1 .\"
2 .\" This file and its contents are supplied under the terms of the
3 .\" Common Development and Distribution License ("CDDL"), version 1.0.
4 .\" You may only use this file in accordance with the terms of version
5 .\" 1.0 of the CDDL.
6 .\"
7 .\" A full copy of the text of the CDDL should have accompanied this
8 .\" source. A copy of the CDDL is also available via the Internet at
9 .\" http://www.illumos.org/license/CDDL.
10 .\"
11 .\"
12 .\" Copyright 2012, Richard Lowe.
13 .\" Copyright (c) 2012, 2017 by Delphix. All rights reserved.
14 .\" Copyright 2017 Nexenta Systems, Inc.
15 .\"
16 .Dd April 14, 2017
17 .Dt ZDB 1M
18 .Os
19 .Sh NAME
20 .Nm zdb
21 .Nd display zpool debugging and consistency information
22 .Sh SYNOPSIS
23 .Nm
24 .Op Fl AbcdDFGhikLMPsvX
25 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
26 .Op Fl I Ar inflight I/Os
27 .Oo Fl o Ar var Ns = Ns Ar value Oc Ns ...
28 .Op Fl t Ar txg
29 .Op Fl U Ar cache
30 .Op Fl x Ar dumpdir
31 .Op Ar poolname Op Ar object ...
32 .Nm
33 .Op Fl AdiPv
34 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
35 .Op Fl U Ar cache
36 .Ar dataset Op Ar object ...
37 .Nm
38 .Fl C
39 .Op Fl A
40 .Op Fl U Ar cache
41 .Nm
42 .Fl E
43 .Op Fl A
44 .Ar word0 Ns \&: Ns Ar word1 Ns :...: Ns Ar word15
45 .Nm
46 .Fl l
47 .Op Fl Aqu
48 .Ar device
49 .Nm
50 .Fl m
51 .Op Fl AFLPX
52 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
53 .Op Fl t Ar txg
54 .Op Fl U Ar cache
55 .Ar poolname Op Ar vdev Op Ar metaslab ...
56 .Nm
57 .Fl O
58 .Ar dataset path
59 .Nm
60 .Fl R
61 .Op Fl A
62 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
63 .Op Fl U Ar cache
64 .Ar poolname vdev Ns \&: Ns Ar offset Ns \&: Ns Ar size Ns Op : Ns Ar flags
65 .Nm
66 .Fl S
67 .Op Fl AP
68 .Op Fl e Oo Fl V Oc Op Fl p Ar path ...
69 .Op Fl U Ar cache
70 .Ar poolname
71 .Sh DESCRIPTION
72 The
73 .Nm
74 utility displays information about a ZFS pool useful for debugging and performs
75 some amount of consistency checking.
76 It is a not a general purpose tool and options
77 .Pq and facilities
78 may change.
79 This is neither a
80 .Xr fsck 1M
81 nor an
82 .Xr fsdb 1M
83 utility.
84 .Pp
85 The output of this command in general reflects the on-disk structure of a ZFS
86 pool, and is inherently unstable.
87 The precise output of most invocations is not documented, a knowledge of ZFS
88 internals is assumed.
89 .Pp
90 If the
91 .Ar dataset
92 argument does not contain any
93 .Qq Sy /
94 or
95 .Qq Sy @
96 characters, it is interpreted as a pool name.
97 The root dataset can be specified as
98 .Ar pool Ns /
99 .Pq pool name followed by a slash .
100 .Pp
101 When operating on an imported and active pool it is possible, though unlikely,
102 that zdb may interpret inconsistent pool data and behave erratically.
103 .Sh OPTIONS
104 Display options:
105 .Bl -tag -width Ds
106 .It Fl b
107 Display statistics regarding the number, size
108 .Pq logical, physical and allocated
109 and deduplication of blocks.
110 .It Fl c
111 Verify the checksum of all metadata blocks while printing block statistics
112 .Po see
113 .Fl b
114 .Pc .
115 .Pp
116 If specified multiple times, verify the checksums of all blocks.
117 .It Fl C
118 Display information about the configuration.
119 If specified with no other options, instead display information about the cache
120 file
121 .Pq Pa /etc/zfs/zpool.cache .
122 To specify the cache file to display, see
123 .Fl U .
124 .Pp
125 If specified multiple times, and a pool name is also specified display both the
126 cached configuration and the on-disk configuration.
127 If specified multiple times with
128 .Fl e
129 also display the configuration that would be used were the pool to be imported.
130 .It Fl d
131 Display information about datasets.
132 Specified once, displays basic dataset information: ID, create transaction,
133 size, and object count.
134 .Pp
135 If specified multiple times provides greater and greater verbosity.
136 .Pp
137 If object IDs are specified, display information about those specific objects
138 only.
139 .It Fl D
140 Display deduplication statistics, including the deduplication ratio
141 .Pq Sy dedup ,
142 compression ratio
143 .Pq Sy compress ,
144 inflation due to the zfs copies property
145 .Pq Sy copies ,
146 and an overall effective ratio
147 .Pq Sy dedup No * Sy compress No / Sy copies .
148 .It Fl DD
149 Display a histogram of deduplication statistics, showing the allocated
150 .Pq physically present on disk
151 and referenced
152 .Pq logically referenced in the pool
153 block counts and sizes by reference count.
154 .It Fl DDD
155 Display the statistics independently for each deduplication table.
156 .It Fl DDDD
157 Dump the contents of the deduplication tables describing duplicate blocks.
158 .It Fl DDDDD
159 Also dump the contents of the deduplication tables describing unique blocks.
160 .It Fl E Ar word0 Ns \&: Ns Ar word1 Ns :...: Ns Ar word15
161 Decode and display block from an embedded block pointer specified by the
162 .Ar word
163 arguments.
164 .It Fl h
165 Display pool history similar to
166 .Nm zpool Cm history ,
167 but include internal changes, transaction, and dataset information.
168 .It Fl i
169 Display information about intent log
170 .Pq ZIL
171 entries relating to each dataset.
172 If specified multiple times, display counts of each intent log transaction type.
173 .It Fl k
174 Examine the checkpointed state of the pool.
175 Note, the on disk format of the pool is not reverted to the checkpointed state.
176 .It Fl l Ar device
177 Read the vdev labels from the specified device.
178 .Nm Fl l
179 will return 0 if valid label was found, 1 if error occurred, and 2 if no valid
180 labels were found.
181 .Pp
182 If the
183 .Fl q
184 option is also specified, don't print the labels.
185 .Pp
186 If the
187 .Fl u
188 option is also specified, also display the uberblocks on this device.
189 .It Fl L
190 Disable leak tracing and the loading of space maps.
191 By default,
192 .Nm
193 verifies that all non-free blocks are referenced, which can be very expensive.
194 .It Fl m
195 Display the offset, spacemap, and free space of each metaslab.
196 .It Fl mm
197 Also display information about the on-disk free space histogram associated with
198 each metaslab.
199 .It Fl mmm
200 Display the maximum contiguous free space, the in-core free space histogram, and
201 the percentage of free space in each space map.
202 .It Fl mmmm
203 Display every spacemap record.
204 .It Fl M
205 Display the offset, spacemap, and free space of each metaslab.
206 .It Fl MM
207 Also display information about the maximum contiguous free space and the
208 percentage of free space in each space map.
209 .It Fl MMM
210 Display every spacemap record.
211 .It Fl O Ar dataset path
212 Look up the specified
213 .Ar path
214 inside of the
215 .Ar dataset
216 and display its metadata and indirect blocks.
217 Specified
218 .Ar path
219 must be relative to the root of
220 .Ar dataset .
221 This option can be combined with
222 .Fl v
223 for increasing verbosity.
224 .It Xo
225 .Fl R Ar poolname vdev Ns \&: Ns Ar offset Ns \&: Ns Ar size Ns Op : Ns Ar flags
226 .Xc
227 Read and display a block from the specified device.
228 By default the block is displayed as a hex dump, but see the description of the
229 .Sy r
230 flag, below.
231 .Pp
232 The block is specified in terms of a colon-separated tuple
233 .Ar vdev
234 .Pq an integer vdev identifier
235 .Ar offset
236 .Pq the offset within the vdev
237 .Ar size
238 .Pq the size of the block to read
239 and, optionally,
240 .Ar flags
241 .Pq a set of flags, described below .
242 .Pp
243 .Bl -tag -compact -width "b offset"
244 .It Sy b Ar offset
245 Print block pointer
246 .It Sy d
247 Decompress the block
248 .It Sy e
249 Byte swap the block
250 .It Sy g
251 Dump gang block header
252 .It Sy i
253 Dump indirect block
254 .It Sy r
255 Dump raw uninterpreted block data
256 .El
257 .It Fl s
258 Report statistics on
259 .Nm zdb
260 I/O.
261 Display operation counts, bandwidth, and error counts of I/O to the pool from
262 .Nm .
263 .It Fl S
264 Simulate the effects of deduplication, constructing a DDT and then display
265 that DDT as with
266 .Fl DD .
267 .It Fl u
268 Display the current uberblock.
269 .El
270 .Pp
271 Other options:
272 .Bl -tag -width Ds
273 .It Fl A
274 Do not abort should any assertion fail.
275 .It Fl AA
276 Enable panic recovery, certain errors which would otherwise be fatal are
277 demoted to warnings.
278 .It Fl AAA
279 Do not abort if asserts fail and also enable panic recovery.
280 .It Fl e Op Fl p Ar path ...
281 Operate on an exported pool, not present in
282 .Pa /etc/zfs/zpool.cache .
283 The
284 .Fl p
285 flag specifies the path under which devices are to be searched.
286 .It Fl x Ar dumpdir
287 All blocks accessed will be copied to files in the specified directory.
288 The blocks will be placed in sparse files whose name is the same as
289 that of the file or device read.
290 .Nm
291 can be then run on the generated files.
292 Note that the
293 .Fl bbc
294 flags are sufficient to access
295 .Pq and thus copy
296 all metadata on the pool.
297 .It Fl F
298 Attempt to make an unreadable pool readable by trying progressively older
299 transactions.
300 .It Fl G
301 Dump the contents of the zfs_dbgmsg buffer before exiting
302 .Nm .
303 zfs_dbgmsg is a buffer used by ZFS to dump advanced debug information.
304 .It Fl I Ar inflight I/Os
305 Limit the number of outstanding checksum I/Os to the specified value.
306 The default value is 200.
307 This option affects the performance of the
308 .Fl c
309 option.
310 .It Fl o Ar var Ns = Ns Ar value ...
311 Set the given global libzpool variable to the provided value.
312 The value must be an unsigned 32-bit integer.
313 Currently only little-endian systems are supported to avoid accidentally setting
314 the high 32 bits of 64-bit variables.
315 .It Fl P
316 Print numbers in an unscaled form more amenable to parsing, eg. 1000000 rather
317 than 1M.
318 .It Fl t Ar transaction
319 Specify the highest transaction to use when searching for uberblocks.
320 See also the
321 .Fl u
322 and
323 .Fl l
324 options for a means to see the available uberblocks and their associated
325 transaction numbers.
326 .It Fl U Ar cachefile
327 Use a cache file other than
328 .Pa /etc/zfs/zpool.cache .
329 .It Fl v
330 Enable verbosity.
331 Specify multiple times for increased verbosity.
332 .It Fl V
333 Attempt verbatim import.
334 This mimics the behavior of the kernel when loading a pool from a cachefile.
335 Only usable with
336 .Fl e .
337 .It Fl X
338 Attempt
339 .Qq extreme
340 transaction rewind, that is attempt the same recovery as
341 .Fl F
342 but read transactions otherwise deemed too old.
343 .El
344 .Pp
345 Specifying a display option more than once enables verbosity for only that
346 option, with more occurrences enabling more verbosity.
347 .Pp
348 If no options are specified, all information about the named pool will be
349 displayed at default verbosity.
350 .Sh EXAMPLES
351 .Bl -tag -width Ds
352 .It Xo
353 .Sy Example 1
354 Display the configuration of imported pool
355 .Pa rpool
356 .Xc
357 .Bd -literal
358 # zdb -C rpool
359
360 MOS Configuration:
361 version: 28
362 name: 'rpool'
363 ...
364 .Ed
365 .It Xo
366 .Sy Example 2
367 Display basic dataset information about
368 .Pa rpool
369 .Xc
370 .Bd -literal
371 # zdb -d rpool
372 Dataset mos [META], ID 0, cr_txg 4, 26.9M, 1051 objects
373 Dataset rpool/swap [ZVOL], ID 59, cr_txg 356, 486M, 2 objects
374 ...
375 .Ed
376 .It Xo
377 .Sy Example 3
378 Display basic information about object 0 in
379 .Pa rpool/export/home
380 .Xc
381 .Bd -literal
382 # zdb -d rpool/export/home 0
383 Dataset rpool/export/home [ZPL], ID 137, cr_txg 1546, 32K, 8 objects
384
385 Object lvl iblk dblk dsize lsize %full type
386 0 7 16K 16K 15.0K 16K 25.00 DMU dnode
387 .Ed
388 .It Xo
389 .Sy Example 4
390 Display the predicted effect of enabling deduplication on
391 .Pa rpool
392 .Xc
393 .Bd -literal
394 # zdb -S rpool
395 Simulated DDT histogram:
396
397 bucket allocated referenced
398 ______ ______________________________ ______________________________
399 refcnt blocks LSIZE PSIZE DSIZE blocks LSIZE PSIZE DSIZE
400 ------ ------ ----- ----- ----- ------ ----- ----- -----
401 1 694K 27.1G 15.0G 15.0G 694K 27.1G 15.0G 15.0G
402 2 35.0K 1.33G 699M 699M 74.7K 2.79G 1.45G 1.45G
403 ...
404 dedup = 1.11, compress = 1.80, copies = 1.00, dedup * compress / copies = 2.00
405 .Ed
406 .El
407 .Sh SEE ALSO
408 .Xr zfs 1M ,
409 .Xr zpool 1M