk size, and must leave about 128Kb | |
430 | of space at the end of the drive for the RAID superblock. | |
431 | If this is not specified | |
432 | (as it normally is not) the smallest drive (or partition) sets the | |
433 | size, though if there is a variance among the drives of greater than 1%, a warning is | |
434 | issued. | |
435 | ||
436 | This value can be set with | |
437 | .B \-\-grow | |
438 | for RAID level 1/4/5/6. If the array was created with a size smaller | |
439 | than the currently active drives, the extra space can be accessed | |
440 | using | |
441 | .BR \-\-grow . | |
442 | The size can be given as | |
443 | .B max | |
444 | which means to choose the largest size that fits on all current drives. | |
445 | ||
446 | This value can not be used with | |
447 | .B CONTAINER | |
448 | metadata such as DDF and IMSM. | |
449 | ||
450 | .TP | |
451 | .BR \-c ", " \-\-chunk= | |
452 | Specify chunk size of kibibytes. The default is 64. | |
453 | ||
454 | .TP | |
455 | .BR \-\-rounding= | |
456 | Specify rounding factor for linear array (==chunk size) | |
457 | ||
458 | .TP | |
459 | .BR \-l ", " \-\-level= | |
460 | Set raid level. When used with | |
461 | .BR \-\-create , | |
462 | options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4, | |
463 | raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container. | |
464 | Obviously some of these are synonymous. | |
465 | ||
466 | When a | |
467 | .B CONTAINER | |
468 | metadata type is requested, only the | |
469 | .B container | |
470 | level is permitted, and it does not need to be explicitly given. | |
471 | ||
472 | When used with | |
473 | .BR \-\-build , | |
474 | only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid. | |
475 | ||
476 | Not yet supported with | |
477 | .BR \-\-grow . | |
478 | ||
479 | .TP | |
480 | .BR \-p ", " \-\-layout= | |
481 | This option configures the fine details of data layout for raid5, | |
482 | and raid10 arrays, and controls the failure modes for | |
483 | .IR faulty . | |
484 | ||
485 | The layout of the raid5 parity block can be one of | |
486 | .BR left\-asymmetric , | |
487 | .BR left\-symmetric , | |
488 | .BR right\-asymmetric , | |
489 | .BR right\-symmetric , | |
490 | .BR la ", " ra ", " ls ", " rs . | |
491 | The default is | |
492 | .BR left\-symmetric . | |
493 | ||
494 | When setting the failure mode for level | |
495 | .I faulty, | |
496 | the options are: | |
497 | .BR write\-transient ", " wt , | |
498 | .BR read\-transient ", " rt , | |
499 | .BR write\-persistent ", " wp , | |
500 | .BR read\-persistent ", " rp , | |
501 | .BR write\-all , | |
502 | .BR read\-fixable ", " rf , | |
503 | .BR clear ", " flush ", " none . | |
504 | ||
505 | Each failure mode can be followed by a number, which is used as a period | |
506 | between fault generation. Without a number, the fault is generated | |
507 | once on the first relevant request. With a number, the fault will be | |
508 | generated after that many requests, and will continue to be generated | |
509 | every time the period elapses. | |
510 | ||
511 | Multiple failure modes can be current simultaneously by using the | |
512 | .B \-\-grow | |
513 | option to set subsequent failure modes. | |
514 | ||
515 | "clear" or "none" will remove any pending or periodic failure modes, | |
516 | and "flush" will clear any persistent faults. | |
517 | ||
518 | To set the parity with | |
519 | .BR \-\-grow , | |
520 | the level of the array ("faulty") | |
521 | must be specified before the fault mode is specified. | |
522 | ||
523 | Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed | |
524 | by a small number. The default is 'n2'. The supported options are: | |
525 | ||
526 | .I 'n' | |
527 | signals 'near' copies. Multiple copies of one data block are at | |
528 | similar offsets in different devices. | |
529 | ||
530 | .I 'o' | |
531 | signals 'offset' copies. Rather than the chunks being duplicated | |
532 | within a stripe, whole stripes are duplicated but are rotated by one | |
533 | device so duplicate blocks are on different devices. Thus subsequent | |
534 | copies of a block are in the next drive, and are one chunk further | |
535 | down. | |
536 | ||
537 | .I 'f' | |
538 | signals 'far' copies | |
539 | (multiple copies have very different offsets). | |
540 | See md(4) for more detail about 'near' and 'far'. | |
541 | ||
542 | The number is the number of copies of each datablock. 2 is normal, 3 | |
543 | can be useful. This number can be at most equal to the number of | |
544 | devices in the array. It does not need to divide evenly into that | |
545 | number (e.g. it is perfectly legal to have an 'n2' layout for an array | |
546 | with an odd number of devices). | |
547 | ||
548 | .TP | |
549 | .BR \-\-parity= | |
550 | same as | |
551 | .B \-\-layout | |
552 | (thus explaining the p of | |
553 | .BR \-p ). | |
554 | ||
555 | .TP | |
556 | .BR \-b ", " \-\-bitmap= | |
557 | Specify a file to store a write-intent bitmap in. The file should not | |
558 | exist unless | |
559 | .B \-\-force | |
560 | is also given. The same file should be provided | |
561 | when assembling the array. If the word | |
562 | .B "internal" | |
563 | is given, then the bitmap is stored with the metadata on the array, | |
564 | and so is replicated on all devices. If the word | |
565 | .B "none" | |
566 | is given with | |
567 | .B \-\-grow | |
568 | mode, then any bitmap that is present is removed. | |
569 | ||
570 | To help catch typing errors, the filename must contain at least one | |
571 | slash ('/') if it is a real file (not 'internal' or 'none'). | |
572 | ||
573 | Note: external bitmaps are only known to work on ext2 and ext3. | |
574 | Storing bitmap files on other filesystems may result in serious problems. | |
575 | ||
576 | .TP | |
577 | .BR \-\-bitmap\-chunk= | |
578 | Set the chunksize of the bitmap. Each bit corresponds to that many | |
579 | Kilobytes of storage. | |
580 | When using a file based bitmap, the default is to use the smallest | |
581 | size that is at-least 4 and requires no more than 2^21 chunks. | |
582 | When using an | |
583 | .B internal | |
584 | bitmap, the chunksize is automatically determined to make best use of | |
585 | available space. | |
586 | ||
587 | ||
588 | .TP | |
589 | .BR \-W ", " \-\-write\-mostly | |
590 | subsequent devices lists in a | |
591 | .BR \-\-build , | |
592 | .BR \-\-create , | |
593 | or | |
594 | .B \-\-add | |
595 | command will be flagged as 'write-mostly'. This is valid for RAID1 | |
596 | only and means that the 'md' driver will avoid reading from these | |
597 | devices if at all possible. This can be useful if mirroring over a | |
598 | slow link. | |
599 | ||
600 | .TP | |
601 | .BR \-\-write\-behind= | |
602 | Specify that write-behind mode should be enabled (valid for RAID1 | |
603 | only). If an argument is specified, it will set the maximum number | |
604 | of outstanding writes allowed. The default value is 256. | |
605 | A write-intent bitmap is required in order to use write-behind | |
606 | mode, and write-behind is only attempted on drives marked as | |
607 | .IR write-mostly . | |
608 | ||
609 | .TP | |
610 | .BR \-\-assume\-clean | |
611 | Tell | |
612 | .I mdadm | |
613 | that the array pre-existed and is known to be clean. It can be useful | |
614 | when trying to recover from a major failure as you can be sure that no | |
615 | data will be affected unless you actually write to the array. It can | |
616 | also be used when creating a RAID1 or RAID10 if you want to avoid the | |
617 | initial resync, however this practice \(em while normally safe \(em is not | |
618 | recommended. Use this only if you really know what you are doing. | |
619 | ||
620 | .TP | |
621 | .BR \-\-backup\-file= | |
622 | This is needed when | |
623 | .B \-\-grow | |
624 | is used to increase the number of | |
625 | raid-devices in a RAID5 if there are no spare devices available. | |
626 | See the section below on RAID_DEVICE CHANGES. The file should be | |
627 | stored on a separate device, not on the raid array being reshaped. | |
628 | ||
629 | .TP | |
630 | .BR \-N ", " \-\-name= | |
631 | Set a | |
632 | .B name | |
633 | for the array. This is currently only effective when creating an | |
634 | array with a version-1 superblock. The name is a simple textual | |
635 | string that can be used to identify array components when assembling. | |
636 | ||
637 | .TP | |
638 | .BR \-R ", " \-\-run | |
639 | Insist that | |
640 | .I mdadm | |
641 | run the array, even if some of the components | |
642 | appear to be active in another array or filesystem. Normally | |
643 | .I mdadm | |
644 | will ask for confirmation before including such components in an | |
645 | array. This option causes that question to be suppressed. | |
646 | ||
647 | .TP | |
648 | .BR \-f ", " \-\-force | |
649 | Insist that | |
650 | .I mdadm | |
651 | accept the geometry and layout specified without question. Normally | |
652 | .I mdadm | |
653 | will not allow creation of an array with only one device, and will try | |
654 | to create a raid5 array with one missing drive (as this makes the | |
655 | initial resync work faster). With | |
656 | .BR \-\-force , | |
657 | .I mdadm | |
658 | will not try to be so clever. | |
659 | ||
660 | .TP | |
661 | .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part,p}{NN}" | |
662 | Instruct mdadm to create the device file if needed, possibly allocating | |
663 | an unused minor number. "md" causes a non-partitionable array | |
664 | to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and | |
665 | later) to be used. "yes" requires the named md device to have | |
666 | a 'standard' format, and the type and minor number will be determined | |
667 | from this. See DEVICE NAMES below. | |
668 | ||
669 | The argument can also come immediately after | |
670 | "\-a". e.g. "\-ap". | |
671 | ||
672 | If | |
673 | .B \-\-auto | |
674 | is not given on the command line or in the config file, then | |
675 | the default will be | |
676 | .BR \-\-auto=yes . | |
677 | ||
678 | If | |
679 | .B \-\-scan | |
680 | is also given, then any | |
681 | .I auto= | |
682 | entries in the config file will override the | |
683 | .B \-\-auto | |
684 | instruction given on the command line. | |
685 | ||
686 | For partitionable arrays, | |
687 | .I mdadm | |
688 | will create the device file for the whole array and for the first 4 | |
689 | partitions. A different number of partitions can be specified at the | |
690 | end of this option (e.g. | |
691 | .BR \-\-auto=p7 ). | |
692 | If the device name ends with a digit, the partition names add a 'p', | |
693 | and a number, e.g. "/dev/md/home1p3". If there is no | |
694 | trailing digit, then the partition names just have a number added, | |
695 | e.g. "/dev/md/scratch3". | |
696 | ||
697 | If the md device name is in a 'standard' format as described in DEVICE | |
698 | NAMES, then it will be created, if necessary, with the appropriate | |
699 | number based on that name. If the device name is not in one of these | |
700 | formats, then a unused minor number will be allocated. The minor | |
701 | number will be considered unused if there is no active array for that | |
702 | number, and there is no entry in /dev for that number and with a | |
703 | non-standard name. Name that are not in 'standard' format are only | |
704 | allowed in "/dev/md/". | |
705 | ||
706 | \".TP | |
707 | \".BR \-\-symlink = no | |
708 | \"Normally when | |
709 | \".B \-\-auto | |
710 | \"causes | |
711 | \".I mdadm | |
712 | \"to create devices in | |
713 | \".B /dev/md/ | |
714 | \"it will also create symlinks from | |
715 | \".B /dev/ | |
716 | \"with names starting with | |
717 | \".B md | |
718 | \"or | |
719 | \".BR md_ . | |
720 | \"Use | |
721 | \".B \-\-symlink=no | |
722 | \"to suppress this, or | |
723 | \".B \-\-symlink=yes | |
724 | \"to enforce this even if it is suppressing | |
725 | \".IR mdadm.conf . | |
726 | \" | |
727 | ||
728 | .SH For assemble: | |
729 | ||
730 | .TP | |
731 | .BR \-u ", " \-\-uuid= | |
732 | uuid of array to assemble. Devices which don't have this uuid are | |
733 | excluded | |
734 | ||
735 | .TP | |
736 | .BR \-m ", " \-\-super\-minor= | |
737 | Minor number of device that array was created for. Devices which | |
738 | don't have this minor number are excluded. If you create an array as | |
739 | /dev/md1, then all superblocks will contain the minor number 1, even if | |
740 | the array is later assembled as /dev/md2. | |
741 | ||
742 | Giving the literal word "dev" for | |
743 | .B \-\-super\-minor | |
744 | will cause | |
745 | .I mdadm | |
746 | to use the minor number of the md device that is being assembled. | |
747 | e.g. when assembling | |
748 | .BR /dev/md0 , | |
749 | .B \-\-super\-minor=dev | |
750 | will look for super blocks with a minor number of 0. | |
751 | ||
752 | .TP | |
753 | .BR \-N ", " \-\-name= | |
754 | Specify the name of the array to assemble. This must be the name | |
755 | that was specified when creating the array. It must either match | |
756 | the name stored in the superblock exactly, or it must match | |
757 | with the current | |
758 | .I homehost | |
759 | prefixed to the start of the given name. | |
760 | ||
761 | .TP | |
762 | .BR \-f ", " \-\-force | |
763 | Assemble the array even if some superblocks appear out-of-date | |
764 | ||
765 | .TP | |
766 | .BR \-R ", " \-\-run | |
767 | Attempt to start the array even if fewer drives were given than were | |
768 | present last time the array was active. Normally if not all the | |
769 | expected drives are found and | |
770 | .B \-\-scan | |
771 | is not used, then the array will be assembled but not started. | |
772 | With | |
773 | .B \-\-run | |
774 | an attempt will be made to start it anyway. | |
775 | ||
776 | .TP | |
777 | .B \-\-no\-degraded | |
778 | This is the reverse of | |
779 | .B \-\-run | |
780 | in that it inhibits the startup of array unless all expected drives | |
781 | are present. This is only needed with | |
782 | .B \-\-scan, | |
783 | and can be used if the physical connections to devices are | |
784 | not as reliable as you would like. | |
785 | ||
786 | .TP | |
787 | .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}" | |
788 | See this option under Create and Build options. | |
789 | ||
790 | .TP | |
791 | .BR \-b ", " \-\-bitmap= | |
792 | Specify the bitmap file that was given when the array was created. If | |
793 | an array has an | |
794 | .B internal | |
795 | bitmap, there is no need to specify this when assembling the array. | |
796 | ||
797 | .TP | |
798 | .BR \-\-backup\-file= | |
799 | If | |
800 | .B \-\-backup\-file | |
801 | was used to grow the number of raid-devices in a RAID5, and the system | |
802 | crashed during the critical section, then the same | |
803 | .B \-\-backup\-file | |
804 | must be presented to | |
805 | .B \-\-assemble | |
806 | to allow possibly corrupted data to be restored. | |
807 | ||
808 | .TP | |
809 | .BR \-U ", " \-\-update= | |
810 | Update the superblock on each device while assembling the array. The | |
811 | argument given to this flag can be one of | |
812 | .BR sparc2.2 , | |
813 | .BR summaries , | |
814 | .BR uuid , | |
815 | .BR name , | |
816 | .BR homehost , | |
817 | .BR resync , | |
818 | .BR byteorder , | |
819 | .BR devicesize , | |
820 | or | |
821 | .BR super\-minor . | |
822 | ||
823 | The | |
824 | .B sparc2.2 | |
825 | option will adjust the superblock of an array what was created on a Sparc | |
826 | machine running a patched 2.2 Linux kernel. This kernel got the | |
827 | alignment of part of the superblock wrong. You can use the | |
828 | .B "\-\-examine \-\-sparc2.2" | |
829 | option to | |
830 | .I mdadm | |
831 | to see what effect this would have. | |
832 | ||
833 | The | |
834 | .B super\-minor | |
835 | option will update the | |
836 | .B "preferred minor" | |
837 | field on each superblock to match the minor number of the array being | |
838 | assembled. | |
839 | This can be useful if | |
840 | .B \-\-examine | |
841 | reports a different "Preferred Minor" to | |
842 | .BR \-\-detail . | |
843 | In some cases this update will be performed automatically | |
844 | by the kernel driver. In particular the update happens automatically | |
845 | at the first write to an array with redundancy (RAID level 1 or | |
846 | greater) on a 2.6 (or later) kernel. | |
847 | ||
848 | The | |
849 | .B uuid | |
850 | option will change the uuid of the array. If a UUID is given with the | |
851 | .B \-\-uuid | |
852 | option that UUID will be used as a new UUID and will | |
853 | .B NOT | |
854 | be used to help identify the devices in the array. | |
855 | If no | |
856 | .B \-\-uuid | |
857 | is given, a random UUID is chosen. | |
858 | ||
859 | The | |
860 | .B name | |
861 | option will change the | |
862 | .I name | |
863 | of the array as stored in the superblock. This is only supported for | |
864 | version-1 superblocks. | |
865 | ||
866 | The | |
867 | .B homehost | |
868 | option will change the | |
869 | .I homehost | |
870 | as recorded in the superblock. For version-0 superblocks, this is the | |
871 | same as updating the UUID. | |
872 | For version-1 superblocks, this involves updating the name. | |
873 | ||
874 | The | |
875 | .B resync | |
876 | option will cause the array to be marked | |
877 | .I dirty | |
878 | meaning that any redundancy in the array (e.g. parity for raid5, | |
879 | copies for raid1) may be incorrect. This will cause the raid system | |
880 | to perform a "resync" pass to make sure that all redundant information | |
881 | is correct. | |
882 | ||
883 | The | |
884 | .B byteorder | |
885 | option allows arrays to be moved between machines with different | |
886 | byte-order. | |
887 | When assembling such an array for the first time after a move, giving | |
888 | .B "\-\-update=byteorder" | |
889 | will cause | |
890 | .I mdadm | |
891 | to expect superblocks to have their byteorder reversed, and will | |
892 | correct that order before assembling the array. This is only valid | |
893 | with original (Version 0.90) superblocks. | |
894 | ||
895 | The | |
896 | .B summaries | |
897 | option will correct the summaries in the superblock. That is the | |
898 | counts of total, working, active, failed, and spare devices. | |
899 | ||
900 | The | |
901 | .B devicesize | |
902 | will rarely be of use. It applies to version 1.1 and 1.2 metadata | |
903 | only (where the metadata is at the start of the device) and is only | |
904 | useful when the component device has changed size (typically become | |
905 | larger). The version 1 metadata records the amount of the device that | |
906 | can be used to store data, so if a device in a version 1.1 or 1.2 | |
907 | array becomes larger, the metadata will still be visible, but the | |
908 | extra space will not. In this case it might be useful to assemble the | |
909 | array with | |
910 | .BR \-\-update=devicesize . | |
911 | This will cause | |
912 | .I mdadm | |
913 | to determine the maximum usable amount of space on each device and | |
914 | update the relevant field in the metadata. | |
915 | ||
916 | .TP | |
917 | .B \-\-auto\-update\-homehost | |
918 | This flag is only meaningful with auto-assembly (see discussion below). | |
919 | In that situation, if no suitable arrays are found for this homehost, | |
920 | .I mdadm | |
921 | will rescan for any arrays at all and will assemble them and update the | |
922 | homehost to match the current host. | |
923 | ||
924 | .SH For Manage mode: | |
925 | ||
926 | .TP | |
927 | .BR \-a ", " \-\-add | |
928 | hot-add listed devices. | |
929 | ||
930 | .TP | |
931 | .BR \-\-re\-add | |
932 | re-add a device that was recently removed from an array. | |
933 | ||
934 | .TP | |
935 | .BR \-r ", " \-\-remove | |
936 | remove listed devices. They must not be active. i.e. they should | |
937 | be failed or spare devices. As well as the name of a device file | |
938 | (e.g. | |
939 | .BR /dev/sda1 ) | |
940 | the words | |
941 | .B failed | |
942 | and | |
943 | .B detached | |
944 | can be given to | |
945 | .BR \-\-remove . | |
946 | The first causes all failed device to be removed. The second causes | |
947 | any device which is no longer connected to the system (i.e an 'open' | |
948 | returns | |
949 | .BR ENXIO ) | |
950 | to be removed. This will only succeed for devices that are spares or | |
951 | have already been marked as failed. | |
952 | ||
953 | .TP | |
954 | .BR \-f ", " \-\-fail | |
955 | mark listed devices as faulty. | |
956 | As well as the name of a device file, the word | |
957 | .B detached | |
958 | can be given. This will cause any device that has been detached from | |
959 | the system to be marked as failed. It can then be removed. | |
960 | ||
961 | .TP | |
962 | .BR \-\-set\-faulty | |
963 | same as | |
964 | .BR \-\-fail . | |
965 | ||
966 | .TP | |
967 | .BR \-\-write\-mostly | |
968 | Subsequent devices that are added or re-added will have the 'write-mostly' | |
969 | flag set. This is only valid for RAID! and means that the 'md' driver | |
970 | will avoid reading from these devices if possible. | |
971 | .TP | |
972 | .BR \-\-readwrite | |
973 | Subsequent devices that are added or re-added will have the 'write-mostly' | |
974 | flag cleared. | |
975 | ||
976 | ||
977 | .P | |
978 | Each of these options require that the first device listed is the array | |
979 | to be acted upon, and the remainder are component devices to be added, | |
980 | removed, or marked as faulty. Several different operations can be | |
981 | specified for different devices, e.g. | |
982 | .in +5 | |
983 | mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1 | |
984 | .in -5 | |
985 | Each operation applies to all devices listed until the next | |
986 | operation. | |
987 | ||
988 | If an array is using a write-intent bitmap, then devices which have | |
989 | been removed can be re-added in a way that avoids a full | |
990 | reconstruction but instead just updates the blocks that have changed | |
991 | since the device was removed. For arrays with persistent metadata | |
992 | (superblocks) this is done automatically. For arrays created with | |
993 | .B \-\-build | |
994 | mdadm needs to be told that this device we removed recently with | |
995 | .BR \-\-re\-add . | |
996 | ||
997 | Devices can only be removed from an array if they are not in active | |
998 | use, i.e. that must be spares or failed devices. To remove an active | |
999 | device, it must first be marked as | |
1000 | .B faulty. | |
1001 | ||
1002 | .SH For Misc mode: | |
1003 | ||
1004 | .TP | |
1005 | .BR \-Q ", " \-\-query | |
1006 | Examine a device to see | |
1007 | (1) if it is an md device and (2) if it is a component of an md | |
1008 | array. | |
1009 | Information about what is discovered is presented. | |
1010 | ||
1011 | .TP | |
1012 | .BR \-D ", " \-\-detail | |
1013 | Print detail of one or more md devices. | |
1014 | ||
1015 | .TP | |
1016 | .BR \-\-detail\-platform | |
1017 | Print detail of the platform's raid capabilities (firmware / hardware | |
1018 | topology) for a given metadata format. | |
1019 | ||
1020 | .TP | |
1021 | .BR \-Y ", " \-\-export | |
1022 | When used with | |
1023 | .B \-\-detail | |
1024 | or | |
1025 | .BR \-\-examine , | |
1026 | output will be formatted as | |
1027 | .B key=value | |
1028 | pairs for easy import into the environment. | |
1029 | ||
1030 | .TP | |
1031 | .BR \-E ", " \-\-examine | |
1032 | Print content of md superblock on device(s). | |
1033 | .TP | |
1034 | .B \-\-sparc2.2 | |
1035 | If an array was created on a 2.2 Linux kernel patched with RAID | |
1036 | support, the superblock will have been created incorrectly, or at | |
1037 | least incompatibly with 2.4 and later kernels. Using the | |
1038 | .B \-\-sparc2.2 | |
1039 | flag with | |
1040 | .B \-\-examine | |
1041 | will fix the superblock before displaying it. If this appears to do | |
1042 | the right thing, then the array can be successfully assembled using | |
1043 | .BR "\-\-assemble \-\-update=sparc2.2" . | |
1044 | ||
1045 | .TP | |
1046 | .BR \-X ", " \-\-examine\-bitmap | |
1047 | Report information about a bitmap file. | |
1048 | The argument is either an external bitmap file or an array component | |
1049 | in case of an internal bitmap. | |
1050 | ||
1051 | .TP | |
1052 | .BR \-R ", " \-\-run | |
1053 | start a partially built array. | |
1054 | ||
1055 | .TP | |
1056 | .BR \-S ", " \-\-stop | |
1057 | deactivate array, releasing all resources. | |
1058 | ||
1059 | .TP | |
1060 | .BR \-o ", " \-\-readonly | |
1061 | mark array as readonly. | |
1062 | ||
1063 | .TP | |
1064 | .BR \-w ", " \-\-readwrite | |
1065 | mark array as readwrite. | |
1066 | ||
1067 | .TP | |
1068 | .B \-\-zero\-superblock | |
1069 | If the device contains a valid md superblock, the block is | |
1070 | overwritten with zeros. With | |
1071 | .B \-\-force | |
1072 | the block where the superblock would be is overwritten even if it | |
1073 | doesn't appear to be valid. | |
1074 | ||
1075 | .TP | |
1076 | .BR \-t ", " \-\-test | |
1077 | When used with | |
1078 | .BR \-\-detail , | |
1079 | the exit status of | |
1080 | .I mdadm | |
1081 | is set to reflect the status of the device. | |
1082 | ||
1083 | .TP | |
1084 | .BR \-W ", " \-\-wait | |
1085 | For each md device given, wait for any resync, recovery, or reshape | |
1086 | activity to finish before returning. | |
1087 | .I mdadm | |
1088 | will return with success if it actually waited for every device | |
1089 | listed, otherwise it will return failure. | |
1090 | ||
1091 | .TP | |
1092 | .BR \-\-wait\-clean | |
1093 | For each md device given, or each device in /proc/mdstat if | |
1094 | .B \-\-scan | |
1095 | is given, arrange for the array to be marked clean as soon as possible. | |
1096 | Also, quiesce resync so that the monitor for external metadata arrays | |
1097 | (mdmon) has an opportunity to checkpoint the resync position. | |
1098 | .I mdadm | |
1099 | will return with success if the array uses external metadata and we | |
1100 | successfully waited. For native arrays this returns immediately as the | |
1101 | kernel handles both dirty-clean transitions and resync checkpointing in | |
1102 | the kernel at shutdown. No action is taken if safe-mode handling is | |
1103 | disabled. | |
1104 | ||
1105 | .SH For Incremental Assembly mode: | |
1106 | .TP | |
1107 | .BR \-\-rebuild\-map ", " \-r | |
1108 | Rebuild the map file | |
1109 | .RB ( /var/run/mdadm/map ) | |
1110 | that | |
1111 | .I mdadm | |
1112 | uses to help track which arrays are currently being assembled. | |
1113 | ||
1114 | .TP | |
1115 | .BR \-\-run ", " \-R | |
1116 | Run any array assembled as soon as a minimal number of devices are | |
1117 | available, rather than waiting until all expected devices are present. | |
1118 | ||
1119 | .TP | |
1120 | .BR \-\-scan ", " \-s | |
1121 | Only meaningful with | |
1122 | .B \-R | |
1123 | this will scan the | |
1124 | .B map | |
1125 | file for arrays that are being incrementally assembled and will try to | |
1126 | start any that are not already started. If any such array is listed | |
1127 | in | |
1128 | .B mdadm.conf | |
1129 | as requiring an external bitmap, that bitmap will be attached first. | |
1130 | ||
1131 | .SH For Monitor mode: | |
1132 | .TP | |
1133 | .BR \-m ", " \-\-mail | |
1134 | Give a mail address to send alerts to. | |
1135 | ||
1136 | .TP | |
1137 | .BR \-p ", " \-\-program ", " \-\-alert | |
1138 | Give a program to be run whenever an event is detected. | |
1139 | ||
1140 | .TP | |
1141 | .BR \-y ", " \-\-syslog | |
1142 | Cause all events to be reported through 'syslog'. The messages have | |
1143 | facility of 'daemon' and varying priorities. | |
1144 | ||
1145 | .TP | |
1146 | .BR \-d ", " \-\-delay | |
1147 | Give a delay in seconds. | |
1148 | .I mdadm | |
1149 | polls the md arrays and then waits this many seconds before polling | |
1150 | again. The default is 60 seconds. | |
1151 | ||
1152 | .TP | |
1153 | .BR \-f ", " \-\-daemonise | |
1154 | Tell | |
1155 | .I mdadm | |
1156 | to run as a background daemon if it decides to monitor anything. This | |
1157 | causes it to fork and run in the child, and to disconnect form the | |
1158 | terminal. The process id of the child is written to stdout. | |
1159 | This is useful with | |
1160 | .B \-\-scan | |
1161 | which will only continue monitoring if a mail address or alert program | |
1162 | is found in the config file. | |
1163 | ||
1164 | .TP | |
1165 | .BR \-i ", " \-\-pid\-file | |
1166 | When | |
1167 | .I mdadm | |
1168 | is running in daemon mode, write the pid of the daemon process to | |
1169 | the specified file, instead of printing it on standard output. | |
1170 | ||
1171 | .TP | |
1172 | .BR \-1 ", " \-\-oneshot | |
1173 | Check arrays only once. This will generate | |
1174 | .B NewArray | |
1175 | events and more significantly | |
1176 | .B DegradedArray | |
1177 | and | |
1178 | .B SparesMissing | |
1179 | events. Running | |
1180 | .in +5 | |
1181 | .B " mdadm \-\-monitor \-\-scan \-1" | |
1182 | .in -5 | |
1183 | from a cron script will ensure regular notification of any degraded arrays. | |
1184 | ||
1185 | .TP | |
1186 | .BR \-t ", " \-\-test | |
1187 | Generate a | |
1188 | .B TestMessage | |
1189 | alert for every array found at startup. This alert gets mailed and | |
1190 | passed to the alert program. This can be used for testing that alert | |
1191 | message do get through successfully. | |
1192 | ||
1193 | .SH ASSEMBLE MODE | |
1194 | ||
1195 | .HP 12 | |
1196 | Usage: | |
1197 | .B mdadm \-\-assemble | |
1198 | .I md-device options-and-component-devices... | |
1199 | .HP 12 | |
1200 | Usage: | |
1201 | .B mdadm \-\-assemble \-\-scan | |
1202 | .I md-devices-and-options... | |
1203 | .HP 12 | |
1204 | Usage: | |
1205 | .B mdadm \-\-assemble \-\-scan | |
1206 | .I options... | |
1207 | ||
1208 | .PP | |
1209 | This usage assembles one or more raid arrays from pre-existing components. | |
1210 | For each array, mdadm needs to know the md device, the identity of the | |
1211 | array, and a number of component-devices. These can be found in a number of ways. | |
1212 | ||
1213 | In the first usage example (without the | |
1214 | .BR \-\-scan ) | |
1215 | the first device given is the md device. | |
1216 | In the second usage example, all devices listed are treated as md | |
1217 | devices and assembly is attempted. | |
1218 | In the third (where no devices are listed) all md devices that are | |
1219 | listed in the configuration file are assembled. Then any arrays that | |
1220 | can be found on unused devices will also be assembled. | |
1221 | ||
1222 | If precisely one device is listed, but | |
1223 | .B \-\-scan | |
1224 | is not given, then | |
1225 | .I mdadm | |
1226 | acts as though | |
1227 | .B \-\-scan | |
1228 | was given and identity information is extracted from the configuration file. | |
1229 | ||
1230 | The identity can be given with the | |
1231 | .B \-\-uuid | |
1232 | option, with the | |
1233 | .B \-\-super\-minor | |
1234 | option, will be taken from the md-device record in the config file, or | |
1235 | will be taken from the super block of the first component-device | |
1236 | listed on the command line. | |
1237 | ||
1238 | Devices can be given on the | |
1239 | .B \-\-assemble | |
1240 | command line or in the config file. Only devices which have an md | |
1241 | superblock which contains the right identity will be considered for | |
1242 | any array. | |
1243 | ||
1244 | The config file is only used if explicitly named with | |
1245 | .B \-\-config | |
1246 | or requested with (a possibly implicit) | |
1247 | .BR \-\-scan . | |
1248 | In the later case, | |
1249 | .B /etc/mdadm.conf | |
1250 | or | |
1251 | .B /etc/mdadm/mdadm.conf | |
1252 | is used. | |
1253 | ||
1254 | If | |
1255 | .B \-\-scan | |
1256 | is not given, then the config file will only be used to find the | |
1257 | identity of md arrays. | |
1258 | ||
1259 | Normally the array will be started after it is assembled. However if | |
1260 | .B \-\-scan | |
1261 | is not given and insufficient drives were listed to start a complete | |
1262 | (non-degraded) array, then the array is not started (to guard against | |
1263 | usage errors). To insist that the array be started in this case (as | |
1264 | may work for RAID1, 4, 5, 6, or 10), give the | |
1265 | .B \-\-run | |
1266 | flag. | |
1267 | ||
1268 | If the md device does not exist, then it will be created providing the | |
1269 | intent is clear. i.e. the name must be in a standard form, or the | |
1270 | .B \-\-auto | |
1271 | option must be given to clarify how and whether the device should be | |
1272 | created. | |
1273 | This can be useful for handling partitioned devices (which don't have | |
1274 | a stable device number \(em it can change after a reboot) and when using | |
1275 | "udev" to manage your | |
1276 | .B /dev | |
1277 | tree (udev cannot handle md devices because of the unusual device | |
1278 | initialisation conventions). | |
1279 | ||
1280 | If the option to "auto" is "mdp" or "part" or (on the command line | |
1281 | only) "p", then mdadm will create a partitionable array, using the | |
1282 | first free one that is not in use and does not already have an entry | |
1283 | in /dev (apart from numeric /dev/md* entries). | |
1284 | ||
1285 | If the option to "auto" is "yes" or "md" or (on the command line) | |
1286 | nothing, then mdadm will create a traditional, non-partitionable md | |
1287 | array. | |
1288 | ||
1289 | It is expected that the "auto" functionality will be used to create | |
1290 | device entries with meaningful names such as "/dev/md/home" or | |
1291 | "/dev/md/root", rather than names based on the numerical array number. | |
1292 | ||
1293 | When using option "auto" to create a partitionable array, the device | |
1294 | files for the first 4 partitions are also created. If a different | |
1295 | number is required it can be simply appended to the auto option. | |
1296 | e.g. "auto=part8". Partition names are created by appending a digit | |
1297 | string to the device name, with an intervening "p" if the device name | |
1298 | ends with a digit. | |
1299 | ||
1300 | The | |
1301 | .B \-\-auto | |
1302 | option is also available in Build and Create modes. As those modes do | |
1303 | not use a config file, the "auto=" config option does not apply to | |
1304 | these modes. | |
1305 | ||
1306 | .SS Auto Assembly | |
1307 | When | |
1308 | .B \-\-assemble | |
1309 | is used with | |
1310 | .B \-\-scan | |
1311 | and no devices are listed, | |
1312 | .I mdadm | |
1313 | will first attempt to assemble all the arrays listed in the config | |
1314 | file. | |
1315 | ||
1316 | It will then look further for possible arrays and will try to assemble | |
1317 | anything that it finds. Arrays which are tagged as belonging to the given | |
1318 | homehost will be assembled and started normally. Arrays which do not | |
1319 | obviously belong to this host are given names that are expected not to | |
1320 | conflict with anything local, and are started "read-auto" so that | |
1321 | nothing is written to any device until the array is written to. i.e. | |
1322 | automatic resync etc is delayed. | |
1323 | ||
1324 | If | |
1325 | .I mdadm | |
1326 | finds a consistent set of devices that look like they should comprise | |
1327 | an array, and if the superblock is tagged as belonging to the given | |
1328 | home host, it will automatically choose a device name and try to | |
1329 | assemble the array. If the array uses version-0.90 metadata, then the | |
1330 | .B minor | |
1331 | number as recorded in the superblock is used to create a name in | |
1332 | .B /dev/md/ | |
1333 | so for example | |
1334 | .BR /dev/md/3 . | |
1335 | If the array uses version-1 metadata, then the | |
1336 | .B name | |
1337 | from the superblock is used to similarly create a name in | |
1338 | .BR /dev/md | |
1339 | (the name will have any 'host' prefix stripped first). | |
1340 | ||
1341 | If | |
1342 | .I mdadm | |
1343 | cannot find any array for the given host at all, and if | |
1344 | .B \-\-auto\-update\-homehost | |
1345 | is given, then | |
1346 | .I mdadm | |
1347 | will search again for any array (not just an array created for this | |
1348 | host) and will assemble each assuming | |
1349 | .BR \-\-update=homehost . | |
1350 | This will change the host tag in the superblock so that on the next run, | |
1351 | these arrays will be found without the second pass. The intention of | |
1352 | this feature is to support transitioning a set of md arrays to using | |
1353 | homehost tagging. | |
1354 | ||
1355 | The reason for requiring arrays to be tagged with the homehost for | |
1356 | auto assembly is to guard against problems that can arise when moving | |
1357 | devices from one host to another. | |
1358 | ||
1359 | .SH BUILD MODE | |
1360 | ||
1361 | .HP 12 | |
1362 | Usage: | |
1363 | .B mdadm \-\-build | |
1364 | .I md-device | |
1365 | .BI \-\-chunk= X | |
1366 | .BI \-\-level= Y | |
1367 | .BI \-\-raid\-devices= Z | |
1368 | .I devices | |
1369 | ||
1370 | .PP | |
1371 | This usage is similar to | |
1372 | .BR \-\-create . | |
1373 | The difference is that it creates an array without a superblock. With | |
1374 | these arrays there is no difference between initially creating the array and | |
1375 | subsequently assembling the array, except that hopefully there is useful | |
1376 | data there in the second case. | |
1377 | ||
1378 | The level may raid0, linear, multipath, or faulty, or one of their | |
1379 | synonyms. All devices must be listed and the array will be started | |
1380 | once complete. | |
1381 | ||
1382 | .SH CREATE MODE | |
1383 | ||
1384 | .HP 12 | |
1385 | Usage: | |
1386 | .B mdadm \-\-create | |
1387 | .I md-device | |
1388 | .BI \-\-chunk= X | |
1389 | .BI \-\-level= Y | |
1390 | .br | |
1391 | .BI \-\-raid\-devices= Z | |
1392 | .I devices | |
1393 | ||
1394 | .PP | |
1395 | This usage will initialise a new md array, associate some devices with | |
1396 | it, and activate the array. | |
1397 | ||
1398 | If the | |
1399 | .B \-\-auto | |
1400 | option is given (as described in more detail in the section on | |
1401 | Assemble mode), then the md device will be created with a suitable | |
1402 | device number if necessary. | |
1403 | ||
1404 | As devices are added, they are checked to see if they contain raid | |
1405 | superblocks or filesystems. They are also checked to see if the variance in | |
1406 | device size exceeds 1%. | |
1407 | ||
1408 | If any discrepancy is found, the array will not automatically be run, though | |
1409 | the presence of a | |
1410 | .B \-\-run | |
1411 | can override this caution. | |
1412 | ||
1413 | To create a "degraded" array in which some devices are missing, simply | |
1414 | give the word "\fBmissing\fP" | |
1415 | in place of a device name. This will cause | |
1416 | .I mdadm | |
1417 | to leave the corresponding slot in the array empty. | |
1418 | For a RAID4 or RAID5 array at most one slot can be | |
1419 | "\fBmissing\fP"; for a RAID6 array at most two slots. | |
1420 | For a RAID1 array, only one real device needs to be given. All of the | |
1421 | others can be | |
1422 | "\fBmissing\fP". | |
1423 | ||
1424 | When creating a RAID5 array, | |
1425 | .I mdadm | |
1426 | will automatically create a degraded array with an extra spare drive. | |
1427 | This is because building the spare into a degraded array is in general faster than resyncing | |
1428 | the parity on a non-degraded, but not clean, array. This feature can | |
1429 | be overridden with the | |
1430 | .B \-\-force | |
1431 | option. | |
1432 | ||
1433 | When creating an array with version-1 metadata a name for the array is | |
1434 | required. | |
1435 | If this is not given with the | |
1436 | .B \-\-name | |
1437 | option, | |
1438 | .I mdadm | |
1439 | will choose a name based on the last component of the name of the | |
1440 | device being created. So if | |
1441 | .B /dev/md3 | |
1442 | is being created, then the name | |
1443 | .B 3 | |
1444 | will be chosen. | |
1445 | If | |
1446 | .B /dev/md/home | |
1447 | is being created, then the name | |
1448 | .B home | |
1449 | will be used. | |
1450 | ||
1451 | When creating a partition based array, using | |
1452 | .I mdadm | |
1453 | with version-1.x metadata, the partition type should be set to | |
1454 | .B 0xDA | |
1455 | (non fs-data). This type selection allows for greater precision since | |
1456 | using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)], | |
1457 | might create problems in the event of array recovery through a live cdrom. | |
1458 | ||
1459 | A new array will normally get a randomly assigned 128bit UUID which is | |
1460 | very likely to be unique. If you have a specific need, you can choose | |
1461 | a UUID for the array by giving the | |
1462 | .B \-\-uuid= | |
1463 | option. Be warned that creating two arrays with the same UUID is a | |
1464 | recipe for disaster. Also, using | |
1465 | .B \-\-uuid= | |
1466 | when creating a v0.90 array will silently override any | |
1467 | .B \-\-homehost= | |
1468 | setting. | |
1469 | .\"If the | |
1470 | .\".B \-\-size | |
1471 | .\"option is given, it is not necessary to list any component-devices in this command. | |
1472 | .\"They can be added later, before a | |
1473 | .\".B \-\-run. | |
1474 | .\"If no | |
1475 | .\".B \-\-size | |
1476 | .\"is given, the apparent size of the smallest drive given is used. | |
1477 | ||
1478 | When creating an array within a | |
1479 | .B CONTAINER | |
1480 | .I mdadm | |
1481 | can be given either the list of devices to use, or simply the name of | |
1482 | the container. The former case gives control over which devices in | |
1483 | the container will be used for the array. The latter case allows | |
1484 | .I mdadm | |
1485 | to automatically choose which devices to use based on how much spare | |
1486 | space is available. | |
1487 | ||
1488 | The General Management options that are valid with | |
1489 | .B \-\-create | |
1490 | are: | |
1491 | .TP | |
1492 | .B \-\-run | |
1493 | insist on running the array even if some devices look like they might | |
1494 | be in use. | |
1495 | ||
1496 | .TP | |
1497 | .B \-\-readonly | |
1498 | start the array readonly \(em not supported yet. | |
1499 | ||
1500 | ||
1501 | .SH MANAGE MODE | |
1502 | .HP 12 | |
1503 | Usage: | |
1504 | .B mdadm | |
1505 | .I device | |
1506 | .I options... devices... | |
1507 | .PP | |
1508 | ||
1509 | This usage will allow individual devices in an array to be failed, | |
1510 | removed or added. It is possible to perform multiple operations with | |
1511 | on command. For example: | |
1512 | .br | |
1513 | .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1" | |
1514 | .br | |
1515 | will firstly mark | |
1516 | .B /dev/hda1 | |
1517 | as faulty in | |
1518 | .B /dev/md0 | |
1519 | and will then remove it from the array and finally add it back | |
1520 | in as a spare. However only one md array can be affected by a single | |
1521 | command. | |
1522 | ||
1523 | .SH MISC MODE | |
1524 | .HP 12 | |
1525 | Usage: | |
1526 | .B mdadm | |
1527 | .I options ... | |
1528 | .I devices ... | |
1529 | .PP | |
1530 | ||
1531 | MISC mode includes a number of distinct operations that | |
1532 | operate on distinct devices. The operations are: | |
1533 | .TP | |
1534 | .B \-\-query | |
1535 | The device is examined to see if it is | |
1536 | (1) an active md array, or | |
1537 | (2) a component of an md array. | |
1538 | The information discovered is reported. | |
1539 | ||
1540 | .TP | |
1541 | .B \-\-detail | |
1542 | The device should be an active md device. | |
1543 | .B mdadm | |
1544 | will display a detailed description of the array. | |
1545 | .B \-\-brief | |
1546 | or | |
1547 | .B \-\-scan | |
1548 | will cause the output to be less detailed and the format to be | |
1549 | suitable for inclusion in | |
1550 | .BR /etc/mdadm.conf . | |
1551 | The exit status of | |
1552 | .I mdadm | |
1553 | will normally be 0 unless | |
1554 | .I mdadm | |
1555 | failed to get useful information about the device(s); however, if the | |
1556 | .B \-\-test | |
1557 | option is given, then the exit status will be: | |
1558 | .RS | |
1559 | .TP | |
1560 | 0 | |
1561 | The array is functioning normally. | |
1562 | .TP | |
1563 | 1 | |
1564 | The array has at least one failed device. | |
1565 | .TP | |
1566 | 2 | |
1567 | The array has multiple failed devices such that it is unusable. | |
1568 | .TP | |
1569 | 4 | |
1570 | There was an error while trying to get information about the device. | |
1571 | .RE | |
1572 | ||
1573 | .TP | |
1574 | .B \-\-detail\-platform | |
1575 | Print detail of the platform's raid capabilities (firmware / hardware | |
1576 | topology). If the metadata is specified with | |
1577 | .B \-e | |
1578 | or | |
1579 | .B \-\-metadata= | |
1580 | then the return status will be: | |
1581 | .RS | |
1582 | .TP | |
1583 | 0 | |
1584 | metadata successfully enumerated its platform components on this system | |
1585 | .TP | |
1586 | 1 | |
1587 | metadata is platform independent | |
1588 | .TP | |
1589 | 2 | |
1590 | metadata failed to find its platform components on this system | |
1591 | .RE | |
1592 | ||
1593 | .TP | |
1594 | .B \-\-examine | |
1595 | The device should be a component of an md array. | |
1596 | .I mdadm | |
1597 | will read the md superblock of the device and display the contents. | |
1598 | If | |
1599 | .B \-\-brief | |
1600 | or | |
1601 | .B \-\-scan | |
1602 | is given, then multiple devices that are components of the one array | |
1603 | are grouped together and reported in a single entry suitable | |
1604 | for inclusion in | |
1605 | .BR /etc/mdadm.conf . | |
1606 | ||
1607 | Having | |
1608 | .B \-\-scan | |
1609 | without listing any devices will cause all devices listed in the | |
1610 | config file to be examined. | |
1611 | ||
1612 | .TP | |
1613 | .B \-\-stop | |
1614 | The devices should be active md arrays which will be deactivated, as | |
1615 | long as they are not currently in use. | |
1616 | ||
1617 | .TP | |
1618 | .B \-\-run | |
1619 | This will fully activate a partially assembled md array. | |
1620 | ||
1621 | .TP | |
1622 | .B \-\-readonly | |
1623 | This will mark an active array as read-only, providing that it is | |
1624 | not currently being used. | |
1625 | ||
1626 | .TP | |
1627 | .B \-\-readwrite | |
1628 | This will change a | |
1629 | .B readonly | |
1630 | array back to being read/write. | |
1631 | ||
1632 | .TP | |
1633 | .B \-\-scan | |
1634 | For all operations except | |
1635 | .BR \-\-examine , | |
1636 | .B \-\-scan | |
1637 | will cause the operation to be applied to all arrays listed in | |
1638 | .BR /proc/mdstat . | |
1639 | For | |
1640 | .BR \-\-examine, | |
1641 | .B \-\-scan | |
1642 | causes all devices listed in the config file to be examined. | |
1643 | ||
1644 | ||
1645 | .SH MONITOR MODE | |
1646 | ||
1647 | .HP 12 | |
1648 | Usage: | |
1649 | .B mdadm \-\-monitor | |
1650 | .I options... devices... | |
1651 | ||
1652 | .PP | |
1653 | This usage causes | |
1654 | .I mdadm | |
1655 | to periodically poll a number of md arrays and to report on any events | |
1656 | noticed. | |
1657 | .I mdadm | |
1658 | will never exit once it decides that there are arrays to be checked, | |
1659 | so it should normally be run in the background. | |
1660 | ||
1661 | As well as reporting events, | |
1662 | .I mdadm | |
1663 | may move a spare drive from one array to another if they are in the | |
1664 | same | |
1665 | .B spare-group | |
1666 | and if the destination array has a failed drive but no spares. | |
1667 | ||
1668 | If any devices are listed on the command line, | |
1669 | .I mdadm | |
1670 | will only monitor those devices. Otherwise all arrays listed in the | |
1671 | configuration file will be monitored. Further, if | |
1672 | .B \-\-scan | |
1673 | is given, then any other md devices that appear in | |
1674 | .B /proc/mdstat | |
1675 | will also be monitored. | |
1676 | ||
1677 | The result of monitoring the arrays is the generation of events. | |
1678 | These events are passed to a separate program (if specified) and may | |
1679 | be mailed to a given E-mail address. | |
1680 | ||
1681 | When passing events to a program, the program is run once for each event, | |
1682 | and is given 2 or 3 command-line arguments: the first is the | |
1683 | name of the event (see below), the second is the name of the | |
1684 | md device which is affected, and the third is the name of a related | |
1685 | device if relevant (such as a component device that has failed). | |
1686 | ||
1687 | If | |
1688 | .B \-\-scan | |
1689 | is given, then a program or an E-mail address must be specified on the | |
1690 | command line or in the config file. If neither are available, then | |
1691 | .I mdadm | |
1692 | will not monitor anything. | |
1693 | Without | |
1694 | .B \-\-scan, | |
1695 | .I mdadm | |
1696 | will continue monitoring as long as something was found to monitor. If | |
1697 | no program or email is given, then each event is reported to | |
1698 | .BR stdout . | |
1699 | ||
1700 | The different events are: | |
1701 | ||
1702 | .RS 4 | |
1703 | .TP | |
1704 | .B DeviceDisappeared | |
1705 | An md array which previously was configured appears to no longer be | |
1706 | configured. (syslog priority: Critical) | |
1707 | ||
1708 | If | |
1709 | .I mdadm | |
1710 | was told to monitor an array which is RAID0 or Linear, then it will | |
1711 | report | |
1712 | .B DeviceDisappeared | |
1713 | with the extra information | |
1714 | .BR Wrong-Level . | |
1715 | This is because RAID0 and Linear do not support the device-failed, | |
1716 | hot-spare and resync operations which are monitored. | |
1717 | ||
1718 | .TP | |
1719 | .B RebuildStarted | |
1720 | An md array started reconstruction. (syslog priority: Warning) | |
1721 | ||
1722 | .TP | |
1723 | .BI Rebuild NN | |
1724 | Where | |
1725 | .I NN | |
1726 | is 20, 40, 60, or 80, this indicates that rebuild has passed that many | |
1727 | percentage of the total. (syslog priority: Warning) | |
1728 | ||
1729 | .TP | |
1730 | .B RebuildFinished | |
1731 | An md array that was rebuilding, isn't any more, either because it | |
1732 | finished normally or was aborted. (syslog priority: Warning) | |
1733 | ||
1734 | .TP | |
1735 | .B Fail | |
1736 | An active component device of an array has been marked as | |
1737 | faulty. (syslog priority: Critical) | |
1738 | ||
1739 | .TP | |
1740 | .B FailSpare | |
1741 | A spare component device which was being rebuilt to replace a faulty | |
1742 | device has failed. (syslog priority: Critical) | |
1743 | ||
1744 | .TP | |
1745 | .B SpareActive | |
1746 | A spare component device which was being rebuilt to replace a faulty | |
1747 | device has been successfully rebuilt and has been made active. | |
1748 | (syslog priority: Info) | |
1749 | ||
1750 | .TP | |
1751 | .B NewArray | |
1752 | A new md array has been detected in the | |
1753 | .B /proc/mdstat | |
1754 | file. (syslog priority: Info) | |
1755 | ||
1756 | .TP | |
1757 | .B DegradedArray | |
1758 | A newly noticed array appears to be degraded. This message is not | |
1759 | generated when | |
1760 | .I mdadm | |
1761 | notices a drive failure which causes degradation, but only when | |
1762 | .I mdadm | |
1763 | notices that an array is degraded when it first sees the array. | |
1764 | (syslog priority: Critical) | |
1765 | ||
1766 | .TP | |
1767 | .B MoveSpare | |
1768 | A spare drive has been moved from one array in a | |
1769 | .B spare-group | |
1770 | to another to allow a failed drive to be replaced. | |
1771 | (syslog priority: Info) | |
1772 | ||
1773 | .TP | |
1774 | .B SparesMissing | |
1775 | If | |
1776 | .I mdadm | |
1777 | has been told, via the config file, that an array should have a certain | |
1778 | number of spare devices, and | |
1779 | .I mdadm | |
1780 | detects that it has fewer than this number when it first sees the | |
1781 | array, it will report a | |
1782 | .B SparesMissing | |
1783 | message. | |
1784 | (syslog priority: Warning) | |
1785 | ||
1786 | .TP | |
1787 | .B TestMessage | |
1788 | An array was found at startup, and the | |
1789 | .B \-\-test | |
1790 | flag was given. | |
1791 | (syslog priority: Info) | |
1792 | .RE | |
1793 | ||
1794 | Only | |
1795 | .B Fail, | |
1796 | .B FailSpare, | |
1797 | .B DegradedArray, | |
1798 | .B SparesMissing | |
1799 | and | |
1800 | .B TestMessage | |
1801 | cause Email to be sent. All events cause the program to be run. | |
1802 | The program is run with two or three arguments: the event | |
1803 | name, the array device and possibly a second device. | |
1804 | ||
1805 | Each event has an associated array device (e.g. | |
1806 | .BR /dev/md1 ) | |
1807 | and possibly a second device. For | |
1808 | .BR Fail , | |
1809 | .BR FailSpare , | |
1810 | and | |
1811 | .B SpareActive | |
1812 | the second device is the relevant component device. | |
1813 | For | |
1814 | .B MoveSpare | |
1815 | the second device is the array that the spare was moved from. | |
1816 | ||
1817 | For | |
1818 | .I mdadm | |
1819 | to move spares from one array to another, the different arrays need to | |
1820 | be labeled with the same | |
1821 | .B spare-group | |
1822 | in the configuration file. The | |
1823 | .B spare-group | |
1824 | name can be any string; it is only necessary that different spare | |
1825 | groups use different names. | |
1826 | ||
1827 | When | |
1828 | .I mdadm | |
1829 | detects that an array in a spare group has fewer active | |
1830 | devices than necessary for the complete array, and has no spare | |
1831 | devices, it will look for another array in the same spare group that | |
1832 | has a full complement of working drive and a spare. It will then | |
1833 | attempt to remove the spare from the second drive and add it to the | |
1834 | first. | |
1835 | If the removal succeeds but the adding fails, then it is added back to | |
1836 | the original array. | |
1837 | ||
1838 | .SH GROW MODE | |
1839 | The GROW mode is used for changing the size or shape of an active | |
1840 | array. | |
1841 | For this to work, the kernel must support the necessary change. | |
1842 | Various types of growth are being added during 2.6 development, | |
1843 | including restructuring a raid5 array to have more active devices. | |
1844 | ||
1845 | Currently the only support available is to | |
1846 | .IP \(bu 4 | |
1847 | change the "size" attribute | |
1848 | for RAID1, RAID5 and RAID6. | |
1849 | .IP \(bu 4 | |
1850 | increase the "raid\-devices" attribute of RAID1, RAID5, and RAID6. | |
1851 | .IP \(bu 4 | |
1852 | add a write-intent bitmap to any array which supports these bitmaps, or | |
1853 | remove a write-intent bitmap from such an array. | |
1854 | .PP | |
1855 | ||
1856 | GROW mode is not currently supported for | |
1857 | .B CONTAINERS | |
1858 | or arrays inside containers. | |
1859 | ||
1860 | .SS SIZE CHANGES | |
1861 | Normally when an array is built the "size" it taken from the smallest | |
1862 | of the drives. If all the small drives in an arrays are, one at a | |
1863 | time, removed and replaced with larger drives, then you could have an | |
1864 | array of large drives with only a small amount used. In this | |
1865 | situation, changing the "size" with "GROW" mode will allow the extra | |
1866 | space to start being used. If the size is increased in this way, a | |
1867 | "resync" process will start to make sure the new parts of the array | |
1868 | are synchronised. | |
1869 | ||
1870 | Note that when an array changes size, any filesystem that may be | |
1871 | stored in the array will not automatically grow to use the space. The | |
1872 | filesystem will need to be explicitly told to use the extra space. | |
1873 | ||
1874 | .SS RAID-DEVICES CHANGES | |
1875 | ||
1876 | A RAID1 array can work with any number of devices from 1 upwards | |
1877 | (though 1 is not very useful). There may be times which you want to | |
1878 | increase or decrease the number of active devices. Note that this is | |
1879 | different to hot-add or hot-remove which changes the number of | |
1880 | inactive devices. | |
1881 | ||
1882 | When reducing the number of devices in a RAID1 array, the slots which | |
1883 | are to be removed from the array must already be vacant. That is, the | |
1884 | devices which were in those slots must be failed and removed. | |
1885 | ||
1886 | When the number of devices is increased, any hot spares that are | |
1887 | present will be activated immediately. | |
1888 | ||
1889 | Increasing the number of active devices in a RAID5 is much more | |
1890 | effort. Every block in the array will need to be read and written | |
1891 | back to a new location. From 2.6.17, the Linux Kernel is able to do | |
1892 | this safely, including restart and interrupted "reshape". | |
1893 | ||
1894 | When relocating the first few stripes on a raid5, it is not possible | |
1895 | to keep the data on disk completely consistent and crash-proof. To | |
1896 | provide the required safety, mdadm disables writes to the array while | |
1897 | this "critical section" is reshaped, and takes a backup of the data | |
1898 | that is in that section. This backup is normally stored in any spare | |
1899 | devices that the array has, however it can also be stored in a | |
1900 | separate file specified with the | |
1901 | .B \-\-backup\-file | |
1902 | option. If this option is used, and the system does crash during the | |
1903 | critical period, the same file must be passed to | |
1904 | .B \-\-assemble | |
1905 | to restore the backup and reassemble the array. | |
1906 | ||
1907 | .SS BITMAP CHANGES | |
1908 | ||
1909 | A write-intent bitmap can be added to, or removed from, an active | |
1910 | array. Either internal bitmaps, or bitmaps stored in a separate file, | |
1911 | can be added. Note that if you add a bitmap stored in a file which is | |
1912 | in a filesystem that is on the raid array being affected, the system | |
1913 | will deadlock. The bitmap must be on a separate filesystem. | |
1914 | ||
1915 | .SH INCREMENTAL MODE | |
1916 | ||
1917 | .HP 12 | |
1918 | Usage: | |
1919 | .B mdadm \-\-incremental | |
1920 | .RB [ \-\-run ] | |
1921 | .RB [ \-\-quiet ] | |
1922 | .I component-device | |
1923 | .HP 12 | |
1924 | Usage: | |
1925 | .B mdadm \-\-incremental \-\-rebuild | |
1926 | .HP 12 | |
1927 | Usage: | |
1928 | .B mdadm \-\-incremental \-\-run \-\-scan | |
1929 | ||
1930 | ||
1931 | .PP | |
1932 | This mode is designed to be used in conjunction with a device | |
1933 | discovery system. As devices are found in a system, they can be | |
1934 | passed to | |
1935 | .B "mdadm \-\-incremental" | |
1936 | to be conditionally added to an appropriate array. | |
1937 | ||
1938 | If the device passed is a | |
1939 | .B CONTAINER | |
1940 | device created by a previous call to | |
1941 | .IR mdadm , | |
1942 | then rather than trying to add that device to an array, all the arrays | |
1943 | described by the metadata of the container will be started. | |
1944 | ||
1945 | .I mdadm | |
1946 | performs a number of tests to determine if the device is part of an | |
1947 | array, and which array it should be part of. If an appropriate array | |
1948 | is found, or can be created, | |
1949 | .I mdadm | |
1950 | adds the device to the array and conditionally starts the array. | |
1951 | ||
1952 | Note that | |
1953 | .I mdadm | |
1954 | will only add devices to an array which were previously working | |
1955 | (active or spare) parts of that array. It does not currently support | |
1956 | automatic inclusion of a new drive as a spare in some array. | |
1957 | ||
1958 | The tests that | |
1959 | .I mdadm | |
1960 | makes are as follow: | |
1961 | .IP + | |
1962 | Is the device permitted by | |
1963 | .BR mdadm.conf ? | |
1964 | That is, is it listed in a | |
1965 | .B DEVICES | |
1966 | line in that file. If | |
1967 | .B DEVICES | |
1968 | is absent then the default it to allow any device. Similar if | |
1969 | .B DEVICES | |
1970 | contains the special word | |
1971 | .B partitions | |
1972 | then any device is allowed. Otherwise the device name given to | |
1973 | .I mdadm | |
1974 | must match one of the names or patterns in a | |
1975 | .B DEVICES | |
1976 | line. | |
1977 | ||
1978 | .IP + | |
1979 | Does the device have a valid md superblock. If a specific metadata | |
1980 | version is request with | |
1981 | .B \-\-metadata | |
1982 | or | |
1983 | .B \-e | |
1984 | then only that style of metadata is accepted, otherwise | |
1985 | .I mdadm | |
1986 | finds any known version of metadata. If no | |
1987 | .I md | |
1988 | metadata is found, the device is rejected. | |
1989 | ||
1990 | .IP + | |
1991 | Does the metadata match an expected array? | |
1992 | The metadata can match in two ways. Either there is an array listed | |
1993 | in | |
1994 | .B mdadm.conf | |
1995 | which identifies the array (either by UUID, by name, by device list, | |
1996 | or by minor-number), or the array was created with a | |
1997 | .B homehost | |
1998 | specified and that | |
1999 | .B homehost | |
2000 | matches the one in | |
2001 | .B mdadm.conf | |
2002 | or on the command line. | |
2003 | If | |
2004 | .I mdadm | |
2005 | is not able to positively identify the array as belonging to the | |
2006 | current host, the device will be rejected. | |
2007 | ||
2008 | .IP + | |
2009 | .I mdadm | |
2010 | keeps a list of arrays that it has partially assembled in | |
2011 | .B /var/run/mdadm/map | |
2012 | (or | |
2013 | .B /var/run/mdadm.map | |
2014 | if the directory doesn't exist). If no array exists which matches | |
2015 | the metadata on the new device, | |
2016 | .I mdadm | |
2017 | must choose a device name and unit number. It does this based on any | |
2018 | name given in | |
2019 | .B mdadm.conf | |
2020 | or any name information stored in the metadata. If this name | |
2021 | suggests a unit number, that number will be used, otherwise a free | |
2022 | unit number will be chosen. Normally | |
2023 | .I mdadm | |
2024 | will prefer to create a partitionable array, however if the | |
2025 | .B CREATE | |
2026 | line in | |
2027 | .B mdadm.conf | |
2028 | suggests that a non-partitionable array is preferred, that will be | |
2029 | honoured. | |
2030 | ||
2031 | .IP + | |
2032 | Once an appropriate array is found or created and the device is added, | |
2033 | .I mdadm | |
2034 | must decide if the array is ready to be started. It will | |
2035 | normally compare the number of available (non-spare) devices to the | |
2036 | number of devices that the metadata suggests need to be active. If | |
2037 | there are at least that many, the array will be started. This means | |
2038 | that if any devices are missing the array will not be restarted. | |
2039 | ||
2040 | As an alternative, | |
2041 | .B \-\-run | |
2042 | may be passed to | |
2043 | .I mdadm | |
2044 | in which case the array will be run as soon as there are enough | |
2045 | devices present for the data to be accessible. For a raid1, that | |
2046 | means one device will start the array. For a clean raid5, the array | |
2047 | will be started as soon as all but one drive is present. | |
2048 | ||
2049 | Note that neither of these approaches is really ideal. If it can | |
2050 | be known that all device discovery has completed, then | |
2051 | .br | |
2052 | .B " mdadm \-IRs" | |
2053 | .br | |
2054 | can be run which will try to start all arrays that are being | |
2055 | incrementally assembled. They are started in "read-auto" mode in | |
2056 | which they are read-only until the first write request. This means | |
2057 | that no metadata updates are made and no attempt at resync or recovery | |
2058 | happens. Further devices that are found before the first write can | |
2059 | still be added safely. | |
2060 | ||
2061 | ||
2062 | .SH ENVIRONMENT | |
2063 | This section describes environment variables that affect how mdadm | |
2064 | operates. | |
2065 | ||
2066 | .TP | |
2067 | .B MDADM_NO_MDMON | |
2068 | Setting this value to 1 will prevent mdadm from automatically launching | |
2069 | mdmon. This variable is intended primarily for debugging mdadm/mdmon. | |
2070 | ||
2071 | .TP | |
2072 | .B MDADM_NO_UDEV | |
2073 | Normally, | |
2074 | .I mdadm | |
2075 | does not create any device nodes in /dev, but leaves that task to | |
2076 | .IR udev . | |
2077 | If | |
2078 | .I udev | |
2079 | appears not to be configured, or if this environment variable is set | |
2080 | to '1', the | |
2081 | .I mdadm | |
2082 | will create and devices that are needed. | |
2083 | ||
2084 | .SH EXAMPLES | |
2085 | ||
2086 | .B " mdadm \-\-query /dev/name-of-device" | |
2087 | .br | |
2088 | This will find out if a given device is a raid array, or is part of | |
2089 | one, and will provide brief information about the device. | |
2090 | ||
2091 | .B " mdadm \-\-assemble \-\-scan" | |
2092 | .br | |
2093 | This will assemble and start all arrays listed in the standard config | |
2094 | file. This command will typically go in a system startup file. | |
2095 | ||
2096 | .B " mdadm \-\-stop \-\-scan" | |
2097 | .br | |
2098 | This will shut down all arrays that can be shut down (i.e. are not | |
2099 | currently in use). This will typically go in a system shutdown script. | |
2100 | ||
2101 | .B " mdadm \-\-follow \-\-scan \-\-delay=120" | |
2102 | .br | |
2103 | If (and only if) there is an Email address or program given in the | |
2104 | standard config file, then | |
2105 | monitor the status of all arrays listed in that file by | |
2106 | polling them ever 2 minutes. | |
2107 | ||
2108 | .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1" | |
2109 | .br | |
2110 | Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1. | |
2111 | ||
2112 | .br | |
2113 | .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf" | |
2114 | .br | |
2115 | .B " mdadm \-\-detail \-\-scan >> mdadm.conf" | |
2116 | .br | |
2117 | This will create a prototype config file that describes currently | |
2118 | active arrays that are known to be made from partitions of IDE or SCSI drives. | |
2119 | This file should be reviewed before being used as it may | |
2120 | contain unwanted detail. | |
2121 | ||
2122 | .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf" | |
2123 | .br | |
2124 | .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf" | |
2125 | .br | |
2126 | This will find arrays which could be assembled from existing IDE and | |
2127 | SCSI whole drives (not partitions), and store the information in the | |
2128 | format of a config file. | |
2129 | This file is very likely to contain unwanted detail, particularly | |
2130 | the | |
2131 | .B devices= | |
2132 | entries. It should be reviewed and edited before being used as an | |
2133 | actual config file. | |
2134 | ||
2135 | .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions" | |
2136 | .br | |
2137 | .B " mdadm \-Ebsc partitions" | |
2138 | .br | |
2139 | Create a list of devices by reading | |
2140 | .BR /proc/partitions , | |
2141 | scan these for RAID superblocks, and printout a brief listing of all | |
2142 | that were found. | |
2143 | ||
2144 | .B " mdadm \-Ac partitions \-m 0 /dev/md0" | |
2145 | .br | |
2146 | Scan all partitions and devices listed in | |
2147 | .BR /proc/partitions | |
2148 | and assemble | |
2149 | .B /dev/md0 | |
2150 | out of all such devices with a RAID superblock with a minor number of 0. | |
2151 | ||
2152 | .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /var/run/mdadm" | |
2153 | .br | |
2154 | If config file contains a mail address or alert program, run mdadm in | |
2155 | the background in monitor mode monitoring all md devices. Also write | |
2156 | pid of mdadm daemon to | |
2157 | .BR /var/run/mdadm . | |
2158 | ||
2159 | .B " mdadm \-Iq /dev/somedevice" | |
2160 | .br | |
2161 | Try to incorporate newly discovered device into some array as | |
2162 | appropriate. | |
2163 | ||
2164 | .B " mdadm \-\-incremental \-\-rebuild \-\-run \-\-scan" | |
2165 | .br | |
2166 | Rebuild the array map from any current arrays, and then start any that | |
2167 | can be started. | |
2168 | ||
2169 | .B " mdadm /dev/md4 --fail detached --remove detached" | |
2170 | .br | |
2171 | Any devices which are components of /dev/md4 will be marked as faulty | |
2172 | and then remove from the array. | |
2173 | ||
2174 | .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]" | |
2175 | .br | |
2176 | Create a DDF array over 6 devices. | |
2177 | ||
2178 | .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf" | |
2179 | .br | |
2180 | Create a raid5 array over any 3 devices in the given DDF set. Use | |
2181 | only 30 gigabytes of each device. | |
2182 | ||
2183 | .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]" | |
2184 | .br | |
2185 | Assemble a pre-exist ddf array. | |
2186 | ||
2187 | .B " mdadm -I /dev/md/ddf1" | |
2188 | .br | |
2189 | Assemble all arrays contained in the ddf array, assigning names as | |
2190 | appropriate. | |
2191 | ||
2192 | .B " mdadm \-\-create \-\-help" | |
2193 | .br | |
2194 | Provide help about the Create mode. | |
2195 | ||
2196 | .B " mdadm \-\-config \-\-help" | |
2197 | .br | |
2198 | Provide help about the format of the config file. | |
2199 | ||
2200 | .B " mdadm \-\-help" | |
2201 | .br | |
2202 | Provide general help. | |
2203 | ||
2204 | ||
2205 | .SH FILES | |
2206 | ||
2207 | .SS /proc/mdstat | |
2208 | ||
2209 | If you're using the | |
2210 | .B /proc | |
2211 | filesystem, | |
2212 | .B /proc/mdstat | |
2213 | lists all active md devices with information about them. | |
2214 | .I mdadm | |
2215 | uses this to find arrays when | |
2216 | .B \-\-scan | |
2217 | is given in Misc mode, and to monitor array reconstruction | |
2218 | on Monitor mode. | |
2219 | ||
2220 | ||
2221 | .SS /etc/mdadm.conf | |
2222 | ||
2223 | The config file lists which devices may be scanned to see if | |
2224 | they contain MD super block, and gives identifying information | |
2225 | (e.g. UUID) about known MD arrays. See | |
2226 | .BR mdadm.conf (5) | |
2227 | for more details. | |
2228 | ||
2229 | .SS /var/run/mdadm/map | |
2230 | When | |
2231 | .B \-\-incremental | |
2232 | mode is used, this file gets a list of arrays currently being created. | |
2233 | If | |
2234 | .B /var/run/mdadm | |
2235 | does not exist as a directory, then | |
2236 | .B /var/run/mdadm.map | |
2237 | is used instead. | |
2238 | ||
2239 | .SH DEVICE NAMES | |
2240 | ||
2241 | .I mdadm | |
2242 | understand two sorts of names for array devices. | |
2243 | ||
2244 | The first is the so-called 'standard' format name, which matches the | |
2245 | names used by the kernel and which appear in | |
2246 | .IR /proc/mdstat . | |
2247 | ||
2248 | The second sort can be freely chosen, but must reside in | |
2249 | .IR /dev/md/ . | |
2250 | When giving a device name to | |
2251 | .I mdadm | |
2252 | to create or assemble an array, either full path name such as | |
2253 | .I /dev/md0 | |
2254 | or | |
2255 | .I /dev/md/home | |
2256 | can be given, or just the suffix of the second sort of name, such as | |
2257 | .I home | |
2258 | can be given. | |
2259 | ||
2260 | When | |
2261 | .I mdadm | |
2262 | chooses device names during auto-assembly, it will normally add a | |
2263 | small sequence number to the end of the name to avoid conflicted | |
2264 | between multiple arrays that have the same name. If | |
2265 | .I mdadm | |
2266 | can reasonably determine that the array really is meant for this host, | |
2267 | either by a hostname in the metadata, or by the presence of the array | |
2268 | in /etc/mdadm.conf, then it will leave of the suffix if possible. | |
2269 | ||
2270 | The standard names for non-partitioned arrays (the only sort of md | |
2271 | array available in 2.4 and earlier) are of the form | |
2272 | .IP | |
2273 | /dev/mdNN | |
2274 | .PP | |
2275 | where NN is a number. | |
2276 | The standard names for partitionable arrays (as available from 2.6 | |
2277 | onwards) are of the form | |
2278 | .IP | |
2279 | /dev/md_dNN | |
2280 | .PP | |
2281 | Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2". | |
2282 | .PP | |
2283 | From kernel version, 2.6.28 the "non-partitioned array" can actually | |
2284 | be partitioned. So the "md_dNN" names are no longer needed, and | |
2285 | partitions such as "/dev/mdNNpXX" are possible. | |
2286 | ||
2287 | .SH NOTE | |
2288 | .I mdadm | |
2289 | was previously known as | |
2290 | .IR mdctl . | |
2291 | .P | |
2292 | .I mdadm | |
2293 | is completely separate from the | |
2294 | .I raidtools | |
2295 | package, and does not use the | |
2296 | .I /etc/raidtab | |
2297 | configuration file at all. | |
2298 | ||
2299 | .SH SEE ALSO | |
2300 | For further information on mdadm usage, MD and the various levels of | |
2301 | RAID, see: | |
2302 | .IP | |
2303 | .B http://linux\-raid.osdl.org/ | |
2304 | .PP | |
2305 | (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO) | |
2306 | .\".PP | |
2307 | .\"for new releases of the RAID driver check out: | |
2308 | .\" | |
2309 | .\".IP | |
2310 | .\".UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2311 | .\"ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2312 | .\".UE | |
2313 | .\".PP | |
2314 | .\"or | |
2315 | .\".IP | |
2316 | .\".UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2317 | .\"http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2318 | .\".UE | |
2319 | .PP | |
2320 | The latest version of | |
2321 | .I mdadm | |
2322 | should always be available from | |
2323 | .IP | |
2324 | .B http://www.kernel.org/pub/linux/utils/raid/mdadm/ | |
2325 | .PP | |
2326 | Related man pages: | |
2327 | .PP | |
2328 | .IR mdadm.conf (5), | |
2329 | .IR md (4). | |
2330 | .PP | |
2331 | .IR raidtab (5), | |
2332 | .IR raid0run (8), | |
2333 | .IR raidstop (8), | |
2334 | .IR mkraid (8). |