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1 '\" t
2 .\"
3 .\" This file and its contents are supplied under the terms of the
4 .\" Common Development and Distribution License ("CDDL"), version 1.0.
5 .\" You may only use this file in accordance with the terms of version
6 .\" 1.0 of the CDDL.
7 .\"
8 .\" A full copy of the text of the CDDL should have accompanied this
9 .\" source. A copy of the CDDL is also available via the Internet at
10 .\" http://www.illumos.org/license/CDDL.
11 .\"
12 .\"
13 .\" Copyright 2012, Richard Lowe.
14 .\" Copyright (c) 2012, 2016 by Delphix. All rights reserved.
15 .\" Copyright 2016 Nexenta Systems, Inc.
16 .\"
17 .TH "ZDB" "8" "April 9, 2016" "" ""
19 .SH "NAME"
20 \fBzdb\fR - Display zpool debugging and consistency information
22 .SH "SYNOPSIS"
23 \fBzdb\fR [-CumdibcsDvhLMXFPAG] [-e [-p \fIpath\fR...]] [-t \fItxg\fR]
24 [-U \fIcache\fR] [-I \fIinflight I/Os\fR] [-x \fIdumpdir\fR]
25 [-o \fIvar\fR=\fIvalue\fR] ... [\fIpoolname\fR [\fIobject\fR ...]]
27 .P
28 \fBzdb\fR [-divPA] [-e [-p \fIpath\fR...]] [-U \fIcache\fR]
29 \fIdataset\fR [\fIobject\fR ...]
31 .P
32 \fBzdb\fR -m [-MLXFPA] [-t \fItxg\fR] [-e [-p \fIpath\fR...]] [-U \fIcache\fR]
33 \fIpoolname\fR [\fIvdev\fR [\fImetaslab\fR ...]]
35 .P
36 \fBzdb\fR -R [-A] [-e [-p \fIpath\fR...]] [-U \fIcache\fR] \fIpoolname\fR
37 \fIvdev\fR:\fIoffset\fR:\fIsize\fR[:\fIflags\fR]
39 .P
40 \fBzdb\fR -S [-AP] [-e [-p \fIpath\fR...]] [-U \fIcache\fR] \fIpoolname\fR
42 .P
43 \fBzdb\fR -l [-Aqu] \fIdevice\fR
45 .P
46 \fBzdb\fR -C [-A] [-U \fIcache\fR]
48 .SH "DESCRIPTION"
49 The \fBzdb\fR utility displays information about a ZFS pool useful for
50 debugging and performs some amount of consistency checking. It is a not a
51 general purpose tool and options (and facilities) may change. This is neither
52 a fsck(8) nor an fsdb(8) utility.
54 .P
55 The output of this command in general reflects the on-disk structure of a ZFS
56 pool, and is inherently unstable. The precise output of most invocations is
57 not documented, a knowledge of ZFS internals is assumed.
59 .P
60 If the \fIdataset\fR argument does not contain any \fB/\fR or \fB@\fR
61 characters, it is interpreted as a pool name. The root dataset can be
62 specified as \fIpool\fB/\fR (pool name followed by a slash).
64 .P
65 When operating on an imported and active pool it is possible, though unlikely,
66 that zdb may interpret inconsistent pool data and behave erratically.
68 .SH "OPTIONS"
69 Display options:
71 .sp
72 .ne 2
73 .na
74 \fB-b\fR
75 .ad
76 .sp .6
77 .RS 4n
78 Display statistics regarding the number, size (logical, physical and
79 allocated) and deduplication of blocks.
80 .RE
82 .sp
83 .ne 2
84 .na
85 \fB-c\fR
86 .ad
87 .sp .6
88 .RS 4n
89 Verify the checksum of all metadata blocks while printing block statistics
90 (see \fB-b\fR).
91 .sp
92 If specified multiple times, verify the checksums of all blocks.
93 .RE
95 .sp
96 .ne 2
97 .na
98 \fB-C\fR
99 .ad
100 .sp .6
101 .RS 4n
102 Display information about the configuration. If specified with no other
103 options, instead display information about the cache file
104 (\fB/etc/zfs/zpool.cache\fR). To specify the cache file to display, see
105 \fB-U\fR.
106 .P
107 If specified multiple times, and a pool name is also specified display both
108 the cached configuration and the on-disk configuration. If specified multiple
109 times with \fB-e\fR also display the configuration that would be used were the
110 pool to be imported.
111 .RE
113 .sp
114 .ne 2
115 .na
116 \fB-d\fR
117 .ad
118 .sp .6
119 .RS 4n
120 Display information about datasets. Specified once, displays basic dataset
121 information: ID, create transaction, size, and object count.
122 .sp
123 If specified multiple times provides greater and greater verbosity.
124 .sp
125 If object IDs are specified, display information about those specific objects only.
126 .RE
128 .sp
129 .ne 2
130 .na
131 \fB-D\fR
132 .ad
133 .sp .6
134 .RS 4n
135 Display deduplication statistics, including the deduplication ratio (dedup),
136 compression ratio (compress), inflation due to the zfs copies property
137 (copies), and an overall effective ratio (dedup * compress / copies).
138 .sp
139 If specified twice, display a histogram of deduplication statistics, showing
140 the allocated (physically present on disk) and referenced (logically
141 referenced in the pool) block counts and sizes by reference count.
142 .sp
143 If specified a third time, display the statistics independently for each deduplication table.
144 .sp
145 If specified a fourth time, dump the contents of the deduplication tables describing duplicate blocks.
146 .sp
147 If specified a fifth time, also dump the contents of the deduplication tables describing unique blocks.
148 .RE
150 .sp
151 .ne 2
152 .na
153 \fB-h\fR
154 .ad
155 .sp .6
156 .RS 4n
157 Display pool history similar to \fBzpool history\fR, but include internal
158 changes, transaction, and dataset information.
159 .RE
161 .sp
162 .ne 2
163 .na
164 \fB-i\fR
165 .ad
166 .sp .6
167 .RS 4n
168 Display information about intent log (ZIL) entries relating to each
169 dataset. If specified multiple times, display counts of each intent log
170 transaction type.
171 .RE
173 .sp
174 .ne 2
175 .na
176 \fB-l\fR \fIdevice\fR
177 .ad
178 .sp .6
179 .RS 4n
180 Read the vdev labels from the specified device. \fBzdb -l\fR will return 0 if
181 valid label was found, 1 if error occured, and 2 if no valid labels were found.
182 .P
183 If the \fB-u\fR option is also specified, also display the uberblocks on this
184 device.
185 .P
186 If the \fB-q\fR option is also specified, don't print the labels.
187 .RE
189 .sp
190 .ne 2
191 .na
192 \fB-L\fR
193 .ad
194 .sp .6
195 .RS 4n
196 Disable leak tracing and the loading of space maps. By default, \fBzdb\fR
197 verifies that all non-free blocks are referenced, which can be very expensive.
198 .RE
200 .sp
201 .ne 2
202 .na
203 \fB-m\fR
204 .ad
205 .sp .6
206 .RS 4n
207 Display the offset, spacemap, and free space of each metaslab.
208 When specified twice, also display information about the on-disk free
209 space histogram associated with each metaslab. When specified three time,
210 display the maximum contiguous free space, the in-core free space histogram,
211 and the percentage of free space in each space map. When specified
212 four times display every spacemap record.
213 .RE
215 .sp
216 .ne 2
217 .na
218 \fB-M\fR
219 .ad
220 .sp .6
221 .RS 4n
222 Display the offset, spacemap, and free space of each metaslab.
223 When specified twice, also display information about the maximum contiguous
224 free space and the percentage of free space in each space map. When specified
225 three times display every spacemap record.
226 .RE
228 .sp
229 .ne 2
230 .na
231 \fB-R\fR \fIpoolname\fR \fIvdev\fR:\fIoffset\fR:\fIsize\fR[:\fIflags\fR]
232 .ad
233 .sp .6
234 .RS 4n
235 Read and display a block from the specified device. By default the block is
236 displayed as a hex dump, but see the description of the \'r\' flag, below.
237 .sp
238 The block is specified in terms of a colon-separated tuple \fIvdev\fR (an
239 integer vdev identifier) \fIoffset\fR (the offset within the vdev) \fIsize\fR
240 (the size of the block to read) and, optionally, \fIflags\fR (a set of flags,
241 described below).
243 .sp
244 .ne 2
245 .na
246 \fBb\fR \fIoffset\fR
247 .ad
248 .sp .6
249 .RS 4n
250 Print block pointer
251 .RE
253 .sp
254 .ne 2
255 .na
256 \fBd\fR
257 .ad
258 .sp .6
259 .RS 4n
260 Decompress the block
261 .RE
263 .sp
264 .ne 2
265 .na
266 \fBe\fR
267 .ad
268 .sp .6
269 .RS 4n
270 Byte swap the block
271 .RE
273 .sp
274 .ne 2
275 .na
276 \fBg\fR
277 .ad
278 .sp .6
279 .RS 4n
280 Dump gang block header
281 .RE
283 .sp
284 .ne 2
285 .na
286 \fBi\fR
287 .ad
288 .sp .6
289 .RS 4n
290 Dump indirect block
291 .RE
293 .sp
294 .ne 2
295 .na
296 \fBr\fR
297 .ad
298 .sp .6
299 .RS 4n
300 Dump raw uninterpreted block data
301 .RE
302 .RE
304 .sp
305 .ne 2
306 .na
307 \fB-s\fR
308 .ad
309 .sp .6
310 .RS 4n
311 Report statistics on \fBzdb\fR\'s I/O. Display operation counts, bandwidth,
312 and error counts of I/O to the pool from \fBzdb\fR.
313 .RE
315 .sp
316 .ne 2
317 .na
318 \fB-S\fR
319 .ad
320 .sp .6
321 .RS 4n
322 Simulate the effects of deduplication, constructing a DDT and then display
323 that DDT as with \fB-DD\fR.
324 .RE
326 .sp
327 .ne 2
328 .na
329 \fB-u\fR
330 .ad
331 .sp .6
332 .RS 4n
333 Display the current uberblock.
334 .RE
336 .P
337 Other options:
339 .sp
340 .ne 2
341 .na
342 \fB-A\fR
343 .ad
344 .sp .6
345 .RS 4n
346 Do not abort should any assertion fail.
347 .RE
349 .sp
350 .ne 2
351 .na
352 \fB-AA\fR
353 .ad
354 .sp .6
355 .RS 4n
356 Enable panic recovery, certain errors which would otherwise be fatal are
357 demoted to warnings.
358 .RE
360 .sp
361 .ne 2
362 .na
363 \fB-AAA\fR
364 .ad
365 .sp .6
366 .RS 4n
367 Do not abort if asserts fail and also enable panic recovery.
368 .RE
370 .sp
371 .ne 2
372 .na
373 \fB-e\fR [-p \fIpath\fR]...
374 .ad
375 .sp .6
376 .RS 4n
377 Operate on an exported pool, not present in \fB/etc/zfs/zpool.cache\fR. The
378 \fB-p\fR flag specifies the path under which devices are to be searched.
379 .RE
381 .sp
382 .ne 2
383 .na
384 \fB-x\fR \fIdumpdir\fR
385 .ad
386 .sp .6
387 .RS 4n
388 All blocks accessed will be copied to files in the specified directory.
389 The blocks will be placed in sparse files whose name is the same as
390 that of the file or device read. zdb can be then run on the generated files.
391 Note that the \fB-bbc\fR flags are sufficient to access (and thus copy)
392 all metadata on the pool.
393 .RE
395 .sp
396 .ne 2
397 .na
398 \fB-F\fR
399 .ad
400 .sp .6
401 .RS 4n
402 Attempt to make an unreadable pool readable by trying progressively older
403 transactions.
404 .RE
406 .sp
407 .ne 2
408 .na
409 \fB-G\fR
410 .ad
411 .sp .6
412 .RS 4n
413 Dump the contents of the zfs_dbgmsg buffer before exiting zdb. zfs_dbgmsg is
414 a buffer used by ZFS to dump advanced debug information.
415 .RE
417 .sp
418 .ne 2
419 .na
420 \fB-I \fIinflight I/Os\fR \fR
421 .ad
422 .sp .6
423 .RS 4n
424 Limit the number of outstanding checksum I/Os to the specified value. The
425 default value is 200. This option affects the performance of the \fB-c\fR
426 option.
427 .RE
429 .sp
430 .ne 2
431 .na
432 \fB-o \fIvar\fR=\fIvalue\fR ... \fR
433 .ad
434 .sp .6
435 .RS 4n
436 Set the given global libzpool variable to the provided value. The value must
437 be an unsigned 32-bit integer. Currently only little-endian systems are
438 supported to avoid accidentally setting the high 32 bits of 64-bit variables.
439 .RE
441 .sp
442 .ne 2
443 .na
444 \fB-P\fR
445 .ad
446 .sp .6
447 .RS 4n
448 Print numbers in an unscaled form more amenable to parsing, eg. 1000000 rather
449 than 1M.
450 .RE
452 .sp
453 .ne 2
454 .na
455 \fB-t\fR \fItransaction\fR
456 .ad
457 .sp .6
458 .RS 4n
459 Specify the highest transaction to use when searching for uberblocks. See also
460 the \fB-u\fR and \fB-l\fR options for a means to see the available uberblocks
461 and their associated transaction numbers.
462 .RE
464 .sp
465 .ne 2
466 .na
467 \fB-U\fR \fIcachefile\fR
468 .ad
469 .sp .6
470 .RS 4n
471 Use a cache file other than \fB/etc/zfs/zpool.cache\fR.
472 .RE
474 .sp
475 .ne 2
476 .na
477 \fB-v\fR
478 .ad
479 .sp .6
480 .RS 4n
481 Enable verbosity. Specify multiple times for increased verbosity.
482 .RE
484 .sp
485 .ne 2
486 .na
487 \fB-X\fR
488 .ad
489 .sp .6
490 .RS 4n
491 Attempt \'extreme\' transaction rewind, that is attempt the same recovery as
492 \fB-F\fR but read transactions otherwise deemed too old.
493 .RE
495 .sp
496 .ne 2
497 .na
498 \fB-V\fR
499 .ad
500 .sp .6
501 .RS 4n
502 Attempt a verbatim import. This mimics the behavior of the kernel when loading
503 a pool from a cachefile.
504 .RE
506 .P
507 Specifying a display option more than once enables verbosity for only that
508 option, with more occurrences enabling more verbosity.
509 .P
510 If no options are specified, all information about the named pool will be
511 displayed at default verbosity.
513 .SH "EXAMPLES"
514 .LP
515 \fBExample 1 \fRDisplay the configuration of imported pool 'rpool'
516 .sp
517 .in +2
518 .nf
519 # zdb -C rpool
521 MOS Configuration:
522 version: 28
523 name: 'rpool'
524 ...
525 .fi
526 .in -2
527 .sp
529 .LP
530 \fBExample 2 \fRDisplay basic dataset information about 'rpool'
531 .sp
532 .in +2
533 .nf
534 # zdb -d rpool
535 Dataset mos [META], ID 0, cr_txg 4, 26.9M, 1051 objects
536 Dataset rpool/swap [ZVOL], ID 59, cr_txg 356, 486M, 2 objects
537 ...
538 .fi
539 .in -2
540 .sp
542 .LP
543 \fBExample 3 \fRDisplay basic information about object 0
544 in 'rpool/export/home'
545 .sp
546 .in +2
547 .nf
548 # zdb -d rpool/export/home 0
549 Dataset rpool/export/home [ZPL], ID 137, cr_txg 1546, 32K, 8 objects
551 Object lvl iblk dblk dsize lsize %full type
552 0 7 16K 16K 15.0K 16K 25.00 DMU dnode
553 .fi
554 .in -2
555 .sp
557 .LP
558 \fBExample 4 \fRDisplay the predicted effect of enabling deduplication on 'rpool'
559 .sp
560 .in +2
561 .nf
562 # zdb -S rpool
563 Simulated DDT histogram:
565 bucket allocated referenced
566 ______ ______________________________ ______________________________
567 refcnt blocks LSIZE PSIZE DSIZE blocks LSIZE PSIZE DSIZE
568 ------ ------ ----- ----- ----- ------ ----- ----- -----
569 1 694K 27.1G 15.0G 15.0G 694K 27.1G 15.0G 15.0G
570 2 35.0K 1.33G 699M 699M 74.7K 2.79G 1.45G 1.45G
571 ...
572 dedup = 1.11, compress = 1.80, copies = 1.00, dedup * compress / copies = 2.00
573 .fi
574 .in -2
575 .sp
577 .SH "ENVIRONMENT VARIABLES"
578 .TP
579 .B "SPA_CONFIG_PATH"
580 Override the default \fBspa_config_path\fR (\fI/etc/zfs/zpool.cache\fR) setting. If \fB-U\fR flag is specified it will override this environment variable settings once again.
582 .SH "SEE ALSO"
583 zfs(8), zpool(8)