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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 "" v3.2.3 | |
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 | New installations should not use md/multipath as it is not well | |
50 | supported and has no ongoing development. Use the Device Mapper based | |
51 | multipath-tools instead. | |
52 | ||
53 | .B FAULTY | |
54 | is also not true RAID, and it only involves one device. It | |
55 | provides a layer over a true device that can be used to inject faults. | |
56 | ||
57 | .B CONTAINER | |
58 | is different again. A | |
59 | .B CONTAINER | |
60 | is a collection of devices that are | |
61 | managed as a set. This is similar to the set of devices connected to | |
62 | a hardware RAID controller. The set of devices may contain a number | |
63 | of different RAID arrays each utilising some (or all) of the blocks from a | |
64 | number of the devices in the set. For example, two devices in a 5-device set | |
65 | might form a RAID1 using the whole devices. The remaining three might | |
66 | have a RAID5 over the first half of each device, and a RAID0 over the | |
67 | second half. | |
68 | ||
69 | With a | |
70 | .BR CONTAINER , | |
71 | there is one set of metadata that describes all of | |
72 | the arrays in the container. So when | |
73 | .I mdadm | |
74 | creates a | |
75 | .B CONTAINER | |
76 | device, the device just represents the metadata. Other normal arrays (RAID1 | |
77 | etc) can be created inside the container. | |
78 | ||
79 | .SH MODES | |
80 | mdadm has several major modes of operation: | |
81 | .TP | |
82 | .B Assemble | |
83 | Assemble the components of a previously created | |
84 | array into an active array. Components can be explicitly given | |
85 | or can be searched for. | |
86 | .I mdadm | |
87 | checks that the components | |
88 | do form a bona fide array, and can, on request, fiddle superblock | |
89 | information so as to assemble a faulty array. | |
90 | ||
91 | .TP | |
92 | .B Build | |
93 | Build an array that doesn't have per-device metadata (superblocks). For these | |
94 | sorts of arrays, | |
95 | .I mdadm | |
96 | cannot differentiate between initial creation and subsequent assembly | |
97 | of an array. It also cannot perform any checks that appropriate | |
98 | components have been requested. Because of this, the | |
99 | .B Build | |
100 | mode should only be used together with a complete understanding of | |
101 | what you are doing. | |
102 | ||
103 | .TP | |
104 | .B Create | |
105 | Create a new array with per-device metadata (superblocks). | |
106 | Appropriate metadata is written to each device, and then the array | |
107 | comprising those devices is activated. A 'resync' process is started | |
108 | to make sure that the array is consistent (e.g. both sides of a mirror | |
109 | contain the same data) but the content of the device is left otherwise | |
110 | untouched. | |
111 | The array can be used as soon as it has been created. There is no | |
112 | need to wait for the initial resync to finish. | |
113 | ||
114 | .TP | |
115 | .B "Follow or Monitor" | |
116 | Monitor one or more md devices and act on any state changes. This is | |
117 | only meaningful for RAID1, 4, 5, 6, 10 or multipath arrays, as | |
118 | only these have interesting state. RAID0 or Linear never have | |
119 | missing, spare, or failed drives, so there is nothing to monitor. | |
120 | ||
121 | .TP | |
122 | .B "Grow" | |
123 | Grow (or shrink) an array, or otherwise reshape it in some way. | |
124 | Currently supported growth options including changing the active size | |
125 | of component devices and changing the number of active devices in | |
126 | Linear and RAID levels 0/1/4/5/6, | |
127 | changing the RAID level between 0, 1, 5, and 6, and between 0 and 10, | |
128 | changing the chunk size and layout for RAID 0,4,5,6, as well as adding or | |
129 | removing a write-intent bitmap. | |
130 | ||
131 | .TP | |
132 | .B "Incremental Assembly" | |
133 | Add a single device to an appropriate array. If the addition of the | |
134 | device makes the array runnable, the array will be started. | |
135 | This provides a convenient interface to a | |
136 | .I hot-plug | |
137 | system. As each device is detected, | |
138 | .I mdadm | |
139 | has a chance to include it in some array as appropriate. | |
140 | Optionally, when the | |
141 | .I \-\-fail | |
142 | flag is passed in we will remove the device from any active array | |
143 | instead of adding it. | |
144 | ||
145 | If a | |
146 | .B CONTAINER | |
147 | is passed to | |
148 | .I mdadm | |
149 | in this mode, then any arrays within that container will be assembled | |
150 | and started. | |
151 | ||
152 | .TP | |
153 | .B Manage | |
154 | This is for doing things to specific components of an array such as | |
155 | adding new spares and removing faulty devices. | |
156 | ||
157 | .TP | |
158 | .B Misc | |
159 | This is an 'everything else' mode that supports operations on active | |
160 | arrays, operations on component devices such as erasing old superblocks, and | |
161 | information gathering operations. | |
162 | .\"This mode allows operations on independent devices such as examine MD | |
163 | .\"superblocks, erasing old superblocks and stopping active arrays. | |
164 | ||
165 | .TP | |
166 | .B Auto-detect | |
167 | This mode does not act on a specific device or array, but rather it | |
168 | requests the Linux Kernel to activate any auto-detected arrays. | |
169 | .SH OPTIONS | |
170 | ||
171 | .SH Options for selecting a mode are: | |
172 | ||
173 | .TP | |
174 | .BR \-A ", " \-\-assemble | |
175 | Assemble a pre-existing array. | |
176 | ||
177 | .TP | |
178 | .BR \-B ", " \-\-build | |
179 | Build a legacy array without superblocks. | |
180 | ||
181 | .TP | |
182 | .BR \-C ", " \-\-create | |
183 | Create a new array. | |
184 | ||
185 | .TP | |
186 | .BR \-F ", " \-\-follow ", " \-\-monitor | |
187 | Select | |
188 | .B Monitor | |
189 | mode. | |
190 | ||
191 | .TP | |
192 | .BR \-G ", " \-\-grow | |
193 | Change the size or shape of an active array. | |
194 | ||
195 | .TP | |
196 | .BR \-I ", " \-\-incremental | |
197 | Add/remove a single device to/from an appropriate array, and possibly start the array. | |
198 | ||
199 | .TP | |
200 | .B \-\-auto-detect | |
201 | Request that the kernel starts any auto-detected arrays. This can only | |
202 | work if | |
203 | .I md | |
204 | is compiled into the kernel \(em not if it is a module. | |
205 | Arrays can be auto-detected by the kernel if all the components are in | |
206 | primary MS-DOS partitions with partition type | |
207 | .BR FD , | |
208 | and all use v0.90 metadata. | |
209 | In-kernel autodetect is not recommended for new installations. Using | |
210 | .I mdadm | |
211 | to detect and assemble arrays \(em possibly in an | |
212 | .I initrd | |
213 | \(em is substantially more flexible and should be preferred. | |
214 | ||
215 | .P | |
216 | If a device is given before any options, or if the first option is | |
217 | .BR \-\-add , | |
218 | .BR \-\-fail , | |
219 | or | |
220 | .BR \-\-remove , | |
221 | then the MANAGE mode is assumed. | |
222 | Anything other than these will cause the | |
223 | .B Misc | |
224 | mode to be assumed. | |
225 | ||
226 | .SH Options that are not mode-specific are: | |
227 | ||
228 | .TP | |
229 | .BR \-h ", " \-\-help | |
230 | Display general help message or, after one of the above options, a | |
231 | mode-specific help message. | |
232 | ||
233 | .TP | |
234 | .B \-\-help\-options | |
235 | Display more detailed help about command line parsing and some commonly | |
236 | used options. | |
237 | ||
238 | .TP | |
239 | .BR \-V ", " \-\-version | |
240 | Print version information for mdadm. | |
241 | ||
242 | .TP | |
243 | .BR \-v ", " \-\-verbose | |
244 | Be more verbose about what is happening. This can be used twice to be | |
245 | extra-verbose. | |
246 | The extra verbosity currently only affects | |
247 | .B \-\-detail \-\-scan | |
248 | and | |
249 | .BR "\-\-examine \-\-scan" . | |
250 | ||
251 | .TP | |
252 | .BR \-q ", " \-\-quiet | |
253 | Avoid printing purely informative messages. With this, | |
254 | .I mdadm | |
255 | will be silent unless there is something really important to report. | |
256 | ||
257 | .TP | |
258 | .BR \-f ", " \-\-force | |
259 | Be more forceful about certain operations. See the various modes for | |
260 | the exact meaning of this option in different contexts. | |
261 | ||
262 | .TP | |
263 | .BR \-c ", " \-\-config= | |
264 | Specify the config file. Default is to use | |
265 | .BR /etc/mdadm.conf , | |
266 | or if that is missing then | |
267 | .BR /etc/mdadm/mdadm.conf . | |
268 | If the config file given is | |
269 | .B "partitions" | |
270 | then nothing will be read, but | |
271 | .I mdadm | |
272 | will act as though the config file contained exactly | |
273 | .B "DEVICE partitions containers" | |
274 | and will read | |
275 | .B /proc/partitions | |
276 | to find a list of devices to scan, and | |
277 | .B /proc/mdstat | |
278 | to find a list of containers to examine. | |
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 | .I 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 | .BR \-e ", " \-\-metadata= | |
306 | Declare the style of RAID metadata (superblock) to be used. The | |
307 | default is {DEFAULT_METADATA} 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 | .ie '{DEFAULT_METADATA}'0.90' | |
320 | .IP "0, 0.90, default" | |
321 | .el | |
322 | .IP "0, 0.90" | |
323 | .. | |
324 | Use the original 0.90 format superblock. This format limits arrays to | |
325 | 28 component devices and limits component devices of levels 1 and | |
326 | greater to 2 terabytes. It is also possible for there to be confusion | |
327 | about whether the superblock applies to a whole device or just the | |
328 | last partition, if that partition starts on a 64K boundary. | |
329 | .ie '{DEFAULT_METADATA}'0.90' | |
330 | .IP "1, 1.0, 1.1, 1.2" | |
331 | .el | |
332 | .IP "1, 1.0, 1.1, 1.2 default" | |
333 | .. | |
334 | Use the new version-1 format superblock. This has fewer restrictions. | |
335 | It can easily be moved between hosts with different endian-ness, and a | |
336 | recovery operation can be checkpointed and restarted. The different | |
337 | sub-versions store the superblock at different locations on the | |
338 | device, either at the end (for 1.0), at the start (for 1.1) or 4K from | |
339 | the start (for 1.2). "1" is equivalent to "1.2" (the commonly | |
340 | preferred 1.x format). | |
341 | 'if '{DEFAULT_METADATA}'1.2' "default" is equivalent to "1.2". | |
342 | .IP ddf | |
343 | Use the "Industry Standard" DDF (Disk Data Format) format defined by | |
344 | SNIA. | |
345 | When creating a DDF array a | |
346 | .B CONTAINER | |
347 | will be created, and normal arrays can be created in that container. | |
348 | .IP imsm | |
349 | Use the Intel(R) Matrix Storage Manager metadata format. This creates a | |
350 | .B CONTAINER | |
351 | which is managed in a similar manner to DDF, and is supported by an | |
352 | option-rom on some platforms: | |
353 | .IP | |
354 | .B http://www.intel.com/design/chipsets/matrixstorage_sb.htm | |
355 | .PP | |
356 | .RE | |
357 | ||
358 | .TP | |
359 | .B \-\-homehost= | |
360 | This will override any | |
361 | .B HOMEHOST | |
362 | setting in the config file and provides the identity of the host which | |
363 | should be considered the home for any arrays. | |
364 | ||
365 | When creating an array, the | |
366 | .B homehost | |
367 | will be recorded in the metadata. For version-1 superblocks, it will | |
368 | be prefixed to the array name. For version-0.90 superblocks, part of | |
369 | the SHA1 hash of the hostname will be stored in the later half of the | |
370 | UUID. | |
371 | ||
372 | When reporting information about an array, any array which is tagged | |
373 | for the given homehost will be reported as such. | |
374 | ||
375 | When using Auto-Assemble, only arrays tagged for the given homehost | |
376 | will be allowed to use 'local' names (i.e. not ending in '_' followed | |
377 | by a digit string). See below under | |
378 | .BR "Auto Assembly" . | |
379 | ||
380 | .SH For create, build, or grow: | |
381 | ||
382 | .TP | |
383 | .BR \-n ", " \-\-raid\-devices= | |
384 | Specify the number of active devices in the array. This, plus the | |
385 | number of spare devices (see below) must equal the number of | |
386 | .I component-devices | |
387 | (including "\fBmissing\fP" devices) | |
388 | that are listed on the command line for | |
389 | .BR \-\-create . | |
390 | Setting a value of 1 is probably | |
391 | a mistake and so requires that | |
392 | .B \-\-force | |
393 | be specified first. A value of 1 will then be allowed for linear, | |
394 | multipath, RAID0 and RAID1. It is never allowed for RAID4, RAID5 or RAID6. | |
395 | .br | |
396 | This number can only be changed using | |
397 | .B \-\-grow | |
398 | for RAID1, RAID4, RAID5 and RAID6 arrays, and only on kernels which provide | |
399 | the necessary support. | |
400 | ||
401 | .TP | |
402 | .BR \-x ", " \-\-spare\-devices= | |
403 | Specify the number of spare (eXtra) devices in the initial array. | |
404 | Spares can also be added | |
405 | and removed later. The number of component devices listed | |
406 | on the command line must equal the number of RAID devices plus the | |
407 | number of spare devices. | |
408 | ||
409 | .TP | |
410 | .BR \-z ", " \-\-size= | |
411 | Amount (in Kibibytes) of space to use from each drive in RAID levels 1/4/5/6. | |
412 | This must be a multiple of the chunk size, and must leave about 128Kb | |
413 | of space at the end of the drive for the RAID superblock. | |
414 | If this is not specified | |
415 | (as it normally is not) the smallest drive (or partition) sets the | |
416 | size, though if there is a variance among the drives of greater than 1%, a warning is | |
417 | issued. | |
418 | ||
419 | A suffix of 'M' or 'G' can be given to indicate Megabytes or | |
420 | Gigabytes respectively. | |
421 | ||
422 | Sometimes a replacement drive can be a little smaller than the | |
423 | original drives though this should be minimised by IDEMA standards. | |
424 | Such a replacement drive will be rejected by | |
425 | .IR md . | |
426 | To guard against this it can be useful to set the initial size | |
427 | slightly smaller than the smaller device with the aim that it will | |
428 | still be larger than any replacement. | |
429 | ||
430 | This value can be set with | |
431 | .B \-\-grow | |
432 | for RAID level 1/4/5/6 though | |
433 | .B CONTAINER | |
434 | based arrays such as those with IMSM metadata may not be able to | |
435 | support this. | |
436 | If the array was created with a size smaller than the currently | |
437 | active drives, the extra space can be accessed using | |
438 | .BR \-\-grow . | |
439 | The size can be given as | |
440 | .B max | |
441 | which means to choose the largest size that fits on all current drives. | |
442 | ||
443 | Before reducing the size of the array (with | |
444 | .BR "\-\-grow \-\-size=" ) | |
445 | you should make sure that space isn't needed. If the device holds a | |
446 | filesystem, you would need to resize the filesystem to use less space. | |
447 | ||
448 | After reducing the array size you should check that the data stored in | |
449 | the device is still available. If the device holds a filesystem, then | |
450 | an 'fsck' of the filesystem is a minimum requirement. If there are | |
451 | problems the array can be made bigger again with no loss with another | |
452 | .B "\-\-grow \-\-size=" | |
453 | command. | |
454 | ||
455 | This value cannot be used when creating a | |
456 | .B CONTAINER | |
457 | such as with DDF and IMSM metadata, though it perfectly valid when | |
458 | creating an array inside a container. | |
459 | ||
460 | .TP | |
461 | .BR \-Z ", " \-\-array\-size= | |
462 | This is only meaningful with | |
463 | .B \-\-grow | |
464 | and its effect is not persistent: when the array is stopped and | |
465 | restarted the default array size will be restored. | |
466 | ||
467 | Setting the array-size causes the array to appear smaller to programs | |
468 | that access the data. This is particularly needed before reshaping an | |
469 | array so that it will be smaller. As the reshape is not reversible, | |
470 | but setting the size with | |
471 | .B \-\-array-size | |
472 | is, it is required that the array size is reduced as appropriate | |
473 | before the number of devices in the array is reduced. | |
474 | ||
475 | Before reducing the size of the array you should make sure that space | |
476 | isn't needed. If the device holds a filesystem, you would need to | |
477 | resize the filesystem to use less space. | |
478 | ||
479 | After reducing the array size you should check that the data stored in | |
480 | the device is still available. If the device holds a filesystem, then | |
481 | an 'fsck' of the filesystem is a minimum requirement. If there are | |
482 | problems the array can be made bigger again with no loss with another | |
483 | .B "\-\-grow \-\-array\-size=" | |
484 | command. | |
485 | ||
486 | A suffix of 'M' or 'G' can be given to indicate Megabytes or | |
487 | Gigabytes respectively. | |
488 | A value of | |
489 | .B max | |
490 | restores the apparent size of the array to be whatever the real | |
491 | amount of available space is. | |
492 | ||
493 | .TP | |
494 | .BR \-c ", " \-\-chunk= | |
495 | Specify chunk size of kibibytes. The default when creating an | |
496 | array is 512KB. To ensure compatibility with earlier versions, the | |
497 | default when Building and array with no persistent metadata is 64KB. | |
498 | This is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10. | |
499 | ||
500 | RAID4, RAID5, RAID6, and RAID10 require the chunk size to be a power | |
501 | of 2. In any case it must be a multiple of 4KB. | |
502 | ||
503 | A suffix of 'M' or 'G' can be given to indicate Megabytes or | |
504 | Gigabytes respectively. | |
505 | ||
506 | .TP | |
507 | .BR \-\-rounding= | |
508 | Specify rounding factor for a Linear array. The size of each | |
509 | component will be rounded down to a multiple of this size. | |
510 | This is a synonym for | |
511 | .B \-\-chunk | |
512 | but highlights the different meaning for Linear as compared to other | |
513 | RAID levels. The default is 64K if a kernel earlier than 2.6.16 is in | |
514 | use, and is 0K (i.e. no rounding) in later kernels. | |
515 | ||
516 | .TP | |
517 | .BR \-l ", " \-\-level= | |
518 | Set RAID level. When used with | |
519 | .BR \-\-create , | |
520 | options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4, | |
521 | raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty, container. | |
522 | Obviously some of these are synonymous. | |
523 | ||
524 | When a | |
525 | .B CONTAINER | |
526 | metadata type is requested, only the | |
527 | .B container | |
528 | level is permitted, and it does not need to be explicitly given. | |
529 | ||
530 | When used with | |
531 | .BR \-\-build , | |
532 | only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid. | |
533 | ||
534 | Can be used with | |
535 | .B \-\-grow | |
536 | to change the RAID level in some cases. See LEVEL CHANGES below. | |
537 | ||
538 | .TP | |
539 | .BR \-p ", " \-\-layout= | |
540 | This option configures the fine details of data layout for RAID5, RAID6, | |
541 | and RAID10 arrays, and controls the failure modes for | |
542 | .IR faulty . | |
543 | ||
544 | The layout of the RAID5 parity block can be one of | |
545 | .BR left\-asymmetric , | |
546 | .BR left\-symmetric , | |
547 | .BR right\-asymmetric , | |
548 | .BR right\-symmetric , | |
549 | .BR la ", " ra ", " ls ", " rs . | |
550 | The default is | |
551 | .BR left\-symmetric . | |
552 | ||
553 | It is also possible to cause RAID5 to use a RAID4-like layout by | |
554 | choosing | |
555 | .BR parity\-first , | |
556 | or | |
557 | .BR parity\-last . | |
558 | ||
559 | Finally for RAID5 there are DDF\-compatible layouts, | |
560 | .BR ddf\-zero\-restart , | |
561 | .BR ddf\-N\-restart , | |
562 | and | |
563 | .BR ddf\-N\-continue . | |
564 | ||
565 | These same layouts are available for RAID6. There are also 4 layouts | |
566 | that will provide an intermediate stage for converting between RAID5 | |
567 | and RAID6. These provide a layout which is identical to the | |
568 | corresponding RAID5 layout on the first N\-1 devices, and has the 'Q' | |
569 | syndrome (the second 'parity' block used by RAID6) on the last device. | |
570 | These layouts are: | |
571 | .BR left\-symmetric\-6 , | |
572 | .BR right\-symmetric\-6 , | |
573 | .BR left\-asymmetric\-6 , | |
574 | .BR right\-asymmetric\-6 , | |
575 | and | |
576 | .BR parity\-first\-6 . | |
577 | ||
578 | When setting the failure mode for level | |
579 | .I faulty, | |
580 | the options are: | |
581 | .BR write\-transient ", " wt , | |
582 | .BR read\-transient ", " rt , | |
583 | .BR write\-persistent ", " wp , | |
584 | .BR read\-persistent ", " rp , | |
585 | .BR write\-all , | |
586 | .BR read\-fixable ", " rf , | |
587 | .BR clear ", " flush ", " none . | |
588 | ||
589 | Each failure mode can be followed by a number, which is used as a period | |
590 | between fault generation. Without a number, the fault is generated | |
591 | once on the first relevant request. With a number, the fault will be | |
592 | generated after that many requests, and will continue to be generated | |
593 | every time the period elapses. | |
594 | ||
595 | Multiple failure modes can be current simultaneously by using the | |
596 | .B \-\-grow | |
597 | option to set subsequent failure modes. | |
598 | ||
599 | "clear" or "none" will remove any pending or periodic failure modes, | |
600 | and "flush" will clear any persistent faults. | |
601 | ||
602 | Finally, the layout options for RAID10 are one of 'n', 'o' or 'f' followed | |
603 | by a small number. The default is 'n2'. The supported options are: | |
604 | ||
605 | .I 'n' | |
606 | signals 'near' copies. Multiple copies of one data block are at | |
607 | similar offsets in different devices. | |
608 | ||
609 | .I 'o' | |
610 | signals 'offset' copies. Rather than the chunks being duplicated | |
611 | within a stripe, whole stripes are duplicated but are rotated by one | |
612 | device so duplicate blocks are on different devices. Thus subsequent | |
613 | copies of a block are in the next drive, and are one chunk further | |
614 | down. | |
615 | ||
616 | .I 'f' | |
617 | signals 'far' copies | |
618 | (multiple copies have very different offsets). | |
619 | See md(4) for more detail about 'near', 'offset', and 'far'. | |
620 | ||
621 | The number is the number of copies of each datablock. 2 is normal, 3 | |
622 | can be useful. This number can be at most equal to the number of | |
623 | devices in the array. It does not need to divide evenly into that | |
624 | number (e.g. it is perfectly legal to have an 'n2' layout for an array | |
625 | with an odd number of devices). | |
626 | ||
627 | When an array is converted between RAID5 and RAID6 an intermediate | |
628 | RAID6 layout is used in which the second parity block (Q) is always on | |
629 | the last device. To convert a RAID5 to RAID6 and leave it in this new | |
630 | layout (which does not require re-striping) use | |
631 | .BR \-\-layout=preserve . | |
632 | This will try to avoid any restriping. | |
633 | ||
634 | The converse of this is | |
635 | .B \-\-layout=normalise | |
636 | which will change a non-standard RAID6 layout into a more standard | |
637 | arrangement. | |
638 | ||
639 | .TP | |
640 | .BR \-\-parity= | |
641 | same as | |
642 | .B \-\-layout | |
643 | (thus explaining the p of | |
644 | .BR \-p ). | |
645 | ||
646 | .TP | |
647 | .BR \-b ", " \-\-bitmap= | |
648 | Specify a file to store a write-intent bitmap in. The file should not | |
649 | exist unless | |
650 | .B \-\-force | |
651 | is also given. The same file should be provided | |
652 | when assembling the array. If the word | |
653 | .B "internal" | |
654 | is given, then the bitmap is stored with the metadata on the array, | |
655 | and so is replicated on all devices. If the word | |
656 | .B "none" | |
657 | is given with | |
658 | .B \-\-grow | |
659 | mode, then any bitmap that is present is removed. | |
660 | ||
661 | To help catch typing errors, the filename must contain at least one | |
662 | slash ('/') if it is a real file (not 'internal' or 'none'). | |
663 | ||
664 | Note: external bitmaps are only known to work on ext2 and ext3. | |
665 | Storing bitmap files on other filesystems may result in serious problems. | |
666 | ||
667 | .TP | |
668 | .BR \-\-bitmap\-chunk= | |
669 | Set the chunksize of the bitmap. Each bit corresponds to that many | |
670 | Kilobytes of storage. | |
671 | When using a file based bitmap, the default is to use the smallest | |
672 | size that is at-least 4 and requires no more than 2^21 chunks. | |
673 | When using an | |
674 | .B internal | |
675 | bitmap, the chunksize defaults to 64Meg, or larger if necessary to | |
676 | fit the bitmap into the available space. | |
677 | ||
678 | A suffix of 'M' or 'G' can be given to indicate Megabytes or | |
679 | Gigabytes respectively. | |
680 | ||
681 | .TP | |
682 | .BR \-W ", " \-\-write\-mostly | |
683 | subsequent devices listed in a | |
684 | .BR \-\-build , | |
685 | .BR \-\-create , | |
686 | or | |
687 | .B \-\-add | |
688 | command will be flagged as 'write-mostly'. This is valid for RAID1 | |
689 | only and means that the 'md' driver will avoid reading from these | |
690 | devices if at all possible. This can be useful if mirroring over a | |
691 | slow link. | |
692 | ||
693 | .TP | |
694 | .BR \-\-write\-behind= | |
695 | Specify that write-behind mode should be enabled (valid for RAID1 | |
696 | only). If an argument is specified, it will set the maximum number | |
697 | of outstanding writes allowed. The default value is 256. | |
698 | A write-intent bitmap is required in order to use write-behind | |
699 | mode, and write-behind is only attempted on drives marked as | |
700 | .IR write-mostly . | |
701 | ||
702 | .TP | |
703 | .BR \-\-assume\-clean | |
704 | Tell | |
705 | .I mdadm | |
706 | that the array pre-existed and is known to be clean. It can be useful | |
707 | when trying to recover from a major failure as you can be sure that no | |
708 | data will be affected unless you actually write to the array. It can | |
709 | also be used when creating a RAID1 or RAID10 if you want to avoid the | |
710 | initial resync, however this practice \(em while normally safe \(em is not | |
711 | recommended. Use this only if you really know what you are doing. | |
712 | .IP | |
713 | When the devices that will be part of a new array were filled | |
714 | with zeros before creation the operator knows the array is | |
715 | actually clean. If that is the case, such as after running | |
716 | badblocks, this argument can be used to tell mdadm the | |
717 | facts the operator knows. | |
718 | .IP | |
719 | When an array is resized to a larger size with | |
720 | .B "\-\-grow \-\-size=" | |
721 | the new space is normally resynced in that same way that the whole | |
722 | array is resynced at creation. From Linux version 3.0, | |
723 | .B \-\-assume\-clean | |
724 | can be used with that command to avoid the automatic resync. | |
725 | ||
726 | .TP | |
727 | .BR \-\-backup\-file= | |
728 | This is needed when | |
729 | .B \-\-grow | |
730 | is used to increase the number of raid-devices in a RAID5 or RAID6 if | |
731 | there are no spare devices available, or to shrink, change RAID level | |
732 | or layout. See the GROW MODE section below on RAID\-DEVICES CHANGES. | |
733 | The file must be stored on a separate device, not on the RAID array | |
734 | being reshaped. | |
735 | ||
736 | .TP | |
737 | .BR \-\-continue | |
738 | This option is complementary to the | |
739 | .B \-\-freeze-reshape | |
740 | option for assembly. It is needed when | |
741 | .B \-\-grow | |
742 | operation is interrupted and it is not restarted automatically due to | |
743 | .B \-\-freeze-reshape | |
744 | usage during array assembly. This option is used together with | |
745 | .BR \-G | |
746 | , ( | |
747 | .BR \-\-grow | |
748 | ) command and device for a pending reshape to be continued. | |
749 | All parameters required for reshape continuation will be read from array metadata. | |
750 | If initial | |
751 | .BR \-\-grow | |
752 | command had required | |
753 | .BR \-\-backup\-file= | |
754 | option to be set, continuation option will require to have exactly the same | |
755 | backup file given as well. | |
756 | .IP | |
757 | Any other parameter passed together with | |
758 | .BR \-\-continue | |
759 | option will be ignored. | |
760 | ||
761 | .TP | |
762 | .BR \-N ", " \-\-name= | |
763 | Set a | |
764 | .B name | |
765 | for the array. This is currently only effective when creating an | |
766 | array with a version-1 superblock, or an array in a DDF container. | |
767 | The name is a simple textual string that can be used to identify array | |
768 | components when assembling. If name is needed but not specified, it | |
769 | is taken from the basename of the device that is being created. | |
770 | e.g. when creating | |
771 | .I /dev/md/home | |
772 | the | |
773 | .B name | |
774 | will default to | |
775 | .IR home . | |
776 | ||
777 | .TP | |
778 | .BR \-R ", " \-\-run | |
779 | Insist that | |
780 | .I mdadm | |
781 | run the array, even if some of the components | |
782 | appear to be active in another array or filesystem. Normally | |
783 | .I mdadm | |
784 | will ask for confirmation before including such components in an | |
785 | array. This option causes that question to be suppressed. | |
786 | ||
787 | .TP | |
788 | .BR \-f ", " \-\-force | |
789 | Insist that | |
790 | .I mdadm | |
791 | accept the geometry and layout specified without question. Normally | |
792 | .I mdadm | |
793 | will not allow creation of an array with only one device, and will try | |
794 | to create a RAID5 array with one missing drive (as this makes the | |
795 | initial resync work faster). With | |
796 | .BR \-\-force , | |
797 | .I mdadm | |
798 | will not try to be so clever. | |
799 | ||
800 | .TP | |
801 | .BR \-a ", " "\-\-auto{=yes,md,mdp,part,p}{NN}" | |
802 | Instruct mdadm how to create the device file if needed, possibly allocating | |
803 | an unused minor number. "md" causes a non-partitionable array | |
804 | to be used (though since Linux 2.6.28, these array devices are in fact | |
805 | partitionable). "mdp", "part" or "p" causes a partitionable array (2.6 and | |
806 | later) to be used. "yes" requires the named md device to have | |
807 | a 'standard' format, and the type and minor number will be determined | |
808 | from this. With mdadm 3.0, device creation is normally left up to | |
809 | .I udev | |
810 | so this option is unlikely to be needed. | |
811 | See DEVICE NAMES below. | |
812 | ||
813 | The argument can also come immediately after | |
814 | "\-a". e.g. "\-ap". | |
815 | ||
816 | If | |
817 | .B \-\-auto | |
818 | is not given on the command line or in the config file, then | |
819 | the default will be | |
820 | .BR \-\-auto=yes . | |
821 | ||
822 | If | |
823 | .B \-\-scan | |
824 | is also given, then any | |
825 | .I auto= | |
826 | entries in the config file will override the | |
827 | .B \-\-auto | |
828 | instruction given on the command line. | |
829 | ||
830 | For partitionable arrays, | |
831 | .I mdadm | |
832 | will create the device file for the whole array and for the first 4 | |
833 | partitions. A different number of partitions can be specified at the | |
834 | end of this option (e.g. | |
835 | .BR \-\-auto=p7 ). | |
836 | If the device name ends with a digit, the partition names add a 'p', | |
837 | and a number, e.g. | |
838 | .IR /dev/md/home1p3 . | |
839 | If there is no trailing digit, then the partition names just have a | |
840 | number added, e.g. | |
841 | .IR /dev/md/scratch3 . | |
842 | ||
843 | If the md device name is in a 'standard' format as described in DEVICE | |
844 | NAMES, then it will be created, if necessary, with the appropriate | |
845 | device number based on that name. If the device name is not in one of these | |
846 | formats, then a unused device number will be allocated. The device | |
847 | number will be considered unused if there is no active array for that | |
848 | number, and there is no entry in /dev for that number and with a | |
849 | non-standard name. Names that are not in 'standard' format are only | |
850 | allowed in "/dev/md/". | |
851 | ||
852 | This is meaningful with | |
853 | .B \-\-create | |
854 | or | |
855 | .BR \-\-build . | |
856 | ||
857 | .ig XX | |
858 | .\".TP | |
859 | .\".BR \-\-symlink = no | |
860 | .\"Normally when | |
861 | .\".B \-\-auto | |
862 | .\"causes | |
863 | .\".I mdadm | |
864 | .\"to create devices in | |
865 | .\".B /dev/md/ | |
866 | .\"it will also create symlinks from | |
867 | .\".B /dev/ | |
868 | .\"with names starting with | |
869 | .\".B md | |
870 | .\"or | |
871 | .\".BR md_ . | |
872 | .\"Use | |
873 | .\".B \-\-symlink=no | |
874 | .\"to suppress this, or | |
875 | .\".B \-\-symlink=yes | |
876 | .\"to enforce this even if it is suppressing | |
877 | .\".IR mdadm.conf . | |
878 | .\" | |
879 | .XX | |
880 | ||
881 | .TP | |
882 | .BR \-a ", " "\-\-add" | |
883 | This option can be used in Grow mode in two cases. | |
884 | ||
885 | If the target array is a Linear array, then | |
886 | .B \-\-add | |
887 | can be used to add one or more devices to the array. They | |
888 | are simply catenated on to the end of the array. Once added, the | |
889 | devices cannot be removed. | |
890 | ||
891 | If the | |
892 | .B \-\-raid\-disks | |
893 | option is being used to increase the number of devices in an array, | |
894 | then | |
895 | .B \-\-add | |
896 | can be used to add some extra devices to be included in the array. | |
897 | In most cases this is not needed as the extra devices can be added as | |
898 | spares first, and then the number of raid-disks can be changed. | |
899 | However for RAID0, it is not possible to add spares. So to increase | |
900 | the number of devices in a RAID0, it is necessary to set the new | |
901 | number of devices, and to add the new devices, in the same command. | |
902 | ||
903 | .SH For assemble: | |
904 | ||
905 | .TP | |
906 | .BR \-u ", " \-\-uuid= | |
907 | uuid of array to assemble. Devices which don't have this uuid are | |
908 | excluded | |
909 | ||
910 | .TP | |
911 | .BR \-m ", " \-\-super\-minor= | |
912 | Minor number of device that array was created for. Devices which | |
913 | don't have this minor number are excluded. If you create an array as | |
914 | /dev/md1, then all superblocks will contain the minor number 1, even if | |
915 | the array is later assembled as /dev/md2. | |
916 | ||
917 | Giving the literal word "dev" for | |
918 | .B \-\-super\-minor | |
919 | will cause | |
920 | .I mdadm | |
921 | to use the minor number of the md device that is being assembled. | |
922 | e.g. when assembling | |
923 | .BR /dev/md0 , | |
924 | .B \-\-super\-minor=dev | |
925 | will look for super blocks with a minor number of 0. | |
926 | ||
927 | .B \-\-super\-minor | |
928 | is only relevant for v0.90 metadata, and should not normally be used. | |
929 | Using | |
930 | .B \-\-uuid | |
931 | is much safer. | |
932 | ||
933 | .TP | |
934 | .BR \-N ", " \-\-name= | |
935 | Specify the name of the array to assemble. This must be the name | |
936 | that was specified when creating the array. It must either match | |
937 | the name stored in the superblock exactly, or it must match | |
938 | with the current | |
939 | .I homehost | |
940 | prefixed to the start of the given name. | |
941 | ||
942 | .TP | |
943 | .BR \-f ", " \-\-force | |
944 | Assemble the array even if the metadata on some devices appears to be | |
945 | out-of-date. If | |
946 | .I mdadm | |
947 | cannot find enough working devices to start the array, but can find | |
948 | some devices that are recorded as having failed, then it will mark | |
949 | those devices as working so that the array can be started. | |
950 | An array which requires | |
951 | .B \-\-force | |
952 | to be started may contain data corruption. Use it carefully. | |
953 | ||
954 | .TP | |
955 | .BR \-R ", " \-\-run | |
956 | Attempt to start the array even if fewer drives were given than were | |
957 | present last time the array was active. Normally if not all the | |
958 | expected drives are found and | |
959 | .B \-\-scan | |
960 | is not used, then the array will be assembled but not started. | |
961 | With | |
962 | .B \-\-run | |
963 | an attempt will be made to start it anyway. | |
964 | ||
965 | .TP | |
966 | .B \-\-no\-degraded | |
967 | This is the reverse of | |
968 | .B \-\-run | |
969 | in that it inhibits the startup of array unless all expected drives | |
970 | are present. This is only needed with | |
971 | .B \-\-scan, | |
972 | and can be used if the physical connections to devices are | |
973 | not as reliable as you would like. | |
974 | ||
975 | .TP | |
976 | .BR \-a ", " "\-\-auto{=no,yes,md,mdp,part}" | |
977 | See this option under Create and Build options. | |
978 | ||
979 | .TP | |
980 | .BR \-b ", " \-\-bitmap= | |
981 | Specify the bitmap file that was given when the array was created. If | |
982 | an array has an | |
983 | .B internal | |
984 | bitmap, there is no need to specify this when assembling the array. | |
985 | ||
986 | .TP | |
987 | .BR \-\-backup\-file= | |
988 | If | |
989 | .B \-\-backup\-file | |
990 | was used while reshaping an array (e.g. changing number of devices or | |
991 | chunk size) and the system crashed during the critical section, then the same | |
992 | .B \-\-backup\-file | |
993 | must be presented to | |
994 | .B \-\-assemble | |
995 | to allow possibly corrupted data to be restored, and the reshape | |
996 | to be completed. | |
997 | ||
998 | .TP | |
999 | .BR \-\-invalid\-backup | |
1000 | If the file needed for the above option is not available for any | |
1001 | reason an empty file can be given together with this option to | |
1002 | indicate that the backup file is invalid. In this case the data that | |
1003 | was being rearranged at the time of the crash could be irrecoverably | |
1004 | lost, but the rest of the array may still be recoverable. This option | |
1005 | should only be used as a last resort if there is no way to recover the | |
1006 | backup file. | |
1007 | ||
1008 | ||
1009 | .TP | |
1010 | .BR \-U ", " \-\-update= | |
1011 | Update the superblock on each device while assembling the array. The | |
1012 | argument given to this flag can be one of | |
1013 | .BR sparc2.2 , | |
1014 | .BR summaries , | |
1015 | .BR uuid , | |
1016 | .BR name , | |
1017 | .BR homehost , | |
1018 | .BR resync , | |
1019 | .BR byteorder , | |
1020 | .BR devicesize , | |
1021 | .BR no\-bitmap , | |
1022 | or | |
1023 | .BR super\-minor . | |
1024 | ||
1025 | The | |
1026 | .B sparc2.2 | |
1027 | option will adjust the superblock of an array what was created on a Sparc | |
1028 | machine running a patched 2.2 Linux kernel. This kernel got the | |
1029 | alignment of part of the superblock wrong. You can use the | |
1030 | .B "\-\-examine \-\-sparc2.2" | |
1031 | option to | |
1032 | .I mdadm | |
1033 | to see what effect this would have. | |
1034 | ||
1035 | The | |
1036 | .B super\-minor | |
1037 | option will update the | |
1038 | .B "preferred minor" | |
1039 | field on each superblock to match the minor number of the array being | |
1040 | assembled. | |
1041 | This can be useful if | |
1042 | .B \-\-examine | |
1043 | reports a different "Preferred Minor" to | |
1044 | .BR \-\-detail . | |
1045 | In some cases this update will be performed automatically | |
1046 | by the kernel driver. In particular the update happens automatically | |
1047 | at the first write to an array with redundancy (RAID level 1 or | |
1048 | greater) on a 2.6 (or later) kernel. | |
1049 | ||
1050 | The | |
1051 | .B uuid | |
1052 | option will change the uuid of the array. If a UUID is given with the | |
1053 | .B \-\-uuid | |
1054 | option that UUID will be used as a new UUID and will | |
1055 | .B NOT | |
1056 | be used to help identify the devices in the array. | |
1057 | If no | |
1058 | .B \-\-uuid | |
1059 | is given, a random UUID is chosen. | |
1060 | ||
1061 | The | |
1062 | .B name | |
1063 | option will change the | |
1064 | .I name | |
1065 | of the array as stored in the superblock. This is only supported for | |
1066 | version-1 superblocks. | |
1067 | ||
1068 | The | |
1069 | .B homehost | |
1070 | option will change the | |
1071 | .I homehost | |
1072 | as recorded in the superblock. For version-0 superblocks, this is the | |
1073 | same as updating the UUID. | |
1074 | For version-1 superblocks, this involves updating the name. | |
1075 | ||
1076 | The | |
1077 | .B resync | |
1078 | option will cause the array to be marked | |
1079 | .I dirty | |
1080 | meaning that any redundancy in the array (e.g. parity for RAID5, | |
1081 | copies for RAID1) may be incorrect. This will cause the RAID system | |
1082 | to perform a "resync" pass to make sure that all redundant information | |
1083 | is correct. | |
1084 | ||
1085 | The | |
1086 | .B byteorder | |
1087 | option allows arrays to be moved between machines with different | |
1088 | byte-order. | |
1089 | When assembling such an array for the first time after a move, giving | |
1090 | .B "\-\-update=byteorder" | |
1091 | will cause | |
1092 | .I mdadm | |
1093 | to expect superblocks to have their byteorder reversed, and will | |
1094 | correct that order before assembling the array. This is only valid | |
1095 | with original (Version 0.90) superblocks. | |
1096 | ||
1097 | The | |
1098 | .B summaries | |
1099 | option will correct the summaries in the superblock. That is the | |
1100 | counts of total, working, active, failed, and spare devices. | |
1101 | ||
1102 | The | |
1103 | .B devicesize | |
1104 | option will rarely be of use. It applies to version 1.1 and 1.2 metadata | |
1105 | only (where the metadata is at the start of the device) and is only | |
1106 | useful when the component device has changed size (typically become | |
1107 | larger). The version 1 metadata records the amount of the device that | |
1108 | can be used to store data, so if a device in a version 1.1 or 1.2 | |
1109 | array becomes larger, the metadata will still be visible, but the | |
1110 | extra space will not. In this case it might be useful to assemble the | |
1111 | array with | |
1112 | .BR \-\-update=devicesize . | |
1113 | This will cause | |
1114 | .I mdadm | |
1115 | to determine the maximum usable amount of space on each device and | |
1116 | update the relevant field in the metadata. | |
1117 | ||
1118 | The | |
1119 | .B no\-bitmap | |
1120 | option can be used when an array has an internal bitmap which is | |
1121 | corrupt in some way so that assembling the array normally fails. It | |
1122 | will cause any internal bitmap to be ignored. | |
1123 | ||
1124 | .TP | |
1125 | .BR \-\-freeze\-reshape | |
1126 | Option is intended to be used in start-up scripts during initrd boot phase. | |
1127 | When array under reshape is assembled during initrd phase, this option | |
1128 | stops reshape after reshape critical section is being restored. This happens | |
1129 | before file system pivot operation and avoids loss of file system context. | |
1130 | Losing file system context would cause reshape to be broken. | |
1131 | ||
1132 | Reshape can be continued later using the | |
1133 | .B \-\-continue | |
1134 | option for the grow command. | |
1135 | ||
1136 | .SH For Manage mode: | |
1137 | ||
1138 | .TP | |
1139 | .BR \-t ", " \-\-test | |
1140 | Unless a more serious error occurred, | |
1141 | .I mdadm | |
1142 | will exit with a status of 2 if no changes were made to the array and | |
1143 | 0 if at least one change was made. | |
1144 | This can be useful when an indirect specifier such as | |
1145 | .BR missing , | |
1146 | .B detached | |
1147 | or | |
1148 | .B faulty | |
1149 | is used in requesting an operation on the array. | |
1150 | .B \-\-test | |
1151 | will report failure if these specifiers didn't find any match. | |
1152 | ||
1153 | .TP | |
1154 | .BR \-a ", " \-\-add | |
1155 | hot-add listed devices. | |
1156 | If a device appears to have recently been part of the array | |
1157 | (possibly it failed or was removed) the device is re\-added as describe | |
1158 | in the next point. | |
1159 | If that fails or the device was never part of the array, the device is | |
1160 | added as a hot-spare. | |
1161 | If the array is degraded, it will immediately start to rebuild data | |
1162 | onto that spare. | |
1163 | ||
1164 | Note that this and the following options are only meaningful on array | |
1165 | with redundancy. They don't apply to RAID0 or Linear. | |
1166 | ||
1167 | .TP | |
1168 | .BR \-\-re\-add | |
1169 | re\-add a device that was previous removed from an array. | |
1170 | If the metadata on the device reports that it is a member of the | |
1171 | array, and the slot that it used is still vacant, then the device will | |
1172 | be added back to the array in the same position. This will normally | |
1173 | cause the data for that device to be recovered. However based on the | |
1174 | event count on the device, the recovery may only require sections that | |
1175 | are flagged a write-intent bitmap to be recovered or may not require | |
1176 | any recovery at all. | |
1177 | ||
1178 | When used on an array that has no metadata (i.e. it was built with | |
1179 | .BR \-\-build) | |
1180 | it will be assumed that bitmap-based recovery is enough to make the | |
1181 | device fully consistent with the array. | |
1182 | ||
1183 | When | |
1184 | .B \-\-re\-add | |
1185 | can be accompanied by | |
1186 | .BR \-\-update=devicesize . | |
1187 | See the description of this option when used in Assemble mode for an | |
1188 | explanation of its use. | |
1189 | ||
1190 | If the device name given is | |
1191 | .B missing | |
1192 | then mdadm will try to find any device that looks like it should be | |
1193 | part of the array but isn't and will try to re\-add all such devices. | |
1194 | ||
1195 | .TP | |
1196 | .BR \-r ", " \-\-remove | |
1197 | remove listed devices. They must not be active. i.e. they should | |
1198 | be failed or spare devices. As well as the name of a device file | |
1199 | (e.g. | |
1200 | .BR /dev/sda1 ) | |
1201 | the words | |
1202 | .B failed | |
1203 | and | |
1204 | .B detached | |
1205 | can be given to | |
1206 | .BR \-\-remove . | |
1207 | The first causes all failed device to be removed. The second causes | |
1208 | any device which is no longer connected to the system (i.e an 'open' | |
1209 | returns | |
1210 | .BR ENXIO ) | |
1211 | to be removed. This will only succeed for devices that are spares or | |
1212 | have already been marked as failed. | |
1213 | ||
1214 | .TP | |
1215 | .BR \-f ", " \-\-fail | |
1216 | mark listed devices as faulty. | |
1217 | As well as the name of a device file, the word | |
1218 | .B detached | |
1219 | can be given. This will cause any device that has been detached from | |
1220 | the system to be marked as failed. It can then be removed. | |
1221 | ||
1222 | .TP | |
1223 | .BR \-\-set\-faulty | |
1224 | same as | |
1225 | .BR \-\-fail . | |
1226 | ||
1227 | .TP | |
1228 | .BR \-\-write\-mostly | |
1229 | Subsequent devices that are added or re\-added will have the 'write-mostly' | |
1230 | flag set. This is only valid for RAID1 and means that the 'md' driver | |
1231 | will avoid reading from these devices if possible. | |
1232 | .TP | |
1233 | .BR \-\-readwrite | |
1234 | Subsequent devices that are added or re\-added will have the 'write-mostly' | |
1235 | flag cleared. | |
1236 | ||
1237 | .P | |
1238 | Each of these options requires that the first device listed is the array | |
1239 | to be acted upon, and the remainder are component devices to be added, | |
1240 | removed, marked as faulty, etc. Several different operations can be | |
1241 | specified for different devices, e.g. | |
1242 | .in +5 | |
1243 | mdadm /dev/md0 \-\-add /dev/sda1 \-\-fail /dev/sdb1 \-\-remove /dev/sdb1 | |
1244 | .in -5 | |
1245 | Each operation applies to all devices listed until the next | |
1246 | operation. | |
1247 | ||
1248 | If an array is using a write-intent bitmap, then devices which have | |
1249 | been removed can be re\-added in a way that avoids a full | |
1250 | reconstruction but instead just updates the blocks that have changed | |
1251 | since the device was removed. For arrays with persistent metadata | |
1252 | (superblocks) this is done automatically. For arrays created with | |
1253 | .B \-\-build | |
1254 | mdadm needs to be told that this device we removed recently with | |
1255 | .BR \-\-re\-add . | |
1256 | ||
1257 | Devices can only be removed from an array if they are not in active | |
1258 | use, i.e. that must be spares or failed devices. To remove an active | |
1259 | device, it must first be marked as | |
1260 | .B faulty. | |
1261 | ||
1262 | .SH For Misc mode: | |
1263 | ||
1264 | .TP | |
1265 | .BR \-Q ", " \-\-query | |
1266 | Examine a device to see | |
1267 | (1) if it is an md device and (2) if it is a component of an md | |
1268 | array. | |
1269 | Information about what is discovered is presented. | |
1270 | ||
1271 | .TP | |
1272 | .BR \-D ", " \-\-detail | |
1273 | Print details of one or more md devices. | |
1274 | ||
1275 | .TP | |
1276 | .BR \-\-detail\-platform | |
1277 | Print details of the platform's RAID capabilities (firmware / hardware | |
1278 | topology) for a given metadata format. | |
1279 | ||
1280 | .TP | |
1281 | .BR \-Y ", " \-\-export | |
1282 | When used with | |
1283 | .B \-\-detail | |
1284 | or | |
1285 | .BR \-\-examine , | |
1286 | output will be formatted as | |
1287 | .B key=value | |
1288 | pairs for easy import into the environment. | |
1289 | ||
1290 | .TP | |
1291 | .BR \-E ", " \-\-examine | |
1292 | Print contents of the metadata stored on the named device(s). | |
1293 | Note the contrast between | |
1294 | .B \-\-examine | |
1295 | and | |
1296 | .BR \-\-detail . | |
1297 | .B \-\-examine | |
1298 | applies to devices which are components of an array, while | |
1299 | .B \-\-detail | |
1300 | applies to a whole array which is currently active. | |
1301 | .TP | |
1302 | .B \-\-sparc2.2 | |
1303 | If an array was created on a SPARC machine with a 2.2 Linux kernel | |
1304 | patched with RAID support, the superblock will have been created | |
1305 | incorrectly, or at least incompatibly with 2.4 and later kernels. | |
1306 | Using the | |
1307 | .B \-\-sparc2.2 | |
1308 | flag with | |
1309 | .B \-\-examine | |
1310 | will fix the superblock before displaying it. If this appears to do | |
1311 | the right thing, then the array can be successfully assembled using | |
1312 | .BR "\-\-assemble \-\-update=sparc2.2" . | |
1313 | ||
1314 | .TP | |
1315 | .BR \-X ", " \-\-examine\-bitmap | |
1316 | Report information about a bitmap file. | |
1317 | The argument is either an external bitmap file or an array component | |
1318 | in case of an internal bitmap. Note that running this on an array | |
1319 | device (e.g. | |
1320 | .BR /dev/md0 ) | |
1321 | does not report the bitmap for that array. | |
1322 | ||
1323 | .TP | |
1324 | .BR \-R ", " \-\-run | |
1325 | start a partially assembled array. If | |
1326 | .B \-\-assemble | |
1327 | did not find enough devices to fully start the array, it might leaving | |
1328 | it partially assembled. If you wish, you can then use | |
1329 | .B \-\-run | |
1330 | to start the array in degraded mode. | |
1331 | ||
1332 | .TP | |
1333 | .BR \-S ", " \-\-stop | |
1334 | deactivate array, releasing all resources. | |
1335 | ||
1336 | .TP | |
1337 | .BR \-o ", " \-\-readonly | |
1338 | mark array as readonly. | |
1339 | ||
1340 | .TP | |
1341 | .BR \-w ", " \-\-readwrite | |
1342 | mark array as readwrite. | |
1343 | ||
1344 | .TP | |
1345 | .B \-\-zero\-superblock | |
1346 | If the device contains a valid md superblock, the block is | |
1347 | overwritten with zeros. With | |
1348 | .B \-\-force | |
1349 | the block where the superblock would be is overwritten even if it | |
1350 | doesn't appear to be valid. | |
1351 | ||
1352 | .TP | |
1353 | .B \-\-kill\-subarray= | |
1354 | If the device is a container and the argument to \-\-kill\-subarray | |
1355 | specifies an inactive subarray in the container, then the subarray is | |
1356 | deleted. Deleting all subarrays will leave an 'empty-container' or | |
1357 | spare superblock on the drives. See \-\-zero\-superblock for completely | |
1358 | removing a superblock. Note that some formats depend on the subarray | |
1359 | index for generating a UUID, this command will fail if it would change | |
1360 | the UUID of an active subarray. | |
1361 | ||
1362 | .TP | |
1363 | .B \-\-update\-subarray= | |
1364 | If the device is a container and the argument to \-\-update\-subarray | |
1365 | specifies a subarray in the container, then attempt to update the given | |
1366 | superblock field in the subarray. See below in | |
1367 | .B MISC MODE | |
1368 | for details. | |
1369 | ||
1370 | .TP | |
1371 | .BR \-t ", " \-\-test | |
1372 | When used with | |
1373 | .BR \-\-detail , | |
1374 | the exit status of | |
1375 | .I mdadm | |
1376 | is set to reflect the status of the device. See below in | |
1377 | .B MISC MODE | |
1378 | for details. | |
1379 | ||
1380 | .TP | |
1381 | .BR \-W ", " \-\-wait | |
1382 | For each md device given, wait for any resync, recovery, or reshape | |
1383 | activity to finish before returning. | |
1384 | .I mdadm | |
1385 | will return with success if it actually waited for every device | |
1386 | listed, otherwise it will return failure. | |
1387 | ||
1388 | .TP | |
1389 | .BR \-\-wait\-clean | |
1390 | For each md device given, or each device in /proc/mdstat if | |
1391 | .B \-\-scan | |
1392 | is given, arrange for the array to be marked clean as soon as possible. | |
1393 | .I mdadm | |
1394 | will return with success if the array uses external metadata and we | |
1395 | successfully waited. For native arrays this returns immediately as the | |
1396 | kernel handles dirty-clean transitions at shutdown. No action is taken | |
1397 | if safe-mode handling is disabled. | |
1398 | ||
1399 | .SH For Incremental Assembly mode: | |
1400 | .TP | |
1401 | .BR \-\-rebuild\-map ", " \-r | |
1402 | Rebuild the map file | |
1403 | .RB ( /var/run/mdadm/map ) | |
1404 | that | |
1405 | .I mdadm | |
1406 | uses to help track which arrays are currently being assembled. | |
1407 | ||
1408 | .TP | |
1409 | .BR \-\-run ", " \-R | |
1410 | Run any array assembled as soon as a minimal number of devices are | |
1411 | available, rather than waiting until all expected devices are present. | |
1412 | ||
1413 | .TP | |
1414 | .BR \-\-scan ", " \-s | |
1415 | Only meaningful with | |
1416 | .B \-R | |
1417 | this will scan the | |
1418 | .B map | |
1419 | file for arrays that are being incrementally assembled and will try to | |
1420 | start any that are not already started. If any such array is listed | |
1421 | in | |
1422 | .B mdadm.conf | |
1423 | as requiring an external bitmap, that bitmap will be attached first. | |
1424 | ||
1425 | .TP | |
1426 | .BR \-\-fail ", " \-f | |
1427 | This allows the hot-plug system to remove devices that have fully disappeared | |
1428 | from the kernel. It will first fail and then remove the device from any | |
1429 | array it belongs to. | |
1430 | The device name given should be a kernel device name such as "sda", | |
1431 | not a name in | |
1432 | .IR /dev . | |
1433 | ||
1434 | .TP | |
1435 | .BR \-\-path= | |
1436 | Only used with \-\-fail. The 'path' given will be recorded so that if | |
1437 | a new device appears at the same location it can be automatically | |
1438 | added to the same array. This allows the failed device to be | |
1439 | automatically replaced by a new device without metadata if it appears | |
1440 | at specified path. This option is normally only set by a | |
1441 | .I udev | |
1442 | script. | |
1443 | ||
1444 | .SH For Monitor mode: | |
1445 | .TP | |
1446 | .BR \-m ", " \-\-mail | |
1447 | Give a mail address to send alerts to. | |
1448 | ||
1449 | .TP | |
1450 | .BR \-p ", " \-\-program ", " \-\-alert | |
1451 | Give a program to be run whenever an event is detected. | |
1452 | ||
1453 | .TP | |
1454 | .BR \-y ", " \-\-syslog | |
1455 | Cause all events to be reported through 'syslog'. The messages have | |
1456 | facility of 'daemon' and varying priorities. | |
1457 | ||
1458 | .TP | |
1459 | .BR \-d ", " \-\-delay | |
1460 | Give a delay in seconds. | |
1461 | .I mdadm | |
1462 | polls the md arrays and then waits this many seconds before polling | |
1463 | again. The default is 60 seconds. Since 2.6.16, there is no need to | |
1464 | reduce this as the kernel alerts | |
1465 | .I mdadm | |
1466 | immediately when there is any change. | |
1467 | ||
1468 | .TP | |
1469 | .BR \-r ", " \-\-increment | |
1470 | Give a percentage increment. | |
1471 | .I mdadm | |
1472 | will generate RebuildNN events with the given percentage increment. | |
1473 | ||
1474 | .TP | |
1475 | .BR \-f ", " \-\-daemonise | |
1476 | Tell | |
1477 | .I mdadm | |
1478 | to run as a background daemon if it decides to monitor anything. This | |
1479 | causes it to fork and run in the child, and to disconnect from the | |
1480 | terminal. The process id of the child is written to stdout. | |
1481 | This is useful with | |
1482 | .B \-\-scan | |
1483 | which will only continue monitoring if a mail address or alert program | |
1484 | is found in the config file. | |
1485 | ||
1486 | .TP | |
1487 | .BR \-i ", " \-\-pid\-file | |
1488 | When | |
1489 | .I mdadm | |
1490 | is running in daemon mode, write the pid of the daemon process to | |
1491 | the specified file, instead of printing it on standard output. | |
1492 | ||
1493 | .TP | |
1494 | .BR \-1 ", " \-\-oneshot | |
1495 | Check arrays only once. This will generate | |
1496 | .B NewArray | |
1497 | events and more significantly | |
1498 | .B DegradedArray | |
1499 | and | |
1500 | .B SparesMissing | |
1501 | events. Running | |
1502 | .in +5 | |
1503 | .B " mdadm \-\-monitor \-\-scan \-1" | |
1504 | .in -5 | |
1505 | from a cron script will ensure regular notification of any degraded arrays. | |
1506 | ||
1507 | .TP | |
1508 | .BR \-t ", " \-\-test | |
1509 | Generate a | |
1510 | .B TestMessage | |
1511 | alert for every array found at startup. This alert gets mailed and | |
1512 | passed to the alert program. This can be used for testing that alert | |
1513 | message do get through successfully. | |
1514 | ||
1515 | .TP | |
1516 | .BR \-\-no\-sharing | |
1517 | This inhibits the functionality for moving spares between arrays. | |
1518 | Only one monitoring process started with | |
1519 | .B \-\-scan | |
1520 | but without this flag is allowed, otherwise the two could interfere | |
1521 | with each other. | |
1522 | ||
1523 | .SH ASSEMBLE MODE | |
1524 | ||
1525 | .HP 12 | |
1526 | Usage: | |
1527 | .B mdadm \-\-assemble | |
1528 | .I md-device options-and-component-devices... | |
1529 | .HP 12 | |
1530 | Usage: | |
1531 | .B mdadm \-\-assemble \-\-scan | |
1532 | .I md-devices-and-options... | |
1533 | .HP 12 | |
1534 | Usage: | |
1535 | .B mdadm \-\-assemble \-\-scan | |
1536 | .I options... | |
1537 | ||
1538 | .PP | |
1539 | This usage assembles one or more RAID arrays from pre-existing components. | |
1540 | For each array, mdadm needs to know the md device, the identity of the | |
1541 | array, and a number of component-devices. These can be found in a number of ways. | |
1542 | ||
1543 | In the first usage example (without the | |
1544 | .BR \-\-scan ) | |
1545 | the first device given is the md device. | |
1546 | In the second usage example, all devices listed are treated as md | |
1547 | devices and assembly is attempted. | |
1548 | In the third (where no devices are listed) all md devices that are | |
1549 | listed in the configuration file are assembled. If no arrays are | |
1550 | described by the configuration file, then any arrays that | |
1551 | can be found on unused devices will be assembled. | |
1552 | ||
1553 | If precisely one device is listed, but | |
1554 | .B \-\-scan | |
1555 | is not given, then | |
1556 | .I mdadm | |
1557 | acts as though | |
1558 | .B \-\-scan | |
1559 | was given and identity information is extracted from the configuration file. | |
1560 | ||
1561 | The identity can be given with the | |
1562 | .B \-\-uuid | |
1563 | option, the | |
1564 | .B \-\-name | |
1565 | option, or the | |
1566 | .B \-\-super\-minor | |
1567 | option, will be taken from the md-device record in the config file, or | |
1568 | will be taken from the super block of the first component-device | |
1569 | listed on the command line. | |
1570 | ||
1571 | Devices can be given on the | |
1572 | .B \-\-assemble | |
1573 | command line or in the config file. Only devices which have an md | |
1574 | superblock which contains the right identity will be considered for | |
1575 | any array. | |
1576 | ||
1577 | The config file is only used if explicitly named with | |
1578 | .B \-\-config | |
1579 | or requested with (a possibly implicit) | |
1580 | .BR \-\-scan . | |
1581 | In the later case, | |
1582 | .B /etc/mdadm.conf | |
1583 | or | |
1584 | .B /etc/mdadm/mdadm.conf | |
1585 | is used. | |
1586 | ||
1587 | If | |
1588 | .B \-\-scan | |
1589 | is not given, then the config file will only be used to find the | |
1590 | identity of md arrays. | |
1591 | ||
1592 | Normally the array will be started after it is assembled. However if | |
1593 | .B \-\-scan | |
1594 | is not given and not all expected drives were listed, then the array | |
1595 | is not started (to guard against usage errors). To insist that the | |
1596 | array be started in this case (as may work for RAID1, 4, 5, 6, or 10), | |
1597 | give the | |
1598 | .B \-\-run | |
1599 | flag. | |
1600 | ||
1601 | If | |
1602 | .I udev | |
1603 | is active, | |
1604 | .I mdadm | |
1605 | does not create any entries in | |
1606 | .B /dev | |
1607 | but leaves that to | |
1608 | .IR udev . | |
1609 | It does record information in | |
1610 | .B /var/run/mdadm/map | |
1611 | which will allow | |
1612 | .I udev | |
1613 | to choose the correct name. | |
1614 | ||
1615 | If | |
1616 | .I mdadm | |
1617 | detects that udev is not configured, it will create the devices in | |
1618 | .B /dev | |
1619 | itself. | |
1620 | ||
1621 | In Linux kernels prior to version 2.6.28 there were two distinctly | |
1622 | different types of md devices that could be created: one that could be | |
1623 | partitioned using standard partitioning tools and one that could not. | |
1624 | Since 2.6.28 that distinction is no longer relevant as both type of | |
1625 | devices can be partitioned. | |
1626 | .I mdadm | |
1627 | will normally create the type that originally could not be partitioned | |
1628 | as it has a well defined major number (9). | |
1629 | ||
1630 | Prior to 2.6.28, it is important that mdadm chooses the correct type | |
1631 | of array device to use. This can be controlled with the | |
1632 | .B \-\-auto | |
1633 | option. In particular, a value of "mdp" or "part" or "p" tells mdadm | |
1634 | to use a partitionable device rather than the default. | |
1635 | ||
1636 | In the no-udev case, the value given to | |
1637 | .B \-\-auto | |
1638 | can be suffixed by a number. This tells | |
1639 | .I mdadm | |
1640 | to create that number of partition devices rather than the default of 4. | |
1641 | ||
1642 | The value given to | |
1643 | .B \-\-auto | |
1644 | can also be given in the configuration file as a word starting | |
1645 | .B auto= | |
1646 | on the ARRAY line for the relevant array. | |
1647 | ||
1648 | .SS Auto Assembly | |
1649 | When | |
1650 | .B \-\-assemble | |
1651 | is used with | |
1652 | .B \-\-scan | |
1653 | and no devices are listed, | |
1654 | .I mdadm | |
1655 | will first attempt to assemble all the arrays listed in the config | |
1656 | file. | |
1657 | ||
1658 | If no arrays are listed in the config (other than those marked | |
1659 | .BR <ignore> ) | |
1660 | it will look through the available devices for possible arrays and | |
1661 | will try to assemble anything that it finds. Arrays which are tagged | |
1662 | as belonging to the given homehost will be assembled and started | |
1663 | normally. Arrays which do not obviously belong to this host are given | |
1664 | names that are expected not to conflict with anything local, and are | |
1665 | started "read-auto" so that nothing is written to any device until the | |
1666 | array is written to. i.e. automatic resync etc is delayed. | |
1667 | ||
1668 | If | |
1669 | .I mdadm | |
1670 | finds a consistent set of devices that look like they should comprise | |
1671 | an array, and if the superblock is tagged as belonging to the given | |
1672 | home host, it will automatically choose a device name and try to | |
1673 | assemble the array. If the array uses version-0.90 metadata, then the | |
1674 | .B minor | |
1675 | number as recorded in the superblock is used to create a name in | |
1676 | .B /dev/md/ | |
1677 | so for example | |
1678 | .BR /dev/md/3 . | |
1679 | If the array uses version-1 metadata, then the | |
1680 | .B name | |
1681 | from the superblock is used to similarly create a name in | |
1682 | .B /dev/md/ | |
1683 | (the name will have any 'host' prefix stripped first). | |
1684 | ||
1685 | This behaviour can be modified by the | |
1686 | .I AUTO | |
1687 | line in the | |
1688 | .I mdadm.conf | |
1689 | configuration file. This line can indicate that specific metadata | |
1690 | type should, or should not, be automatically assembled. If an array | |
1691 | is found which is not listed in | |
1692 | .I mdadm.conf | |
1693 | and has a metadata format that is denied by the | |
1694 | .I AUTO | |
1695 | line, then it will not be assembled. | |
1696 | The | |
1697 | .I AUTO | |
1698 | line can also request that all arrays identified as being for this | |
1699 | homehost should be assembled regardless of their metadata type. | |
1700 | See | |
1701 | .IR mdadm.conf (5) | |
1702 | for further details. | |
1703 | ||
1704 | Note: Auto assembly cannot be used for assembling and activating some | |
1705 | arrays which are undergoing reshape. In particular as the | |
1706 | .B backup\-file | |
1707 | cannot be given, any reshape which requires a backup-file to continue | |
1708 | cannot be started by auto assembly. An array which is growing to more | |
1709 | devices and has passed the critical section can be assembled using | |
1710 | auto-assembly. | |
1711 | ||
1712 | .SH BUILD MODE | |
1713 | ||
1714 | .HP 12 | |
1715 | Usage: | |
1716 | .B mdadm \-\-build | |
1717 | .I md-device | |
1718 | .BI \-\-chunk= X | |
1719 | .BI \-\-level= Y | |
1720 | .BI \-\-raid\-devices= Z | |
1721 | .I devices | |
1722 | ||
1723 | .PP | |
1724 | This usage is similar to | |
1725 | .BR \-\-create . | |
1726 | The difference is that it creates an array without a superblock. With | |
1727 | these arrays there is no difference between initially creating the array and | |
1728 | subsequently assembling the array, except that hopefully there is useful | |
1729 | data there in the second case. | |
1730 | ||
1731 | The level may raid0, linear, raid1, raid10, multipath, or faulty, or | |
1732 | one of their synonyms. All devices must be listed and the array will | |
1733 | be started once complete. It will often be appropriate to use | |
1734 | .B \-\-assume\-clean | |
1735 | with levels raid1 or raid10. | |
1736 | ||
1737 | .SH CREATE MODE | |
1738 | ||
1739 | .HP 12 | |
1740 | Usage: | |
1741 | .B mdadm \-\-create | |
1742 | .I md-device | |
1743 | .BI \-\-chunk= X | |
1744 | .BI \-\-level= Y | |
1745 | .br | |
1746 | .BI \-\-raid\-devices= Z | |
1747 | .I devices | |
1748 | ||
1749 | .PP | |
1750 | This usage will initialise a new md array, associate some devices with | |
1751 | it, and activate the array. | |
1752 | ||
1753 | The named device will normally not exist when | |
1754 | .I "mdadm \-\-create" | |
1755 | is run, but will be created by | |
1756 | .I udev | |
1757 | once the array becomes active. | |
1758 | ||
1759 | As devices are added, they are checked to see if they contain RAID | |
1760 | superblocks or filesystems. They are also checked to see if the variance in | |
1761 | device size exceeds 1%. | |
1762 | ||
1763 | If any discrepancy is found, the array will not automatically be run, though | |
1764 | the presence of a | |
1765 | .B \-\-run | |
1766 | can override this caution. | |
1767 | ||
1768 | To create a "degraded" array in which some devices are missing, simply | |
1769 | give the word "\fBmissing\fP" | |
1770 | in place of a device name. This will cause | |
1771 | .I mdadm | |
1772 | to leave the corresponding slot in the array empty. | |
1773 | For a RAID4 or RAID5 array at most one slot can be | |
1774 | "\fBmissing\fP"; for a RAID6 array at most two slots. | |
1775 | For a RAID1 array, only one real device needs to be given. All of the | |
1776 | others can be | |
1777 | "\fBmissing\fP". | |
1778 | ||
1779 | When creating a RAID5 array, | |
1780 | .I mdadm | |
1781 | will automatically create a degraded array with an extra spare drive. | |
1782 | This is because building the spare into a degraded array is in general | |
1783 | faster than resyncing the parity on a non-degraded, but not clean, | |
1784 | array. This feature can be overridden with the | |
1785 | .B \-\-force | |
1786 | option. | |
1787 | ||
1788 | When creating an array with version-1 metadata a name for the array is | |
1789 | required. | |
1790 | If this is not given with the | |
1791 | .B \-\-name | |
1792 | option, | |
1793 | .I mdadm | |
1794 | will choose a name based on the last component of the name of the | |
1795 | device being created. So if | |
1796 | .B /dev/md3 | |
1797 | is being created, then the name | |
1798 | .B 3 | |
1799 | will be chosen. | |
1800 | If | |
1801 | .B /dev/md/home | |
1802 | is being created, then the name | |
1803 | .B home | |
1804 | will be used. | |
1805 | ||
1806 | When creating a partition based array, using | |
1807 | .I mdadm | |
1808 | with version-1.x metadata, the partition type should be set to | |
1809 | .B 0xDA | |
1810 | (non fs-data). This type selection allows for greater precision since | |
1811 | using any other [RAID auto-detect (0xFD) or a GNU/Linux partition (0x83)], | |
1812 | might create problems in the event of array recovery through a live cdrom. | |
1813 | ||
1814 | A new array will normally get a randomly assigned 128bit UUID which is | |
1815 | very likely to be unique. If you have a specific need, you can choose | |
1816 | a UUID for the array by giving the | |
1817 | .B \-\-uuid= | |
1818 | option. Be warned that creating two arrays with the same UUID is a | |
1819 | recipe for disaster. Also, using | |
1820 | .B \-\-uuid= | |
1821 | when creating a v0.90 array will silently override any | |
1822 | .B \-\-homehost= | |
1823 | setting. | |
1824 | .\"If the | |
1825 | .\".B \-\-size | |
1826 | .\"option is given, it is not necessary to list any component-devices in this command. | |
1827 | .\"They can be added later, before a | |
1828 | .\".B \-\-run. | |
1829 | .\"If no | |
1830 | .\".B \-\-size | |
1831 | .\"is given, the apparent size of the smallest drive given is used. | |
1832 | ||
1833 | When creating an array within a | |
1834 | .B CONTAINER | |
1835 | .I mdadm | |
1836 | can be given either the list of devices to use, or simply the name of | |
1837 | the container. The former case gives control over which devices in | |
1838 | the container will be used for the array. The latter case allows | |
1839 | .I mdadm | |
1840 | to automatically choose which devices to use based on how much spare | |
1841 | space is available. | |
1842 | ||
1843 | The General Management options that are valid with | |
1844 | .B \-\-create | |
1845 | are: | |
1846 | .TP | |
1847 | .B \-\-run | |
1848 | insist on running the array even if some devices look like they might | |
1849 | be in use. | |
1850 | ||
1851 | .TP | |
1852 | .B \-\-readonly | |
1853 | start the array readonly \(em not supported yet. | |
1854 | ||
1855 | .SH MANAGE MODE | |
1856 | .HP 12 | |
1857 | Usage: | |
1858 | .B mdadm | |
1859 | .I device | |
1860 | .I options... devices... | |
1861 | .PP | |
1862 | ||
1863 | This usage will allow individual devices in an array to be failed, | |
1864 | removed or added. It is possible to perform multiple operations with | |
1865 | on command. For example: | |
1866 | .br | |
1867 | .B " mdadm /dev/md0 \-f /dev/hda1 \-r /dev/hda1 \-a /dev/hda1" | |
1868 | .br | |
1869 | will firstly mark | |
1870 | .B /dev/hda1 | |
1871 | as faulty in | |
1872 | .B /dev/md0 | |
1873 | and will then remove it from the array and finally add it back | |
1874 | in as a spare. However only one md array can be affected by a single | |
1875 | command. | |
1876 | ||
1877 | When a device is added to an active array, mdadm checks to see if it | |
1878 | has metadata on it which suggests that it was recently a member of the | |
1879 | array. If it does, it tries to "re\-add" the device. If there have | |
1880 | been no changes since the device was removed, or if the array has a | |
1881 | write-intent bitmap which has recorded whatever changes there were, | |
1882 | then the device will immediately become a full member of the array and | |
1883 | those differences recorded in the bitmap will be resolved. | |
1884 | ||
1885 | .SH MISC MODE | |
1886 | .HP 12 | |
1887 | Usage: | |
1888 | .B mdadm | |
1889 | .I options ... | |
1890 | .I devices ... | |
1891 | .PP | |
1892 | ||
1893 | MISC mode includes a number of distinct operations that | |
1894 | operate on distinct devices. The operations are: | |
1895 | .TP | |
1896 | .B \-\-query | |
1897 | The device is examined to see if it is | |
1898 | (1) an active md array, or | |
1899 | (2) a component of an md array. | |
1900 | The information discovered is reported. | |
1901 | ||
1902 | .TP | |
1903 | .B \-\-detail | |
1904 | The device should be an active md device. | |
1905 | .B mdadm | |
1906 | will display a detailed description of the array. | |
1907 | .B \-\-brief | |
1908 | or | |
1909 | .B \-\-scan | |
1910 | will cause the output to be less detailed and the format to be | |
1911 | suitable for inclusion in | |
1912 | .BR mdadm.conf . | |
1913 | The exit status of | |
1914 | .I mdadm | |
1915 | will normally be 0 unless | |
1916 | .I mdadm | |
1917 | failed to get useful information about the device(s); however, if the | |
1918 | .B \-\-test | |
1919 | option is given, then the exit status will be: | |
1920 | .RS | |
1921 | .TP | |
1922 | 0 | |
1923 | The array is functioning normally. | |
1924 | .TP | |
1925 | 1 | |
1926 | The array has at least one failed device. | |
1927 | .TP | |
1928 | 2 | |
1929 | The array has multiple failed devices such that it is unusable. | |
1930 | .TP | |
1931 | 4 | |
1932 | There was an error while trying to get information about the device. | |
1933 | .RE | |
1934 | ||
1935 | .TP | |
1936 | .B \-\-detail\-platform | |
1937 | Print detail of the platform's RAID capabilities (firmware / hardware | |
1938 | topology). If the metadata is specified with | |
1939 | .B \-e | |
1940 | or | |
1941 | .B \-\-metadata= | |
1942 | then the return status will be: | |
1943 | .RS | |
1944 | .TP | |
1945 | 0 | |
1946 | metadata successfully enumerated its platform components on this system | |
1947 | .TP | |
1948 | 1 | |
1949 | metadata is platform independent | |
1950 | .TP | |
1951 | 2 | |
1952 | metadata failed to find its platform components on this system | |
1953 | .RE | |
1954 | ||
1955 | .TP | |
1956 | .B \-\-update\-subarray= | |
1957 | If the device is a container and the argument to \-\-update\-subarray | |
1958 | specifies a subarray in the container, then attempt to update the given | |
1959 | superblock field in the subarray. Similar to updating an array in | |
1960 | "assemble" mode, the field to update is selected by | |
1961 | .B \-U | |
1962 | or | |
1963 | .B \-\-update= | |
1964 | option. Currently only | |
1965 | .B name | |
1966 | is supported. | |
1967 | ||
1968 | The | |
1969 | .B name | |
1970 | option updates the subarray name in the metadata, it may not affect the | |
1971 | device node name or the device node symlink until the subarray is | |
1972 | re\-assembled. If updating | |
1973 | .B name | |
1974 | would change the UUID of an active subarray this operation is blocked, | |
1975 | and the command will end in an error. | |
1976 | ||
1977 | .TP | |
1978 | .B \-\-examine | |
1979 | The device should be a component of an md array. | |
1980 | .I mdadm | |
1981 | will read the md superblock of the device and display the contents. | |
1982 | If | |
1983 | .B \-\-brief | |
1984 | or | |
1985 | .B \-\-scan | |
1986 | is given, then multiple devices that are components of the one array | |
1987 | are grouped together and reported in a single entry suitable | |
1988 | for inclusion in | |
1989 | .BR mdadm.conf . | |
1990 | ||
1991 | Having | |
1992 | .B \-\-scan | |
1993 | without listing any devices will cause all devices listed in the | |
1994 | config file to be examined. | |
1995 | ||
1996 | .TP | |
1997 | .B \-\-stop | |
1998 | The devices should be active md arrays which will be deactivated, as | |
1999 | long as they are not currently in use. | |
2000 | ||
2001 | .TP | |
2002 | .B \-\-run | |
2003 | This will fully activate a partially assembled md array. | |
2004 | ||
2005 | .TP | |
2006 | .B \-\-readonly | |
2007 | This will mark an active array as read-only, providing that it is | |
2008 | not currently being used. | |
2009 | ||
2010 | .TP | |
2011 | .B \-\-readwrite | |
2012 | This will change a | |
2013 | .B readonly | |
2014 | array back to being read/write. | |
2015 | ||
2016 | .TP | |
2017 | .B \-\-scan | |
2018 | For all operations except | |
2019 | .BR \-\-examine , | |
2020 | .B \-\-scan | |
2021 | will cause the operation to be applied to all arrays listed in | |
2022 | .BR /proc/mdstat . | |
2023 | For | |
2024 | .BR \-\-examine, | |
2025 | .B \-\-scan | |
2026 | causes all devices listed in the config file to be examined. | |
2027 | ||
2028 | .TP | |
2029 | .BR \-b ", " \-\-brief | |
2030 | Be less verbose. This is used with | |
2031 | .B \-\-detail | |
2032 | and | |
2033 | .BR \-\-examine . | |
2034 | Using | |
2035 | .B \-\-brief | |
2036 | with | |
2037 | .B \-\-verbose | |
2038 | gives an intermediate level of verbosity. | |
2039 | ||
2040 | .SH MONITOR MODE | |
2041 | ||
2042 | .HP 12 | |
2043 | Usage: | |
2044 | .B mdadm \-\-monitor | |
2045 | .I options... devices... | |
2046 | ||
2047 | .PP | |
2048 | This usage causes | |
2049 | .I mdadm | |
2050 | to periodically poll a number of md arrays and to report on any events | |
2051 | noticed. | |
2052 | .I mdadm | |
2053 | will never exit once it decides that there are arrays to be checked, | |
2054 | so it should normally be run in the background. | |
2055 | ||
2056 | As well as reporting events, | |
2057 | .I mdadm | |
2058 | may move a spare drive from one array to another if they are in the | |
2059 | same | |
2060 | .B spare-group | |
2061 | or | |
2062 | .B domain | |
2063 | and if the destination array has a failed drive but no spares. | |
2064 | ||
2065 | If any devices are listed on the command line, | |
2066 | .I mdadm | |
2067 | will only monitor those devices. Otherwise all arrays listed in the | |
2068 | configuration file will be monitored. Further, if | |
2069 | .B \-\-scan | |
2070 | is given, then any other md devices that appear in | |
2071 | .B /proc/mdstat | |
2072 | will also be monitored. | |
2073 | ||
2074 | The result of monitoring the arrays is the generation of events. | |
2075 | These events are passed to a separate program (if specified) and may | |
2076 | be mailed to a given E-mail address. | |
2077 | ||
2078 | When passing events to a program, the program is run once for each event, | |
2079 | and is given 2 or 3 command-line arguments: the first is the | |
2080 | name of the event (see below), the second is the name of the | |
2081 | md device which is affected, and the third is the name of a related | |
2082 | device if relevant (such as a component device that has failed). | |
2083 | ||
2084 | If | |
2085 | .B \-\-scan | |
2086 | is given, then a program or an E-mail address must be specified on the | |
2087 | command line or in the config file. If neither are available, then | |
2088 | .I mdadm | |
2089 | will not monitor anything. | |
2090 | Without | |
2091 | .B \-\-scan, | |
2092 | .I mdadm | |
2093 | will continue monitoring as long as something was found to monitor. If | |
2094 | no program or email is given, then each event is reported to | |
2095 | .BR stdout . | |
2096 | ||
2097 | The different events are: | |
2098 | ||
2099 | .RS 4 | |
2100 | .TP | |
2101 | .B DeviceDisappeared | |
2102 | An md array which previously was configured appears to no longer be | |
2103 | configured. (syslog priority: Critical) | |
2104 | ||
2105 | If | |
2106 | .I mdadm | |
2107 | was told to monitor an array which is RAID0 or Linear, then it will | |
2108 | report | |
2109 | .B DeviceDisappeared | |
2110 | with the extra information | |
2111 | .BR Wrong-Level . | |
2112 | This is because RAID0 and Linear do not support the device-failed, | |
2113 | hot-spare and resync operations which are monitored. | |
2114 | ||
2115 | .TP | |
2116 | .B RebuildStarted | |
2117 | An md array started reconstruction. (syslog priority: Warning) | |
2118 | ||
2119 | .TP | |
2120 | .BI Rebuild NN | |
2121 | Where | |
2122 | .I NN | |
2123 | is a two-digit number (ie. 05, 48). This indicates that rebuild | |
2124 | has passed that many percent of the total. The events are generated | |
2125 | with fixed increment since 0. Increment size may be specified with | |
2126 | a commandline option (default is 20). (syslog priority: Warning) | |
2127 | ||
2128 | .TP | |
2129 | .B RebuildFinished | |
2130 | An md array that was rebuilding, isn't any more, either because it | |
2131 | finished normally or was aborted. (syslog priority: Warning) | |
2132 | ||
2133 | .TP | |
2134 | .B Fail | |
2135 | An active component device of an array has been marked as | |
2136 | faulty. (syslog priority: Critical) | |
2137 | ||
2138 | .TP | |
2139 | .B FailSpare | |
2140 | A spare component device which was being rebuilt to replace a faulty | |
2141 | device has failed. (syslog priority: Critical) | |
2142 | ||
2143 | .TP | |
2144 | .B SpareActive | |
2145 | A spare component device which was being rebuilt to replace a faulty | |
2146 | device has been successfully rebuilt and has been made active. | |
2147 | (syslog priority: Info) | |
2148 | ||
2149 | .TP | |
2150 | .B NewArray | |
2151 | A new md array has been detected in the | |
2152 | .B /proc/mdstat | |
2153 | file. (syslog priority: Info) | |
2154 | ||
2155 | .TP | |
2156 | .B DegradedArray | |
2157 | A newly noticed array appears to be degraded. This message is not | |
2158 | generated when | |
2159 | .I mdadm | |
2160 | notices a drive failure which causes degradation, but only when | |
2161 | .I mdadm | |
2162 | notices that an array is degraded when it first sees the array. | |
2163 | (syslog priority: Critical) | |
2164 | ||
2165 | .TP | |
2166 | .B MoveSpare | |
2167 | A spare drive has been moved from one array in a | |
2168 | .B spare-group | |
2169 | or | |
2170 | .B domain | |
2171 | to another to allow a failed drive to be replaced. | |
2172 | (syslog priority: Info) | |
2173 | ||
2174 | .TP | |
2175 | .B SparesMissing | |
2176 | If | |
2177 | .I mdadm | |
2178 | has been told, via the config file, that an array should have a certain | |
2179 | number of spare devices, and | |
2180 | .I mdadm | |
2181 | detects that it has fewer than this number when it first sees the | |
2182 | array, it will report a | |
2183 | .B SparesMissing | |
2184 | message. | |
2185 | (syslog priority: Warning) | |
2186 | ||
2187 | .TP | |
2188 | .B TestMessage | |
2189 | An array was found at startup, and the | |
2190 | .B \-\-test | |
2191 | flag was given. | |
2192 | (syslog priority: Info) | |
2193 | .RE | |
2194 | ||
2195 | Only | |
2196 | .B Fail, | |
2197 | .B FailSpare, | |
2198 | .B DegradedArray, | |
2199 | .B SparesMissing | |
2200 | and | |
2201 | .B TestMessage | |
2202 | cause Email to be sent. All events cause the program to be run. | |
2203 | The program is run with two or three arguments: the event | |
2204 | name, the array device and possibly a second device. | |
2205 | ||
2206 | Each event has an associated array device (e.g. | |
2207 | .BR /dev/md1 ) | |
2208 | and possibly a second device. For | |
2209 | .BR Fail , | |
2210 | .BR FailSpare , | |
2211 | and | |
2212 | .B SpareActive | |
2213 | the second device is the relevant component device. | |
2214 | For | |
2215 | .B MoveSpare | |
2216 | the second device is the array that the spare was moved from. | |
2217 | ||
2218 | For | |
2219 | .I mdadm | |
2220 | to move spares from one array to another, the different arrays need to | |
2221 | be labeled with the same | |
2222 | .B spare-group | |
2223 | or the spares must be allowed to migrate through matching POLICY domains | |
2224 | in the configuration file. The | |
2225 | .B spare-group | |
2226 | name can be any string; it is only necessary that different spare | |
2227 | groups use different names. | |
2228 | ||
2229 | When | |
2230 | .I mdadm | |
2231 | detects that an array in a spare group has fewer active | |
2232 | devices than necessary for the complete array, and has no spare | |
2233 | devices, it will look for another array in the same spare group that | |
2234 | has a full complement of working drive and a spare. It will then | |
2235 | attempt to remove the spare from the second drive and add it to the | |
2236 | first. | |
2237 | If the removal succeeds but the adding fails, then it is added back to | |
2238 | the original array. | |
2239 | ||
2240 | If the spare group for a degraded array is not defined, | |
2241 | .I mdadm | |
2242 | will look at the rules of spare migration specified by POLICY lines in | |
2243 | .B mdadm.conf | |
2244 | and then follow similar steps as above if a matching spare is found. | |
2245 | ||
2246 | .SH GROW MODE | |
2247 | The GROW mode is used for changing the size or shape of an active | |
2248 | array. | |
2249 | For this to work, the kernel must support the necessary change. | |
2250 | Various types of growth are being added during 2.6 development. | |
2251 | ||
2252 | Currently the supported changes include | |
2253 | .IP \(bu 4 | |
2254 | change the "size" attribute for RAID1, RAID4, RAID5 and RAID6. | |
2255 | .IP \(bu 4 | |
2256 | increase or decrease the "raid\-devices" attribute of RAID0, RAID1, RAID4, | |
2257 | RAID5, and RAID6. | |
2258 | .IP \(bu 4 | |
2259 | change the chunk-size and layout of RAID0, RAID4, RAID5 and RAID6. | |
2260 | .IP \(bu 4 | |
2261 | convert between RAID1 and RAID5, between RAID5 and RAID6, between | |
2262 | RAID0, RAID4, and RAID5, and between RAID0 and RAID10 (in the near-2 mode). | |
2263 | .IP \(bu 4 | |
2264 | add a write-intent bitmap to any array which supports these bitmaps, or | |
2265 | remove a write-intent bitmap from such an array. | |
2266 | .PP | |
2267 | ||
2268 | Using GROW on containers is currently supported only for Intel's IMSM | |
2269 | container format. The number of devices in a container can be | |
2270 | increased - which affects all arrays in the container - or an array | |
2271 | in a container can be converted between levels where those levels are | |
2272 | supported by the container, and the conversion is on of those listed | |
2273 | above. Resizing arrays in an IMSM container with | |
2274 | .B "--grow --size" | |
2275 | is not yet supported. | |
2276 | ||
2277 | Grow functionality (e.g. expand a number of raid devices) for Intel's | |
2278 | IMSM container format has an experimental status. It is guarded by the | |
2279 | .B MDADM_EXPERIMENTAL | |
2280 | environment variable which must be set to '1' for a GROW command to | |
2281 | succeed. | |
2282 | This is for the following reasons: | |
2283 | ||
2284 | .IP 1. | |
2285 | Intel's native IMSM check-pointing is not fully tested yet. | |
2286 | This can causes IMSM incompatibility during the grow process: an array | |
2287 | which is growing cannot roam between Microsoft Windows(R) and Linux | |
2288 | systems. | |
2289 | ||
2290 | .IP 2. | |
2291 | Interrupting a grow operation is not recommended, because it | |
2292 | has not been fully tested for Intel's IMSM container format yet. | |
2293 | ||
2294 | .PP | |
2295 | Note: Intel's native checkpointing doesn't use | |
2296 | .B --backup-file | |
2297 | option and it is transparent for assembly feature. | |
2298 | ||
2299 | .SS SIZE CHANGES | |
2300 | Normally when an array is built the "size" is taken from the smallest | |
2301 | of the drives. If all the small drives in an arrays are, one at a | |
2302 | time, removed and replaced with larger drives, then you could have an | |
2303 | array of large drives with only a small amount used. In this | |
2304 | situation, changing the "size" with "GROW" mode will allow the extra | |
2305 | space to start being used. If the size is increased in this way, a | |
2306 | "resync" process will start to make sure the new parts of the array | |
2307 | are synchronised. | |
2308 | ||
2309 | Note that when an array changes size, any filesystem that may be | |
2310 | stored in the array will not automatically grow or shrink to use or | |
2311 | vacate the space. The | |
2312 | filesystem will need to be explicitly told to use the extra space | |
2313 | after growing, or to reduce its size | |
2314 | .B prior | |
2315 | to shrinking the array. | |
2316 | ||
2317 | Also the size of an array cannot be changed while it has an active | |
2318 | bitmap. If an array has a bitmap, it must be removed before the size | |
2319 | can be changed. Once the change is complete a new bitmap can be created. | |
2320 | ||
2321 | .SS RAID\-DEVICES CHANGES | |
2322 | ||
2323 | A RAID1 array can work with any number of devices from 1 upwards | |
2324 | (though 1 is not very useful). There may be times which you want to | |
2325 | increase or decrease the number of active devices. Note that this is | |
2326 | different to hot-add or hot-remove which changes the number of | |
2327 | inactive devices. | |
2328 | ||
2329 | When reducing the number of devices in a RAID1 array, the slots which | |
2330 | are to be removed from the array must already be vacant. That is, the | |
2331 | devices which were in those slots must be failed and removed. | |
2332 | ||
2333 | When the number of devices is increased, any hot spares that are | |
2334 | present will be activated immediately. | |
2335 | ||
2336 | Changing the number of active devices in a RAID5 or RAID6 is much more | |
2337 | effort. Every block in the array will need to be read and written | |
2338 | back to a new location. From 2.6.17, the Linux Kernel is able to | |
2339 | increase the number of devices in a RAID5 safely, including restarting | |
2340 | an interrupted "reshape". From 2.6.31, the Linux Kernel is able to | |
2341 | increase or decrease the number of devices in a RAID5 or RAID6. | |
2342 | ||
2343 | From 2.6.35, the Linux Kernel is able to convert a RAID0 in to a RAID4 | |
2344 | or RAID5. | |
2345 | .I mdadm | |
2346 | uses this functionality and the ability to add | |
2347 | devices to a RAID4 to allow devices to be added to a RAID0. When | |
2348 | requested to do this, | |
2349 | .I mdadm | |
2350 | will convert the RAID0 to a RAID4, add the necessary disks and make | |
2351 | the reshape happen, and then convert the RAID4 back to RAID0. | |
2352 | ||
2353 | When decreasing the number of devices, the size of the array will also | |
2354 | decrease. If there was data in the array, it could get destroyed and | |
2355 | this is not reversible, so you should firstly shrink the filesystem on | |
2356 | the array to fit within the new size. To help prevent accidents, | |
2357 | .I mdadm | |
2358 | requires that the size of the array be decreased first with | |
2359 | .BR "mdadm --grow --array-size" . | |
2360 | This is a reversible change which simply makes the end of the array | |
2361 | inaccessible. The integrity of any data can then be checked before | |
2362 | the non-reversible reduction in the number of devices is request. | |
2363 | ||
2364 | When relocating the first few stripes on a RAID5 or RAID6, it is not | |
2365 | possible to keep the data on disk completely consistent and | |
2366 | crash-proof. To provide the required safety, mdadm disables writes to | |
2367 | the array while this "critical section" is reshaped, and takes a | |
2368 | backup of the data that is in that section. For grows, this backup may be | |
2369 | stored in any spare devices that the array has, however it can also be | |
2370 | stored in a separate file specified with the | |
2371 | .B \-\-backup\-file | |
2372 | option, and is required to be specified for shrinks, RAID level | |
2373 | changes and layout changes. If this option is used, and the system | |
2374 | does crash during the critical period, the same file must be passed to | |
2375 | .B \-\-assemble | |
2376 | to restore the backup and reassemble the array. When shrinking rather | |
2377 | than growing the array, the reshape is done from the end towards the | |
2378 | beginning, so the "critical section" is at the end of the reshape. | |
2379 | ||
2380 | .SS LEVEL CHANGES | |
2381 | ||
2382 | Changing the RAID level of any array happens instantaneously. However | |
2383 | in the RAID5 to RAID6 case this requires a non-standard layout of the | |
2384 | RAID6 data, and in the RAID6 to RAID5 case that non-standard layout is | |
2385 | required before the change can be accomplished. So while the level | |
2386 | change is instant, the accompanying layout change can take quite a | |
2387 | long time. A | |
2388 | .B \-\-backup\-file | |
2389 | is required. If the array is not simultaneously being grown or | |
2390 | shrunk, so that the array size will remain the same - for example, | |
2391 | reshaping a 3-drive RAID5 into a 4-drive RAID6 - the backup file will | |
2392 | be used not just for a "cricital section" but throughout the reshape | |
2393 | operation, as described below under LAYOUT CHANGES. | |
2394 | ||
2395 | .SS CHUNK-SIZE AND LAYOUT CHANGES | |
2396 | ||
2397 | Changing the chunk-size of layout without also changing the number of | |
2398 | devices as the same time will involve re-writing all blocks in-place. | |
2399 | To ensure against data loss in the case of a crash, a | |
2400 | .B --backup-file | |
2401 | must be provided for these changes. Small sections of the array will | |
2402 | be copied to the backup file while they are being rearranged. This | |
2403 | means that all the data is copied twice, once to the backup and once | |
2404 | to the new layout on the array, so this type of reshape will go very | |
2405 | slowly. | |
2406 | ||
2407 | If the reshape is interrupted for any reason, this backup file must be | |
2408 | made available to | |
2409 | .B "mdadm --assemble" | |
2410 | so the array can be reassembled. Consequently the file cannot be | |
2411 | stored on the device being reshaped. | |
2412 | ||
2413 | ||
2414 | .SS BITMAP CHANGES | |
2415 | ||
2416 | A write-intent bitmap can be added to, or removed from, an active | |
2417 | array. Either internal bitmaps, or bitmaps stored in a separate file, | |
2418 | can be added. Note that if you add a bitmap stored in a file which is | |
2419 | in a filesystem that is on the RAID array being affected, the system | |
2420 | will deadlock. The bitmap must be on a separate filesystem. | |
2421 | ||
2422 | .SH INCREMENTAL MODE | |
2423 | ||
2424 | .HP 12 | |
2425 | Usage: | |
2426 | .B mdadm \-\-incremental | |
2427 | .RB [ \-\-run ] | |
2428 | .RB [ \-\-quiet ] | |
2429 | .I component-device | |
2430 | .HP 12 | |
2431 | Usage: | |
2432 | .B mdadm \-\-incremental \-\-fail | |
2433 | .I component-device | |
2434 | .HP 12 | |
2435 | Usage: | |
2436 | .B mdadm \-\-incremental \-\-rebuild\-map | |
2437 | .HP 12 | |
2438 | Usage: | |
2439 | .B mdadm \-\-incremental \-\-run \-\-scan | |
2440 | ||
2441 | .PP | |
2442 | This mode is designed to be used in conjunction with a device | |
2443 | discovery system. As devices are found in a system, they can be | |
2444 | passed to | |
2445 | .B "mdadm \-\-incremental" | |
2446 | to be conditionally added to an appropriate array. | |
2447 | ||
2448 | Conversely, it can also be used with the | |
2449 | .B \-\-fail | |
2450 | flag to do just the opposite and find whatever array a particular device | |
2451 | is part of and remove the device from that array. | |
2452 | ||
2453 | If the device passed is a | |
2454 | .B CONTAINER | |
2455 | device created by a previous call to | |
2456 | .IR mdadm , | |
2457 | then rather than trying to add that device to an array, all the arrays | |
2458 | described by the metadata of the container will be started. | |
2459 | ||
2460 | .I mdadm | |
2461 | performs a number of tests to determine if the device is part of an | |
2462 | array, and which array it should be part of. If an appropriate array | |
2463 | is found, or can be created, | |
2464 | .I mdadm | |
2465 | adds the device to the array and conditionally starts the array. | |
2466 | ||
2467 | Note that | |
2468 | .I mdadm | |
2469 | will normally only add devices to an array which were previously working | |
2470 | (active or spare) parts of that array. The support for automatic | |
2471 | inclusion of a new drive as a spare in some array requires | |
2472 | a configuration through POLICY in config file. | |
2473 | ||
2474 | The tests that | |
2475 | .I mdadm | |
2476 | makes are as follow: | |
2477 | .IP + | |
2478 | Is the device permitted by | |
2479 | .BR mdadm.conf ? | |
2480 | That is, is it listed in a | |
2481 | .B DEVICES | |
2482 | line in that file. If | |
2483 | .B DEVICES | |
2484 | is absent then the default it to allow any device. Similar if | |
2485 | .B DEVICES | |
2486 | contains the special word | |
2487 | .B partitions | |
2488 | then any device is allowed. Otherwise the device name given to | |
2489 | .I mdadm | |
2490 | must match one of the names or patterns in a | |
2491 | .B DEVICES | |
2492 | line. | |
2493 | ||
2494 | .IP + | |
2495 | Does the device have a valid md superblock? If a specific metadata | |
2496 | version is requested with | |
2497 | .B \-\-metadata | |
2498 | or | |
2499 | .B \-e | |
2500 | then only that style of metadata is accepted, otherwise | |
2501 | .I mdadm | |
2502 | finds any known version of metadata. If no | |
2503 | .I md | |
2504 | metadata is found, the device may be still added to an array | |
2505 | as a spare if POLICY allows. | |
2506 | ||
2507 | .ig | |
2508 | .IP + | |
2509 | Does the metadata match an expected array? | |
2510 | The metadata can match in two ways. Either there is an array listed | |
2511 | in | |
2512 | .B mdadm.conf | |
2513 | which identifies the array (either by UUID, by name, by device list, | |
2514 | or by minor-number), or the array was created with a | |
2515 | .B homehost | |
2516 | specified and that | |
2517 | .B homehost | |
2518 | matches the one in | |
2519 | .B mdadm.conf | |
2520 | or on the command line. | |
2521 | If | |
2522 | .I mdadm | |
2523 | is not able to positively identify the array as belonging to the | |
2524 | current host, the device will be rejected. | |
2525 | .. | |
2526 | ||
2527 | .PP | |
2528 | .I mdadm | |
2529 | keeps a list of arrays that it has partially assembled in | |
2530 | .B /var/run/mdadm/map | |
2531 | (or | |
2532 | .B /var/run/mdadm.map | |
2533 | if the directory doesn't exist. Or maybe even | |
2534 | .BR /dev/.mdadm.map ). | |
2535 | If no array exists which matches | |
2536 | the metadata on the new device, | |
2537 | .I mdadm | |
2538 | must choose a device name and unit number. It does this based on any | |
2539 | name given in | |
2540 | .B mdadm.conf | |
2541 | or any name information stored in the metadata. If this name | |
2542 | suggests a unit number, that number will be used, otherwise a free | |
2543 | unit number will be chosen. Normally | |
2544 | .I mdadm | |
2545 | will prefer to create a partitionable array, however if the | |
2546 | .B CREATE | |
2547 | line in | |
2548 | .B mdadm.conf | |
2549 | suggests that a non-partitionable array is preferred, that will be | |
2550 | honoured. | |
2551 | ||
2552 | If the array is not found in the config file and its metadata does not | |
2553 | identify it as belonging to the "homehost", then | |
2554 | .I mdadm | |
2555 | will choose a name for the array which is certain not to conflict with | |
2556 | any array which does belong to this host. It does this be adding an | |
2557 | underscore and a small number to the name preferred by the metadata. | |
2558 | ||
2559 | Once an appropriate array is found or created and the device is added, | |
2560 | .I mdadm | |
2561 | must decide if the array is ready to be started. It will | |
2562 | normally compare the number of available (non-spare) devices to the | |
2563 | number of devices that the metadata suggests need to be active. If | |
2564 | there are at least that many, the array will be started. This means | |
2565 | that if any devices are missing the array will not be restarted. | |
2566 | ||
2567 | As an alternative, | |
2568 | .B \-\-run | |
2569 | may be passed to | |
2570 | .I mdadm | |
2571 | in which case the array will be run as soon as there are enough | |
2572 | devices present for the data to be accessible. For a RAID1, that | |
2573 | means one device will start the array. For a clean RAID5, the array | |
2574 | will be started as soon as all but one drive is present. | |
2575 | ||
2576 | Note that neither of these approaches is really ideal. If it can | |
2577 | be known that all device discovery has completed, then | |
2578 | .br | |
2579 | .B " mdadm \-IRs" | |
2580 | .br | |
2581 | can be run which will try to start all arrays that are being | |
2582 | incrementally assembled. They are started in "read-auto" mode in | |
2583 | which they are read-only until the first write request. This means | |
2584 | that no metadata updates are made and no attempt at resync or recovery | |
2585 | happens. Further devices that are found before the first write can | |
2586 | still be added safely. | |
2587 | ||
2588 | .SH ENVIRONMENT | |
2589 | This section describes environment variables that affect how mdadm | |
2590 | operates. | |
2591 | ||
2592 | .TP | |
2593 | .B MDADM_NO_MDMON | |
2594 | Setting this value to 1 will prevent mdadm from automatically launching | |
2595 | mdmon. This variable is intended primarily for debugging mdadm/mdmon. | |
2596 | ||
2597 | .TP | |
2598 | .B MDADM_NO_UDEV | |
2599 | Normally, | |
2600 | .I mdadm | |
2601 | does not create any device nodes in /dev, but leaves that task to | |
2602 | .IR udev . | |
2603 | If | |
2604 | .I udev | |
2605 | appears not to be configured, or if this environment variable is set | |
2606 | to '1', the | |
2607 | .I mdadm | |
2608 | will create and devices that are needed. | |
2609 | ||
2610 | .SH EXAMPLES | |
2611 | ||
2612 | .B " mdadm \-\-query /dev/name-of-device" | |
2613 | .br | |
2614 | This will find out if a given device is a RAID array, or is part of | |
2615 | one, and will provide brief information about the device. | |
2616 | ||
2617 | .B " mdadm \-\-assemble \-\-scan" | |
2618 | .br | |
2619 | This will assemble and start all arrays listed in the standard config | |
2620 | file. This command will typically go in a system startup file. | |
2621 | ||
2622 | .B " mdadm \-\-stop \-\-scan" | |
2623 | .br | |
2624 | This will shut down all arrays that can be shut down (i.e. are not | |
2625 | currently in use). This will typically go in a system shutdown script. | |
2626 | ||
2627 | .B " mdadm \-\-follow \-\-scan \-\-delay=120" | |
2628 | .br | |
2629 | If (and only if) there is an Email address or program given in the | |
2630 | standard config file, then | |
2631 | monitor the status of all arrays listed in that file by | |
2632 | polling them ever 2 minutes. | |
2633 | ||
2634 | .B " mdadm \-\-create /dev/md0 \-\-level=1 \-\-raid\-devices=2 /dev/hd[ac]1" | |
2635 | .br | |
2636 | Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1. | |
2637 | ||
2638 | .br | |
2639 | .B " echo 'DEVICE /dev/hd*[0\-9] /dev/sd*[0\-9]' > mdadm.conf" | |
2640 | .br | |
2641 | .B " mdadm \-\-detail \-\-scan >> mdadm.conf" | |
2642 | .br | |
2643 | This will create a prototype config file that describes currently | |
2644 | active arrays that are known to be made from partitions of IDE or SCSI drives. | |
2645 | This file should be reviewed before being used as it may | |
2646 | contain unwanted detail. | |
2647 | ||
2648 | .B " echo 'DEVICE /dev/hd[a\-z] /dev/sd*[a\-z]' > mdadm.conf" | |
2649 | .br | |
2650 | .B " mdadm \-\-examine \-\-scan \-\-config=mdadm.conf >> mdadm.conf" | |
2651 | .br | |
2652 | This will find arrays which could be assembled from existing IDE and | |
2653 | SCSI whole drives (not partitions), and store the information in the | |
2654 | format of a config file. | |
2655 | This file is very likely to contain unwanted detail, particularly | |
2656 | the | |
2657 | .B devices= | |
2658 | entries. It should be reviewed and edited before being used as an | |
2659 | actual config file. | |
2660 | ||
2661 | .B " mdadm \-\-examine \-\-brief \-\-scan \-\-config=partitions" | |
2662 | .br | |
2663 | .B " mdadm \-Ebsc partitions" | |
2664 | .br | |
2665 | Create a list of devices by reading | |
2666 | .BR /proc/partitions , | |
2667 | scan these for RAID superblocks, and printout a brief listing of all | |
2668 | that were found. | |
2669 | ||
2670 | .B " mdadm \-Ac partitions \-m 0 /dev/md0" | |
2671 | .br | |
2672 | Scan all partitions and devices listed in | |
2673 | .BR /proc/partitions | |
2674 | and assemble | |
2675 | .B /dev/md0 | |
2676 | out of all such devices with a RAID superblock with a minor number of 0. | |
2677 | ||
2678 | .B " mdadm \-\-monitor \-\-scan \-\-daemonise > /var/run/mdadm" | |
2679 | .br | |
2680 | If config file contains a mail address or alert program, run mdadm in | |
2681 | the background in monitor mode monitoring all md devices. Also write | |
2682 | pid of mdadm daemon to | |
2683 | .BR /var/run/mdadm . | |
2684 | ||
2685 | .B " mdadm \-Iq /dev/somedevice" | |
2686 | .br | |
2687 | Try to incorporate newly discovered device into some array as | |
2688 | appropriate. | |
2689 | ||
2690 | .B " mdadm \-\-incremental \-\-rebuild\-map \-\-run \-\-scan" | |
2691 | .br | |
2692 | Rebuild the array map from any current arrays, and then start any that | |
2693 | can be started. | |
2694 | ||
2695 | .B " mdadm /dev/md4 --fail detached --remove detached" | |
2696 | .br | |
2697 | Any devices which are components of /dev/md4 will be marked as faulty | |
2698 | and then remove from the array. | |
2699 | ||
2700 | .B " mdadm --grow /dev/md4 --level=6 --backup-file=/root/backup-md4" | |
2701 | .br | |
2702 | The array | |
2703 | .B /dev/md4 | |
2704 | which is currently a RAID5 array will be converted to RAID6. There | |
2705 | should normally already be a spare drive attached to the array as a | |
2706 | RAID6 needs one more drive than a matching RAID5. | |
2707 | ||
2708 | .B " mdadm --create /dev/md/ddf --metadata=ddf --raid-disks 6 /dev/sd[a-f]" | |
2709 | .br | |
2710 | Create a DDF array over 6 devices. | |
2711 | ||
2712 | .B " mdadm --create /dev/md/home -n3 -l5 -z 30000000 /dev/md/ddf" | |
2713 | .br | |
2714 | Create a RAID5 array over any 3 devices in the given DDF set. Use | |
2715 | only 30 gigabytes of each device. | |
2716 | ||
2717 | .B " mdadm -A /dev/md/ddf1 /dev/sd[a-f]" | |
2718 | .br | |
2719 | Assemble a pre-exist ddf array. | |
2720 | ||
2721 | .B " mdadm -I /dev/md/ddf1" | |
2722 | .br | |
2723 | Assemble all arrays contained in the ddf array, assigning names as | |
2724 | appropriate. | |
2725 | ||
2726 | .B " mdadm \-\-create \-\-help" | |
2727 | .br | |
2728 | Provide help about the Create mode. | |
2729 | ||
2730 | .B " mdadm \-\-config \-\-help" | |
2731 | .br | |
2732 | Provide help about the format of the config file. | |
2733 | ||
2734 | .B " mdadm \-\-help" | |
2735 | .br | |
2736 | Provide general help. | |
2737 | ||
2738 | .SH FILES | |
2739 | ||
2740 | .SS /proc/mdstat | |
2741 | ||
2742 | If you're using the | |
2743 | .B /proc | |
2744 | filesystem, | |
2745 | .B /proc/mdstat | |
2746 | lists all active md devices with information about them. | |
2747 | .I mdadm | |
2748 | uses this to find arrays when | |
2749 | .B \-\-scan | |
2750 | is given in Misc mode, and to monitor array reconstruction | |
2751 | on Monitor mode. | |
2752 | ||
2753 | .SS /etc/mdadm.conf | |
2754 | ||
2755 | The config file lists which devices may be scanned to see if | |
2756 | they contain MD super block, and gives identifying information | |
2757 | (e.g. UUID) about known MD arrays. See | |
2758 | .BR mdadm.conf (5) | |
2759 | for more details. | |
2760 | ||
2761 | .SS /var/run/mdadm/map | |
2762 | When | |
2763 | .B \-\-incremental | |
2764 | mode is used, this file gets a list of arrays currently being created. | |
2765 | If | |
2766 | .B /var/run/mdadm | |
2767 | does not exist as a directory, then | |
2768 | .B /var/run/mdadm.map | |
2769 | is used instead. If | |
2770 | .B /var/run | |
2771 | is not available (as may be the case during early boot), | |
2772 | .B /dev/.mdadm.map | |
2773 | is used on the basis that | |
2774 | .B /dev | |
2775 | is usually available very early in boot. | |
2776 | ||
2777 | .SH DEVICE NAMES | |
2778 | ||
2779 | .I mdadm | |
2780 | understand two sorts of names for array devices. | |
2781 | ||
2782 | The first is the so-called 'standard' format name, which matches the | |
2783 | names used by the kernel and which appear in | |
2784 | .IR /proc/mdstat . | |
2785 | ||
2786 | The second sort can be freely chosen, but must reside in | |
2787 | .IR /dev/md/ . | |
2788 | When giving a device name to | |
2789 | .I mdadm | |
2790 | to create or assemble an array, either full path name such as | |
2791 | .I /dev/md0 | |
2792 | or | |
2793 | .I /dev/md/home | |
2794 | can be given, or just the suffix of the second sort of name, such as | |
2795 | .I home | |
2796 | can be given. | |
2797 | ||
2798 | When | |
2799 | .I mdadm | |
2800 | chooses device names during auto-assembly or incremental assembly, it | |
2801 | will sometimes add a small sequence number to the end of the name to | |
2802 | avoid conflicted between multiple arrays that have the same name. If | |
2803 | .I mdadm | |
2804 | can reasonably determine that the array really is meant for this host, | |
2805 | either by a hostname in the metadata, or by the presence of the array | |
2806 | in | |
2807 | .BR mdadm.conf , | |
2808 | then it will leave off the suffix if possible. | |
2809 | Also if the homehost is specified as | |
2810 | .B <ignore> | |
2811 | .I mdadm | |
2812 | will only use a suffix if a different array of the same name already | |
2813 | exists or is listed in the config file. | |
2814 | ||
2815 | The standard names for non-partitioned arrays (the only sort of md | |
2816 | array available in 2.4 and earlier) are of the form | |
2817 | .IP | |
2818 | /dev/mdNN | |
2819 | .PP | |
2820 | where NN is a number. | |
2821 | The standard names for partitionable arrays (as available from 2.6 | |
2822 | onwards) are of the form | |
2823 | .IP | |
2824 | /dev/md_dNN | |
2825 | .PP | |
2826 | Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2". | |
2827 | .PP | |
2828 | From kernel version, 2.6.28 the "non-partitioned array" can actually | |
2829 | be partitioned. So the "md_dNN" names are no longer needed, and | |
2830 | partitions such as "/dev/mdNNpXX" are possible. | |
2831 | ||
2832 | .SH NOTE | |
2833 | .I mdadm | |
2834 | was previously known as | |
2835 | .IR mdctl . | |
2836 | .P | |
2837 | .I mdadm | |
2838 | is completely separate from the | |
2839 | .I raidtools | |
2840 | package, and does not use the | |
2841 | .I /etc/raidtab | |
2842 | configuration file at all. | |
2843 | ||
2844 | .SH SEE ALSO | |
2845 | For further information on mdadm usage, MD and the various levels of | |
2846 | RAID, see: | |
2847 | .IP | |
2848 | .B http://raid.wiki.kernel.org/ | |
2849 | .PP | |
2850 | (based upon Jakob \(/Ostergaard's Software\-RAID.HOWTO) | |
2851 | .\".PP | |
2852 | .\"for new releases of the RAID driver check out: | |
2853 | .\" | |
2854 | .\".IP | |
2855 | .\".UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2856 | .\"ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2857 | .\".UE | |
2858 | .\".PP | |
2859 | .\"or | |
2860 | .\".IP | |
2861 | .\".UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2862 | .\"http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2863 | .\".UE | |
2864 | .PP | |
2865 | The latest version of | |
2866 | .I mdadm | |
2867 | should always be available from | |
2868 | .IP | |
2869 | .B http://www.kernel.org/pub/linux/utils/raid/mdadm/ | |
2870 | .PP | |
2871 | Related man pages: | |
2872 | .PP | |
2873 | .IR mdmon (8), | |
2874 | .IR mdadm.conf (5), | |
2875 | .IR md (4). | |
2876 | .PP | |
2877 | .IR raidtab (5), | |
2878 | .IR raid0run (8), | |
2879 | .IR raidstop (8), | |
2880 | .IR mkraid (8). |