man/man8/zdb.8

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