e2fsck/e2fsck.8.in

   1 .\" -*- nroff -*-
   2 .\" Copyright 1993, 1994, 1995 by Theodore Ts'o.  All Rights Reserved.
   3 .\" This file may be copied under the terms of the GNU Public License.
   4 .\"
   5 .TH E2FSCK 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
   6 .SH NAME
   7 e2fsck \- check a Linux ext2/ext3/ext4 file system
   8 .SH SYNOPSIS
   9 .B e2fsck
  10 [
  11 .B \-pacnyrdfkvtDFV
  12 ]
  13 [
  14 .B \-b
  15 .I superblock
  16 ]
  17 [
  18 .B \-B
  19 .I blocksize
  20 ]
  21 [
  22 .BR \-l | \-L
  23 .I bad_blocks_file
  24 ]
  25 [
  26 .B \-C
  27 .I fd
  28 ]
  29 @JDEV@[
  30 @JDEV@.B \-j
  31 @JDEV@.I external-journal
  32 @JDEV@]
  33 [
  34 .B \-E
  35 .I extended_options
  36 ]
  37 [
  38 .B \-z
  39 .I undo_file
  40 ]
  41 .I device
  42 .SH DESCRIPTION
  43 .B e2fsck
  44 is used to check the ext2/ext3/ext4 family of file systems.
  45 For ext3 and ext4 filesystems that use a journal, if the system has been
  46 shut down uncleanly without any errors, normally, after replaying the
  47 committed transactions  in the journal, the file system should be
  48 marked as clean.   Hence, for filesystems that use journalling,
  49 .B e2fsck
  50 will normally replay the journal and exit, unless its superblock
  51 indicates that further checking is required.
  52 .PP
  53 .I device
  54 is a block device (e.g.,
  55 .IR /dev/sdc1 )
  56 or file containing the file system.
  57 .PP
  58 Note that in general it is not safe to run
  59 .B e2fsck
  60 on mounted filesystems.  The only exception is if the
  61 .B \-n
  62 option is specified, and
  63 .BR \-c ,
  64 .BR \-l ,
  65 or
  66 .B -L
  67 options are
  68 .I not
  69 specified.   However, even if it is safe to do so, the results printed by
  70 .B e2fsck
  71 are not valid if the filesystem is mounted.   If
  72 .B e2fsck
  73 asks whether or not you should check a filesystem which is mounted,
  74 the only correct answer is ``no''.  Only experts who really know what
  75 they are doing should consider answering this question in any other way.
  76 .PP
  77 If
  78 .B e2fsck
  79 is run in interactive mode (meaning that none of
  80 .BR \-y ,
  81 .BR \-n ,
  82 or
  83 .BR \-p
  84 are specified), the program will ask the user to fix each problem found in the
  85 filesystem.  A response of 'y' will fix the error; 'n' will leave the error
  86 unfixed; and 'a' will fix the problem and all subsequent problems; pressing
  87 Enter will proceed with the default response, which is printed before the
  88 question mark.  Pressing Control-C terminates e2fsck immediately.
  89 .SH OPTIONS
  90 .TP
  91 .B \-a
  92 This option does the same thing as the
  93 .B \-p
  94 option.  It is provided for backwards compatibility only; it is
  95 suggested that people use
  96 .B \-p
  97 option whenever possible.
  98 .TP
  99 .BI \-b " superblock"
 100 Instead of using the normal superblock, use an alternative superblock
 101 specified by
 102 .IR superblock .
 103 This option is normally used when the primary superblock has been
 104 corrupted.  The location of backup superblocks is dependent on the
 105 filesystem's blocksize, the number of blocks per group, and features
 106 such as
 107 .BR sparse_super .
 108 .IP
 109 Additional backup superblocks can be determined by using the
 110 .B mke2fs
 111 program using the
 112 .B \-n
 113 option to print out where the superblocks exist, supposing
 114 .B mke2fs
 115 is supplied with arguments that are consistent with the filesystem's layout
 116 (e.g. blocksize, blocks per group,
 117 .BR sparse_super ,
 118 etc.).
 119 .IP
 120 If an alternative superblock is specified and
 121 the filesystem is not opened read-only, e2fsck will make sure that the
 122 primary superblock is updated appropriately upon completion of the
 123 filesystem check.
 124 .TP
 125 .BI \-B " blocksize"
 126 Normally,
 127 .B e2fsck
 128 will search for the superblock at various different
 129 block sizes in an attempt to find the appropriate block size.
 130 This search can be fooled in some cases.  This option forces
 131 .B e2fsck
 132 to only try locating the superblock at a particular blocksize.
 133 If the superblock is not found,
 134 .B e2fsck
 135 will terminate with a fatal error.
 136 .TP
 137 .B \-c
 138 This option causes
 139 .B e2fsck
 140 to use
 141 .BR badblocks (8)
 142 program to do a read-only scan of the device in order to find any bad
 143 blocks.  If any bad blocks are found, they are added to the bad block
 144 inode to prevent them from being allocated to a file or directory.  If
 145 this option is specified twice, then the bad block scan will be done
 146 using a non-destructive read-write test.
 147 .TP
 148 .BI \-C " fd"
 149 This option causes
 150 .B e2fsck
 151 to write completion information to the specified file descriptor
 152 so that the progress of the filesystem
 153 check can be monitored.  This option is typically used by programs
 154 which are running
 155 .BR e2fsck .
 156 If the file descriptor number is negative, then absolute value of
 157 the file descriptor will be used, and the progress information will be
 158 suppressed initially.  It can later be enabled by sending the
 159 .B e2fsck
 160 process a SIGUSR1 signal.
 161 If the file descriptor specified is 0,
 162 .B e2fsck
 163 will print a completion bar as it goes about its business.  This requires
 164 that e2fsck is running on a video console or terminal.
 165 .TP
 166 .B \-d
 167 Print debugging output (useless unless you are debugging
 168 .BR e2fsck ).
 169 .TP
 170 .B \-D
 171 Optimize directories in filesystem.  This option causes e2fsck to
 172 try to optimize all directories, either by reindexing them if the
 173 filesystem supports directory indexing,  or by sorting and compressing
 174 directories for smaller directories, or for filesystems using
 175 traditional linear directories.
 176 .IP
 177 Even without the
 178 .B \-D
 179 option,
 180 .B e2fsck
 181 may sometimes optimize a few directories --- for example, if
 182 directory indexing is enabled and a directory is not indexed and would
 183 benefit from being indexed, or if the index structures are corrupted
 184 and need to be rebuilt.  The
 185 .B \-D
 186 option forces all directories in the filesystem to be optimized.  This can
 187 sometimes make them a little smaller and slightly faster to search, but
 188 in practice, you should rarely need to use this option.
 189 .IP
 190 The
 191 .B \-D
 192 option will detect directory entries with duplicate names in a single
 193 directory, which e2fsck normally does not enforce for performance reasons.
 194 .TP
 195 .BI \-E " extended_options"
 196 Set e2fsck extended options.  Extended options are comma
 197 separated, and may take an argument using the equals ('=') sign.  The
 198 following options are supported:
 199 .RS 1.2i
 200 .TP
 201 .BI ea_ver= extended_attribute_version
 202 Set the version of the extended attribute blocks which
 203 .B e2fsck
 204 will require while checking the filesystem.  The version number may
 205 be 1 or 2.  The default extended attribute version format is 2.
 206 .TP
 207 .BI journal_only
 208 Only replay the journal if required, but do not perform any further checks
 209 or repairs.
 210 .TP
 211 .BI fragcheck
 212 During pass 1, print a detailed report of any discontiguous blocks for
 213 files in the filesystem.
 214 .TP
 215 .BI discard
 216 Attempt to discard free blocks and unused inode blocks after the full
 217 filesystem check (discarding blocks is useful on solid state devices and sparse
 218 / thin-provisioned storage). Note that discard is done in pass 5 AFTER the
 219 filesystem has been fully checked and only if it does not contain recognizable
 220 errors. However there might be cases where
 221 .B e2fsck
 222 does not fully recognize a problem and hence in this case this
 223 option may prevent you from further manual data recovery.
 224 .TP
 225 .BI nodiscard
 226 Do not attempt to discard free blocks and unused inode blocks. This option is
 227 exactly the opposite of discard option. This is set as default.
 228 .TP
 229 .BI no_optimize_extents
 230 Do not offer to optimize the extent tree by eliminating unnecessary
 231 width or depth.  This can also be enabled in the options section of
 232 .BR /etc/e2fsck.conf .
 233 .TP
 234 .BI optimize_extents
 235 Offer to optimize the extent tree by eliminating unnecessary
 236 width or depth.  This is the default unless otherwise specified in
 237 .BR /etc/e2fsck.conf .
 238 .TP
 239 .BI inode_count_fullmap
 240 Trade off using memory for speed when checking a file system with a
 241 large number of hard-linked files.  The amount of memory required is
 242 proportional to the number of inodes in the file system.  For large file
 243 systems, this can be gigabytes of memory.  (For example, a 40TB file system
 244 with 2.8 billion inodes will consume an additional 5.7 GB memory if this
 245 optimization is enabled.)  This optimization can also be enabled in the
 246 options section of
 247 .BR /etc/e2fsck.conf .
 248 .TP
 249 .BI no_inode_count_fullmap
 250 Disable the
 251 .B inode_count_fullmap
 252 optimization.  This is the default unless otherwise specified in
 253 .BR /etc/e2fsck.conf .
 254 .TP
 255 .BI readahead_kb
 256 Use this many KiB of memory to pre-fetch metadata in the hopes of reducing
 257 e2fsck runtime.  By default, this is set to the size of two block groups' inode
 258 tables (typically 4MiB on a regular ext4 filesystem); if this amount is more
 259 than 1/50th of total physical memory, readahead is disabled.  Set this to zero
 260 to disable readahead entirely.
 261 .TP
 262 .BI bmap2extent
 263 Convert block-mapped files to extent-mapped files.
 264 .TP
 265 .BI fixes_only
 266 Only fix damaged metadata; do not optimize htree directories or compress
 267 extent trees.  This option is incompatible with the -D and -E bmap2extent
 268 options.
 269 .TP
 270 .BI unshare_blocks
 271 If the filesystem has shared blocks, with the shared blocks read-only feature
 272 enabled, then this will unshare all shared blocks and unset the read-only
 273 feature bit. If there is not enough free space then the operation will fail.
 274 If the filesystem does not have the read-only feature bit, but has shared
 275 blocks anyway, then this option will have no effect. Note when using this
 276 option, if there is no free space to clone blocks, there is no prompt to
 277 delete files and instead the operation will fail.
 278 .IP
 279 Note that unshare_blocks implies the "-f" option to ensure that all passes
 280 are run. Additionally, if "-n" is also specified, e2fsck will simulate trying
 281 to allocate enough space to deduplicate. If this fails, the exit code will
 282 be non-zero.
 283 .RE
 284 .TP
 285 .B \-f
 286 Force checking even if the file system seems clean.
 287 .TP
 288 .B \-F
 289 Flush the filesystem device's buffer caches before beginning.  Only
 290 really useful for doing
 291 .B e2fsck
 292 time trials.
 293 @JDEV@.TP
 294 @JDEV@.BI \-j " external-journal"
 295 @JDEV@Set the pathname where the external-journal for this filesystem can be
 296 @JDEV@found.
 297 .TP
 298 .BI \-k
 299 When combined with the
 300 .B \-c
 301 option, any existing bad blocks in the bad blocks list are preserved,
 302 and any new bad blocks found by running
 303 .BR badblocks (8)
 304 will be added to the existing bad blocks list.
 305 .TP
 306 .BI \-l " filename"
 307 Add the block numbers listed in the file specified by
 308 .I filename
 309 to the list of bad blocks.  The format of this file is the same as the
 310 one generated by the
 311 .BR badblocks (8)
 312 program.  Note that the block numbers are based on the blocksize
 313 of the filesystem.  Hence,
 314 .BR badblocks (8)
 315 must be given the blocksize of the filesystem in order to obtain correct
 316 results.  As a result, it is much simpler and safer to use the
 317 .B -c
 318 option to
 319 .BR e2fsck ,
 320 since it will assure that the correct parameters are passed to the
 321 .B badblocks
 322 program.
 323 .TP
 324 .BI \-L " filename"
 325 Set the bad blocks list to be the list of blocks specified by
 326 .IR filename .
 327 (This option is the same as the
 328 .B \-l
 329 option, except the bad blocks list is cleared before the blocks listed
 330 in the file are added to the bad blocks list.)
 331 .TP
 332 .B \-n
 333 Open the filesystem read-only, and assume an answer of `no' to all
 334 questions.  Allows
 335 .B e2fsck
 336 to be used non-interactively.  This option
 337 may not be specified at the same time as the
 338 .B \-p
 339 or
 340 .B \-y
 341 options.
 342 .TP
 343 .B \-p
 344 Automatically repair ("preen") the file system.  This option will cause
 345 .B e2fsck
 346 to automatically
 347 fix any filesystem problems that can be safely fixed without human
 348 intervention.  If
 349 .B e2fsck
 350 discovers a problem which may require the system administrator
 351 to take additional corrective action,
 352 .B e2fsck
 353 will print a description of the problem and then exit with the value 4
 354 logically or'ed into the exit code.  (See the \fBEXIT CODE\fR section.)
 355 This option is normally used by the system's boot scripts.  It may not
 356 be specified at the same time as the
 357 .B \-n
 358 or
 359 .B \-y
 360 options.
 361 .TP
 362 .B \-r
 363 This option does nothing at all; it is provided only for backwards
 364 compatibility.
 365 .TP
 366 .B \-t
 367 Print timing statistics for
 368 .BR e2fsck .
 369 If this option is used twice, additional timing statistics are printed
 370 on a pass by pass basis.
 371 .TP
 372 .B \-v
 373 Verbose mode.
 374 .TP
 375 .B \-V
 376 Print version information and exit.
 377 .TP
 378 .B \-y
 379 Assume an answer of `yes' to all questions; allows
 380 .B e2fsck
 381 to be used non-interactively.  This option
 382 may not be specified at the same time as the
 383 .B \-n
 384 or
 385 .B \-p
 386 options.
 387 .TP
 388 .BI \-z " undo_file"
 389 Before overwriting a file system block, write the old contents of the block to
 390 an undo file.  This undo file can be used with e2undo(8) to restore the old
 391 contents of the file system should something go wrong.  If the empty string is
 392 passed as the undo_file argument, the undo file will be written to a file named
 393 e2fsck-\fIdevice\fR.e2undo in the directory specified via the
 394 \fIE2FSPROGS_UNDO_DIR\fR environment variable.
 395
 396 WARNING: The undo file cannot be used to recover from a power or system crash.
 397 .SH EXIT CODE
 398 The exit code returned by
 399 .B e2fsck
 400 is the sum of the following conditions:
 401 .br
 402 \       0\      \-\ No errors
 403 .br
 404 \       1\      \-\ File system errors corrected
 405 .br
 406 \       2\      \-\ File system errors corrected, system should
 407 .br
 408 \       \       \ \ be rebooted
 409 .br
 410 \       4\      \-\ File system errors left uncorrected
 411 .br
 412 \       8\      \-\ Operational error
 413 .br
 414 \       16\     \-\ Usage or syntax error
 415 .br
 416 \       32\     \-\ E2fsck canceled by user request
 417 .br
 418 \       128\    \-\ Shared library error
 419 .br
 420 .SH SIGNALS
 421 The following signals have the following effect when sent to
 422 .BR e2fsck .
 423 .TP
 424 .B SIGUSR1
 425 This signal causes
 426 .B e2fsck
 427 to start displaying a completion bar or emitting progress information.
 428 (See discussion of the
 429 .B \-C
 430 option.)
 431 .TP
 432 .B SIGUSR2
 433 This signal causes
 434 .B e2fsck
 435 to stop displaying a completion bar or emitting progress information.
 436 .SH REPORTING BUGS
 437 Almost any piece of software will have bugs.  If you manage to find a
 438 filesystem which causes
 439 .B e2fsck
 440 to crash, or which
 441 .B e2fsck
 442 is unable to repair, please report it to the author.
 443 .PP
 444 Please include as much information as possible in your bug report.
 445 Ideally, include a complete transcript of the
 446 .B e2fsck
 447 run, so I can see exactly what error messages are displayed.  (Make sure
 448 the messages printed by
 449 .B e2fsck
 450 are in English; if your system has been
 451 configured so that
 452 .BR e2fsck 's
 453 messages have been translated into another language, please set the the
 454 .B LC_ALL
 455 environment variable to
 456 .B C
 457 so that the transcript of e2fsck's output will be useful to me.)
 458 If you
 459 have a writable filesystem where the transcript can be stored, the
 460 .BR script (1)
 461 program is a handy way to save the output of
 462 .B e2fsck
 463 to a file.
 464 .PP
 465 It is also useful to send the output of
 466 .BR dumpe2fs (8).
 467 If a specific inode or inodes seems to be giving
 468 .B e2fsck
 469 trouble, try running the
 470 .BR debugfs (8)
 471 command and send the output of the
 472 .BR stat (1u)
 473 command run on the relevant inode(s).  If the inode is a directory, the
 474 .B debugfs
 475 .I dump
 476 command will allow you to extract the contents of the directory inode,
 477 which can sent to me after being first run through
 478 .BR uuencode (1).
 479 The most useful data you can send to help reproduce
 480 the bug is a compressed raw image dump of the filesystem, generated using
 481 .BR e2image (8).
 482 See the
 483 .BR e2image (8)
 484 man page for more details.
 485 .PP
 486 Always include the full version string which
 487 .B e2fsck
 488 displays when it is run, so I know which version you are running.
 489 .SH ENVIRONMENT
 490 .TP
 491 .BI E2FSCK_CONFIG
 492 Determines the location of the configuration file (see
 493 .BR e2fsck.conf (5)).
 494 .SH AUTHOR
 495 This version of
 496 .B e2fsck
 497 was written by Theodore Ts'o <tytso@mit.edu>.
 498 .SH SEE ALSO
 499 .BR e2fsck.conf (5),
 500 .BR badblocks (8),
 501 .BR dumpe2fs (8),
 502 .BR debugfs (8),
 503 .BR e2image (8),
 504 .BR mke2fs (8),
 505 .BR tune2fs (8)