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52826846 | 1 | .\" -*- nroff -*- |
90fc992e NB |
2 | ''' Copyright Neil Brown and others. |
3 | ''' This program is free software; you can redistribute it and/or modify | |
4 | ''' it under the terms of the GNU General Public License as published by | |
5 | ''' the Free Software Foundation; either version 2 of the License, or | |
6 | ''' (at your option) any later version. | |
7 | ''' See file COPYING in distribution for details. | |
9255bbc8 | 8 | .TH MDADM 8 "" v2.5.6 |
52826846 | 9 | .SH NAME |
9a9dab36 | 10 | mdadm \- manage MD devices |
cd29a5c8 NB |
11 | .I aka |
12 | Linux Software Raid. | |
13 | ||
52826846 NB |
14 | .SH SYNOPSIS |
15 | ||
e0d19036 | 16 | .BI mdadm " [mode] <raiddevice> [options] <component-devices>" |
52826846 | 17 | |
2ae555c3 | 18 | .SH DESCRIPTION |
52826846 | 19 | RAID devices are virtual devices created from two or more |
cd29a5c8 NB |
20 | real block devices. This allows multiple devices (typically disk |
21 | drives or partitions there-of) to be combined into a single device to | |
22 | hold (for example) a single filesystem. | |
2d465520 | 23 | Some RAID levels include redundancy and so can survive some degree of |
cd29a5c8 NB |
24 | device failure. |
25 | ||
2d465520 NB |
26 | Linux Software RAID devices are implemented through the md (Multiple |
27 | Devices) device driver. | |
cd29a5c8 NB |
28 | |
29 | Currently, Linux supports | |
30 | .B LINEAR | |
31 | md devices, | |
32 | .B RAID0 | |
33 | (striping), | |
34 | .B RAID1 | |
35 | (mirroring), | |
d013a55e NB |
36 | .BR RAID4 , |
37 | .BR RAID5 , | |
98c6faba | 38 | .BR RAID6 , |
1a7dfc35 | 39 | .BR RAID10 , |
b5e64645 | 40 | .BR MULTIPATH , |
cd29a5c8 | 41 | and |
b5e64645 | 42 | .BR FAULTY . |
d013a55e | 43 | |
a9d69660 NB |
44 | .B MULTIPATH |
45 | is not a Software RAID mechanism, but does involve | |
d013a55e NB |
46 | multiple devices. For |
47 | .B MULTIPATH | |
48 | each device is a path to one common physical storage device. | |
49 | ||
a9d69660 NB |
50 | .B FAULTY |
51 | is also not true RAID, and it only involves one device. It | |
b5e64645 | 52 | provides a layer over a true device that can be used to inject faults. |
52826846 | 53 | |
a9d69660 NB |
54 | '''.B mdadm |
55 | '''is a program that can be used to create, manage, and monitor | |
56 | '''MD devices. As | |
57 | '''such it provides a similar set of functionality to the | |
58 | '''.B raidtools | |
59 | '''packages. | |
60 | '''The key differences between | |
61 | '''.B mdadm | |
62 | '''and | |
63 | '''.B raidtools | |
64 | '''are: | |
65 | '''.IP \(bu 4 | |
66 | '''.B mdadm | |
67 | '''is a single program and not a collection of programs. | |
68 | '''.IP \(bu 4 | |
69 | '''.B mdadm | |
70 | '''can perform (almost) all of its functions without having a | |
71 | '''configuration file and does not use one by default. Also | |
72 | '''.B mdadm | |
73 | '''helps with management of the configuration | |
74 | '''file. | |
75 | '''.IP \(bu 4 | |
76 | '''.B mdadm | |
77 | '''can provide information about your arrays (through Query, Detail, and Examine) | |
78 | '''that | |
79 | '''.B raidtools | |
80 | '''cannot. | |
81 | '''.P | |
82 | '''.I mdadm | |
83 | '''does not use | |
84 | '''.IR /etc/raidtab , | |
85 | '''the | |
86 | '''.B raidtools | |
87 | '''configuration file, at all. It has a different configuration file | |
98b24a2a | 88 | '''with a different format and a different purpose. |
52826846 NB |
89 | |
90 | .SH MODES | |
8382f19b | 91 | mdadm has several major modes of operation: |
cd29a5c8 NB |
92 | .TP |
93 | .B Assemble | |
94 | Assemble the parts of a previously created | |
52826846 | 95 | array into an active array. Components can be explicitly given |
2ae555c3 | 96 | or can be searched for. |
9a9dab36 | 97 | .B mdadm |
cd29a5c8 NB |
98 | checks that the components |
99 | do form a bona fide array, and can, on request, fiddle superblock | |
100 | information so as to assemble a faulty array. | |
101 | ||
102 | .TP | |
103 | .B Build | |
a9d69660 NB |
104 | Build an array that doesn't have per-device superblocks. For these |
105 | sorts of arrays, | |
106 | .I mdadm | |
107 | cannot differentiate between initial creation and subsequent assembly | |
108 | of an array. It also cannot perform any checks that appropriate | |
109 | devices have been requested. Because of this, the | |
110 | .B Build | |
111 | mode should only be used together with a complete understanding of | |
112 | what you are doing. | |
cd29a5c8 NB |
113 | |
114 | .TP | |
115 | .B Create | |
116 | Create a new array with per-device superblocks. | |
117 | '''It can progress | |
118 | '''in several step create-add-add-run or it can all happen with one command. | |
119 | ||
cd29a5c8 NB |
120 | .TP |
121 | .B "Follow or Monitor" | |
5787fa49 | 122 | Monitor one or more md devices and act on any state changes. This is |
1a7dfc35 | 123 | only meaningful for raid1, 4, 5, 6, 10 or multipath arrays as |
98c6faba NB |
124 | only these have interesting state. raid0 or linear never have |
125 | missing, spare, or failed drives, so there is nothing to monitor. | |
5787fa49 | 126 | |
dd0781e5 NB |
127 | .TP |
128 | .B "Grow" | |
129 | Grow (or shrink) an array, or otherwise reshape it in some way. | |
130 | Currently supported growth options including changing the active size | |
2ae555c3 | 131 | of component devices in RAID level 1/4/5/6 and changing the number of |
dd0781e5 | 132 | active devices in RAID1. |
cd29a5c8 | 133 | |
8382f19b NB |
134 | .TP |
135 | .B "Incremental Assembly" | |
136 | Add a single device to an appropriate array. If the addition of the | |
137 | device makes the array runnable, the array will be started. | |
138 | This provides a convenient interface to a | |
139 | .I hot-plug | |
140 | system. As each device is detected, | |
141 | .I mdadm | |
142 | has a chance to include it in some array as appropriate. | |
143 | ||
2ae555c3 NB |
144 | .TP |
145 | .B Manage | |
146 | This is for doing things to specific components of an array such as | |
147 | adding new spares and removing faulty devices. | |
148 | ||
149 | .TP | |
150 | .B Misc | |
151 | This is an 'everything else' mode that supports operations on active | |
152 | arrays, operations on component devices such as erasing old superblocks, and | |
153 | information gathering operations. | |
154 | '''This mode allows operations on independent devices such as examine MD | |
155 | '''superblocks, erasing old superblocks and stopping active arrays. | |
156 | ||
52826846 NB |
157 | .SH OPTIONS |
158 | ||
2ae555c3 | 159 | .SH Options for selecting a mode are: |
52826846 | 160 | |
cd29a5c8 NB |
161 | .TP |
162 | .BR -A ", " --assemble | |
2d465520 | 163 | Assemble a pre-existing array. |
52826846 | 164 | |
cd29a5c8 NB |
165 | .TP |
166 | .BR -B ", " --build | |
167 | Build a legacy array without superblocks. | |
52826846 | 168 | |
cd29a5c8 NB |
169 | .TP |
170 | .BR -C ", " --create | |
171 | Create a new array. | |
52826846 | 172 | |
cd29a5c8 NB |
173 | .TP |
174 | .BR -F ", " --follow ", " --monitor | |
175 | Select | |
176 | .B Monitor | |
177 | mode. | |
52826846 | 178 | |
dd0781e5 NB |
179 | .TP |
180 | .BR -G ", " --grow | |
181 | Change the size or shape of an active array. | |
8382f19b NB |
182 | |
183 | .TP | |
184 | .BE -I ", " --incremental | |
185 | Add a single device into an appropriate array, and possibly start the array. | |
186 | ||
2ae555c3 NB |
187 | .P |
188 | If a device is given before any options, or if the first option is | |
189 | .BR --add , | |
190 | .BR --fail , | |
191 | or | |
192 | .BR --remove , | |
193 | then the MANAGE mode is assume. | |
194 | Anything other than these will cause the | |
195 | .B Misc | |
196 | mode to be assumed. | |
dd0781e5 | 197 | |
2ae555c3 | 198 | .SH Options that are not mode-specific are: |
e793c2e5 | 199 | |
cd29a5c8 NB |
200 | .TP |
201 | .BR -h ", " --help | |
a9d69660 NB |
202 | Display general help message or, after one of the above options, a |
203 | mode specific help message. | |
56eedc1a NB |
204 | |
205 | .TP | |
206 | .B --help-options | |
207 | Display more detailed help about command line parsing and some commonly | |
208 | used options. | |
52826846 | 209 | |
cd29a5c8 NB |
210 | .TP |
211 | .BR -V ", " --version | |
9a9dab36 | 212 | Print version information for mdadm. |
52826846 | 213 | |
cd29a5c8 NB |
214 | .TP |
215 | .BR -v ", " --verbose | |
22892d56 NB |
216 | Be more verbose about what is happening. This can be used twice to be |
217 | extra-verbose. | |
a9d69660 | 218 | The extra verbosity currently only affects |
22892d56 NB |
219 | .B --detail --scan |
220 | and | |
221 | .BR "--examine --scan" . | |
52826846 | 222 | |
dab6685f NB |
223 | .TP |
224 | .BR -q ", " --quiet | |
225 | Avoid printing purely informative messages. With this, | |
226 | .B mdadm | |
227 | will be silent unless there is something really important to report. | |
228 | ||
cd29a5c8 NB |
229 | .TP |
230 | .BR -b ", " --brief | |
231 | Be less verbose. This is used with | |
232 | .B --detail | |
233 | and | |
234 | .BR --examine . | |
22892d56 NB |
235 | Using |
236 | .B --brief | |
237 | with | |
238 | .B --verbose | |
239 | gives an intermediate level of verbosity. | |
52826846 | 240 | |
e0d19036 NB |
241 | .TP |
242 | .BR -f ", " --force | |
243 | Be more forceful about certain operations. See the various modes of | |
244 | the exact meaning of this option in different contexts. | |
245 | ||
246 | .TP | |
247 | .BR -c ", " --config= | |
2ae555c3 NB |
248 | Specify the config file. Default is to use |
249 | .BR /etc/mdadm.conf , | |
250 | or if that is missing, then | |
251 | .BR /etc/mdadm/mdadm.conf . | |
5787fa49 NB |
252 | If the config file given is |
253 | .B partitions | |
254 | then nothing will be read, but | |
255 | .I mdadm | |
256 | will act as though the config file contained exactly | |
257 | .B "DEVICE partitions" | |
258 | and will read | |
259 | .B /proc/partitions | |
260 | to find a list of devices to scan. | |
d013a55e NB |
261 | If the word |
262 | .B none | |
263 | is given for the config file, then | |
264 | .I mdadm | |
265 | will act as though the config file were empty. | |
e0d19036 NB |
266 | |
267 | .TP | |
268 | .BR -s ", " --scan | |
269 | scan config file or | |
270 | .B /proc/mdstat | |
271 | for missing information. | |
272 | In general, this option gives | |
273 | .B mdadm | |
274 | permission to get any missing information, like component devices, | |
275 | array devices, array identities, and alert destination from the | |
276 | configuration file: | |
277 | .BR /etc/mdadm.conf . | |
278 | One exception is MISC mode when using | |
279 | .B --detail | |
280 | or | |
281 | .B --stop | |
282 | in which case | |
283 | .B --scan | |
284 | says to get a list of array devices from | |
285 | .BR /proc/mdstat . | |
286 | ||
570c0542 NB |
287 | .TP |
288 | .B -e ", " --metadata= | |
289 | Declare the style of superblock (raid metadata) to be used. The | |
290 | default is 0.90 for --create, and to guess for other operations. | |
2790ffe3 GB |
291 | The default can be overridden by setting the |
292 | .B metadata | |
293 | value for the | |
294 | .B CREATE | |
295 | keyword in | |
296 | .BR mdadm.conf . | |
570c0542 NB |
297 | |
298 | Options are: | |
299 | .RS | |
300 | .IP "0, 0.90, default" | |
301 | Use the original 0.90 format superblock. This format limits arrays to | |
302 | 28 componenet devices and limits component devices of levels 1 and | |
303 | greater to 2 terabytes. | |
304 | .IP "1, 1.0, 1.1, 1.2" | |
305 | Use the new version-1 format superblock. This has few restrictions. | |
306 | The different subversion store the superblock at different locations | |
307 | on the device, either at the end (for 1.0), at the start (for 1.1) or | |
308 | 4K from the start (for 1.2). | |
309 | .RE | |
310 | ||
41a3b72a NB |
311 | .TP |
312 | .B --homehost= | |
313 | This will over-ride any | |
314 | .B HOMEHOST | |
315 | setting in the config file and provides the identify of the host which | |
316 | should be considered the home for any arrays. | |
317 | ||
318 | When creating an array, the | |
319 | .B homehost | |
320 | will be recorded in the superblock. For version-1 superblocks, it will | |
321 | be prefixed to the array name. For version-0.90 superblocks part of | |
322 | the SHA1 hash of the hostname will be stored in the later half of the | |
323 | UUID. | |
324 | ||
325 | When reporting information about an array, any array which is tagged | |
326 | for the given homehost will be reported as such. | |
327 | ||
328 | When using Auto-Assemble, only arrays tagged for the given homehost | |
329 | will be assembled. | |
330 | ||
2ae555c3 NB |
331 | .SH For create, build, or grow: |
332 | ||
333 | .TP | |
334 | .BR -n ", " --raid-devices= | |
335 | Specify the number of active devices in the array. This, plus the | |
336 | number of spare devices (see below) must equal the number of | |
337 | .I component-devices | |
338 | (including "\fBmissing\fP" devices) | |
339 | that are listed on the command line for | |
340 | .BR --create . | |
341 | Setting a value of 1 is probably | |
342 | a mistake and so requires that | |
343 | .B --force | |
344 | be specified first. A value of 1 will then be allowed for linear, | |
345 | multipath, raid0 and raid1. It is never allowed for raid4 or raid5. | |
346 | .br | |
347 | This number can only be changed using | |
348 | .B --grow | |
349 | for RAID1 arrays, and only on kernels which provide necessary support. | |
350 | ||
351 | .TP | |
352 | .BR -x ", " --spare-devices= | |
353 | Specify the number of spare (eXtra) devices in the initial array. | |
354 | Spares can also be added | |
355 | and removed later. The number of component devices listed | |
356 | on the command line must equal the number of raid devices plus the | |
357 | number of spare devices. | |
358 | ||
359 | ||
360 | .TP | |
361 | .BR -z ", " --size= | |
362 | Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6. | |
363 | This must be a multiple of the chunk size, and must leave about 128Kb | |
364 | of space at the end of the drive for the RAID superblock. | |
365 | If this is not specified | |
366 | (as it normally is not) the smallest drive (or partition) sets the | |
367 | size, though if there is a variance among the drives of greater than 1%, a warning is | |
368 | issued. | |
369 | ||
370 | This value can be set with | |
371 | .B --grow | |
372 | for RAID level 1/4/5/6. If the array was created with a size smaller | |
373 | than the currently active drives, the extra space can be accessed | |
374 | using | |
375 | .BR --grow . | |
376 | The size can be given as | |
377 | .B max | |
378 | which means to choose the largest size that fits on all current drives. | |
52826846 | 379 | |
cd29a5c8 NB |
380 | .TP |
381 | .BR -c ", " --chunk= | |
382 | Specify chunk size of kibibytes. The default is 64. | |
52826846 | 383 | |
cd29a5c8 NB |
384 | .TP |
385 | .BR --rounding= | |
386 | Specify rounding factor for linear array (==chunk size) | |
52826846 | 387 | |
cd29a5c8 NB |
388 | .TP |
389 | .BR -l ", " --level= | |
aa88f531 NB |
390 | Set raid level. When used with |
391 | .IR --create , | |
98c6faba | 392 | options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4, |
2ae555c3 | 393 | raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty. Obviously some of these are synonymous. |
aa88f531 NB |
394 | |
395 | When used with | |
396 | .IR --build , | |
a9d69660 | 397 | only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid. |
52826846 | 398 | |
2ae555c3 NB |
399 | Not yet supported with |
400 | .IR --grow . | |
401 | ||
cd29a5c8 | 402 | .TP |
1a7dfc35 NB |
403 | .BR -p ", " --layout= |
404 | This option configures the fine details of data layout for raid5, | |
405 | and raid10 arrays, and controls the failure modes for | |
406 | .IR faulty . | |
407 | ||
408 | The layout of the raid5 parity block can be one of | |
2d465520 NB |
409 | left-asymmetric, |
410 | left-symmetric, | |
411 | right-asymmetric, | |
412 | right-symmetric, | |
413 | la, ra, ls, rs. The default is left-symmetric. | |
52826846 | 414 | |
1a7dfc35 NB |
415 | When setting the failure mode for |
416 | .I faulty | |
417 | the options are: | |
b5e64645 NB |
418 | write-transient, |
419 | wt, | |
420 | read-transient, | |
421 | rt, | |
2ae555c3 | 422 | write-persistent, |
b5e64645 NB |
423 | wp, |
424 | read-persistent, | |
425 | rp, | |
426 | write-all, | |
427 | read-fixable, | |
428 | rf, | |
429 | clear, | |
430 | flush, | |
431 | none. | |
432 | ||
433 | Each mode can be followed by a number which is used as a period | |
434 | between fault generation. Without a number, the fault is generated | |
435 | once on the first relevant request. With a number, the fault will be | |
436 | generated after that many request, and will continue to be generated | |
437 | every time the period elapses. | |
438 | ||
439 | Multiple failure modes can be current simultaneously by using the | |
440 | "--grow" option to set subsequent failure modes. | |
441 | ||
442 | "clear" or "none" will remove any pending or periodic failure modes, | |
2ae555c3 | 443 | and "flush" will clear any persistent faults. |
b5e64645 NB |
444 | |
445 | To set the parity with "--grow", the level of the array ("faulty") | |
446 | must be specified before the fault mode is specified. | |
447 | ||
b578481c | 448 | Finally, the layout options for RAID10 are one of 'n', 'o' or 'p' followed |
1a7dfc35 NB |
449 | by a small number. The default is 'n2'. |
450 | ||
451 | .I n | |
b578481c NB |
452 | signals 'near' copies. Multiple copies of one data block are at |
453 | similar offsets in different devices. | |
454 | ||
455 | .I o | |
456 | signals 'offset' copies. Rather than the chunks being duplicated | |
457 | within a stripe, whole stripes are duplicated but are rotated by one | |
458 | device so duplicate blocks are on different devices. Thus subsequent | |
459 | copies of a block are in the next drive, and are one chunk further | |
460 | down. | |
461 | ||
1a7dfc35 NB |
462 | .I f |
463 | signals 'far' copies | |
464 | (multiple copies have very different offsets). See md(4) for more | |
465 | detail about 'near' and 'far'. | |
466 | ||
467 | The number is the number of copies of each datablock. 2 is normal, 3 | |
468 | can be useful. This number can be at most equal to the number of | |
469 | devices in the array. It does not need to divide evenly into that | |
470 | number (e.g. it is perfectly legal to have an 'n2' layout for an array | |
471 | with an odd number of devices). | |
472 | ||
cd29a5c8 | 473 | .TP |
1a7dfc35 NB |
474 | .BR --parity= |
475 | same as --layout (thus explaining the p of | |
476 | .IR -p ). | |
52826846 | 477 | |
e793c2e5 NB |
478 | .TP |
479 | .BR -b ", " --bitmap= | |
480 | Specify a file to store a write-intent bitmap in. The file should not | |
481 | exist unless --force is also given. The same file should be provided | |
2ae555c3 NB |
482 | when assembling the array. If the word |
483 | .B internal | |
484 | is given, then the bitmap is stored with the metadata on the array, | |
485 | and so is replicated on all devices. If the word | |
486 | .B none | |
487 | is given with | |
488 | .B --grow | |
489 | mode, then any bitmap that is present is removed. | |
e793c2e5 | 490 | |
2ae555c3 NB |
491 | To help catch typing errors, the filename must contain at least one |
492 | slash ('/') if it is a real file (not 'internal' or 'none'). | |
493 | ||
494 | Note: external bitmaps are only known to work on ext2 and ext3. | |
495 | Storing bitmap files on other filesystems may result in serious problems. | |
e793c2e5 | 496 | |
cd29a5c8 | 497 | .TP |
2ae555c3 NB |
498 | .BR --bitmap-chunk= |
499 | Set the chunksize of the bitmap. Each bit corresponds to that many | |
1bfdbe01 NB |
500 | Kilobytes of storage. |
501 | When using a file based bitmap, the default is to use the smallest | |
502 | size that is atleast 4 and requires no more than 2^21 chunks. | |
2ae555c3 NB |
503 | When using an |
504 | .B internal | |
505 | bitmap, the chunksize is automatically determined to make best use of | |
506 | available space. | |
5787fa49 | 507 | |
cd29a5c8 NB |
508 | |
509 | .TP | |
2ae555c3 NB |
510 | .BR -W ", " --write-mostly |
511 | subsequent devices lists in a | |
512 | .BR --build , | |
513 | .BR --create , | |
514 | or | |
515 | .B --add | |
516 | command will be flagged as 'write-mostly'. This is valid for RAID1 | |
517 | only and means that the 'md' driver will avoid reading from these | |
518 | devices if at all possible. This can be useful if mirroring over a | |
519 | slow link. | |
52826846 | 520 | |
2ae555c3 NB |
521 | .TP |
522 | .BR --write-behind= | |
523 | Specify that write-behind mode should be enabled (valid for RAID1 | |
524 | only). If an argument is specified, it will set the maximum number | |
525 | of outstanding writes allowed. The default value is 256. | |
526 | A write-intent bitmap is required in order to use write-behind | |
527 | mode, and write-behind is only attempted on drives marked as | |
528 | .IR write-mostly . | |
dd0781e5 NB |
529 | |
530 | .TP | |
531 | .BR --assume-clean | |
532 | Tell | |
533 | .I mdadm | |
47d79ef8 NB |
534 | that the array pre-existed and is known to be clean. It can be useful |
535 | when trying to recover from a major failure as you can be sure that no | |
536 | data will be affected unless you actually write to the array. It can | |
537 | also be used when creating a RAID1 or RAID10 if you want to avoid the | |
538 | initial resync, however this practice - while normally safe - is not | |
539 | recommended. Use this ony if you really know what you are doing. | |
dd0781e5 | 540 | |
2ae555c3 NB |
541 | .TP |
542 | .BR --backup-file= | |
543 | This is needed when --grow is used to increase the number of | |
544 | raid-devices in a RAID5 if there are no spare devices available. | |
545 | See the section below on RAID_DEVICE CHANGES. The file should be | |
546 | stored on a separate device, not on the raid array being reshaped. | |
547 | ||
947fd4dd NB |
548 | .TP |
549 | .BR -N ", " --name= | |
550 | Set a | |
551 | .B name | |
552 | for the array. This is currently only effective when creating an | |
553 | array with a version-1 superblock. The name is a simple textual | |
554 | string that can be used to identify array components when assembling. | |
555 | ||
dd0781e5 NB |
556 | .TP |
557 | .BR -R ", " --run | |
558 | Insist that | |
559 | .I mdadm | |
560 | run the array, even if some of the components | |
561 | appear to be active in another array or filesystem. Normally | |
562 | .I mdadm | |
563 | will ask for confirmation before including such components in an | |
564 | array. This option causes that question to be suppressed. | |
565 | ||
566 | .TP | |
567 | .BR -f ", " --force | |
568 | Insist that | |
569 | .I mdadm | |
570 | accept the geometry and layout specified without question. Normally | |
571 | .I mdadm | |
572 | will not allow creation of an array with only one device, and will try | |
573 | to create a raid5 array with one missing drive (as this makes the | |
574 | initial resync work faster). With | |
575 | .BR --force , | |
576 | .I mdadm | |
577 | will not try to be so clever. | |
578 | ||
579 | .TP | |
580 | .BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}" | |
48f7b27a NB |
581 | Instruct mdadm to create the device file if needed, possibly allocating |
582 | an unused minor number. "md" causes a non-partitionable array | |
dd0781e5 | 583 | to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and |
2ae555c3 | 584 | later) to be used. "yes" requires the named md device to have |
f9c25f1d | 585 | a 'standard' format, and the type and minor number will be determined |
48f7b27a NB |
586 | from this. See DEVICE NAMES below. |
587 | ||
a9d69660 | 588 | The argument can also come immediately after |
dd0781e5 NB |
589 | "-a". e.g. "-ap". |
590 | ||
75723446 NB |
591 | If --auto is not given on the command line or in the config file, then |
592 | the default will be | |
593 | .BR --auto=yes . | |
594 | ||
1337546d NB |
595 | If |
596 | .I --scan | |
597 | is also given, then any | |
598 | .I auto= | |
599 | entries in the config file will over-ride the | |
600 | .I --auto | |
601 | instruction given on the command line. | |
602 | ||
dd0781e5 NB |
603 | For partitionable arrays, |
604 | .I mdadm | |
605 | will create the device file for the whole array and for the first 4 | |
606 | partitions. A different number of partitions can be specified at the | |
607 | end of this option (e.g. | |
608 | .BR --auto=p7 ). | |
2ae555c3 | 609 | If the device name ends with a digit, the partition names add a 'p', |
48f7b27a | 610 | and a number, e.g. "/dev/home1p3". If there is no |
dd0781e5 NB |
611 | trailing digit, then the partition names just have a number added, |
612 | e.g. "/dev/scratch3". | |
613 | ||
48f7b27a NB |
614 | If the md device name is in a 'standard' format as described in DEVICE |
615 | NAMES, then it will be created, if necessary, with the appropriate | |
616 | number based on that name. If the device name is not in one of these | |
a9d69660 | 617 | formats, then a unused minor number will be allocated. The minor |
48f7b27a NB |
618 | number will be considered unused if there is no active array for that |
619 | number, and there is no entry in /dev for that number and with a | |
620 | non-standard name. | |
621 | ||
38098016 NB |
622 | .TP |
623 | .BR --symlink = no | |
624 | Normally when | |
625 | .B --auto | |
626 | causes | |
627 | .I mdadm | |
628 | to create devices in | |
629 | .B /dev/md/ | |
630 | it will also create symlinks from | |
631 | .B /dev/ | |
632 | with names starting with | |
633 | .B md | |
634 | or | |
635 | .BR md_ . | |
636 | Use | |
637 | .B --symlink=no | |
638 | to suppress this, or | |
639 | .B --symlink=yes | |
640 | to enforce this even if it is suppressing | |
641 | .IR mdadm.conf . | |
642 | ||
643 | ||
52826846 NB |
644 | .SH For assemble: |
645 | ||
cd29a5c8 NB |
646 | .TP |
647 | .BR -u ", " --uuid= | |
648 | uuid of array to assemble. Devices which don't have this uuid are | |
649 | excluded | |
650 | ||
651 | .TP | |
652 | .BR -m ", " --super-minor= | |
653 | Minor number of device that array was created for. Devices which | |
654 | don't have this minor number are excluded. If you create an array as | |
2d465520 | 655 | /dev/md1, then all superblocks will contain the minor number 1, even if |
cd29a5c8 NB |
656 | the array is later assembled as /dev/md2. |
657 | ||
d013a55e NB |
658 | Giving the literal word "dev" for |
659 | .B --super-minor | |
660 | will cause | |
661 | .I mdadm | |
662 | to use the minor number of the md device that is being assembled. | |
663 | e.g. when assembling | |
664 | .BR /dev/md0 , | |
665 | .M --super-minor=dev | |
666 | will look for super blocks with a minor number of 0. | |
667 | ||
947fd4dd NB |
668 | .TP |
669 | .BR -N ", " --name= | |
670 | Specify the name of the array to assemble. This must be the name | |
624920bb NB |
671 | that was specified when creating the array. It must either match |
672 | then name stored in the superblock exactly, or it must match | |
41a3b72a | 673 | with the current |
624920bb NB |
674 | .I homehost |
675 | is added to the start of the given name. | |
947fd4dd | 676 | |
cd29a5c8 NB |
677 | .TP |
678 | .BR -f ", " --force | |
52826846 NB |
679 | Assemble the array even if some superblocks appear out-of-date |
680 | ||
cd29a5c8 NB |
681 | .TP |
682 | .BR -R ", " --run | |
b8a8ccf9 NB |
683 | Attempt to start the array even if fewer drives were given than were |
684 | present last time the array was active. Normally if not all the | |
685 | expected drives are found and | |
cd29a5c8 NB |
686 | .B --scan |
687 | is not used, then the array will be assembled but not started. | |
688 | With | |
689 | .B --run | |
690 | an attempt will be made to start it anyway. | |
52826846 | 691 | |
b8a8ccf9 NB |
692 | .TP |
693 | .B --no-degraded | |
694 | This is the reverse of | |
695 | .B --run | |
696 | in that it inhibits the started if array unless all expected drives | |
697 | are present. This is only needed with | |
698 | .B --scan | |
699 | and can be used if you physical connections to devices are | |
700 | not as reliable as you would like. | |
701 | ||
dd0781e5 NB |
702 | .TP |
703 | .BR -a ", " "--auto{=no,yes,md,mdp,part}" | |
704 | See this option under Create and Build options. | |
705 | ||
e793c2e5 NB |
706 | .TP |
707 | .BR -b ", " --bitmap= | |
2ae555c3 NB |
708 | Specify the bitmap file that was given when the array was created. If |
709 | an array has an | |
710 | .B internal | |
711 | bitmap, there is no need to specify this when assembling the array. | |
712 | ||
713 | .TP | |
714 | .BR --backup-file= | |
715 | If | |
716 | .B --backup-file | |
717 | was used to grow the number of raid-devices in a RAID5, and the system | |
718 | crashed during the critical section, then the same | |
719 | .B --backup-file | |
720 | must be presented to --assemble to allow possibly corrupted data to be | |
721 | restored. | |
e793c2e5 | 722 | |
5787fa49 NB |
723 | .TP |
724 | .BR -U ", " --update= | |
725 | Update the superblock on each device while assembling the array. The | |
feb716e9 NB |
726 | argument given to this flag can be one of |
727 | .BR sparc2.2 , | |
728 | .BR summaries , | |
7d99579f | 729 | .BR uuid , |
c4f12c13 | 730 | .BR name , |
0237e0ca | 731 | .BR homehost , |
e5329c37 | 732 | .BR resync , |
586ed405 | 733 | .BR byteorder , |
bee8ec56 | 734 | .BR devicesize , |
5787fa49 NB |
735 | or |
736 | .BR super-minor . | |
737 | ||
738 | The | |
739 | .B sparc2.2 | |
7d99579f | 740 | option will adjust the superblock of an array what was created on a Sparc |
5787fa49 NB |
741 | machine running a patched 2.2 Linux kernel. This kernel got the |
742 | alignment of part of the superblock wrong. You can use the | |
743 | .B "--examine --sparc2.2" | |
744 | option to | |
745 | .I mdadm | |
746 | to see what effect this would have. | |
747 | ||
748 | The | |
749 | .B super-minor | |
750 | option will update the | |
2ae555c3 | 751 | .B "preferred minor" |
5787fa49 | 752 | field on each superblock to match the minor number of the array being |
45c073c9 NB |
753 | assembled. |
754 | This can be useful if | |
755 | .B --examine | |
756 | reports a different "Preferred Minor" to | |
757 | .BR --detail . | |
758 | In some cases this update will be performed automatically | |
759 | by the kernel driver. In particular the update happens automatically | |
760 | at the first write to an array with redundancy (RAID level 1 or | |
761 | greater) on a 2.6 (or later) kernel. | |
5787fa49 | 762 | |
7d99579f NB |
763 | The |
764 | .B uuid | |
765 | option will change the uuid of the array. If a UUID is given with the | |
38dbfd8a | 766 | "--uuid" option that UUID will be used as a new UUID and will |
7d99579f NB |
767 | .B NOT |
768 | be used to help identify the devices in the array. | |
769 | If no "--uuid" is given, a random uuid is chosen. | |
770 | ||
c4f12c13 NB |
771 | The |
772 | .B name | |
773 | option will change the | |
774 | .I name | |
775 | of the array as stored in the superblock. This is only supported for | |
776 | version-1 superblocks. | |
777 | ||
0237e0ca NB |
778 | The |
779 | .B homehost | |
780 | option will change the | |
781 | .I homehost | |
782 | as recorded in the superblock. For version-0 superblocks, this is the | |
783 | same as updating the UUID. | |
784 | For version-1 superblocks, this involves updating the name. | |
785 | ||
e5329c37 NB |
786 | The |
787 | .B resync | |
788 | option will cause the array to be marked | |
789 | .I dirty | |
790 | meaning that any redundancy in the array (e.g. parity for raid5, | |
791 | copies for raid1) may be incorrect. This will cause the raid system | |
792 | to perform a "resync" pass to make sure that all redundant information | |
793 | is correct. | |
794 | ||
586ed405 NB |
795 | The |
796 | .B byteorder | |
797 | option allows arrays to be moved between machines with different | |
798 | byte-order. | |
2ae555c3 | 799 | When assembling such an array for the first time after a move, giving |
586ed405 NB |
800 | .B "--update=byteorder" |
801 | will cause | |
802 | .I mdadm | |
803 | to expect superblocks to have their byteorder reversed, and will | |
804 | correct that order before assembling the array. This is only valid | |
2ae555c3 | 805 | with original (Version 0.90) superblocks. |
586ed405 | 806 | |
feb716e9 NB |
807 | The |
808 | .B summaries | |
809 | option will correct the summaries in the superblock. That is the | |
810 | counts of total, working, active, failed, and spare devices. | |
5787fa49 | 811 | |
bee8ec56 NB |
812 | The |
813 | .B devicesize | |
814 | will rarely be of use. It applies to version 1.1 and 1.2 metadata | |
815 | only (where the metadata is at the start of the device) and is only | |
816 | useful when the component device has changed size (typically become | |
817 | larger). The version 1 metadata records the amount of the device that | |
818 | can be used to store data, so if a device in a version 1.1 or 1.2 | |
819 | array becomes larger, the metadata will still be visible, but the | |
820 | extra space will not. In this case it might be useful to assemble the | |
821 | array with | |
822 | .BR --update=devicesize . | |
823 | This will cause | |
824 | .I mdadm | |
825 | to determine the maximum usable amount of space on each device and | |
826 | update the relevant field in the metadata. | |
827 | ||
41a3b72a NB |
828 | .TP |
829 | .B --auto-update-homehost | |
830 | This flag is only meaning with auto-assembly (see discussion below). | |
831 | In that situation, if no suitable arrays are found for this homehost, | |
832 | .I mdadm | |
833 | will recan for any arrays at all and will assemble them and update the | |
834 | homehost to match the current host. | |
835 | ||
e0d19036 | 836 | .SH For Manage mode: |
52826846 | 837 | |
cd29a5c8 NB |
838 | .TP |
839 | .BR -a ", " --add | |
2ae555c3 | 840 | hot-add listed devices. |
52826846 | 841 | |
fe80f49b NB |
842 | .TP |
843 | .BR --re-add | |
2ae555c3 | 844 | re-add a device that was recently removed from an array. |
fe80f49b | 845 | |
cd29a5c8 NB |
846 | .TP |
847 | .BR -r ", " --remove | |
2d465520 | 848 | remove listed devices. They must not be active. i.e. they should |
cd29a5c8 | 849 | be failed or spare devices. |
52826846 | 850 | |
cd29a5c8 NB |
851 | .TP |
852 | .BR -f ", " --fail | |
853 | mark listed devices as faulty. | |
52826846 | 854 | |
cd29a5c8 NB |
855 | .TP |
856 | .BR --set-faulty | |
857 | same as --fail. | |
52826846 | 858 | |
2ae555c3 NB |
859 | .P |
860 | Each of these options require that the first device list is the array | |
861 | to be acted upon and the remainder are component devices to be added, | |
862 | removed, or marked as fault. Several different operations can be | |
863 | specified for different devices, e.g. | |
864 | .in +5 | |
865 | mdadm /dev/md0 --add /dev/sda1 --fail /dev/sdb1 --remove /dev/sdb1 | |
866 | .in -5 | |
867 | Each operation applies to all devices listed until the next | |
868 | operations. | |
869 | ||
870 | If an array is using a write-intent bitmap, then devices which have | |
871 | been removed can be re-added in a way that avoids a full | |
872 | reconstruction but instead just updated the blocks that have changed | |
873 | since the device was removed. For arrays with persistent metadata | |
874 | (superblocks) this is done automatically. For arrays created with | |
875 | .B --build | |
876 | mdadm needs to be told that this device we removed recently with | |
877 | .B --re-add. | |
878 | ||
879 | Devices can only be removed from an array if they are not in active | |
880 | use. i.e. that must be spares or failed devices. To remove an active | |
881 | device, it must be marked as | |
882 | .B faulty | |
883 | first. | |
884 | ||
885 | .SH For Misc mode: | |
886 | ||
887 | .TP | |
888 | .BR -Q ", " --query | |
889 | Examine a device to see | |
890 | (1) if it is an md device and (2) if it is a component of an md | |
891 | array. | |
892 | Information about what is discovered is presented. | |
893 | ||
894 | .TP | |
895 | .BR -D ", " --detail | |
896 | Print detail of one or more md devices. | |
5787fa49 | 897 | |
2ae555c3 NB |
898 | .TP |
899 | .BR -E ", " --examine | |
900 | Print content of md superblock on device(s). | |
5787fa49 NB |
901 | .TP |
902 | .B --sparc2.2 | |
a9d69660 | 903 | If an array was created on a 2.2 Linux kernel patched with RAID |
5787fa49 NB |
904 | support, the superblock will have been created incorrectly, or at |
905 | least incompatibly with 2.4 and later kernels. Using the | |
906 | .B --sparc2.2 | |
907 | flag with | |
908 | .B --examine | |
909 | will fix the superblock before displaying it. If this appears to do | |
910 | the right thing, then the array can be successfully assembled using | |
911 | .BR "--assemble --update=sparc2.2" . | |
912 | ||
2ae555c3 NB |
913 | .TP |
914 | .BR -X ", " --examine-bitmap | |
915 | Report information about a bitmap file. | |
e0d19036 | 916 | |
cd29a5c8 NB |
917 | .TP |
918 | .BR -R ", " --run | |
919 | start a partially built array. | |
52826846 | 920 | |
cd29a5c8 NB |
921 | .TP |
922 | .BR -S ", " --stop | |
923 | deactivate array, releasing all resources. | |
52826846 | 924 | |
cd29a5c8 NB |
925 | .TP |
926 | .BR -o ", " --readonly | |
927 | mark array as readonly. | |
52826846 | 928 | |
cd29a5c8 NB |
929 | .TP |
930 | .BR -w ", " --readwrite | |
931 | mark array as readwrite. | |
52826846 | 932 | |
e0d19036 NB |
933 | .TP |
934 | .B --zero-superblock | |
935 | If the device contains a valid md superblock, the block is | |
936 | over-written with zeros. With | |
937 | --force | |
938 | the block where the superblock would be is over-written even if it | |
939 | doesn't appear to be valid. | |
52826846 | 940 | |
feb716e9 NB |
941 | .TP |
942 | .BR -t ", " --test | |
943 | When used with | |
944 | .BR --detail , | |
945 | the exit status of | |
946 | .I mdadm | |
947 | is set to reflect the status of the device. | |
948 | ||
b90c0e9a NB |
949 | .TP |
950 | .BR -W ", " --wait | |
951 | For each md device given, wait for any resync, recovery, or reshape | |
952 | activity to finish before returning. | |
953 | .I mdadm | |
954 | will return with success if it actually waited for every device | |
955 | listed, otherwise it will return failure. | |
956 | ||
8382f19b NB |
957 | .SH For Incremental Assembly mode: |
958 | .TP | |
959 | .BR --rebuild-map ", " -r | |
960 | Rebuild the map file | |
961 | .RB ( /var/run/mdadm/map ) | |
962 | that | |
963 | .I mdadm | |
964 | uses to help track which arrays are currently being assembled. | |
965 | ||
966 | .TP | |
967 | .BR --run ", " -R | |
968 | Run any array assembled as soon as a minimal number of devices are | |
969 | available, rather than waiting until all expected devices are present. | |
970 | ||
971 | .TP | |
972 | .BR --scan ", " -s | |
973 | Only meaningful with | |
974 | .B -R | |
975 | this will scan the | |
976 | .B map | |
977 | file for arrays that are being incrementally assembled and will try to | |
978 | start any that are not already started. If any such array is listed | |
979 | in | |
980 | .B mdadm.conf | |
981 | as requiring an external bitmap, that bitmap will be attached first. | |
982 | ||
e0d19036 NB |
983 | .SH For Monitor mode: |
984 | .TP | |
985 | .BR -m ", " --mail | |
986 | Give a mail address to send alerts to. | |
987 | ||
988 | .TP | |
989 | .BR -p ", " --program ", " --alert | |
990 | Give a program to be run whenever an event is detected. | |
991 | ||
773135f5 NB |
992 | .TP |
993 | .BR -y ", " --syslog | |
994 | Cause all events to be reported through 'syslog'. The messages have | |
995 | facility of 'daemon' and varying priorities. | |
996 | ||
e0d19036 NB |
997 | .TP |
998 | .BR -d ", " --delay | |
999 | Give a delay in seconds. | |
1000 | .B mdadm | |
1001 | polls the md arrays and then waits this many seconds before polling | |
1002 | again. The default is 60 seconds. | |
1003 | ||
d013a55e NB |
1004 | .TP |
1005 | .BR -f ", " --daemonise | |
1006 | Tell | |
1007 | .B mdadm | |
1008 | to run as a background daemon if it decides to monitor anything. This | |
1009 | causes it to fork and run in the child, and to disconnect form the | |
1010 | terminal. The process id of the child is written to stdout. | |
1011 | This is useful with | |
1012 | .B --scan | |
1013 | which will only continue monitoring if a mail address or alert program | |
1014 | is found in the config file. | |
1015 | ||
b5e64645 NB |
1016 | .TP |
1017 | .BR -i ", " --pid-file | |
1018 | When | |
1019 | .B mdadm | |
1020 | is running in daemon mode, write the pid of the daemon process to | |
1021 | the specified file, instead of printing it on standard output. | |
1022 | ||
aa88f531 NB |
1023 | .TP |
1024 | .BR -1 ", " --oneshot | |
1025 | Check arrays only once. This will generate | |
1026 | .B NewArray | |
1027 | events and more significantly | |
1028 | .B DegradedArray | |
a9d69660 NB |
1029 | and |
1030 | .B SparesMissing | |
aa88f531 NB |
1031 | events. Running |
1032 | .in +5 | |
1033 | .B " mdadm --monitor --scan -1" | |
1034 | .in -5 | |
1035 | from a cron script will ensure regular notification of any degraded arrays. | |
1036 | ||
98c6faba NB |
1037 | .TP |
1038 | .BR -t ", " --test | |
1039 | Generate a | |
1040 | .B TestMessage | |
1041 | alert for every array found at startup. This alert gets mailed and | |
1042 | passed to the alert program. This can be used for testing that alert | |
a9d69660 | 1043 | message do get through successfully. |
98c6faba | 1044 | |
e0d19036 | 1045 | .SH ASSEMBLE MODE |
52826846 | 1046 | |
cd29a5c8 NB |
1047 | .HP 12 |
1048 | Usage: | |
9a9dab36 | 1049 | .B mdadm --assemble |
5787fa49 NB |
1050 | .I md-device options-and-component-devices... |
1051 | .HP 12 | |
1052 | Usage: | |
1053 | .B mdadm --assemble --scan | |
1054 | .I md-devices-and-options... | |
cd29a5c8 NB |
1055 | .HP 12 |
1056 | Usage: | |
9a9dab36 | 1057 | .B mdadm --assemble --scan |
cd29a5c8 | 1058 | .I options... |
52826846 | 1059 | |
cd29a5c8 | 1060 | .PP |
52826846 | 1061 | This usage assembles one or more raid arrays from pre-existing components. |
9a9dab36 | 1062 | For each array, mdadm needs to know the md device, the identity of the |
e0d19036 | 1063 | array, and a number of component-devices. These can be found in a number of ways. |
52826846 | 1064 | |
5787fa49 NB |
1065 | In the first usage example (without the |
1066 | .BR --scan ) | |
1067 | the first device given is the md device. | |
1068 | In the second usage example, all devices listed are treated as md | |
1069 | devices and assembly is attempted. | |
1070 | In the third (where no devices are listed) all md devices that are | |
1071 | listed in the configuration file are assembled. | |
52826846 | 1072 | |
d013a55e NB |
1073 | If precisely one device is listed, but |
1074 | .B --scan | |
dd0781e5 | 1075 | is not given, then |
d013a55e NB |
1076 | .I mdadm |
1077 | acts as though | |
1078 | .B --scan | |
1079 | was given and identify information is extracted from the configuration file. | |
1080 | ||
2ae555c3 | 1081 | The identity can be given with the |
52826846 | 1082 | .B --uuid |
cd29a5c8 NB |
1083 | option, with the |
1084 | .B --super-minor | |
5787fa49 | 1085 | option, can be found in the config file, or will be taken from the |
e0d19036 | 1086 | super block on the first component-device listed on the command line. |
52826846 | 1087 | |
2ae555c3 | 1088 | Devices can be given on the |
52826846 | 1089 | .B --assemble |
5787fa49 NB |
1090 | command line or in the config file. Only devices which have an md |
1091 | superblock which contains the right identity will be considered for | |
1092 | any array. | |
52826846 | 1093 | |
2ae555c3 | 1094 | The config file is only used if explicitly named with |
52826846 | 1095 | .B --config |
d013a55e | 1096 | or requested with (a possibly implicit) |
2ae555c3 | 1097 | .B --scan. |
52826846 | 1098 | In the later case, |
9a9dab36 | 1099 | .B /etc/mdadm.conf |
52826846 NB |
1100 | is used. |
1101 | ||
2ae555c3 | 1102 | If |
52826846 | 1103 | .B --scan |
cd29a5c8 NB |
1104 | is not given, then the config file will only be used to find the |
1105 | identity of md arrays. | |
52826846 | 1106 | |
2d465520 | 1107 | Normally the array will be started after it is assembled. However if |
cd29a5c8 | 1108 | .B --scan |
2d465520 | 1109 | is not given and insufficient drives were listed to start a complete |
cd29a5c8 NB |
1110 | (non-degraded) array, then the array is not started (to guard against |
1111 | usage errors). To insist that the array be started in this case (as | |
1a7dfc35 | 1112 | may work for RAID1, 4, 5, 6, or 10), give the |
cd29a5c8 NB |
1113 | .B --run |
1114 | flag. | |
52826846 | 1115 | |
75723446 NB |
1116 | If the md device does not exist, then it will be created providing the |
1117 | intent is clear. i.e. the name must be in a standard form, or the | |
1118 | .I --auto | |
1119 | option must be given to clarify how and whether the device should be | |
1120 | created. | |
dd0781e5 NB |
1121 | |
1122 | This can be useful for handling partitioned devices (which don't have | |
1123 | a stable device number - it can change after a reboot) and when using | |
1124 | "udev" to manage your | |
1125 | .B /dev | |
1126 | tree (udev cannot handle md devices because of the unusual device | |
1127 | initialisation conventions). | |
1128 | ||
1129 | If the option to "auto" is "mdp" or "part" or (on the command line | |
1130 | only) "p", then mdadm will create a partitionable array, using the | |
2ae555c3 | 1131 | first free one that is not in use, and does not already have an entry |
dd0781e5 NB |
1132 | in /dev (apart from numeric /dev/md* entries). |
1133 | ||
1134 | If the option to "auto" is "yes" or "md" or (on the command line) | |
1135 | nothing, then mdadm will create a traditional, non-partitionable md | |
1136 | array. | |
1137 | ||
1138 | It is expected that the "auto" functionality will be used to create | |
1139 | device entries with meaningful names such as "/dev/md/home" or | |
1140 | "/dev/md/root", rather than names based on the numerical array number. | |
1141 | ||
1142 | When using this option to create a partitionable array, the device | |
1143 | files for the first 4 partitions are also created. If a different | |
1144 | number is required it can be simply appended to the auto option. | |
1145 | e.g. "auto=part8". Partition names are created by appending a digit | |
a9d69660 | 1146 | string to the device name, with an intervening "p" if the device name |
dd0781e5 NB |
1147 | ends with a digit. |
1148 | ||
1149 | The | |
1150 | .B --auto | |
1151 | option is also available in Build and Create modes. As those modes do | |
1152 | not use a config file, the "auto=" config option does not apply to | |
1153 | these modes. | |
52826846 | 1154 | |
41a3b72a NB |
1155 | .SS Auto Assembly |
1156 | When | |
1157 | .B --assemble | |
1158 | is used with | |
1159 | .B --scan | |
1160 | and no devices are listed, | |
1161 | .I mdadm | |
1162 | will first attempt to assemble all the arrays listed in the config | |
1163 | file. | |
1164 | ||
1165 | If a | |
1166 | .B homehost | |
1167 | has been specified (either in the config file or on the command line), | |
1168 | .I mdadm | |
1169 | will look further for possible arrays and will try to assemble | |
1170 | anything that it finds which is tagged as belonging to the given | |
1171 | homehost. This is the only situation where | |
1172 | .I mdadm | |
1173 | will assemble arrays without being given specific device name or | |
1174 | identify information for the array. | |
1175 | ||
1176 | If | |
1177 | .I mdadm | |
1178 | finds a consistent set of devices that look like they should comprise | |
1179 | an array, and if the superblock is tagged as belonging to the given | |
1180 | home host, it will automatically choose a device name and try to | |
1181 | assemble the array. If the array uses version-0.90 metadata, then the | |
1182 | .B minor | |
1183 | number as recorded in the superblock is used to create a name in | |
1184 | .B /dev/md/ | |
1185 | so for example | |
1186 | .BR /dev/md/3 . | |
1187 | If the array uses version-1 metadata, then the | |
1188 | .B name | |
1189 | from the superblock is used to similarly create a name in | |
1190 | .BR /dev/md . | |
1191 | The name will have any 'host' prefix stripped first. | |
1192 | ||
1193 | If | |
1194 | .I mdadm | |
1195 | cannot find any array for the given host at all, and if | |
1196 | .B --auto-update-homehost | |
1197 | is given, then | |
1198 | .I mdadm | |
1199 | will search again for any array (not just an array created for this | |
1200 | host) and will assemble each assuming | |
1201 | .IR --update=homehost . | |
1202 | This will change the host tag in the superblock so that on the next run, | |
1203 | these arrays will be found without the second pass. The intention of | |
1204 | this feature is to support transitioning a set of md arrays to using | |
1205 | homehost tagging. | |
1206 | ||
1207 | The reason for requiring arrays to be tagged with the homehost for | |
1208 | auto assembly is to guard against problems that can arise when moving | |
1209 | devices from one host to another. | |
1210 | ||
cd29a5c8 | 1211 | .SH BUILD MODE |
52826846 | 1212 | |
cd29a5c8 NB |
1213 | .HP 12 |
1214 | Usage: | |
9a9dab36 | 1215 | .B mdadm --build |
cd29a5c8 NB |
1216 | .I device |
1217 | .BI --chunk= X | |
1218 | .BI --level= Y | |
b83d95f3 | 1219 | .BI --raid-devices= Z |
cd29a5c8 NB |
1220 | .I devices |
1221 | ||
1222 | .PP | |
2ae555c3 | 1223 | This usage is similar to |
cd29a5c8 | 1224 | .BR --create . |
a9d69660 | 1225 | The difference is that it creates an array without a superblock. With |
cd29a5c8 | 1226 | these arrays there is no difference between initially creating the array and |
52826846 NB |
1227 | subsequently assembling the array, except that hopefully there is useful |
1228 | data there in the second case. | |
1229 | ||
a9d69660 NB |
1230 | The level may raid0, linear, multipath, or faulty, or one of their |
1231 | synonyms. All devices must be listed and the array will be started | |
1232 | once complete. | |
cd29a5c8 NB |
1233 | |
1234 | .SH CREATE MODE | |
1235 | ||
1236 | .HP 12 | |
1237 | Usage: | |
9a9dab36 | 1238 | .B mdadm --create |
cd29a5c8 NB |
1239 | .I device |
1240 | .BI --chunk= X | |
1241 | .BI --level= Y | |
1242 | .br | |
b83d95f3 | 1243 | .BI --raid-devices= Z |
cd29a5c8 NB |
1244 | .I devices |
1245 | ||
1246 | .PP | |
1247 | This usage will initialise a new md array, associate some devices with | |
1248 | it, and activate the array. | |
1249 | ||
a9d69660 | 1250 | If the |
dd0781e5 NB |
1251 | .B --auto |
1252 | option is given (as described in more detail in the section on | |
1253 | Assemble mode), then the md device will be created with a suitable | |
1254 | device number if necessary. | |
1255 | ||
cd29a5c8 | 1256 | As devices are added, they are checked to see if they contain raid |
2d465520 | 1257 | superblocks or filesystems. They are also checked to see if the variance in |
cd29a5c8 NB |
1258 | device size exceeds 1%. |
1259 | ||
1260 | If any discrepancy is found, the array will not automatically be run, though | |
2ae555c3 | 1261 | the presence of a |
cd29a5c8 NB |
1262 | .B --run |
1263 | can override this caution. | |
1264 | ||
2d465520 | 1265 | To create a "degraded" array in which some devices are missing, simply |
d013a55e | 1266 | give the word "\fBmissing\fP" |
2d465520 NB |
1267 | in place of a device name. This will cause |
1268 | .B mdadm | |
1269 | to leave the corresponding slot in the array empty. | |
1270 | For a RAID4 or RAID5 array at most one slot can be | |
98c6faba | 1271 | "\fBmissing\fP"; for a RAID6 array at most two slots. |
2d465520 NB |
1272 | For a RAID1 array, only one real device needs to be given. All of the |
1273 | others can be | |
d013a55e | 1274 | "\fBmissing\fP". |
2d465520 | 1275 | |
feb716e9 NB |
1276 | When creating a RAID5 array, |
1277 | .B mdadm | |
1278 | will automatically create a degraded array with an extra spare drive. | |
1279 | This is because building the spare into a degraded array is in general faster than resyncing | |
1280 | the parity on a non-degraded, but not clean, array. This feature can | |
1281 | be over-ridden with the | |
b5e64645 | 1282 | .I --force |
feb716e9 NB |
1283 | option. |
1284 | ||
41a3b72a NB |
1285 | When creating an array with version-1 metadata a name for the host is |
1286 | required. | |
1287 | If this is not given with the | |
1288 | .B --name | |
1289 | option, | |
1290 | .I mdadm | |
1291 | will chose a name based on the last component of the name of the | |
1292 | device being created. So if | |
1293 | .B /dev/md3 | |
1294 | is being created, then the name | |
1295 | .B 3 | |
1296 | will be chosen. | |
1297 | If | |
1298 | .B /dev/md/home | |
1299 | is being created, then the name | |
1300 | .B home | |
1301 | will be used. | |
1302 | ||
3d3dd91e NB |
1303 | A new array will normally get a randomly assigned 128bit UUID which is |
1304 | very likely to be unique. If you have a specific need, you can choose | |
1305 | a UUID for the array by giving the | |
1306 | .B --uuid= | |
1307 | option. Be warned that creating two arrays with the same UUID is a | |
1308 | recipe for disaster. Also, using | |
1309 | .B --uuid= | |
1310 | when creating a v0.90 array will silently override any | |
1311 | .B --homehost= | |
1312 | setting. | |
2ae555c3 | 1313 | '''If the |
cd29a5c8 | 1314 | '''.B --size |
e0d19036 | 1315 | '''option is given, it is not necessary to list any component-devices in this command. |
cd29a5c8 | 1316 | '''They can be added later, before a |
2ae555c3 NB |
1317 | '''.B --run. |
1318 | '''If no | |
cd29a5c8 NB |
1319 | '''.B --size |
1320 | '''is given, the apparent size of the smallest drive given is used. | |
1321 | ||
1322 | The General Management options that are valid with --create are: | |
1323 | .TP | |
1324 | .B --run | |
dd0781e5 | 1325 | insist on running the array even if some devices look like they might |
cd29a5c8 NB |
1326 | be in use. |
1327 | ||
1328 | .TP | |
1329 | .B --readonly | |
1330 | start the array readonly - not supported yet. | |
52826846 | 1331 | |
2ae555c3 | 1332 | |
e0d19036 | 1333 | .SH MANAGE MODE |
cd29a5c8 NB |
1334 | .HP 12 |
1335 | Usage: | |
e0d19036 NB |
1336 | .B mdadm |
1337 | .I device | |
1338 | .I options... devices... | |
cd29a5c8 NB |
1339 | .PP |
1340 | ||
e0d19036 NB |
1341 | This usage will allow individual devices in an array to be failed, |
1342 | removed or added. It is possible to perform multiple operations with | |
1343 | on command. For example: | |
1344 | .br | |
5787fa49 | 1345 | .B " mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1" |
e0d19036 NB |
1346 | .br |
1347 | will firstly mark | |
1348 | .B /dev/hda1 | |
1349 | as faulty in | |
1350 | .B /dev/md0 | |
1351 | and will then remove it from the array and finally add it back | |
2d465520 | 1352 | in as a spare. However only one md array can be affected by a single |
2ae555c3 | 1353 | command. |
e0d19036 NB |
1354 | |
1355 | .SH MISC MODE | |
1356 | .HP 12 | |
1357 | Usage: | |
9a9dab36 | 1358 | .B mdadm |
e0d19036 NB |
1359 | .I options ... |
1360 | .I devices ... | |
1361 | .PP | |
cd29a5c8 | 1362 | |
b5e64645 | 1363 | MISC mode includes a number of distinct operations that |
e0d19036 NB |
1364 | operate on distinct devices. The operations are: |
1365 | .TP | |
1366 | --query | |
1367 | The device is examined to see if it is | |
1368 | (1) an active md array, or | |
1369 | (2) a component of an md array. | |
1370 | The information discovered is reported. | |
1371 | ||
1372 | .TP | |
1373 | --detail | |
2d465520 NB |
1374 | The device should be an active md device. |
1375 | .B mdadm | |
1376 | will display a detailed description of the array. | |
cd29a5c8 | 1377 | .B --brief |
2d465520 NB |
1378 | or |
1379 | .B --scan | |
1380 | will cause the output to be less detailed and the format to be | |
e0d19036 | 1381 | suitable for inclusion in |
9a9dab36 | 1382 | .BR /etc/mdadm.conf . |
feb716e9 NB |
1383 | The exit status of |
1384 | .I mdadm | |
1385 | will normally be 0 unless | |
1386 | .I mdadm | |
1387 | failed to get useful information about the device(s). However if the | |
1388 | .B --test | |
1389 | option is given, then the exit status will be: | |
1390 | .RS | |
1391 | .TP | |
1392 | 0 | |
1393 | The array is functioning normally. | |
1394 | .TP | |
1395 | 1 | |
1396 | The array has at least one failed device. | |
1397 | .TP | |
1398 | 2 | |
1399 | The array has multiple failed devices and hence is unusable (raid4 or | |
1400 | raid5). | |
1401 | .TP | |
1402 | 4 | |
1403 | There was an error while trying to get information about the device. | |
1404 | .RE | |
cd29a5c8 | 1405 | |
e0d19036 NB |
1406 | .TP |
1407 | --examine | |
2d465520 NB |
1408 | The device should be a component of an md array. |
1409 | .B mdadm | |
1410 | will read the md superblock of the device and display the contents. | |
e0d19036 NB |
1411 | If |
1412 | .B --brief | |
1413 | is given, or | |
1414 | .B --scan | |
1415 | then multiple devices that are components of the one array | |
1416 | are grouped together and reported in a single entry suitable | |
1417 | for inclusion in | |
1418 | .BR /etc/mdadm.conf . | |
1419 | ||
2d465520 | 1420 | Having |
e0d19036 NB |
1421 | .B --scan |
1422 | without listing any devices will cause all devices listed in the | |
1423 | config file to be examined. | |
1424 | ||
1425 | .TP | |
1426 | --stop | |
98c6faba NB |
1427 | The devices should be active md arrays which will be deactivated, as |
1428 | long as they are not currently in use. | |
e0d19036 NB |
1429 | |
1430 | .TP | |
1431 | --run | |
1432 | This will fully activate a partially assembled md array. | |
1433 | ||
1434 | .TP | |
1435 | --readonly | |
1436 | This will mark an active array as read-only, providing that it is | |
1437 | not currently being used. | |
1438 | ||
1439 | .TP | |
1440 | --readwrite | |
1441 | This will change a | |
1442 | .B readonly | |
1443 | array back to being read/write. | |
1444 | ||
2d465520 NB |
1445 | .TP |
1446 | --scan | |
1447 | For all operations except | |
1448 | .BR --examine , | |
1449 | .B --scan | |
1450 | will cause the operation to be applied to all arrays listed in | |
1451 | .BR /proc/mdstat . | |
1452 | For | |
1453 | .BR --examine, | |
1454 | .B --scan | |
1455 | causes all devices listed in the config file to be examined. | |
1456 | ||
1457 | ||
e0d19036 NB |
1458 | .SH MONITOR MODE |
1459 | ||
cd29a5c8 NB |
1460 | .HP 12 |
1461 | Usage: | |
e0d19036 NB |
1462 | .B mdadm --monitor |
1463 | .I options... devices... | |
1464 | ||
cd29a5c8 | 1465 | .PP |
e0d19036 NB |
1466 | This usage causes |
1467 | .B mdadm | |
1468 | to periodically poll a number of md arrays and to report on any events | |
1469 | noticed. | |
1470 | .B mdadm | |
1471 | will never exit once it decides that there are arrays to be checked, | |
1472 | so it should normally be run in the background. | |
1473 | ||
2d465520 NB |
1474 | As well as reporting events, |
1475 | .B mdadm | |
1476 | may move a spare drive from one array to another if they are in the | |
1477 | same | |
1478 | .B spare-group | |
a9d69660 | 1479 | and if the destination array has a failed drive but no spares. |
2d465520 | 1480 | |
e0d19036 NB |
1481 | If any devices are listed on the command line, |
1482 | .B mdadm | |
1483 | will only monitor those devices. Otherwise all arrays listed in the | |
1484 | configuration file will be monitored. Further, if | |
1485 | .B --scan | |
1486 | is given, then any other md devices that appear in | |
1487 | .B /proc/mdstat | |
1488 | will also be monitored. | |
1489 | ||
1490 | The result of monitoring the arrays is the generation of events. | |
bd526cee | 1491 | These events are passed to a separate program (if specified) and may |
2d465520 | 1492 | be mailed to a given E-mail address. |
e0d19036 | 1493 | |
bd526cee | 1494 | When passing event to program, the program is run once for each event |
2ae555c3 | 1495 | and is given 2 or 3 command-line arguments. The first is the |
bd526cee NB |
1496 | name of the event (see below). The second is the name of the |
1497 | md device which is affected, and the third is the name of a related | |
1498 | device if relevant, such as a component device that has failed. | |
cd29a5c8 NB |
1499 | |
1500 | If | |
1501 | .B --scan | |
e0d19036 NB |
1502 | is given, then a program or an E-mail address must be specified on the |
1503 | command line or in the config file. If neither are available, then | |
1504 | .B mdadm | |
1505 | will not monitor anything. | |
1506 | Without | |
cd29a5c8 | 1507 | .B --scan |
e0d19036 | 1508 | .B mdadm |
2d465520 | 1509 | will continue monitoring as long as something was found to monitor. If |
e0d19036 NB |
1510 | no program or email is given, then each event is reported to |
1511 | .BR stdout . | |
cd29a5c8 | 1512 | |
e0d19036 NB |
1513 | The different events are: |
1514 | ||
1515 | .RS 4 | |
1516 | .TP | |
1517 | .B DeviceDisappeared | |
2d465520 | 1518 | An md array which previously was configured appears to no longer be |
773135f5 | 1519 | configured. (syslog priority: Critical) |
e0d19036 | 1520 | |
b8f72a62 NB |
1521 | If |
1522 | .I mdadm | |
1523 | was told to monitor an array which is RAID0 or Linear, then it will | |
1524 | report | |
1525 | .B DeviceDisappeared | |
1526 | with the extra information | |
1527 | .BR Wrong-Level . | |
1528 | This is because RAID0 and Linear do not support the device-failed, | |
1529 | hot-spare and resync operations which are monitored. | |
1530 | ||
e0d19036 NB |
1531 | .TP |
1532 | .B RebuildStarted | |
773135f5 | 1533 | An md array started reconstruction. (syslog priority: Warning) |
e0d19036 NB |
1534 | |
1535 | .TP | |
1536 | .BI Rebuild NN | |
1537 | Where | |
1538 | .I NN | |
1539 | is 20, 40, 60, or 80, this indicates that rebuild has passed that many | |
773135f5 | 1540 | percentage of the total. (syslog priority: Warning) |
e0d19036 | 1541 | |
98c6faba NB |
1542 | .TP |
1543 | .B RebuildFinished | |
1544 | An md array that was rebuilding, isn't any more, either because it | |
773135f5 | 1545 | finished normally or was aborted. (syslog priority: Warning) |
98c6faba | 1546 | |
e0d19036 NB |
1547 | .TP |
1548 | .B Fail | |
773135f5 NB |
1549 | An active component device of an array has been marked as |
1550 | faulty. (syslog priority: Critical) | |
e0d19036 NB |
1551 | |
1552 | .TP | |
1553 | .B FailSpare | |
1554 | A spare component device which was being rebuilt to replace a faulty | |
773135f5 | 1555 | device has failed. (syslog priority: Critial) |
e0d19036 NB |
1556 | |
1557 | .TP | |
1558 | .B SpareActive | |
1559 | A spare component device which was being rebuilt to replace a faulty | |
98b24a2a | 1560 | device has been successfully rebuilt and has been made active. |
773135f5 | 1561 | (syslog priority: Info) |
e0d19036 NB |
1562 | |
1563 | .TP | |
1564 | .B NewArray | |
1565 | A new md array has been detected in the | |
1566 | .B /proc/mdstat | |
773135f5 | 1567 | file. (syslog priority: Info) |
e0d19036 | 1568 | |
aa88f531 NB |
1569 | .TP |
1570 | .B DegradedArray | |
1571 | A newly noticed array appears to be degraded. This message is not | |
1572 | generated when | |
1573 | .I mdadm | |
1574 | notices a drive failure which causes degradation, but only when | |
1575 | .I mdadm | |
1576 | notices that an array is degraded when it first sees the array. | |
773135f5 | 1577 | (syslog priority: Critial) |
aa88f531 | 1578 | |
e0d19036 NB |
1579 | .TP |
1580 | .B MoveSpare | |
1581 | A spare drive has been moved from one array in a | |
1582 | .B spare-group | |
1583 | to another to allow a failed drive to be replaced. | |
773135f5 | 1584 | (syslog priority: Info) |
e0d19036 | 1585 | |
b8f72a62 NB |
1586 | .TP |
1587 | .B SparesMissing | |
1588 | If | |
1589 | .I mdadm | |
1590 | has been told, via the config file, that an array should have a certain | |
1591 | number of spare devices, and | |
1592 | .I mdadm | |
1593 | detects that it has fewer that this number when it first sees the | |
1594 | array, it will report a | |
1595 | .B SparesMissing | |
1596 | message. | |
d1732eeb | 1597 | (syslog priority: Warning) |
b8f72a62 | 1598 | |
98c6faba NB |
1599 | .TP |
1600 | .B TestMessage | |
1601 | An array was found at startup, and the | |
1602 | .B --test | |
1603 | flag was given. | |
773135f5 | 1604 | (syslog priority: Info) |
e0d19036 NB |
1605 | .RE |
1606 | ||
1607 | Only | |
98c6faba NB |
1608 | .B Fail , |
1609 | .B FailSpare , | |
1610 | .B DegradedArray , | |
d1732eeb | 1611 | .B SparesMissing , |
e0d19036 | 1612 | and |
98c6faba | 1613 | .B TestMessage |
e0d19036 NB |
1614 | cause Email to be sent. All events cause the program to be run. |
1615 | The program is run with two or three arguments, they being the event | |
1616 | name, the array device and possibly a second device. | |
1617 | ||
1618 | Each event has an associated array device (e.g. | |
1619 | .BR /dev/md1 ) | |
1620 | and possibly a second device. For | |
1621 | .BR Fail , | |
1622 | .BR FailSpare , | |
1623 | and | |
1624 | .B SpareActive | |
1625 | the second device is the relevant component device. | |
1626 | For | |
1627 | .B MoveSpare | |
1628 | the second device is the array that the spare was moved from. | |
1629 | ||
1630 | For | |
1631 | .B mdadm | |
1632 | to move spares from one array to another, the different arrays need to | |
1633 | be labelled with the same | |
1634 | .B spare-group | |
1635 | in the configuration file. The | |
1636 | .B spare-group | |
1637 | name can be any string. It is only necessary that different spare | |
2d465520 | 1638 | groups use different names. |
e0d19036 NB |
1639 | |
1640 | When | |
9a9dab36 | 1641 | .B mdadm |
e0d19036 NB |
1642 | detects that an array which is in a spare group has fewer active |
1643 | devices than necessary for the complete array, and has no spare | |
1644 | devices, it will look for another array in the same spare group that | |
1645 | has a full complement of working drive and a spare. It will then | |
1646 | attempt to remove the spare from the second drive and add it to the | |
1647 | first. | |
1648 | If the removal succeeds but the adding fails, then it is added back to | |
1649 | the original array. | |
1650 | ||
dd0781e5 NB |
1651 | .SH GROW MODE |
1652 | The GROW mode is used for changing the size or shape of an active | |
1653 | array. | |
1654 | For this to work, the kernel must support the necessary change. | |
2ae555c3 | 1655 | Various types of growth are being added during 2.6 development, |
dd0781e5 NB |
1656 | including restructuring a raid5 array to have more active devices. |
1657 | ||
dfd4d8ee NB |
1658 | Currently the only support available is to |
1659 | .IP \(bu 4 | |
1660 | change the "size" attribute | |
1661 | for RAID1, RAID5 and RAID6. | |
1662 | .IP \(bu 4 | |
2ae555c3 | 1663 | increase the "raid-disks" attribute of RAID1 and RAID5. |
dfd4d8ee | 1664 | .IP \(bu 4 |
2ae555c3 NB |
1665 | add a write-intent bitmap to any array which support these bitmaps, or |
1666 | remove a write-intent bitmap from such an array. | |
dfd4d8ee | 1667 | .PP |
dd0781e5 | 1668 | |
2ae555c3 | 1669 | .SS SIZE CHANGES |
fe80f49b | 1670 | Normally when an array is built the "size" it taken from the smallest |
dd0781e5 NB |
1671 | of the drives. If all the small drives in an arrays are, one at a |
1672 | time, removed and replaced with larger drives, then you could have an | |
1673 | array of large drives with only a small amount used. In this | |
1674 | situation, changing the "size" with "GROW" mode will allow the extra | |
1675 | space to start being used. If the size is increased in this way, a | |
1676 | "resync" process will start to make sure the new parts of the array | |
1677 | are synchronised. | |
1678 | ||
1679 | Note that when an array changes size, any filesystem that may be | |
1680 | stored in the array will not automatically grow to use the space. The | |
1681 | filesystem will need to be explicitly told to use the extra space. | |
1682 | ||
2ae555c3 NB |
1683 | .SS RAID-DEVICES CHANGES |
1684 | ||
dd0781e5 NB |
1685 | A RAID1 array can work with any number of devices from 1 upwards |
1686 | (though 1 is not very useful). There may be times which you want to | |
1687 | increase or decrease the number of active devices. Note that this is | |
1688 | different to hot-add or hot-remove which changes the number of | |
1689 | inactive devices. | |
1690 | ||
1691 | When reducing the number of devices in a RAID1 array, the slots which | |
1692 | are to be removed from the array must already be vacant. That is, the | |
1693 | devices that which were in those slots must be failed and removed. | |
1694 | ||
1695 | When the number of devices is increased, any hot spares that are | |
a9d69660 | 1696 | present will be activated immediately. |
dd0781e5 | 1697 | |
2ae555c3 NB |
1698 | Increasing the number of active devices in a RAID5 is much more |
1699 | effort. Every block in the array will need to be read and written | |
1700 | back to a new location. From 2.6.17, the Linux Kernel is able to do | |
1701 | this safely, including restart and interrupted "reshape". | |
1702 | ||
1703 | When relocating the first few stripes on a raid5, it is not possible | |
1704 | to keep the data on disk completely consistent and crash-proof. To | |
1705 | provide the required safety, mdadm disables writes to the array while | |
1706 | this "critical section" is reshaped, and takes a backup of the data | |
1707 | that is in that section. This backup is normally stored in any spare | |
1708 | devices that the array has, however it can also be stored in a | |
1709 | separate file specified with the | |
1710 | .B --backup-file | |
1711 | option. If this option is used, and the system does crash during the | |
1712 | critical period, the same file must be passed to | |
1713 | .B --assemble | |
1714 | to restore the backup and reassemble the array. | |
1715 | ||
1716 | .SS BITMAP CHANGES | |
1717 | ||
1718 | A write-intent bitmap can be added to, or removed from, an active | |
1719 | array. Either internal bitmaps, or bitmaps stored in a separate file | |
fe80f49b NB |
1720 | can be added. Note that if you add a bitmap stored in a file which is |
1721 | in a filesystem that is on the raid array being affected, the system | |
1722 | will deadlock. The bitmap must be on a separate filesystem. | |
1723 | ||
8382f19b NB |
1724 | .SH INCREMENTAL MODE |
1725 | ||
1726 | .HP 12 | |
1727 | Usage: | |
1728 | .B mdadm --incremental | |
1729 | .RB [ --run ] | |
1730 | .RB [ --quiet ] | |
1731 | .I component-device | |
1732 | .HP 12 | |
1733 | Usage: | |
1734 | .B mdadm --incremental --rebuild | |
1735 | .HP 12 | |
1736 | Usage: | |
1737 | .B mdadm --incremental --run --scan | |
1738 | ||
1739 | ||
1740 | .PP | |
1741 | This mode is designed to be used in conjunction with a device | |
1742 | discovery system. As devices are found in a system, they can be | |
1743 | passed to | |
1744 | .B "mdadm --incremental" | |
1745 | to be conditionally added to an appropriate array. | |
1746 | ||
1747 | .I mdadm | |
1748 | performs a number of tests to determine if the device is part of an | |
1749 | array, and which array is should be part of. If an appropriate array | |
1750 | is found, or can be created, | |
1751 | .I mdadm | |
1752 | adds the device to the array and conditionally starts the array. | |
1753 | ||
1754 | Note that | |
1755 | .I mdadm | |
1756 | will only add devices to an array which were previously working | |
1757 | (active or spare) parts of that array. It does not currently support | |
1758 | automatic inclusion of a new drive as a spare in some array. | |
1759 | ||
1760 | .B "mdadm --incremental" | |
1761 | requires a bug present in all kernels through 2.6.19, to be fixed. | |
1762 | Hopefully this will be fixed in 2.6.20. Alternately apply the patch | |
1763 | which is included with the mdadm source distribution. If | |
1764 | .I mdadm | |
1765 | detects that this bug is present, it will abort any attempt to use | |
1766 | .BR --incremental . | |
1767 | ||
1768 | The tests that | |
1769 | .I mdadm | |
1770 | makes are as follow: | |
1771 | .IP + | |
1772 | Is the device permitted by | |
1773 | .BR mdadm.conf ? | |
1774 | That is, is it listed in a | |
1775 | .B DEVICES | |
1776 | line in that file. If | |
1777 | .B DEVICES | |
1778 | is absent then the default it to allow any device. Similar if | |
1779 | .B DEVICES | |
1780 | contains the special word | |
1781 | .B partitions | |
1782 | then any device is allowed. Otherwise the device name given to | |
1783 | .I mdadm | |
1784 | must match one of the names or patterns in a | |
1785 | .B DEVICES | |
1786 | line. | |
1787 | ||
1788 | .IP + | |
1789 | Does the device have a valid md superblock. If a specific metadata | |
1790 | version is request with | |
1791 | .B --metadata | |
1792 | or | |
1793 | .B -e | |
1794 | then only that style of metadata is accepted, otherwise | |
1795 | .I mdadm | |
1796 | finds any known version of metadata. If no | |
1797 | .I md | |
1798 | metadata is found, the device is rejected. | |
1799 | ||
1800 | .IP + | |
1801 | Does the metadata match an expected array? | |
1802 | The metadata can match in two ways. Either there is an array listed | |
1803 | in | |
1804 | .B mdadm.conf | |
1805 | which identifies the array (either by UUID, by name, by device list, | |
1806 | or by minor-number), the array was created with a | |
1807 | .B homehost | |
1808 | specified, and that | |
1809 | .B homehost | |
1810 | matches that which is given in | |
1811 | .B mdadm.conf | |
1812 | or on the command line. | |
1813 | If | |
1814 | .I mdadm | |
1815 | is not able to positively identify the array as belonging to the | |
1816 | current host, the device will be rejected. | |
1817 | ||
1818 | .IP + | |
1819 | .I mdadm | |
1820 | keeps a list of arrays that is has partly assembled in | |
1821 | .B /var/run/mdadm/map | |
1822 | (or | |
1823 | .B /var/run/mdadm.map | |
1824 | if the directory doesn't exist). If no array exists which matches | |
1825 | the metadata on the new device, | |
1826 | .I mdadm | |
1827 | must choose a device name and unit number. It does this based on any | |
1828 | name given in | |
1829 | .B mdadm.conf | |
1830 | or any name information stored in the metadata. If this name | |
1831 | suggests a unit number, that number will be used, otherwise a free | |
1832 | unit number will be chosen. Normally | |
1833 | .I mdadm | |
1834 | will prefer to create a partitionable array, however if the | |
1835 | .B CREATE | |
1836 | line in | |
1837 | .B mdadm.conf | |
1838 | suggests that a non-partitionable array is preferred, that will be | |
1839 | honoured. | |
1840 | ||
1841 | .IP + | |
1842 | Once an appropriate array is found or created and the device is added, | |
1843 | .I mdadm | |
1844 | must decide if the array is ready to be started. It will | |
1845 | normally compare the number of available (non-spare) devices to the | |
1846 | number of devices that the metadata suggests need to be active. If | |
1847 | there are at least that many, the array will be started. This means | |
1848 | that if any devices are missing the array will not be restarted. | |
1849 | ||
1850 | As an alternative, | |
1851 | .B --run | |
1852 | may be passed to | |
1853 | .B mdadm | |
1854 | in which case the array will be run as soon as there are enough | |
1855 | devices present for the data to be accessible. For a raid1, that | |
1856 | means one device will start the array. For a clean raid5, the array | |
1857 | will be started as soon as all but one drive is present. | |
1858 | ||
1859 | Note that neither of these approaches is really ideal. If it is can | |
1860 | be known that all device discovery has completed, then | |
1861 | .br | |
1862 | .B " mdadm -IRs" | |
1863 | .br | |
1864 | can be run which will try to start all arrays that are being | |
1865 | incrementally assembled. They are started in "read-auto" mode in | |
1866 | which they are read-only until the first write request. This means | |
1867 | that no metadata updates are made and no attempt at resync or recovery | |
1868 | happens. Further devices that are found before the first write can | |
1869 | still be added safely. | |
1870 | ||
2d465520 NB |
1871 | .SH EXAMPLES |
1872 | ||
5787fa49 | 1873 | .B " mdadm --query /dev/name-of-device" |
2d465520 | 1874 | .br |
5787fa49 NB |
1875 | This will find out if a given device is a raid array, or is part of |
1876 | one, and will provide brief information about the device. | |
2d465520 | 1877 | |
5787fa49 | 1878 | .B " mdadm --assemble --scan" |
2d465520 | 1879 | .br |
2ae555c3 | 1880 | This will assemble and start all arrays listed in the standard config file |
5787fa49 | 1881 | file. This command will typically go in a system startup file. |
2d465520 | 1882 | |
2d465520 | 1883 | .B " mdadm --stop --scan" |
5787fa49 NB |
1884 | .br |
1885 | This will shut down all array that can be shut down (i.e. are not | |
19f8b8fc | 1886 | currently in use). This will typically go in a system shutdown script. |
2d465520 | 1887 | |
5787fa49 | 1888 | .B " mdadm --follow --scan --delay=120" |
2d465520 | 1889 | .br |
5787fa49 NB |
1890 | If (and only if) there is an Email address or program given in the |
1891 | standard config file, then | |
1892 | monitor the status of all arrays listed in that file by | |
1893 | polling them ever 2 minutes. | |
2d465520 | 1894 | |
5787fa49 | 1895 | .B " mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[ac]1" |
2d465520 | 1896 | .br |
5787fa49 | 1897 | Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1. |
2d465520 | 1898 | |
2d465520 NB |
1899 | .br |
1900 | .B " echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > mdadm.conf" | |
1901 | .br | |
1902 | .B " mdadm --detail --scan >> mdadm.conf" | |
1903 | .br | |
5787fa49 NB |
1904 | This will create a prototype config file that describes currently |
1905 | active arrays that are known to be made from partitions of IDE or SCSI drives. | |
2d465520 NB |
1906 | This file should be reviewed before being used as it may |
1907 | contain unwanted detail. | |
1908 | ||
2d465520 NB |
1909 | .B " echo 'DEVICE /dev/hd[a-z] /dev/sd*[a-z]' > mdadm.conf" |
1910 | .br | |
5787fa49 NB |
1911 | .B " mdadm --examine --scan --config=mdadm.conf >> mdadm.conf" |
1912 | .ber | |
2ae555c3 | 1913 | This will find what arrays could be assembled from existing IDE and |
5787fa49 NB |
1914 | SCSI whole drives (not partitions) and store the information is the |
1915 | format of a config file. | |
2d465520 NB |
1916 | This file is very likely to contain unwanted detail, particularly |
1917 | the | |
1918 | .B devices= | |
5787fa49 NB |
1919 | entries. It should be reviewed and edited before being used as an |
1920 | actual config file. | |
2d465520 | 1921 | |
5787fa49 | 1922 | .B " mdadm --examine --brief --scan --config=partitions" |
2d465520 | 1923 | .br |
5787fa49 NB |
1924 | .B " mdadm -Ebsc partitions" |
1925 | .br | |
1926 | Create a list of devices by reading | |
1927 | .BR /proc/partitions , | |
1928 | scan these for RAID superblocks, and printout a brief listing of all | |
1929 | that was found. | |
2d465520 | 1930 | |
5787fa49 | 1931 | .B " mdadm -Ac partitions -m 0 /dev/md0" |
2d465520 | 1932 | .br |
5787fa49 NB |
1933 | Scan all partitions and devices listed in |
1934 | .BR /proc/partitions | |
1935 | and assemble | |
1936 | .B /dev/md0 | |
1937 | out of all such devices with a RAID superblock with a minor number of 0. | |
2d465520 | 1938 | |
d013a55e NB |
1939 | .B " mdadm --monitor --scan --daemonise > /var/run/mdadm" |
1940 | .br | |
1941 | If config file contains a mail address or alert program, run mdadm in | |
1942 | the background in monitor mode monitoring all md devices. Also write | |
1943 | pid of mdadm daemon to | |
1944 | .BR /var/run/mdadm . | |
1945 | ||
8382f19b NB |
1946 | .B " mdadm -Iq /dev/somedevice" |
1947 | .br | |
1948 | Try to incorporate newly discovered device into some array as | |
1949 | appropriate. | |
1950 | ||
1951 | .B " mdadm --incremental --rebuild --run --scan" | |
1952 | .br | |
1953 | Rebuild the array map from any current arrays, and then start any that | |
1954 | can be started. | |
1955 | ||
5787fa49 | 1956 | .B " mdadm --create --help" |
2d465520 | 1957 | .br |
2ae555c3 | 1958 | Provide help about the Create mode. |
2d465520 | 1959 | |
5787fa49 NB |
1960 | .B " mdadm --config --help" |
1961 | .br | |
1962 | Provide help about the format of the config file. | |
2d465520 | 1963 | |
5787fa49 NB |
1964 | .B " mdadm --help" |
1965 | .br | |
1966 | Provide general help. | |
cd29a5c8 | 1967 | |
cd29a5c8 NB |
1968 | |
1969 | .SH FILES | |
1970 | ||
1971 | .SS /proc/mdstat | |
1972 | ||
2ae555c3 NB |
1973 | If you're using the |
1974 | .B /proc | |
cd29a5c8 NB |
1975 | filesystem, |
1976 | .B /proc/mdstat | |
2d465520 NB |
1977 | lists all active md devices with information about them. |
1978 | .B mdadm | |
1979 | uses this to find arrays when | |
1980 | .B --scan | |
1981 | is given in Misc mode, and to monitor array reconstruction | |
1982 | on Monitor mode. | |
1983 | ||
cd29a5c8 | 1984 | |
9a9dab36 | 1985 | .SS /etc/mdadm.conf |
cd29a5c8 | 1986 | |
11a3e71d NB |
1987 | The config file lists which devices may be scanned to see if |
1988 | they contain MD super block, and gives identifying information | |
1989 | (e.g. UUID) about known MD arrays. See | |
1990 | .BR mdadm.conf (5) | |
1991 | for more details. | |
cd29a5c8 | 1992 | |
8382f19b NB |
1993 | .SS /var/run/mdadm/map |
1994 | When | |
1995 | .I --incremental | |
1996 | mode is used. this file gets a list of arrays currently being created. | |
1997 | If | |
1998 | .B /var/run/mdadm | |
1999 | does not exist as a directory, then | |
2000 | .B /var/run/mdadm.map | |
2001 | is used instead. | |
2002 | ||
48f7b27a NB |
2003 | .SH DEVICE NAMES |
2004 | ||
2005 | While entries in the /dev directory can have any format you like, | |
2006 | .I mdadm | |
2007 | has an understanding of 'standard' formats which it uses to guide its | |
2008 | behaviour when creating device files via the | |
2009 | .I --auto | |
2010 | option. | |
2011 | ||
2012 | The standard names for non-partitioned arrays (the only sort of md | |
2013 | array available in 2.4 and earlier) either of | |
2014 | .IP | |
2015 | /dev/mdNN | |
2016 | .br | |
2017 | /dev/md/NN | |
2018 | .PP | |
2019 | where NN is a number. | |
2020 | The standard names for partitionable arrays (as available from 2.6 | |
2021 | onwards) is one of | |
2022 | .IP | |
2023 | /dev/md/dNN | |
2024 | .br | |
2025 | /dev/md_dNN | |
2026 | .PP | |
2027 | Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2". | |
52826846 | 2028 | |
2d465520 NB |
2029 | .SH NOTE |
2030 | .B mdadm | |
2031 | was previously known as | |
2032 | .BR mdctl . | |
a9d69660 NB |
2033 | .P |
2034 | .B mdadm | |
2035 | is completely separate from the | |
2036 | .B raidtools | |
2037 | package, and does not use the | |
2038 | .I /etc/raidtab | |
2039 | configuration file at all. | |
2040 | ||
52826846 | 2041 | .SH SEE ALSO |
cd29a5c8 NB |
2042 | For information on the various levels of |
2043 | RAID, check out: | |
2044 | ||
2045 | .IP | |
2046 | .UR http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/ | |
2047 | http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/ | |
2048 | .UE | |
a9d69660 NB |
2049 | '''.PP |
2050 | '''for new releases of the RAID driver check out: | |
2051 | ''' | |
2052 | '''.IP | |
2053 | '''.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2054 | '''ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
2055 | '''.UE | |
2056 | '''.PP | |
2057 | '''or | |
2058 | '''.IP | |
2059 | '''.UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2060 | '''http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
2061 | '''.UE | |
cd29a5c8 | 2062 | .PP |
2ae555c3 | 2063 | The latest version of |
a9d69660 NB |
2064 | .I mdadm |
2065 | should always be available from | |
cd29a5c8 | 2066 | .IP |
a9d69660 NB |
2067 | .UR http://www.kernel.org/pub/linux/utils/raid/mdadm/ |
2068 | http://www.kernel.org/pub/linux/utils/raid/mdadm/ | |
cd29a5c8 NB |
2069 | .UE |
2070 | .PP | |
a9d69660 NB |
2071 | .IR mdadm.conf (5), |
2072 | .IR md (4). | |
56eb10c0 | 2073 | .PP |
52826846 NB |
2074 | .IR raidtab (5), |
2075 | .IR raid0run (8), | |
2076 | .IR raidstop (8), | |
a9d69660 | 2077 | .IR mkraid (8). |