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52826846 | 1 | .\" -*- nroff -*- |
90d0adf4 | 2 | .TH MDADM 8 "" v2.4.1 |
52826846 | 3 | .SH NAME |
9a9dab36 | 4 | mdadm \- manage MD devices |
cd29a5c8 NB |
5 | .I aka |
6 | Linux Software Raid. | |
7 | ||
52826846 NB |
8 | .SH SYNOPSIS |
9 | ||
e0d19036 | 10 | .BI mdadm " [mode] <raiddevice> [options] <component-devices>" |
52826846 | 11 | |
2ae555c3 | 12 | .SH DESCRIPTION |
52826846 | 13 | RAID devices are virtual devices created from two or more |
cd29a5c8 NB |
14 | real block devices. This allows multiple devices (typically disk |
15 | drives or partitions there-of) to be combined into a single device to | |
16 | hold (for example) a single filesystem. | |
2d465520 | 17 | Some RAID levels include redundancy and so can survive some degree of |
cd29a5c8 NB |
18 | device failure. |
19 | ||
2d465520 NB |
20 | Linux Software RAID devices are implemented through the md (Multiple |
21 | Devices) device driver. | |
cd29a5c8 NB |
22 | |
23 | Currently, Linux supports | |
24 | .B LINEAR | |
25 | md devices, | |
26 | .B RAID0 | |
27 | (striping), | |
28 | .B RAID1 | |
29 | (mirroring), | |
d013a55e NB |
30 | .BR RAID4 , |
31 | .BR RAID5 , | |
98c6faba | 32 | .BR RAID6 , |
1a7dfc35 | 33 | .BR RAID10 , |
b5e64645 | 34 | .BR MULTIPATH , |
cd29a5c8 | 35 | and |
b5e64645 | 36 | .BR FAULTY . |
d013a55e | 37 | |
a9d69660 NB |
38 | .B MULTIPATH |
39 | is not a Software RAID mechanism, but does involve | |
d013a55e NB |
40 | multiple devices. For |
41 | .B MULTIPATH | |
42 | each device is a path to one common physical storage device. | |
43 | ||
a9d69660 NB |
44 | .B FAULTY |
45 | is also not true RAID, and it only involves one device. It | |
b5e64645 | 46 | provides a layer over a true device that can be used to inject faults. |
52826846 | 47 | |
a9d69660 NB |
48 | '''.B mdadm |
49 | '''is a program that can be used to create, manage, and monitor | |
50 | '''MD devices. As | |
51 | '''such it provides a similar set of functionality to the | |
52 | '''.B raidtools | |
53 | '''packages. | |
54 | '''The key differences between | |
55 | '''.B mdadm | |
56 | '''and | |
57 | '''.B raidtools | |
58 | '''are: | |
59 | '''.IP \(bu 4 | |
60 | '''.B mdadm | |
61 | '''is a single program and not a collection of programs. | |
62 | '''.IP \(bu 4 | |
63 | '''.B mdadm | |
64 | '''can perform (almost) all of its functions without having a | |
65 | '''configuration file and does not use one by default. Also | |
66 | '''.B mdadm | |
67 | '''helps with management of the configuration | |
68 | '''file. | |
69 | '''.IP \(bu 4 | |
70 | '''.B mdadm | |
71 | '''can provide information about your arrays (through Query, Detail, and Examine) | |
72 | '''that | |
73 | '''.B raidtools | |
74 | '''cannot. | |
75 | '''.P | |
76 | '''.I mdadm | |
77 | '''does not use | |
78 | '''.IR /etc/raidtab , | |
79 | '''the | |
80 | '''.B raidtools | |
81 | '''configuration file, at all. It has a different configuration file | |
98b24a2a | 82 | '''with a different format and a different purpose. |
52826846 NB |
83 | |
84 | .SH MODES | |
dd0781e5 | 85 | mdadm has 7 major modes of operation: |
cd29a5c8 NB |
86 | .TP |
87 | .B Assemble | |
88 | Assemble the parts of a previously created | |
52826846 | 89 | array into an active array. Components can be explicitly given |
2ae555c3 | 90 | or can be searched for. |
9a9dab36 | 91 | .B mdadm |
cd29a5c8 NB |
92 | checks that the components |
93 | do form a bona fide array, and can, on request, fiddle superblock | |
94 | information so as to assemble a faulty array. | |
95 | ||
96 | .TP | |
97 | .B Build | |
a9d69660 NB |
98 | Build an array that doesn't have per-device superblocks. For these |
99 | sorts of arrays, | |
100 | .I mdadm | |
101 | cannot differentiate between initial creation and subsequent assembly | |
102 | of an array. It also cannot perform any checks that appropriate | |
103 | devices have been requested. Because of this, the | |
104 | .B Build | |
105 | mode should only be used together with a complete understanding of | |
106 | what you are doing. | |
cd29a5c8 NB |
107 | |
108 | .TP | |
109 | .B Create | |
110 | Create a new array with per-device superblocks. | |
111 | '''It can progress | |
112 | '''in several step create-add-add-run or it can all happen with one command. | |
113 | ||
cd29a5c8 NB |
114 | .TP |
115 | .B "Follow or Monitor" | |
5787fa49 | 116 | Monitor one or more md devices and act on any state changes. This is |
1a7dfc35 | 117 | only meaningful for raid1, 4, 5, 6, 10 or multipath arrays as |
98c6faba NB |
118 | only these have interesting state. raid0 or linear never have |
119 | missing, spare, or failed drives, so there is nothing to monitor. | |
5787fa49 | 120 | |
dd0781e5 NB |
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 | |
2ae555c3 | 125 | of component devices in RAID level 1/4/5/6 and changing the number of |
dd0781e5 | 126 | active devices in RAID1. |
cd29a5c8 | 127 | |
2ae555c3 NB |
128 | .TP |
129 | .B Manage | |
130 | This is for doing things to specific components of an array such as | |
131 | adding new spares and removing faulty devices. | |
132 | ||
133 | .TP | |
134 | .B Misc | |
135 | This is an 'everything else' mode that supports operations on active | |
136 | arrays, operations on component devices such as erasing old superblocks, and | |
137 | information gathering operations. | |
138 | '''This mode allows operations on independent devices such as examine MD | |
139 | '''superblocks, erasing old superblocks and stopping active arrays. | |
140 | ||
52826846 NB |
141 | .SH OPTIONS |
142 | ||
2ae555c3 | 143 | .SH Options for selecting a mode are: |
52826846 | 144 | |
cd29a5c8 NB |
145 | .TP |
146 | .BR -A ", " --assemble | |
2d465520 | 147 | Assemble a pre-existing array. |
52826846 | 148 | |
cd29a5c8 NB |
149 | .TP |
150 | .BR -B ", " --build | |
151 | Build a legacy array without superblocks. | |
52826846 | 152 | |
cd29a5c8 NB |
153 | .TP |
154 | .BR -C ", " --create | |
155 | Create a new array. | |
52826846 | 156 | |
cd29a5c8 NB |
157 | .TP |
158 | .BR -F ", " --follow ", " --monitor | |
159 | Select | |
160 | .B Monitor | |
161 | mode. | |
52826846 | 162 | |
dd0781e5 NB |
163 | .TP |
164 | .BR -G ", " --grow | |
165 | Change the size or shape of an active array. | |
2ae555c3 NB |
166 | .P |
167 | If a device is given before any options, or if the first option is | |
168 | .BR --add , | |
169 | .BR --fail , | |
170 | or | |
171 | .BR --remove , | |
172 | then the MANAGE mode is assume. | |
173 | Anything other than these will cause the | |
174 | .B Misc | |
175 | mode to be assumed. | |
dd0781e5 | 176 | |
2ae555c3 | 177 | .SH Options that are not mode-specific are: |
e793c2e5 | 178 | |
cd29a5c8 NB |
179 | .TP |
180 | .BR -h ", " --help | |
a9d69660 NB |
181 | Display general help message or, after one of the above options, a |
182 | mode specific help message. | |
56eedc1a NB |
183 | |
184 | .TP | |
185 | .B --help-options | |
186 | Display more detailed help about command line parsing and some commonly | |
187 | used options. | |
52826846 | 188 | |
cd29a5c8 NB |
189 | .TP |
190 | .BR -V ", " --version | |
9a9dab36 | 191 | Print version information for mdadm. |
52826846 | 192 | |
cd29a5c8 NB |
193 | .TP |
194 | .BR -v ", " --verbose | |
22892d56 NB |
195 | Be more verbose about what is happening. This can be used twice to be |
196 | extra-verbose. | |
a9d69660 | 197 | The extra verbosity currently only affects |
22892d56 NB |
198 | .B --detail --scan |
199 | and | |
200 | .BR "--examine --scan" . | |
52826846 | 201 | |
dab6685f NB |
202 | .TP |
203 | .BR -q ", " --quiet | |
204 | Avoid printing purely informative messages. With this, | |
205 | .B mdadm | |
206 | will be silent unless there is something really important to report. | |
207 | ||
cd29a5c8 NB |
208 | .TP |
209 | .BR -b ", " --brief | |
210 | Be less verbose. This is used with | |
211 | .B --detail | |
212 | and | |
213 | .BR --examine . | |
22892d56 NB |
214 | Using |
215 | .B --brief | |
216 | with | |
217 | .B --verbose | |
218 | gives an intermediate level of verbosity. | |
52826846 | 219 | |
e0d19036 NB |
220 | .TP |
221 | .BR -f ", " --force | |
222 | Be more forceful about certain operations. See the various modes of | |
223 | the exact meaning of this option in different contexts. | |
224 | ||
225 | .TP | |
226 | .BR -c ", " --config= | |
2ae555c3 NB |
227 | Specify the config file. Default is to use |
228 | .BR /etc/mdadm.conf , | |
229 | or if that is missing, then | |
230 | .BR /etc/mdadm/mdadm.conf . | |
5787fa49 NB |
231 | If the config file given is |
232 | .B partitions | |
233 | then nothing will be read, but | |
234 | .I mdadm | |
235 | will act as though the config file contained exactly | |
236 | .B "DEVICE partitions" | |
237 | and will read | |
238 | .B /proc/partitions | |
239 | to find a list of devices to scan. | |
d013a55e NB |
240 | If the word |
241 | .B none | |
242 | is given for the config file, then | |
243 | .I mdadm | |
244 | will act as though the config file were empty. | |
e0d19036 NB |
245 | |
246 | .TP | |
247 | .BR -s ", " --scan | |
248 | scan config file or | |
249 | .B /proc/mdstat | |
250 | for missing information. | |
251 | In general, this option gives | |
252 | .B mdadm | |
253 | permission to get any missing information, like component devices, | |
254 | array devices, array identities, and alert destination from the | |
255 | configuration file: | |
256 | .BR /etc/mdadm.conf . | |
257 | One exception is MISC mode when using | |
258 | .B --detail | |
259 | or | |
260 | .B --stop | |
261 | in which case | |
262 | .B --scan | |
263 | says to get a list of array devices from | |
264 | .BR /proc/mdstat . | |
265 | ||
570c0542 NB |
266 | .TP |
267 | .B -e ", " --metadata= | |
268 | Declare the style of superblock (raid metadata) to be used. The | |
269 | default is 0.90 for --create, and to guess for other operations. | |
270 | ||
271 | Options are: | |
272 | .RS | |
273 | .IP "0, 0.90, default" | |
274 | Use the original 0.90 format superblock. This format limits arrays to | |
275 | 28 componenet devices and limits component devices of levels 1 and | |
276 | greater to 2 terabytes. | |
277 | .IP "1, 1.0, 1.1, 1.2" | |
278 | Use the new version-1 format superblock. This has few restrictions. | |
279 | The different subversion store the superblock at different locations | |
280 | on the device, either at the end (for 1.0), at the start (for 1.1) or | |
281 | 4K from the start (for 1.2). | |
282 | .RE | |
283 | ||
2ae555c3 NB |
284 | .SH For create, build, or grow: |
285 | ||
286 | .TP | |
287 | .BR -n ", " --raid-devices= | |
288 | Specify the number of active devices in the array. This, plus the | |
289 | number of spare devices (see below) must equal the number of | |
290 | .I component-devices | |
291 | (including "\fBmissing\fP" devices) | |
292 | that are listed on the command line for | |
293 | .BR --create . | |
294 | Setting a value of 1 is probably | |
295 | a mistake and so requires that | |
296 | .B --force | |
297 | be specified first. A value of 1 will then be allowed for linear, | |
298 | multipath, raid0 and raid1. It is never allowed for raid4 or raid5. | |
299 | .br | |
300 | This number can only be changed using | |
301 | .B --grow | |
302 | for RAID1 arrays, and only on kernels which provide necessary support. | |
303 | ||
304 | .TP | |
305 | .BR -x ", " --spare-devices= | |
306 | Specify the number of spare (eXtra) devices in the initial array. | |
307 | Spares can also be added | |
308 | and removed later. The number of component devices listed | |
309 | on the command line must equal the number of raid devices plus the | |
310 | number of spare devices. | |
311 | ||
312 | ||
313 | .TP | |
314 | .BR -z ", " --size= | |
315 | Amount (in Kibibytes) of space to use from each drive in RAID1/4/5/6. | |
316 | This must be a multiple of the chunk size, and must leave about 128Kb | |
317 | of space at the end of the drive for the RAID superblock. | |
318 | If this is not specified | |
319 | (as it normally is not) the smallest drive (or partition) sets the | |
320 | size, though if there is a variance among the drives of greater than 1%, a warning is | |
321 | issued. | |
322 | ||
323 | This value can be set with | |
324 | .B --grow | |
325 | for RAID level 1/4/5/6. If the array was created with a size smaller | |
326 | than the currently active drives, the extra space can be accessed | |
327 | using | |
328 | .BR --grow . | |
329 | The size can be given as | |
330 | .B max | |
331 | which means to choose the largest size that fits on all current drives. | |
52826846 | 332 | |
cd29a5c8 NB |
333 | .TP |
334 | .BR -c ", " --chunk= | |
335 | Specify chunk size of kibibytes. The default is 64. | |
52826846 | 336 | |
cd29a5c8 NB |
337 | .TP |
338 | .BR --rounding= | |
339 | Specify rounding factor for linear array (==chunk size) | |
52826846 | 340 | |
cd29a5c8 NB |
341 | .TP |
342 | .BR -l ", " --level= | |
aa88f531 NB |
343 | Set raid level. When used with |
344 | .IR --create , | |
98c6faba | 345 | options are: linear, raid0, 0, stripe, raid1, 1, mirror, raid4, 4, |
2ae555c3 | 346 | raid5, 5, raid6, 6, raid10, 10, multipath, mp, faulty. Obviously some of these are synonymous. |
aa88f531 NB |
347 | |
348 | When used with | |
349 | .IR --build , | |
a9d69660 | 350 | only linear, stripe, raid0, 0, raid1, multipath, mp, and faulty are valid. |
52826846 | 351 | |
2ae555c3 NB |
352 | Not yet supported with |
353 | .IR --grow . | |
354 | ||
cd29a5c8 | 355 | .TP |
1a7dfc35 NB |
356 | .BR -p ", " --layout= |
357 | This option configures the fine details of data layout for raid5, | |
358 | and raid10 arrays, and controls the failure modes for | |
359 | .IR faulty . | |
360 | ||
361 | The layout of the raid5 parity block can be one of | |
2d465520 NB |
362 | left-asymmetric, |
363 | left-symmetric, | |
364 | right-asymmetric, | |
365 | right-symmetric, | |
366 | la, ra, ls, rs. The default is left-symmetric. | |
52826846 | 367 | |
1a7dfc35 NB |
368 | When setting the failure mode for |
369 | .I faulty | |
370 | the options are: | |
b5e64645 NB |
371 | write-transient, |
372 | wt, | |
373 | read-transient, | |
374 | rt, | |
2ae555c3 | 375 | write-persistent, |
b5e64645 NB |
376 | wp, |
377 | read-persistent, | |
378 | rp, | |
379 | write-all, | |
380 | read-fixable, | |
381 | rf, | |
382 | clear, | |
383 | flush, | |
384 | none. | |
385 | ||
386 | Each mode can be followed by a number which is used as a period | |
387 | between fault generation. Without a number, the fault is generated | |
388 | once on the first relevant request. With a number, the fault will be | |
389 | generated after that many request, and will continue to be generated | |
390 | every time the period elapses. | |
391 | ||
392 | Multiple failure modes can be current simultaneously by using the | |
393 | "--grow" option to set subsequent failure modes. | |
394 | ||
395 | "clear" or "none" will remove any pending or periodic failure modes, | |
2ae555c3 | 396 | and "flush" will clear any persistent faults. |
b5e64645 NB |
397 | |
398 | To set the parity with "--grow", the level of the array ("faulty") | |
399 | must be specified before the fault mode is specified. | |
400 | ||
b578481c | 401 | Finally, the layout options for RAID10 are one of 'n', 'o' or 'p' followed |
1a7dfc35 NB |
402 | by a small number. The default is 'n2'. |
403 | ||
404 | .I n | |
b578481c NB |
405 | signals 'near' copies. Multiple copies of one data block are at |
406 | similar offsets in different devices. | |
407 | ||
408 | .I o | |
409 | signals 'offset' copies. Rather than the chunks being duplicated | |
410 | within a stripe, whole stripes are duplicated but are rotated by one | |
411 | device so duplicate blocks are on different devices. Thus subsequent | |
412 | copies of a block are in the next drive, and are one chunk further | |
413 | down. | |
414 | ||
1a7dfc35 NB |
415 | .I f |
416 | signals 'far' copies | |
417 | (multiple copies have very different offsets). See md(4) for more | |
418 | detail about 'near' and 'far'. | |
419 | ||
420 | The number is the number of copies of each datablock. 2 is normal, 3 | |
421 | can be useful. This number can be at most equal to the number of | |
422 | devices in the array. It does not need to divide evenly into that | |
423 | number (e.g. it is perfectly legal to have an 'n2' layout for an array | |
424 | with an odd number of devices). | |
425 | ||
cd29a5c8 | 426 | .TP |
1a7dfc35 NB |
427 | .BR --parity= |
428 | same as --layout (thus explaining the p of | |
429 | .IR -p ). | |
52826846 | 430 | |
e793c2e5 NB |
431 | .TP |
432 | .BR -b ", " --bitmap= | |
433 | Specify a file to store a write-intent bitmap in. The file should not | |
434 | exist unless --force is also given. The same file should be provided | |
2ae555c3 NB |
435 | when assembling the array. If the word |
436 | .B internal | |
437 | is given, then the bitmap is stored with the metadata on the array, | |
438 | and so is replicated on all devices. If the word | |
439 | .B none | |
440 | is given with | |
441 | .B --grow | |
442 | mode, then any bitmap that is present is removed. | |
e793c2e5 | 443 | |
2ae555c3 NB |
444 | To help catch typing errors, the filename must contain at least one |
445 | slash ('/') if it is a real file (not 'internal' or 'none'). | |
446 | ||
447 | Note: external bitmaps are only known to work on ext2 and ext3. | |
448 | Storing bitmap files on other filesystems may result in serious problems. | |
e793c2e5 | 449 | |
cd29a5c8 | 450 | .TP |
2ae555c3 NB |
451 | .BR --bitmap-chunk= |
452 | Set the chunksize of the bitmap. Each bit corresponds to that many | |
1bfdbe01 NB |
453 | Kilobytes of storage. |
454 | When using a file based bitmap, the default is to use the smallest | |
455 | size that is atleast 4 and requires no more than 2^21 chunks. | |
2ae555c3 NB |
456 | When using an |
457 | .B internal | |
458 | bitmap, the chunksize is automatically determined to make best use of | |
459 | available space. | |
5787fa49 | 460 | |
cd29a5c8 NB |
461 | |
462 | .TP | |
2ae555c3 NB |
463 | .BR -W ", " --write-mostly |
464 | subsequent devices lists in a | |
465 | .BR --build , | |
466 | .BR --create , | |
467 | or | |
468 | .B --add | |
469 | command will be flagged as 'write-mostly'. This is valid for RAID1 | |
470 | only and means that the 'md' driver will avoid reading from these | |
471 | devices if at all possible. This can be useful if mirroring over a | |
472 | slow link. | |
52826846 | 473 | |
2ae555c3 NB |
474 | .TP |
475 | .BR --write-behind= | |
476 | Specify that write-behind mode should be enabled (valid for RAID1 | |
477 | only). If an argument is specified, it will set the maximum number | |
478 | of outstanding writes allowed. The default value is 256. | |
479 | A write-intent bitmap is required in order to use write-behind | |
480 | mode, and write-behind is only attempted on drives marked as | |
481 | .IR write-mostly . | |
dd0781e5 NB |
482 | |
483 | .TP | |
484 | .BR --assume-clean | |
485 | Tell | |
486 | .I mdadm | |
47d79ef8 NB |
487 | that the array pre-existed and is known to be clean. It can be useful |
488 | when trying to recover from a major failure as you can be sure that no | |
489 | data will be affected unless you actually write to the array. It can | |
490 | also be used when creating a RAID1 or RAID10 if you want to avoid the | |
491 | initial resync, however this practice - while normally safe - is not | |
492 | recommended. Use this ony if you really know what you are doing. | |
dd0781e5 | 493 | |
2ae555c3 NB |
494 | .TP |
495 | .BR --backup-file= | |
496 | This is needed when --grow is used to increase the number of | |
497 | raid-devices in a RAID5 if there are no spare devices available. | |
498 | See the section below on RAID_DEVICE CHANGES. The file should be | |
499 | stored on a separate device, not on the raid array being reshaped. | |
500 | ||
947fd4dd NB |
501 | .TP |
502 | .BR -N ", " --name= | |
503 | Set a | |
504 | .B name | |
505 | for the array. This is currently only effective when creating an | |
506 | array with a version-1 superblock. The name is a simple textual | |
507 | string that can be used to identify array components when assembling. | |
508 | ||
dd0781e5 NB |
509 | .TP |
510 | .BR -R ", " --run | |
511 | Insist that | |
512 | .I mdadm | |
513 | run the array, even if some of the components | |
514 | appear to be active in another array or filesystem. Normally | |
515 | .I mdadm | |
516 | will ask for confirmation before including such components in an | |
517 | array. This option causes that question to be suppressed. | |
518 | ||
519 | .TP | |
520 | .BR -f ", " --force | |
521 | Insist that | |
522 | .I mdadm | |
523 | accept the geometry and layout specified without question. Normally | |
524 | .I mdadm | |
525 | will not allow creation of an array with only one device, and will try | |
526 | to create a raid5 array with one missing drive (as this makes the | |
527 | initial resync work faster). With | |
528 | .BR --force , | |
529 | .I mdadm | |
530 | will not try to be so clever. | |
531 | ||
532 | .TP | |
533 | .BR -a ", " "--auto{=no,yes,md,mdp,part,p}{NN}" | |
48f7b27a NB |
534 | Instruct mdadm to create the device file if needed, possibly allocating |
535 | an unused minor number. "md" causes a non-partitionable array | |
dd0781e5 | 536 | to be used. "mdp", "part" or "p" causes a partitionable array (2.6 and |
2ae555c3 | 537 | later) to be used. "yes" requires the named md device to have |
f9c25f1d | 538 | a 'standard' format, and the type and minor number will be determined |
48f7b27a NB |
539 | from this. See DEVICE NAMES below. |
540 | ||
a9d69660 | 541 | The argument can also come immediately after |
dd0781e5 NB |
542 | "-a". e.g. "-ap". |
543 | ||
1337546d NB |
544 | If |
545 | .I --scan | |
546 | is also given, then any | |
547 | .I auto= | |
548 | entries in the config file will over-ride the | |
549 | .I --auto | |
550 | instruction given on the command line. | |
551 | ||
dd0781e5 NB |
552 | For partitionable arrays, |
553 | .I mdadm | |
554 | will create the device file for the whole array and for the first 4 | |
555 | partitions. A different number of partitions can be specified at the | |
556 | end of this option (e.g. | |
557 | .BR --auto=p7 ). | |
2ae555c3 | 558 | If the device name ends with a digit, the partition names add a 'p', |
48f7b27a | 559 | and a number, e.g. "/dev/home1p3". If there is no |
dd0781e5 NB |
560 | trailing digit, then the partition names just have a number added, |
561 | e.g. "/dev/scratch3". | |
562 | ||
48f7b27a NB |
563 | If the md device name is in a 'standard' format as described in DEVICE |
564 | NAMES, then it will be created, if necessary, with the appropriate | |
565 | number based on that name. If the device name is not in one of these | |
a9d69660 | 566 | formats, then a unused minor number will be allocated. The minor |
48f7b27a NB |
567 | number will be considered unused if there is no active array for that |
568 | number, and there is no entry in /dev for that number and with a | |
569 | non-standard name. | |
570 | ||
52826846 NB |
571 | .SH For assemble: |
572 | ||
cd29a5c8 NB |
573 | .TP |
574 | .BR -u ", " --uuid= | |
575 | uuid of array to assemble. Devices which don't have this uuid are | |
576 | excluded | |
577 | ||
578 | .TP | |
579 | .BR -m ", " --super-minor= | |
580 | Minor number of device that array was created for. Devices which | |
581 | don't have this minor number are excluded. If you create an array as | |
2d465520 | 582 | /dev/md1, then all superblocks will contain the minor number 1, even if |
cd29a5c8 NB |
583 | the array is later assembled as /dev/md2. |
584 | ||
d013a55e NB |
585 | Giving the literal word "dev" for |
586 | .B --super-minor | |
587 | will cause | |
588 | .I mdadm | |
589 | to use the minor number of the md device that is being assembled. | |
590 | e.g. when assembling | |
591 | .BR /dev/md0 , | |
592 | .M --super-minor=dev | |
593 | will look for super blocks with a minor number of 0. | |
594 | ||
947fd4dd NB |
595 | .TP |
596 | .BR -N ", " --name= | |
597 | Specify the name of the array to assemble. This must be the name | |
598 | that was specified when creating the array. | |
599 | ||
cd29a5c8 NB |
600 | .TP |
601 | .BR -f ", " --force | |
52826846 NB |
602 | Assemble the array even if some superblocks appear out-of-date |
603 | ||
cd29a5c8 NB |
604 | .TP |
605 | .BR -R ", " --run | |
b8a8ccf9 NB |
606 | Attempt to start the array even if fewer drives were given than were |
607 | present last time the array was active. Normally if not all the | |
608 | expected drives are found and | |
cd29a5c8 NB |
609 | .B --scan |
610 | is not used, then the array will be assembled but not started. | |
611 | With | |
612 | .B --run | |
613 | an attempt will be made to start it anyway. | |
52826846 | 614 | |
b8a8ccf9 NB |
615 | .TP |
616 | .B --no-degraded | |
617 | This is the reverse of | |
618 | .B --run | |
619 | in that it inhibits the started if array unless all expected drives | |
620 | are present. This is only needed with | |
621 | .B --scan | |
622 | and can be used if you physical connections to devices are | |
623 | not as reliable as you would like. | |
624 | ||
dd0781e5 NB |
625 | .TP |
626 | .BR -a ", " "--auto{=no,yes,md,mdp,part}" | |
627 | See this option under Create and Build options. | |
628 | ||
e793c2e5 NB |
629 | .TP |
630 | .BR -b ", " --bitmap= | |
2ae555c3 NB |
631 | Specify the bitmap file that was given when the array was created. If |
632 | an array has an | |
633 | .B internal | |
634 | bitmap, there is no need to specify this when assembling the array. | |
635 | ||
636 | .TP | |
637 | .BR --backup-file= | |
638 | If | |
639 | .B --backup-file | |
640 | was used to grow the number of raid-devices in a RAID5, and the system | |
641 | crashed during the critical section, then the same | |
642 | .B --backup-file | |
643 | must be presented to --assemble to allow possibly corrupted data to be | |
644 | restored. | |
e793c2e5 | 645 | |
5787fa49 NB |
646 | .TP |
647 | .BR -U ", " --update= | |
648 | Update the superblock on each device while assembling the array. The | |
feb716e9 NB |
649 | argument given to this flag can be one of |
650 | .BR sparc2.2 , | |
651 | .BR summaries , | |
7d99579f | 652 | .BR uuid , |
e5329c37 | 653 | .BR resync , |
586ed405 | 654 | .BR byteorder , |
5787fa49 NB |
655 | or |
656 | .BR super-minor . | |
657 | ||
658 | The | |
659 | .B sparc2.2 | |
7d99579f | 660 | option will adjust the superblock of an array what was created on a Sparc |
5787fa49 NB |
661 | machine running a patched 2.2 Linux kernel. This kernel got the |
662 | alignment of part of the superblock wrong. You can use the | |
663 | .B "--examine --sparc2.2" | |
664 | option to | |
665 | .I mdadm | |
666 | to see what effect this would have. | |
667 | ||
668 | The | |
669 | .B super-minor | |
670 | option will update the | |
2ae555c3 | 671 | .B "preferred minor" |
5787fa49 | 672 | field on each superblock to match the minor number of the array being |
feb716e9 | 673 | assembled. This is not needed on 2.6 and later kernels as they make |
5787fa49 NB |
674 | this adjustment automatically. |
675 | ||
7d99579f NB |
676 | The |
677 | .B uuid | |
678 | option will change the uuid of the array. If a UUID is given with the | |
679 | "--uuid" option that UUID will be used as a new UUID and with | |
680 | .B NOT | |
681 | be used to help identify the devices in the array. | |
682 | If no "--uuid" is given, a random uuid is chosen. | |
683 | ||
e5329c37 NB |
684 | The |
685 | .B resync | |
686 | option will cause the array to be marked | |
687 | .I dirty | |
688 | meaning that any redundancy in the array (e.g. parity for raid5, | |
689 | copies for raid1) may be incorrect. This will cause the raid system | |
690 | to perform a "resync" pass to make sure that all redundant information | |
691 | is correct. | |
692 | ||
586ed405 NB |
693 | The |
694 | .B byteorder | |
695 | option allows arrays to be moved between machines with different | |
696 | byte-order. | |
2ae555c3 | 697 | When assembling such an array for the first time after a move, giving |
586ed405 NB |
698 | .B "--update=byteorder" |
699 | will cause | |
700 | .I mdadm | |
701 | to expect superblocks to have their byteorder reversed, and will | |
702 | correct that order before assembling the array. This is only valid | |
2ae555c3 | 703 | with original (Version 0.90) superblocks. |
586ed405 | 704 | |
feb716e9 NB |
705 | The |
706 | .B summaries | |
707 | option will correct the summaries in the superblock. That is the | |
708 | counts of total, working, active, failed, and spare devices. | |
5787fa49 | 709 | |
e0d19036 | 710 | .SH For Manage mode: |
52826846 | 711 | |
cd29a5c8 NB |
712 | .TP |
713 | .BR -a ", " --add | |
2ae555c3 | 714 | hot-add listed devices. |
52826846 | 715 | |
fe80f49b NB |
716 | .TP |
717 | .BR --re-add | |
2ae555c3 | 718 | re-add a device that was recently removed from an array. |
fe80f49b | 719 | |
cd29a5c8 NB |
720 | .TP |
721 | .BR -r ", " --remove | |
2d465520 | 722 | remove listed devices. They must not be active. i.e. they should |
cd29a5c8 | 723 | be failed or spare devices. |
52826846 | 724 | |
cd29a5c8 NB |
725 | .TP |
726 | .BR -f ", " --fail | |
727 | mark listed devices as faulty. | |
52826846 | 728 | |
cd29a5c8 NB |
729 | .TP |
730 | .BR --set-faulty | |
731 | same as --fail. | |
52826846 | 732 | |
2ae555c3 NB |
733 | .P |
734 | Each of these options require that the first device list is the array | |
735 | to be acted upon and the remainder are component devices to be added, | |
736 | removed, or marked as fault. Several different operations can be | |
737 | specified for different devices, e.g. | |
738 | .in +5 | |
739 | mdadm /dev/md0 --add /dev/sda1 --fail /dev/sdb1 --remove /dev/sdb1 | |
740 | .in -5 | |
741 | Each operation applies to all devices listed until the next | |
742 | operations. | |
743 | ||
744 | If an array is using a write-intent bitmap, then devices which have | |
745 | been removed can be re-added in a way that avoids a full | |
746 | reconstruction but instead just updated the blocks that have changed | |
747 | since the device was removed. For arrays with persistent metadata | |
748 | (superblocks) this is done automatically. For arrays created with | |
749 | .B --build | |
750 | mdadm needs to be told that this device we removed recently with | |
751 | .B --re-add. | |
752 | ||
753 | Devices can only be removed from an array if they are not in active | |
754 | use. i.e. that must be spares or failed devices. To remove an active | |
755 | device, it must be marked as | |
756 | .B faulty | |
757 | first. | |
758 | ||
759 | .SH For Misc mode: | |
760 | ||
761 | .TP | |
762 | .BR -Q ", " --query | |
763 | Examine a device to see | |
764 | (1) if it is an md device and (2) if it is a component of an md | |
765 | array. | |
766 | Information about what is discovered is presented. | |
767 | ||
768 | .TP | |
769 | .BR -D ", " --detail | |
770 | Print detail of one or more md devices. | |
5787fa49 | 771 | |
2ae555c3 NB |
772 | .TP |
773 | .BR -E ", " --examine | |
774 | Print content of md superblock on device(s). | |
5787fa49 NB |
775 | .TP |
776 | .B --sparc2.2 | |
a9d69660 | 777 | If an array was created on a 2.2 Linux kernel patched with RAID |
5787fa49 NB |
778 | support, the superblock will have been created incorrectly, or at |
779 | least incompatibly with 2.4 and later kernels. Using the | |
780 | .B --sparc2.2 | |
781 | flag with | |
782 | .B --examine | |
783 | will fix the superblock before displaying it. If this appears to do | |
784 | the right thing, then the array can be successfully assembled using | |
785 | .BR "--assemble --update=sparc2.2" . | |
786 | ||
2ae555c3 NB |
787 | .TP |
788 | .BR -X ", " --examine-bitmap | |
789 | Report information about a bitmap file. | |
e0d19036 | 790 | |
cd29a5c8 NB |
791 | .TP |
792 | .BR -R ", " --run | |
793 | start a partially built array. | |
52826846 | 794 | |
cd29a5c8 NB |
795 | .TP |
796 | .BR -S ", " --stop | |
797 | deactivate array, releasing all resources. | |
52826846 | 798 | |
cd29a5c8 NB |
799 | .TP |
800 | .BR -o ", " --readonly | |
801 | mark array as readonly. | |
52826846 | 802 | |
cd29a5c8 NB |
803 | .TP |
804 | .BR -w ", " --readwrite | |
805 | mark array as readwrite. | |
52826846 | 806 | |
e0d19036 NB |
807 | .TP |
808 | .B --zero-superblock | |
809 | If the device contains a valid md superblock, the block is | |
810 | over-written with zeros. With | |
811 | --force | |
812 | the block where the superblock would be is over-written even if it | |
813 | doesn't appear to be valid. | |
52826846 | 814 | |
feb716e9 NB |
815 | .TP |
816 | .BR -t ", " --test | |
817 | When used with | |
818 | .BR --detail , | |
819 | the exit status of | |
820 | .I mdadm | |
821 | is set to reflect the status of the device. | |
822 | ||
e0d19036 NB |
823 | .SH For Monitor mode: |
824 | .TP | |
825 | .BR -m ", " --mail | |
826 | Give a mail address to send alerts to. | |
827 | ||
828 | .TP | |
829 | .BR -p ", " --program ", " --alert | |
830 | Give a program to be run whenever an event is detected. | |
831 | ||
773135f5 NB |
832 | .TP |
833 | .BR -y ", " --syslog | |
834 | Cause all events to be reported through 'syslog'. The messages have | |
835 | facility of 'daemon' and varying priorities. | |
836 | ||
e0d19036 NB |
837 | .TP |
838 | .BR -d ", " --delay | |
839 | Give a delay in seconds. | |
840 | .B mdadm | |
841 | polls the md arrays and then waits this many seconds before polling | |
842 | again. The default is 60 seconds. | |
843 | ||
d013a55e NB |
844 | .TP |
845 | .BR -f ", " --daemonise | |
846 | Tell | |
847 | .B mdadm | |
848 | to run as a background daemon if it decides to monitor anything. This | |
849 | causes it to fork and run in the child, and to disconnect form the | |
850 | terminal. The process id of the child is written to stdout. | |
851 | This is useful with | |
852 | .B --scan | |
853 | which will only continue monitoring if a mail address or alert program | |
854 | is found in the config file. | |
855 | ||
b5e64645 NB |
856 | .TP |
857 | .BR -i ", " --pid-file | |
858 | When | |
859 | .B mdadm | |
860 | is running in daemon mode, write the pid of the daemon process to | |
861 | the specified file, instead of printing it on standard output. | |
862 | ||
aa88f531 NB |
863 | .TP |
864 | .BR -1 ", " --oneshot | |
865 | Check arrays only once. This will generate | |
866 | .B NewArray | |
867 | events and more significantly | |
868 | .B DegradedArray | |
a9d69660 NB |
869 | and |
870 | .B SparesMissing | |
aa88f531 NB |
871 | events. Running |
872 | .in +5 | |
873 | .B " mdadm --monitor --scan -1" | |
874 | .in -5 | |
875 | from a cron script will ensure regular notification of any degraded arrays. | |
876 | ||
98c6faba NB |
877 | .TP |
878 | .BR -t ", " --test | |
879 | Generate a | |
880 | .B TestMessage | |
881 | alert for every array found at startup. This alert gets mailed and | |
882 | passed to the alert program. This can be used for testing that alert | |
a9d69660 | 883 | message do get through successfully. |
98c6faba | 884 | |
e0d19036 | 885 | .SH ASSEMBLE MODE |
52826846 | 886 | |
cd29a5c8 NB |
887 | .HP 12 |
888 | Usage: | |
9a9dab36 | 889 | .B mdadm --assemble |
5787fa49 NB |
890 | .I md-device options-and-component-devices... |
891 | .HP 12 | |
892 | Usage: | |
893 | .B mdadm --assemble --scan | |
894 | .I md-devices-and-options... | |
cd29a5c8 NB |
895 | .HP 12 |
896 | Usage: | |
9a9dab36 | 897 | .B mdadm --assemble --scan |
cd29a5c8 | 898 | .I options... |
52826846 | 899 | |
cd29a5c8 | 900 | .PP |
52826846 | 901 | This usage assembles one or more raid arrays from pre-existing components. |
9a9dab36 | 902 | For each array, mdadm needs to know the md device, the identity of the |
e0d19036 | 903 | array, and a number of component-devices. These can be found in a number of ways. |
52826846 | 904 | |
5787fa49 NB |
905 | In the first usage example (without the |
906 | .BR --scan ) | |
907 | the first device given is the md device. | |
908 | In the second usage example, all devices listed are treated as md | |
909 | devices and assembly is attempted. | |
910 | In the third (where no devices are listed) all md devices that are | |
911 | listed in the configuration file are assembled. | |
52826846 | 912 | |
d013a55e NB |
913 | If precisely one device is listed, but |
914 | .B --scan | |
dd0781e5 | 915 | is not given, then |
d013a55e NB |
916 | .I mdadm |
917 | acts as though | |
918 | .B --scan | |
919 | was given and identify information is extracted from the configuration file. | |
920 | ||
2ae555c3 | 921 | The identity can be given with the |
52826846 | 922 | .B --uuid |
cd29a5c8 NB |
923 | option, with the |
924 | .B --super-minor | |
5787fa49 | 925 | option, can be found in the config file, or will be taken from the |
e0d19036 | 926 | super block on the first component-device listed on the command line. |
52826846 | 927 | |
2ae555c3 | 928 | Devices can be given on the |
52826846 | 929 | .B --assemble |
5787fa49 NB |
930 | command line or in the config file. Only devices which have an md |
931 | superblock which contains the right identity will be considered for | |
932 | any array. | |
52826846 | 933 | |
2ae555c3 | 934 | The config file is only used if explicitly named with |
52826846 | 935 | .B --config |
d013a55e | 936 | or requested with (a possibly implicit) |
2ae555c3 | 937 | .B --scan. |
52826846 | 938 | In the later case, |
9a9dab36 | 939 | .B /etc/mdadm.conf |
52826846 NB |
940 | is used. |
941 | ||
2ae555c3 | 942 | If |
52826846 | 943 | .B --scan |
cd29a5c8 NB |
944 | is not given, then the config file will only be used to find the |
945 | identity of md arrays. | |
52826846 | 946 | |
2d465520 | 947 | Normally the array will be started after it is assembled. However if |
cd29a5c8 | 948 | .B --scan |
2d465520 | 949 | is not given and insufficient drives were listed to start a complete |
cd29a5c8 NB |
950 | (non-degraded) array, then the array is not started (to guard against |
951 | usage errors). To insist that the array be started in this case (as | |
1a7dfc35 | 952 | may work for RAID1, 4, 5, 6, or 10), give the |
cd29a5c8 NB |
953 | .B --run |
954 | flag. | |
52826846 | 955 | |
dd0781e5 NB |
956 | If an |
957 | .B auto | |
958 | option is given, either on the command line (--auto) or in the | |
959 | configuration file (e.g. auto=part), then | |
960 | .I mdadm | |
961 | will create the md device if necessary or will re-create it if it | |
962 | doesn't look usable as it is. | |
963 | ||
964 | This can be useful for handling partitioned devices (which don't have | |
965 | a stable device number - it can change after a reboot) and when using | |
966 | "udev" to manage your | |
967 | .B /dev | |
968 | tree (udev cannot handle md devices because of the unusual device | |
969 | initialisation conventions). | |
970 | ||
971 | If the option to "auto" is "mdp" or "part" or (on the command line | |
972 | only) "p", then mdadm will create a partitionable array, using the | |
2ae555c3 | 973 | first free one that is not in use, and does not already have an entry |
dd0781e5 NB |
974 | in /dev (apart from numeric /dev/md* entries). |
975 | ||
976 | If the option to "auto" is "yes" or "md" or (on the command line) | |
977 | nothing, then mdadm will create a traditional, non-partitionable md | |
978 | array. | |
979 | ||
980 | It is expected that the "auto" functionality will be used to create | |
981 | device entries with meaningful names such as "/dev/md/home" or | |
982 | "/dev/md/root", rather than names based on the numerical array number. | |
983 | ||
984 | When using this option to create a partitionable array, the device | |
985 | files for the first 4 partitions are also created. If a different | |
986 | number is required it can be simply appended to the auto option. | |
987 | e.g. "auto=part8". Partition names are created by appending a digit | |
a9d69660 | 988 | string to the device name, with an intervening "p" if the device name |
dd0781e5 NB |
989 | ends with a digit. |
990 | ||
991 | The | |
992 | .B --auto | |
993 | option is also available in Build and Create modes. As those modes do | |
994 | not use a config file, the "auto=" config option does not apply to | |
995 | these modes. | |
52826846 | 996 | |
cd29a5c8 | 997 | .SH BUILD MODE |
52826846 | 998 | |
cd29a5c8 NB |
999 | .HP 12 |
1000 | Usage: | |
9a9dab36 | 1001 | .B mdadm --build |
cd29a5c8 NB |
1002 | .I device |
1003 | .BI --chunk= X | |
1004 | .BI --level= Y | |
b83d95f3 | 1005 | .BI --raid-devices= Z |
cd29a5c8 NB |
1006 | .I devices |
1007 | ||
1008 | .PP | |
2ae555c3 | 1009 | This usage is similar to |
cd29a5c8 | 1010 | .BR --create . |
a9d69660 | 1011 | The difference is that it creates an array without a superblock. With |
cd29a5c8 | 1012 | these arrays there is no difference between initially creating the array and |
52826846 NB |
1013 | subsequently assembling the array, except that hopefully there is useful |
1014 | data there in the second case. | |
1015 | ||
a9d69660 NB |
1016 | The level may raid0, linear, multipath, or faulty, or one of their |
1017 | synonyms. All devices must be listed and the array will be started | |
1018 | once complete. | |
cd29a5c8 NB |
1019 | |
1020 | .SH CREATE MODE | |
1021 | ||
1022 | .HP 12 | |
1023 | Usage: | |
9a9dab36 | 1024 | .B mdadm --create |
cd29a5c8 NB |
1025 | .I device |
1026 | .BI --chunk= X | |
1027 | .BI --level= Y | |
1028 | .br | |
b83d95f3 | 1029 | .BI --raid-devices= Z |
cd29a5c8 NB |
1030 | .I devices |
1031 | ||
1032 | .PP | |
1033 | This usage will initialise a new md array, associate some devices with | |
1034 | it, and activate the array. | |
1035 | ||
a9d69660 | 1036 | If the |
dd0781e5 NB |
1037 | .B --auto |
1038 | option is given (as described in more detail in the section on | |
1039 | Assemble mode), then the md device will be created with a suitable | |
1040 | device number if necessary. | |
1041 | ||
cd29a5c8 | 1042 | As devices are added, they are checked to see if they contain raid |
2d465520 | 1043 | superblocks or filesystems. They are also checked to see if the variance in |
cd29a5c8 NB |
1044 | device size exceeds 1%. |
1045 | ||
1046 | If any discrepancy is found, the array will not automatically be run, though | |
2ae555c3 | 1047 | the presence of a |
cd29a5c8 NB |
1048 | .B --run |
1049 | can override this caution. | |
1050 | ||
2d465520 | 1051 | To create a "degraded" array in which some devices are missing, simply |
d013a55e | 1052 | give the word "\fBmissing\fP" |
2d465520 NB |
1053 | in place of a device name. This will cause |
1054 | .B mdadm | |
1055 | to leave the corresponding slot in the array empty. | |
1056 | For a RAID4 or RAID5 array at most one slot can be | |
98c6faba | 1057 | "\fBmissing\fP"; for a RAID6 array at most two slots. |
2d465520 NB |
1058 | For a RAID1 array, only one real device needs to be given. All of the |
1059 | others can be | |
d013a55e | 1060 | "\fBmissing\fP". |
2d465520 | 1061 | |
feb716e9 NB |
1062 | When creating a RAID5 array, |
1063 | .B mdadm | |
1064 | will automatically create a degraded array with an extra spare drive. | |
1065 | This is because building the spare into a degraded array is in general faster than resyncing | |
1066 | the parity on a non-degraded, but not clean, array. This feature can | |
1067 | be over-ridden with the | |
b5e64645 | 1068 | .I --force |
feb716e9 NB |
1069 | option. |
1070 | ||
2ae555c3 | 1071 | '''If the |
cd29a5c8 | 1072 | '''.B --size |
e0d19036 | 1073 | '''option is given, it is not necessary to list any component-devices in this command. |
cd29a5c8 | 1074 | '''They can be added later, before a |
2ae555c3 NB |
1075 | '''.B --run. |
1076 | '''If no | |
cd29a5c8 NB |
1077 | '''.B --size |
1078 | '''is given, the apparent size of the smallest drive given is used. | |
1079 | ||
1080 | The General Management options that are valid with --create are: | |
1081 | .TP | |
1082 | .B --run | |
dd0781e5 | 1083 | insist on running the array even if some devices look like they might |
cd29a5c8 NB |
1084 | be in use. |
1085 | ||
1086 | .TP | |
1087 | .B --readonly | |
1088 | start the array readonly - not supported yet. | |
52826846 | 1089 | |
2ae555c3 | 1090 | |
e0d19036 | 1091 | .SH MANAGE MODE |
cd29a5c8 NB |
1092 | .HP 12 |
1093 | Usage: | |
e0d19036 NB |
1094 | .B mdadm |
1095 | .I device | |
1096 | .I options... devices... | |
cd29a5c8 NB |
1097 | .PP |
1098 | ||
e0d19036 NB |
1099 | This usage will allow individual devices in an array to be failed, |
1100 | removed or added. It is possible to perform multiple operations with | |
1101 | on command. For example: | |
1102 | .br | |
5787fa49 | 1103 | .B " mdadm /dev/md0 -f /dev/hda1 -r /dev/hda1 -a /dev/hda1" |
e0d19036 NB |
1104 | .br |
1105 | will firstly mark | |
1106 | .B /dev/hda1 | |
1107 | as faulty in | |
1108 | .B /dev/md0 | |
1109 | and will then remove it from the array and finally add it back | |
2d465520 | 1110 | in as a spare. However only one md array can be affected by a single |
2ae555c3 | 1111 | command. |
e0d19036 NB |
1112 | |
1113 | .SH MISC MODE | |
1114 | .HP 12 | |
1115 | Usage: | |
9a9dab36 | 1116 | .B mdadm |
e0d19036 NB |
1117 | .I options ... |
1118 | .I devices ... | |
1119 | .PP | |
cd29a5c8 | 1120 | |
b5e64645 | 1121 | MISC mode includes a number of distinct operations that |
e0d19036 NB |
1122 | operate on distinct devices. The operations are: |
1123 | .TP | |
1124 | --query | |
1125 | The device is examined to see if it is | |
1126 | (1) an active md array, or | |
1127 | (2) a component of an md array. | |
1128 | The information discovered is reported. | |
1129 | ||
1130 | .TP | |
1131 | --detail | |
2d465520 NB |
1132 | The device should be an active md device. |
1133 | .B mdadm | |
1134 | will display a detailed description of the array. | |
cd29a5c8 | 1135 | .B --brief |
2d465520 NB |
1136 | or |
1137 | .B --scan | |
1138 | will cause the output to be less detailed and the format to be | |
e0d19036 | 1139 | suitable for inclusion in |
9a9dab36 | 1140 | .BR /etc/mdadm.conf . |
feb716e9 NB |
1141 | The exit status of |
1142 | .I mdadm | |
1143 | will normally be 0 unless | |
1144 | .I mdadm | |
1145 | failed to get useful information about the device(s). However if the | |
1146 | .B --test | |
1147 | option is given, then the exit status will be: | |
1148 | .RS | |
1149 | .TP | |
1150 | 0 | |
1151 | The array is functioning normally. | |
1152 | .TP | |
1153 | 1 | |
1154 | The array has at least one failed device. | |
1155 | .TP | |
1156 | 2 | |
1157 | The array has multiple failed devices and hence is unusable (raid4 or | |
1158 | raid5). | |
1159 | .TP | |
1160 | 4 | |
1161 | There was an error while trying to get information about the device. | |
1162 | .RE | |
cd29a5c8 | 1163 | |
e0d19036 NB |
1164 | .TP |
1165 | --examine | |
2d465520 NB |
1166 | The device should be a component of an md array. |
1167 | .B mdadm | |
1168 | will read the md superblock of the device and display the contents. | |
e0d19036 NB |
1169 | If |
1170 | .B --brief | |
1171 | is given, or | |
1172 | .B --scan | |
1173 | then multiple devices that are components of the one array | |
1174 | are grouped together and reported in a single entry suitable | |
1175 | for inclusion in | |
1176 | .BR /etc/mdadm.conf . | |
1177 | ||
2d465520 | 1178 | Having |
e0d19036 NB |
1179 | .B --scan |
1180 | without listing any devices will cause all devices listed in the | |
1181 | config file to be examined. | |
1182 | ||
1183 | .TP | |
1184 | --stop | |
98c6faba NB |
1185 | The devices should be active md arrays which will be deactivated, as |
1186 | long as they are not currently in use. | |
e0d19036 NB |
1187 | |
1188 | .TP | |
1189 | --run | |
1190 | This will fully activate a partially assembled md array. | |
1191 | ||
1192 | .TP | |
1193 | --readonly | |
1194 | This will mark an active array as read-only, providing that it is | |
1195 | not currently being used. | |
1196 | ||
1197 | .TP | |
1198 | --readwrite | |
1199 | This will change a | |
1200 | .B readonly | |
1201 | array back to being read/write. | |
1202 | ||
2d465520 NB |
1203 | .TP |
1204 | --scan | |
1205 | For all operations except | |
1206 | .BR --examine , | |
1207 | .B --scan | |
1208 | will cause the operation to be applied to all arrays listed in | |
1209 | .BR /proc/mdstat . | |
1210 | For | |
1211 | .BR --examine, | |
1212 | .B --scan | |
1213 | causes all devices listed in the config file to be examined. | |
1214 | ||
1215 | ||
e0d19036 NB |
1216 | .SH MONITOR MODE |
1217 | ||
cd29a5c8 NB |
1218 | .HP 12 |
1219 | Usage: | |
e0d19036 NB |
1220 | .B mdadm --monitor |
1221 | .I options... devices... | |
1222 | ||
cd29a5c8 | 1223 | .PP |
e0d19036 NB |
1224 | This usage causes |
1225 | .B mdadm | |
1226 | to periodically poll a number of md arrays and to report on any events | |
1227 | noticed. | |
1228 | .B mdadm | |
1229 | will never exit once it decides that there are arrays to be checked, | |
1230 | so it should normally be run in the background. | |
1231 | ||
2d465520 NB |
1232 | As well as reporting events, |
1233 | .B mdadm | |
1234 | may move a spare drive from one array to another if they are in the | |
1235 | same | |
1236 | .B spare-group | |
a9d69660 | 1237 | and if the destination array has a failed drive but no spares. |
2d465520 | 1238 | |
e0d19036 NB |
1239 | If any devices are listed on the command line, |
1240 | .B mdadm | |
1241 | will only monitor those devices. Otherwise all arrays listed in the | |
1242 | configuration file will be monitored. Further, if | |
1243 | .B --scan | |
1244 | is given, then any other md devices that appear in | |
1245 | .B /proc/mdstat | |
1246 | will also be monitored. | |
1247 | ||
1248 | The result of monitoring the arrays is the generation of events. | |
bd526cee | 1249 | These events are passed to a separate program (if specified) and may |
2d465520 | 1250 | be mailed to a given E-mail address. |
e0d19036 | 1251 | |
bd526cee | 1252 | When passing event to program, the program is run once for each event |
2ae555c3 | 1253 | and is given 2 or 3 command-line arguments. The first is the |
bd526cee NB |
1254 | name of the event (see below). The second is the name of the |
1255 | md device which is affected, and the third is the name of a related | |
1256 | device if relevant, such as a component device that has failed. | |
cd29a5c8 NB |
1257 | |
1258 | If | |
1259 | .B --scan | |
e0d19036 NB |
1260 | is given, then a program or an E-mail address must be specified on the |
1261 | command line or in the config file. If neither are available, then | |
1262 | .B mdadm | |
1263 | will not monitor anything. | |
1264 | Without | |
cd29a5c8 | 1265 | .B --scan |
e0d19036 | 1266 | .B mdadm |
2d465520 | 1267 | will continue monitoring as long as something was found to monitor. If |
e0d19036 NB |
1268 | no program or email is given, then each event is reported to |
1269 | .BR stdout . | |
cd29a5c8 | 1270 | |
e0d19036 NB |
1271 | The different events are: |
1272 | ||
1273 | .RS 4 | |
1274 | .TP | |
1275 | .B DeviceDisappeared | |
2d465520 | 1276 | An md array which previously was configured appears to no longer be |
773135f5 | 1277 | configured. (syslog priority: Critical) |
e0d19036 | 1278 | |
b8f72a62 NB |
1279 | If |
1280 | .I mdadm | |
1281 | was told to monitor an array which is RAID0 or Linear, then it will | |
1282 | report | |
1283 | .B DeviceDisappeared | |
1284 | with the extra information | |
1285 | .BR Wrong-Level . | |
1286 | This is because RAID0 and Linear do not support the device-failed, | |
1287 | hot-spare and resync operations which are monitored. | |
1288 | ||
e0d19036 NB |
1289 | .TP |
1290 | .B RebuildStarted | |
773135f5 | 1291 | An md array started reconstruction. (syslog priority: Warning) |
e0d19036 NB |
1292 | |
1293 | .TP | |
1294 | .BI Rebuild NN | |
1295 | Where | |
1296 | .I NN | |
1297 | is 20, 40, 60, or 80, this indicates that rebuild has passed that many | |
773135f5 | 1298 | percentage of the total. (syslog priority: Warning) |
e0d19036 | 1299 | |
98c6faba NB |
1300 | .TP |
1301 | .B RebuildFinished | |
1302 | An md array that was rebuilding, isn't any more, either because it | |
773135f5 | 1303 | finished normally or was aborted. (syslog priority: Warning) |
98c6faba | 1304 | |
e0d19036 NB |
1305 | .TP |
1306 | .B Fail | |
773135f5 NB |
1307 | An active component device of an array has been marked as |
1308 | faulty. (syslog priority: Critical) | |
e0d19036 NB |
1309 | |
1310 | .TP | |
1311 | .B FailSpare | |
1312 | A spare component device which was being rebuilt to replace a faulty | |
773135f5 | 1313 | device has failed. (syslog priority: Critial) |
e0d19036 NB |
1314 | |
1315 | .TP | |
1316 | .B SpareActive | |
1317 | A spare component device which was being rebuilt to replace a faulty | |
98b24a2a | 1318 | device has been successfully rebuilt and has been made active. |
773135f5 | 1319 | (syslog priority: Info) |
e0d19036 NB |
1320 | |
1321 | .TP | |
1322 | .B NewArray | |
1323 | A new md array has been detected in the | |
1324 | .B /proc/mdstat | |
773135f5 | 1325 | file. (syslog priority: Info) |
e0d19036 | 1326 | |
aa88f531 NB |
1327 | .TP |
1328 | .B DegradedArray | |
1329 | A newly noticed array appears to be degraded. This message is not | |
1330 | generated when | |
1331 | .I mdadm | |
1332 | notices a drive failure which causes degradation, but only when | |
1333 | .I mdadm | |
1334 | notices that an array is degraded when it first sees the array. | |
773135f5 | 1335 | (syslog priority: Critial) |
aa88f531 | 1336 | |
e0d19036 NB |
1337 | .TP |
1338 | .B MoveSpare | |
1339 | A spare drive has been moved from one array in a | |
1340 | .B spare-group | |
1341 | to another to allow a failed drive to be replaced. | |
773135f5 | 1342 | (syslog priority: Info) |
e0d19036 | 1343 | |
b8f72a62 NB |
1344 | .TP |
1345 | .B SparesMissing | |
1346 | If | |
1347 | .I mdadm | |
1348 | has been told, via the config file, that an array should have a certain | |
1349 | number of spare devices, and | |
1350 | .I mdadm | |
1351 | detects that it has fewer that this number when it first sees the | |
1352 | array, it will report a | |
1353 | .B SparesMissing | |
1354 | message. | |
d1732eeb | 1355 | (syslog priority: Warning) |
b8f72a62 | 1356 | |
98c6faba NB |
1357 | .TP |
1358 | .B TestMessage | |
1359 | An array was found at startup, and the | |
1360 | .B --test | |
1361 | flag was given. | |
773135f5 | 1362 | (syslog priority: Info) |
e0d19036 NB |
1363 | .RE |
1364 | ||
1365 | Only | |
98c6faba NB |
1366 | .B Fail , |
1367 | .B FailSpare , | |
1368 | .B DegradedArray , | |
d1732eeb | 1369 | .B SparesMissing , |
e0d19036 | 1370 | and |
98c6faba | 1371 | .B TestMessage |
e0d19036 NB |
1372 | cause Email to be sent. All events cause the program to be run. |
1373 | The program is run with two or three arguments, they being the event | |
1374 | name, the array device and possibly a second device. | |
1375 | ||
1376 | Each event has an associated array device (e.g. | |
1377 | .BR /dev/md1 ) | |
1378 | and possibly a second device. For | |
1379 | .BR Fail , | |
1380 | .BR FailSpare , | |
1381 | and | |
1382 | .B SpareActive | |
1383 | the second device is the relevant component device. | |
1384 | For | |
1385 | .B MoveSpare | |
1386 | the second device is the array that the spare was moved from. | |
1387 | ||
1388 | For | |
1389 | .B mdadm | |
1390 | to move spares from one array to another, the different arrays need to | |
1391 | be labelled with the same | |
1392 | .B spare-group | |
1393 | in the configuration file. The | |
1394 | .B spare-group | |
1395 | name can be any string. It is only necessary that different spare | |
2d465520 | 1396 | groups use different names. |
e0d19036 NB |
1397 | |
1398 | When | |
9a9dab36 | 1399 | .B mdadm |
e0d19036 NB |
1400 | detects that an array which is in a spare group has fewer active |
1401 | devices than necessary for the complete array, and has no spare | |
1402 | devices, it will look for another array in the same spare group that | |
1403 | has a full complement of working drive and a spare. It will then | |
1404 | attempt to remove the spare from the second drive and add it to the | |
1405 | first. | |
1406 | If the removal succeeds but the adding fails, then it is added back to | |
1407 | the original array. | |
1408 | ||
dd0781e5 NB |
1409 | .SH GROW MODE |
1410 | The GROW mode is used for changing the size or shape of an active | |
1411 | array. | |
1412 | For this to work, the kernel must support the necessary change. | |
2ae555c3 | 1413 | Various types of growth are being added during 2.6 development, |
dd0781e5 NB |
1414 | including restructuring a raid5 array to have more active devices. |
1415 | ||
dfd4d8ee NB |
1416 | Currently the only support available is to |
1417 | .IP \(bu 4 | |
1418 | change the "size" attribute | |
1419 | for RAID1, RAID5 and RAID6. | |
1420 | .IP \(bu 4 | |
2ae555c3 | 1421 | increase the "raid-disks" attribute of RAID1 and RAID5. |
dfd4d8ee | 1422 | .IP \(bu 4 |
2ae555c3 NB |
1423 | add a write-intent bitmap to any array which support these bitmaps, or |
1424 | remove a write-intent bitmap from such an array. | |
dfd4d8ee | 1425 | .PP |
dd0781e5 | 1426 | |
2ae555c3 | 1427 | .SS SIZE CHANGES |
fe80f49b | 1428 | Normally when an array is built the "size" it taken from the smallest |
dd0781e5 NB |
1429 | of the drives. If all the small drives in an arrays are, one at a |
1430 | time, removed and replaced with larger drives, then you could have an | |
1431 | array of large drives with only a small amount used. In this | |
1432 | situation, changing the "size" with "GROW" mode will allow the extra | |
1433 | space to start being used. If the size is increased in this way, a | |
1434 | "resync" process will start to make sure the new parts of the array | |
1435 | are synchronised. | |
1436 | ||
1437 | Note that when an array changes size, any filesystem that may be | |
1438 | stored in the array will not automatically grow to use the space. The | |
1439 | filesystem will need to be explicitly told to use the extra space. | |
1440 | ||
2ae555c3 NB |
1441 | .SS RAID-DEVICES CHANGES |
1442 | ||
dd0781e5 NB |
1443 | A RAID1 array can work with any number of devices from 1 upwards |
1444 | (though 1 is not very useful). There may be times which you want to | |
1445 | increase or decrease the number of active devices. Note that this is | |
1446 | different to hot-add or hot-remove which changes the number of | |
1447 | inactive devices. | |
1448 | ||
1449 | When reducing the number of devices in a RAID1 array, the slots which | |
1450 | are to be removed from the array must already be vacant. That is, the | |
1451 | devices that which were in those slots must be failed and removed. | |
1452 | ||
1453 | When the number of devices is increased, any hot spares that are | |
a9d69660 | 1454 | present will be activated immediately. |
dd0781e5 | 1455 | |
2ae555c3 NB |
1456 | Increasing the number of active devices in a RAID5 is much more |
1457 | effort. Every block in the array will need to be read and written | |
1458 | back to a new location. From 2.6.17, the Linux Kernel is able to do | |
1459 | this safely, including restart and interrupted "reshape". | |
1460 | ||
1461 | When relocating the first few stripes on a raid5, it is not possible | |
1462 | to keep the data on disk completely consistent and crash-proof. To | |
1463 | provide the required safety, mdadm disables writes to the array while | |
1464 | this "critical section" is reshaped, and takes a backup of the data | |
1465 | that is in that section. This backup is normally stored in any spare | |
1466 | devices that the array has, however it can also be stored in a | |
1467 | separate file specified with the | |
1468 | .B --backup-file | |
1469 | option. If this option is used, and the system does crash during the | |
1470 | critical period, the same file must be passed to | |
1471 | .B --assemble | |
1472 | to restore the backup and reassemble the array. | |
1473 | ||
1474 | .SS BITMAP CHANGES | |
1475 | ||
1476 | A write-intent bitmap can be added to, or removed from, an active | |
1477 | array. Either internal bitmaps, or bitmaps stored in a separate file | |
fe80f49b NB |
1478 | can be added. Note that if you add a bitmap stored in a file which is |
1479 | in a filesystem that is on the raid array being affected, the system | |
1480 | will deadlock. The bitmap must be on a separate filesystem. | |
1481 | ||
2d465520 NB |
1482 | .SH EXAMPLES |
1483 | ||
5787fa49 | 1484 | .B " mdadm --query /dev/name-of-device" |
2d465520 | 1485 | .br |
5787fa49 NB |
1486 | This will find out if a given device is a raid array, or is part of |
1487 | one, and will provide brief information about the device. | |
2d465520 | 1488 | |
5787fa49 | 1489 | .B " mdadm --assemble --scan" |
2d465520 | 1490 | .br |
2ae555c3 | 1491 | This will assemble and start all arrays listed in the standard config file |
5787fa49 | 1492 | file. This command will typically go in a system startup file. |
2d465520 | 1493 | |
2d465520 | 1494 | .B " mdadm --stop --scan" |
5787fa49 NB |
1495 | .br |
1496 | This will shut down all array that can be shut down (i.e. are not | |
19f8b8fc | 1497 | currently in use). This will typically go in a system shutdown script. |
2d465520 | 1498 | |
5787fa49 | 1499 | .B " mdadm --follow --scan --delay=120" |
2d465520 | 1500 | .br |
5787fa49 NB |
1501 | If (and only if) there is an Email address or program given in the |
1502 | standard config file, then | |
1503 | monitor the status of all arrays listed in that file by | |
1504 | polling them ever 2 minutes. | |
2d465520 | 1505 | |
5787fa49 | 1506 | .B " mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/hd[ac]1" |
2d465520 | 1507 | .br |
5787fa49 | 1508 | Create /dev/md0 as a RAID1 array consisting of /dev/hda1 and /dev/hdc1. |
2d465520 | 1509 | |
2d465520 NB |
1510 | .br |
1511 | .B " echo 'DEVICE /dev/hd*[0-9] /dev/sd*[0-9]' > mdadm.conf" | |
1512 | .br | |
1513 | .B " mdadm --detail --scan >> mdadm.conf" | |
1514 | .br | |
5787fa49 NB |
1515 | This will create a prototype config file that describes currently |
1516 | active arrays that are known to be made from partitions of IDE or SCSI drives. | |
2d465520 NB |
1517 | This file should be reviewed before being used as it may |
1518 | contain unwanted detail. | |
1519 | ||
2d465520 NB |
1520 | .B " echo 'DEVICE /dev/hd[a-z] /dev/sd*[a-z]' > mdadm.conf" |
1521 | .br | |
5787fa49 NB |
1522 | .B " mdadm --examine --scan --config=mdadm.conf >> mdadm.conf" |
1523 | .ber | |
2ae555c3 | 1524 | This will find what arrays could be assembled from existing IDE and |
5787fa49 NB |
1525 | SCSI whole drives (not partitions) and store the information is the |
1526 | format of a config file. | |
2d465520 NB |
1527 | This file is very likely to contain unwanted detail, particularly |
1528 | the | |
1529 | .B devices= | |
5787fa49 NB |
1530 | entries. It should be reviewed and edited before being used as an |
1531 | actual config file. | |
2d465520 | 1532 | |
5787fa49 | 1533 | .B " mdadm --examine --brief --scan --config=partitions" |
2d465520 | 1534 | .br |
5787fa49 NB |
1535 | .B " mdadm -Ebsc partitions" |
1536 | .br | |
1537 | Create a list of devices by reading | |
1538 | .BR /proc/partitions , | |
1539 | scan these for RAID superblocks, and printout a brief listing of all | |
1540 | that was found. | |
2d465520 | 1541 | |
5787fa49 | 1542 | .B " mdadm -Ac partitions -m 0 /dev/md0" |
2d465520 | 1543 | .br |
5787fa49 NB |
1544 | Scan all partitions and devices listed in |
1545 | .BR /proc/partitions | |
1546 | and assemble | |
1547 | .B /dev/md0 | |
1548 | out of all such devices with a RAID superblock with a minor number of 0. | |
2d465520 | 1549 | |
d013a55e NB |
1550 | .B " mdadm --monitor --scan --daemonise > /var/run/mdadm" |
1551 | .br | |
1552 | If config file contains a mail address or alert program, run mdadm in | |
1553 | the background in monitor mode monitoring all md devices. Also write | |
1554 | pid of mdadm daemon to | |
1555 | .BR /var/run/mdadm . | |
1556 | ||
5787fa49 | 1557 | .B " mdadm --create --help" |
2d465520 | 1558 | .br |
2ae555c3 | 1559 | Provide help about the Create mode. |
2d465520 | 1560 | |
5787fa49 NB |
1561 | .B " mdadm --config --help" |
1562 | .br | |
1563 | Provide help about the format of the config file. | |
2d465520 | 1564 | |
5787fa49 NB |
1565 | .B " mdadm --help" |
1566 | .br | |
1567 | Provide general help. | |
cd29a5c8 | 1568 | |
cd29a5c8 NB |
1569 | |
1570 | .SH FILES | |
1571 | ||
1572 | .SS /proc/mdstat | |
1573 | ||
2ae555c3 NB |
1574 | If you're using the |
1575 | .B /proc | |
cd29a5c8 NB |
1576 | filesystem, |
1577 | .B /proc/mdstat | |
2d465520 NB |
1578 | lists all active md devices with information about them. |
1579 | .B mdadm | |
1580 | uses this to find arrays when | |
1581 | .B --scan | |
1582 | is given in Misc mode, and to monitor array reconstruction | |
1583 | on Monitor mode. | |
1584 | ||
cd29a5c8 | 1585 | |
9a9dab36 | 1586 | .SS /etc/mdadm.conf |
cd29a5c8 | 1587 | |
11a3e71d NB |
1588 | The config file lists which devices may be scanned to see if |
1589 | they contain MD super block, and gives identifying information | |
1590 | (e.g. UUID) about known MD arrays. See | |
1591 | .BR mdadm.conf (5) | |
1592 | for more details. | |
cd29a5c8 | 1593 | |
48f7b27a NB |
1594 | .SH DEVICE NAMES |
1595 | ||
1596 | While entries in the /dev directory can have any format you like, | |
1597 | .I mdadm | |
1598 | has an understanding of 'standard' formats which it uses to guide its | |
1599 | behaviour when creating device files via the | |
1600 | .I --auto | |
1601 | option. | |
1602 | ||
1603 | The standard names for non-partitioned arrays (the only sort of md | |
1604 | array available in 2.4 and earlier) either of | |
1605 | .IP | |
1606 | /dev/mdNN | |
1607 | .br | |
1608 | /dev/md/NN | |
1609 | .PP | |
1610 | where NN is a number. | |
1611 | The standard names for partitionable arrays (as available from 2.6 | |
1612 | onwards) is one of | |
1613 | .IP | |
1614 | /dev/md/dNN | |
1615 | .br | |
1616 | /dev/md_dNN | |
1617 | .PP | |
1618 | Partition numbers should be indicated by added "pMM" to these, thus "/dev/md/d1p2". | |
52826846 | 1619 | |
2d465520 NB |
1620 | .SH NOTE |
1621 | .B mdadm | |
1622 | was previously known as | |
1623 | .BR mdctl . | |
a9d69660 NB |
1624 | .P |
1625 | .B mdadm | |
1626 | is completely separate from the | |
1627 | .B raidtools | |
1628 | package, and does not use the | |
1629 | .I /etc/raidtab | |
1630 | configuration file at all. | |
1631 | ||
52826846 | 1632 | .SH SEE ALSO |
cd29a5c8 NB |
1633 | For information on the various levels of |
1634 | RAID, check out: | |
1635 | ||
1636 | .IP | |
1637 | .UR http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/ | |
1638 | http://ostenfeld.dk/~jakob/Software-RAID.HOWTO/ | |
1639 | .UE | |
a9d69660 NB |
1640 | '''.PP |
1641 | '''for new releases of the RAID driver check out: | |
1642 | ''' | |
1643 | '''.IP | |
1644 | '''.UR ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
1645 | '''ftp://ftp.kernel.org/pub/linux/kernel/people/mingo/raid-patches | |
1646 | '''.UE | |
1647 | '''.PP | |
1648 | '''or | |
1649 | '''.IP | |
1650 | '''.UR http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
1651 | '''http://www.cse.unsw.edu.au/~neilb/patches/linux-stable/ | |
1652 | '''.UE | |
cd29a5c8 | 1653 | .PP |
2ae555c3 | 1654 | The latest version of |
a9d69660 NB |
1655 | .I mdadm |
1656 | should always be available from | |
cd29a5c8 | 1657 | .IP |
a9d69660 NB |
1658 | .UR http://www.kernel.org/pub/linux/utils/raid/mdadm/ |
1659 | http://www.kernel.org/pub/linux/utils/raid/mdadm/ | |
cd29a5c8 NB |
1660 | .UE |
1661 | .PP | |
a9d69660 NB |
1662 | .IR mdadm.conf (5), |
1663 | .IR md (4). | |
56eb10c0 | 1664 | .PP |
52826846 NB |
1665 | .IR raidtab (5), |
1666 | .IR raid0run (8), | |
1667 | .IR raidstop (8), | |
a9d69660 | 1668 | .IR mkraid (8). |