xref: /freebsd/sys/contrib/openzfs/man/man8/zdb.8 (revision 19261079b74319502c6ffa1249920079f0f69a72)
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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.
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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
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10.\"
11.\" Copyright 2012, Richard Lowe.
12.\" Copyright (c) 2012, 2019 by Delphix. All rights reserved.
13.\" Copyright 2017 Nexenta Systems, Inc.
14.\" Copyright (c) 2017 Lawrence Livermore National Security, LLC.
15.\" Copyright (c) 2017 Intel Corporation.
16.\"
17.Dd October 7, 2020
18.Dt ZDB 8
19.Os
20.
21.Sh NAME
22.Nm zdb
23.Nd display ZFS storage pool debugging and consistency information
24.Sh SYNOPSIS
25.Nm
26.Op Fl AbcdDFGhikLMPsvXYy
27.Op Fl e Oo Fl V Oc Oo Fl p Ar path Oc Ns …
28.Op Fl I Ar inflight I/Os
29.Oo Fl o Ar var Ns = Ns Ar value Oc Ns …
30.Op Fl t Ar txg
31.Op Fl U Ar cache
32.Op Fl x Ar dumpdir
33.Op Ar poolname Ns Op / Ns Ar dataset | objset ID
34.Op Ar object Ns | Ns Ar range Ns …
35.Nm
36.Op Fl AdiPv
37.Op Fl e Oo Fl V Oc Oo Fl p Ar path Oc Ns …
38.Op Fl U Ar cache
39.Ar poolname Ns Op Ar / Ns Ar dataset | objset ID
40.Op Ar object Ns | Ns Ar range Ns …
41.Nm
42.Fl C
43.Op Fl A
44.Op Fl U Ar cache
45.Nm
46.Fl E
47.Op Fl A
48.Ar word0 : Ns Ar word1 Ns :…: Ns Ar word15
49.Nm
50.Fl l
51.Op Fl Aqu
52.Ar device
53.Nm
54.Fl m
55.Op Fl AFLPXY
56.Op Fl e Oo Fl V Oc Oo Fl p Ar path Oc Ns …
57.Op Fl t Ar txg
58.Op Fl U Ar cache
59.Ar poolname Op Ar vdev Oo Ar metaslab Oc Ns …
60.Nm
61.Fl O
62.Ar dataset path
63.Nm
64.Fl r
65.Ar dataset path destination
66.Nm
67.Fl R
68.Op Fl A
69.Op Fl e Oo Fl V Oc Oo Fl p Ar path Oc Ns …
70.Op Fl U Ar cache
71.Ar poolname vdev : Ns Ar offset : Ns Oo Ar lsize Ns / Oc Ns Ar psize Ns Op : Ns Ar flags
72.Nm
73.Fl S
74.Op Fl AP
75.Op Fl e Oo Fl V Oc Oo Fl p Ar path Oc Ns …
76.Op Fl U Ar cache
77.Ar poolname
78.
79.Sh DESCRIPTION
80The
81.Nm
82utility displays information about a ZFS pool useful for debugging and performs
83some amount of consistency checking.
84It is a not a general purpose tool and options
85.Pq and facilities
86may change.
87This is not a
88.Xr fsck 8
89utility.
90.Pp
91The output of this command in general reflects the on-disk structure of a ZFS
92pool, and is inherently unstable.
93The precise output of most invocations is not documented, a knowledge of ZFS
94internals is assumed.
95.Pp
96If the
97.Ar dataset
98argument does not contain any
99.Qq Sy /
100or
101.Qq Sy @
102characters, it is interpreted as a pool name.
103The root dataset can be specified as
104.Qq Ar pool Ns / .
105.Pp
106When operating on an imported and active pool it is possible, though unlikely,
107that zdb may interpret inconsistent pool data and behave erratically.
108.
109.Sh OPTIONS
110Display options:
111.Bl -tag -width Ds
112.It Fl b
113Display statistics regarding the number, size
114.Pq logical, physical and allocated
115and deduplication of blocks.
116.It Fl c
117Verify the checksum of all metadata blocks while printing block statistics
118.Po see
119.Fl b
120.Pc .
121.Pp
122If specified multiple times, verify the checksums of all blocks.
123.It Fl C
124Display information about the configuration.
125If specified with no other options, instead display information about the cache
126file
127.Pq Pa /etc/zfs/zpool.cache .
128To specify the cache file to display, see
129.Fl U .
130.Pp
131If specified multiple times, and a pool name is also specified display both the
132cached configuration and the on-disk configuration.
133If specified multiple times with
134.Fl e
135also display the configuration that would be used were the pool to be imported.
136.It Fl d
137Display information about datasets.
138Specified once, displays basic dataset information: ID, create transaction,
139size, and object count.
140.Pp
141If specified multiple times provides greater and greater verbosity.
142.Pp
143If object IDs or object ID ranges are specified, display information about
144those specific objects or ranges only.
145.Pp
146An object ID range is specified in terms of a colon-separated tuple of
147the form
148.Ao start Ac : Ns Ao end Ac Ns Op : Ns Ao flags Ac .
149The fields
150.Ar start
151and
152.Ar end
153are integer object identifiers that denote the upper and lower bounds
154of the range.
155An
156.Ar end
157value of -1 specifies a range with no upper bound.
158The
159.Ar flags
160field optionally specifies a set of flags, described below, that control
161which object types are dumped.
162By default, all object types are dumped.
163A minus sign
164.Pq -
165negates the effect of the flag that follows it and has no effect unless
166preceded by the
167.Ar A
168flag.
169For example, the range 0:-1:A-d will dump all object types except for directories.
170.Pp
171.Bl -tag -compact -width Ds
172.It Sy A
173Dump all objects (this is the default)
174.It Sy d
175Dump ZFS directory objects
176.It Sy f
177Dump ZFS plain file objects
178.It Sy m
179Dump SPA space map objects
180.It Sy z
181Dump ZAP objects
182.It Sy -
183Negate the effect of next flag
184.El
185.It Fl D
186Display deduplication statistics, including the deduplication ratio
187.Pq Sy dedup ,
188compression ratio
189.Pq Sy compress ,
190inflation due to the zfs copies property
191.Pq Sy copies ,
192and an overall effective ratio
193.Pq Sy dedup No * Sy compress No / Sy copies .
194.It Fl DD
195Display a histogram of deduplication statistics, showing the allocated
196.Pq physically present on disk
197and referenced
198.Pq logically referenced in the pool
199block counts and sizes by reference count.
200.It Fl DDD
201Display the statistics independently for each deduplication table.
202.It Fl DDDD
203Dump the contents of the deduplication tables describing duplicate blocks.
204.It Fl DDDDD
205Also dump the contents of the deduplication tables describing unique blocks.
206.It Fl E Ar word0 : Ns Ar word1 Ns :…: Ns Ar word15
207Decode and display block from an embedded block pointer specified by the
208.Ar word
209arguments.
210.It Fl h
211Display pool history similar to
212.Nm zpool Cm history ,
213but include internal changes, transaction, and dataset information.
214.It Fl i
215Display information about intent log
216.Pq ZIL
217entries relating to each dataset.
218If specified multiple times, display counts of each intent log transaction type.
219.It Fl k
220Examine the checkpointed state of the pool.
221Note, the on disk format of the pool is not reverted to the checkpointed state.
222.It Fl l Ar device
223Read the vdev labels and L2ARC header from the specified device.
224.Nm Fl l
225will return 0 if valid label was found, 1 if error occurred, and 2 if no valid
226labels were found.
227The presence of L2ARC header is indicated by a specific
228sequence (L2ARC_DEV_HDR_MAGIC).
229If there is an accounting error in the size or the number of L2ARC log blocks
230.Nm Fl l
231will return 1.
232Each unique configuration is displayed only once.
233.It Fl ll Ar device
234In addition display label space usage stats.
235If a valid L2ARC header was found
236also display the properties of log blocks used for restoring L2ARC contents
237(persistent L2ARC).
238.It Fl lll Ar device
239Display every configuration, unique or not.
240If a valid L2ARC header was found
241also display the properties of log entries in log blocks used for restoring
242L2ARC contents (persistent L2ARC).
243.Pp
244If the
245.Fl q
246option is also specified, don't print the labels or the L2ARC header.
247.Pp
248If the
249.Fl u
250option is also specified, also display the uberblocks on this device.
251Specify multiple times to increase verbosity.
252.It Fl L
253Disable leak detection and the loading of space maps.
254By default,
255.Nm
256verifies that all non-free blocks are referenced, which can be very expensive.
257.It Fl m
258Display the offset, spacemap, free space of each metaslab, all the log
259spacemaps and their obsolete entry statistics.
260.It Fl mm
261Also display information about the on-disk free space histogram associated with
262each metaslab.
263.It Fl mmm
264Display the maximum contiguous free space, the in-core free space histogram, and
265the percentage of free space in each space map.
266.It Fl mmmm
267Display every spacemap record.
268.It Fl M
269Display the offset, spacemap, and free space of each metaslab.
270.It Fl MM
271Also display information about the maximum contiguous free space and the
272percentage of free space in each space map.
273.It Fl MMM
274Display every spacemap record.
275.It Fl O Ar dataset path
276Look up the specified
277.Ar path
278inside of the
279.Ar dataset
280and display its metadata and indirect blocks.
281Specified
282.Ar path
283must be relative to the root of
284.Ar dataset .
285This option can be combined with
286.Fl v
287for increasing verbosity.
288.It Fl r Ar dataset path destination
289Copy the specified
290.Ar path
291inside of the
292.Ar dataset
293to the specified destination.
294Specified
295.Ar path
296must be relative to the root of
297.Ar dataset .
298This option can be combined with
299.Fl v
300for increasing verbosity.
301.It Xo
302.Fl R Ar poolname vdev : Ns Ar offset : Ns Oo Ar lsize Ns / Oc Ns Ar psize Ns Op : Ns Ar flags
303.Xc
304Read and display a block from the specified device.
305By default the block is displayed as a hex dump, but see the description of the
306.Sy r
307flag, below.
308.Pp
309The block is specified in terms of a colon-separated tuple
310.Ar vdev
311.Pq an integer vdev identifier
312.Ar offset
313.Pq the offset within the vdev
314.Ar size
315.Pq the physical size, or logical size / physical size
316of the block to read and, optionally,
317.Ar flags
318.Pq a set of flags, described below .
319.Pp
320.Bl -tag -compact -width "b offset"
321.It Sy b Ar offset
322Print block pointer at hex offset
323.It Sy c
324Calculate and display checksums
325.It Sy d
326Decompress the block.
327Set environment variable
328.Nm ZDB_NO_ZLE
329to skip zle when guessing.
330.It Sy e
331Byte swap the block
332.It Sy g
333Dump gang block header
334.It Sy i
335Dump indirect block
336.It Sy r
337Dump raw uninterpreted block data
338.It Sy v
339Verbose output for guessing compression algorithm
340.El
341.It Fl s
342Report statistics on
343.Nm zdb
344I/O.
345Display operation counts, bandwidth, and error counts of I/O to the pool from
346.Nm .
347.It Fl S
348Simulate the effects of deduplication, constructing a DDT and then display
349that DDT as with
350.Fl DD .
351.It Fl u
352Display the current uberblock.
353.El
354.Pp
355Other options:
356.Bl -tag -width Ds
357.It Fl A
358Do not abort should any assertion fail.
359.It Fl AA
360Enable panic recovery, certain errors which would otherwise be fatal are
361demoted to warnings.
362.It Fl AAA
363Do not abort if asserts fail and also enable panic recovery.
364.It Fl e Oo Fl p Ar path Oc Ns …
365Operate on an exported pool, not present in
366.Pa /etc/zfs/zpool.cache .
367The
368.Fl p
369flag specifies the path under which devices are to be searched.
370.It Fl x Ar dumpdir
371All blocks accessed will be copied to files in the specified directory.
372The blocks will be placed in sparse files whose name is the same as
373that of the file or device read.
374.Nm
375can be then run on the generated files.
376Note that the
377.Fl bbc
378flags are sufficient to access
379.Pq and thus copy
380all metadata on the pool.
381.It Fl F
382Attempt to make an unreadable pool readable by trying progressively older
383transactions.
384.It Fl G
385Dump the contents of the zfs_dbgmsg buffer before exiting
386.Nm .
387zfs_dbgmsg is a buffer used by ZFS to dump advanced debug information.
388.It Fl I Ar inflight I/Os
389Limit the number of outstanding checksum I/Os to the specified value.
390The default value is 200.
391This option affects the performance of the
392.Fl c
393option.
394.It Fl o Ar var Ns = Ns Ar value …
395Set the given global libzpool variable to the provided value.
396The value must be an unsigned 32-bit integer.
397Currently only little-endian systems are supported to avoid accidentally setting
398the high 32 bits of 64-bit variables.
399.It Fl P
400Print numbers in an unscaled form more amenable to parsing, e.g.\&
401.Sy 1000000
402rather than
403.Sy 1M .
404.It Fl t Ar transaction
405Specify the highest transaction to use when searching for uberblocks.
406See also the
407.Fl u
408and
409.Fl l
410options for a means to see the available uberblocks and their associated
411transaction numbers.
412.It Fl U Ar cachefile
413Use a cache file other than
414.Pa /etc/zfs/zpool.cache .
415.It Fl v
416Enable verbosity.
417Specify multiple times for increased verbosity.
418.It Fl V
419Attempt verbatim import.
420This mimics the behavior of the kernel when loading a pool from a cachefile.
421Only usable with
422.Fl e .
423.It Fl X
424Attempt
425.Qq extreme
426transaction rewind, that is attempt the same recovery as
427.Fl F
428but read transactions otherwise deemed too old.
429.It Fl Y
430Attempt all possible combinations when reconstructing indirect split blocks.
431This flag disables the individual I/O deadman timer in order to allow as
432much time as required for the attempted reconstruction.
433.It Fl y
434Perform validation for livelists that are being deleted.
435Scans through the livelist and metaslabs, checking for duplicate entries
436and compares the two, checking for potential double frees.
437If it encounters issues, warnings will be printed, but the command will not
438necessarily fail.
439.El
440.Pp
441Specifying a display option more than once enables verbosity for only that
442option, with more occurrences enabling more verbosity.
443.Pp
444If no options are specified, all information about the named pool will be
445displayed at default verbosity.
446.
447.Sh EXAMPLES
448.Bl -tag -width Ds
449.It Xo
450.Sy Example 1 :
451Display the configuration of imported pool
452.Ar rpool
453.Xc
454.Bd -literal
455.No # Nm zdb Fl C Ar rpool
456MOS Configuration:
457        version: 28
458        name: 'rpool'
459460.Ed
461.It Xo
462.Sy Example 2 :
463Display basic dataset information about
464.Ar rpool
465.Xc
466.Bd -literal
467.No # Nm zdb Fl d Ar rpool
468Dataset mos [META], ID 0, cr_txg 4, 26.9M, 1051 objects
469Dataset rpool/swap [ZVOL], ID 59, cr_txg 356, 486M, 2 objects
470471.Ed
472.It Xo
473.Sy Example 3 :
474Display basic information about object 0 in
475.Ar rpool/export/home
476.Xc
477.Bd -literal
478.No # Nm zdb Fl d Ar rpool/export/home 0
479Dataset rpool/export/home [ZPL], ID 137, cr_txg 1546, 32K, 8 objects
480
481    Object  lvl   iblk   dblk  dsize  lsize   %full  type
482         0    7    16K    16K  15.0K    16K   25.00  DMU dnode
483.Ed
484.It Xo
485.Sy Example 4 :
486Display the predicted effect of enabling deduplication on
487.Ar rpool
488.Xc
489.Bd -literal
490.No # Nm zdb Fl S Ar rpool
491Simulated DDT histogram:
492
493bucket              allocated                       referenced
494______   ______________________________   ______________________________
495refcnt   blocks   LSIZE   PSIZE   DSIZE   blocks   LSIZE   PSIZE   DSIZE
496------   ------   -----   -----   -----   ------   -----   -----   -----
497     1     694K   27.1G   15.0G   15.0G     694K   27.1G   15.0G   15.0G
498     2    35.0K   1.33G    699M    699M    74.7K   2.79G   1.45G   1.45G
499500dedup = 1.11, compress = 1.80, copies = 1.00, dedup * compress / copies = 2.00
501.Ed
502.El
503.
504.Sh SEE ALSO
505.Xr zfs 8 ,
506.Xr zpool 8
507