disk-utils/fsck.8

   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 FSCK 8 "February 2009" "util-linux" "System Administration"
   6 .SH NAME
   7 fsck \- check and repair a Linux filesystem
   8 .SH SYNOPSIS
   9 .B fsck
  10 .RB [ \-lrsAVRTMNP ]
  11 .RB [ \-C
  12 .RI [ fd ]]
  13 .RB [ \-t
  14 .IR fstype ]
  15 .RI [ filesystem ...]
  16 .RB [ \-\- ]
  17 .RI [ fs-specific-options ]
  18 .SH DESCRIPTION
  19 .B fsck
  20 is used to check and optionally repair one or more Linux filesystems.
  21 .I filesys
  22 can be a device name (e.g.
  23 .IR /dev/hdc1 ", " /dev/sdb2 ),
  24 a mount point (e.g.
  25 .IR / ", " /usr ", " /home ),
  26 or an ext2 label or UUID specifier (e.g.
  27 UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root).
  28 Normally, the
  29 .B fsck
  30 program will try to handle filesystems on different physical disk drives
  31 in parallel to reduce the total amount of time needed to check all of them.
  32 .PP
  33 If no filesystems are specified on the command line, and the
  34 .B \-A
  35 option is not specified,
  36 .B fsck
  37 will default to checking filesystems in
  38 .B /etc/fstab
  39 serially.  This is equivalent to the
  40 .B \-As
  41 options.
  42 .PP
  43 The exit code returned by
  44 .B fsck
  45 is the sum of the following conditions:
  46 .PP
  47 .RS
  48 .PD 0
  49 .TP
  50 .B 0
  51 No errors
  52 .TP
  53 .B 1
  54 Filesystem errors corrected
  55 .TP
  56 .B 2
  57 System should be rebooted
  58 .TP
  59 .B 4
  60 Filesystem errors left uncorrected
  61 .TP
  62 .B 8
  63 Operational error
  64 .TP
  65 .B 16
  66 Usage or syntax error
  67 .TP
  68 .B 32
  69 Checking canceled by user request
  70 .TP
  71 .B 128
  72 Shared-library error
  73 .PD
  74 .RE
  75 .PP
  76 The exit code returned when multiple filesystems are checked
  77 is the bit-wise OR of the exit codes for each
  78 filesystem that is checked.
  79 .PP
  80 In actuality,
  81 .B fsck
  82 is simply a front-end for the various filesystem checkers
  83 (\fBfsck\fR.\fIfstype\fR) available under Linux.  The
  84 filesystem-specific checker is searched for in
  85 .I /sbin
  86 first, then in
  87 .I /etc/fs
  88 and
  89 .IR /etc ,
  90 and finally in the directories listed in the PATH environment
  91 variable.  Please see the filesystem-specific checker manual pages for
  92 further details.
  93 .SH OPTIONS
  94 .TP
  95 .B \-l
  96 Lock the whole-disk device by an exclusive
  97 .BR flock (2).
  98 This option can be used with one device only (this means that \fB-A\fR and
  99 \fB-l\fR are mutually exclusive).  This option is recommended when more
 100 .BR fsck (8)
 101 instances are executed in the same time.  The option is ignored when used for
 102 multiple devices or for non-rotating disks.  \fBfsck\fR does not lock underlying
 103 devices when executed to check stacked devices (e.g. MD or DM) -- this feature is
 104 not implemented yet.
 105 .TP
 106 .B \-r
 107 Report certain statistics for each fsck when it completes. These statistics
 108 include the exit status, the maximum run set size (in kilobytes), the elapsed
 109 all-clock time and the user and system CPU time used by the fsck run. For
 110 example:
 111
 112 /dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592, sys 0.86186
 113 .TP
 114 .B \-s
 115 Serialize
 116 .B fsck
 117 operations.  This is a good idea if you are checking multiple
 118 filesystems and the checkers are in an interactive mode.  (Note:
 119 .BR e2fsck (8)
 120 runs in an interactive mode by default.  To make
 121 .BR e2fsck (8)
 122 run in a non-interactive mode, you must either specify the
 123 .B \-p
 124 or
 125 .B \-a
 126 option, if you wish for errors to be corrected automatically, or the
 127 .B \-n
 128 option if you do not.)
 129 .TP
 130 .BI \-t " fslist"
 131 Specifies the type(s) of filesystem to be checked.  When the
 132 .B \-A
 133 flag is specified, only filesystems that match
 134 .I fslist
 135 are checked.  The
 136 .I fslist
 137 parameter is a comma-separated list of filesystems and options
 138 specifiers.  All of the filesystems in this comma-separated list may be
 139 prefixed by a negation operator
 140 .RB ' no '
 141 or
 142 .RB ' ! ',
 143 which requests that only those filesystems not listed in
 144 .I fslist
 145 will be checked.  If none of the filesystems in
 146 .I fslist
 147 is prefixed by a negation operator, then only those listed filesystems
 148 will be checked.
 149 .sp
 150 Options specifiers may be included in the comma-separated
 151 .IR fslist .
 152 They must have the format
 153 .BI opts= fs-option\fR.
 154 If an options specifier is present, then only filesystems which contain
 155 .I fs-option
 156 in their mount options field of
 157 .B /etc/fstab
 158 will be checked.  If the options specifier is prefixed by a negation
 159 operator, then only
 160 those filesystems that do not have
 161 .I fs-option
 162 in their mount options field of
 163 .B /etc/fstab
 164 will be checked.
 165 .sp
 166 For example, if
 167 .B opts=ro
 168 appears in
 169 .IR fslist ,
 170 then only filesystems listed in
 171 .B /etc/fstab
 172 with the
 173 .B ro
 174 option will be checked.
 175 .sp
 176 For compatibility with Mandrake distributions whose boot scripts
 177 depend upon an unauthorized UI change to the
 178 .B fsck
 179 program, if a filesystem type of
 180 .B loop
 181 is found in
 182 .IR fslist ,
 183 it is treated as if
 184 .B opts=loop
 185 were specified as an argument to the
 186 .B \-t
 187 option.
 188 .sp
 189 Normally, the filesystem type is deduced by searching for
 190 .I filesys
 191 in the
 192 .I /etc/fstab
 193 file and using the corresponding entry.
 194 If the type can not be deduced, and there is only a single filesystem
 195 given as an argument to the
 196 .B \-t
 197 option,
 198 .B fsck
 199 will use the specified filesystem type.  If this type is not
 200 available, then the default filesystem type (currently ext2) is used.
 201 .TP
 202 .B \-A
 203 Walk through the
 204 .I /etc/fstab
 205 file and try to check all filesystems in one run.  This option is
 206 typically used from the
 207 .I /etc/rc
 208 system initialization file, instead of multiple commands for checking
 209 a single filesystem.
 210 .sp
 211 The root filesystem will be checked first unless the
 212 .B \-P
 213 option is specified (see below).  After that,
 214 filesystems will be checked in the order specified by the
 215 .I fs_passno
 216 (the sixth) field in the
 217 .I /etc/fstab
 218 file.
 219 Filesystems with a
 220 .I fs_passno
 221 value of 0 are skipped and are not checked at all.  Filesystems with a
 222 .I fs_passno
 223 value of greater than zero will be checked in order,
 224 with filesystems with the lowest
 225 .I fs_passno
 226 number being checked first.
 227 If there are multiple filesystems with the same pass number,
 228 .B fsck
 229 will attempt to check them in parallel, although it will avoid running
 230 multiple filesystem checks on the same physical disk.
 231 .sp
 232 .B fsck
 233 does not check stacked devices (RAIDs, dm-crypt, ...) in parallel with any other
 234 device.  See below for FSCK_FORCE_ALL_PARALLEL setting.  The /sys filesystem is
 235 used to detemine dependencies between devices.
 236 .sp
 237 Hence, a very common configuration in
 238 .I /etc/fstab
 239 files is to set the root filesystem to have a
 240 .I fs_passno
 241 value of 1
 242 and to set all other filesystems to have a
 243 .I fs_passno
 244 value of 2.  This will allow
 245 .B fsck
 246 to automatically run filesystem checkers in parallel if it is advantageous
 247 to do so.  System administrators might choose
 248 not to use this configuration if they need to avoid multiple filesystem
 249 checks running in parallel for some reason --- for example, if the
 250 machine in question is short on memory so that
 251 excessive paging is a concern.
 252 .sp
 253 .B fsck
 254 normally does not check whether the device actually exists before
 255 calling a filesystem specific checker.  Therefore non-existing
 256 devices may cause the system to enter filesystem repair mode during
 257 boot if the filesystem specific checker returns a fatal error.  The
 258 .B /etc/fstab
 259 mount option
 260 .B nofail
 261 may be used to have
 262 .B fsck
 263 skip non-existing devices.
 264 .B fsck
 265 also skips non-existing devices that have the special filesystem type
 266 .BR auto .
 267 .TP
 268 .BR \-C \ [ \fIfd\fR ]
 269 Display completion/progress bars for those filesystem checkers (currently
 270 only for ext2 and ext3) which support them.  \fBfsck\fR will manage the
 271 filesystem checkers so that only one of them will display
 272 a progress bar at a time.  GUI front-ends may specify a file descriptor
 273 .IR fd ,
 274 in which case the progress bar information will be sent to that file descriptor.
 275 .TP
 276 .B \-M
 277 Do not check mounted filesystems and return an exit code of 0
 278 for mounted filesystems.
 279 .TP
 280 .B \-N
 281 Don't execute, just show what would be done.
 282 .TP
 283 .B \-P
 284 When the
 285 .B \-A
 286 flag is set, check the root filesystem in parallel with the other filesystems.
 287 This is not the safest thing in the world to do,
 288 since if the root filesystem is in doubt things like the
 289 .BR e2fsck (8)
 290 executable might be corrupted!  This option is mainly provided
 291 for those sysadmins who don't want to repartition the root
 292 filesystem to be small and compact (which is really the right solution).
 293 .TP
 294 .B \-R
 295 When checking all filesystems with the
 296 .B \-A
 297 flag, skip the root filesystem.  (This is useful in case the root
 298 filesystem has already been mounted read-write.)
 299 .TP
 300 .B \-T
 301 Don't show the title on startup.
 302 .TP
 303 .B \-V
 304 Produce verbose output, including all filesystem-specific commands
 305 that are executed.
 306 .TP
 307 .B fs-specific-options
 308 Options which are not understood by
 309 .B fsck
 310 are passed to the filesystem-specific checker.  These options
 311 .B must
 312 not take arguments, as there is no
 313 way for
 314 .B fsck
 315 to be able to properly guess which options take arguments and which
 316 don't.
 317 .IP
 318 Options and arguments which follow the
 319 .B \-\-
 320 are treated as filesystem-specific options to be passed to the
 321 filesystem-specific checker.
 322 .IP
 323 Please note that \fBfsck\fR is not
 324 designed to pass arbitrarily complicated options to filesystem-specific
 325 checkers.  If you're doing something complicated, please just
 326 execute the filesystem-specific checker directly.  If you pass
 327 .B fsck
 328 some horribly complicated options and arguments, and it doesn't do
 329 what you expect,
 330 .B don't bother reporting it as a bug.
 331 You're almost certainly doing something that you shouldn't be doing
 332 with
 333 .BR fsck.
 334 .PP
 335 Options to different filesystem-specific fsck's are not standardized.
 336 If in doubt, please consult the man pages of the filesystem-specific
 337 checker.  Although not guaranteed, the following options are supported
 338 by most filesystem checkers:
 339 .TP
 340 .B \-a
 341 Automatically repair the filesystem without any questions (use
 342 this option with caution).  Note that
 343 .BR e2fsck (8)
 344 supports
 345 .B \-a
 346 for backward compatibility only.  This option is mapped to
 347 .BR e2fsck 's
 348 .B \-p
 349 option which is safe to use, unlike the
 350 .B \-a
 351 option that some filesystem checkers support.
 352 .TP
 353 .B \-n
 354 For some filesystem-specific checkers, the
 355 .B \-n
 356 option will cause the fs-specific fsck to avoid attempting to repair any
 357 problems, but simply report such problems to stdout.  This is however
 358 not true for all filesystem-specific checkers.  In particular,
 359 .BR fsck.reiserfs (8)
 360 will not report any corruption if given this option.
 361 .BR fsck.minix (8)
 362 does not support the
 363 .B \-n
 364 option at all.
 365 .TP
 366 .B \-r
 367 Interactively repair the filesystem (ask for confirmations).  Note: It
 368 is generally a bad idea to use this option if multiple fsck's are being
 369 run in parallel.  Also note that this is
 370 .BR e2fsck 's
 371 default behavior; it supports this option for backward compatibility
 372 reasons only.
 373 .TP
 374 .B \-y
 375 For some filesystem-specific checkers, the
 376 .B \-y
 377 option will cause the fs-specific fsck to always attempt to fix any
 378 detected filesystem corruption automatically.  Sometimes an expert may
 379 be able to do better driving the fsck manually.  Note that
 380 .B not
 381 all filesystem-specific checkers implement this option.  In particular
 382 .BR fsck.minix (8)
 383 and
 384 .BR fsck.cramfs (8)
 385 do not support the
 386 .B -y
 387 option as of this writing.
 388 .SH FILES
 389 .IR /etc/fstab .
 390 .SH ENVIRONMENT VARIABLES
 391 The
 392 .B fsck
 393 program's behavior is affected by the following environment variables:
 394 .TP
 395 .B FSCK_FORCE_ALL_PARALLEL
 396 If this environment variable is set,
 397 .B fsck
 398 will attempt to check all of the specified filesystems in parallel, regardless of
 399 whether the filesystems appear to be on the same device.  (This is useful for
 400 RAID systems or high-end storage systems such as those sold by companies such
 401 as IBM or EMC.)  Note that the fs_passno value is still used.
 402 .TP
 403 .B FSCK_MAX_INST
 404 This environment variable will limit the maximum number of filesystem
 405 checkers that can be running at one time.  This allows configurations
 406 which have a large number of disks to avoid
 407 .B fsck
 408 starting too many filesystem checkers at once, which might overload
 409 CPU and memory resources available on the system.  If this value is
 410 zero, then an unlimited number of processes can be spawned.  This is
 411 currently the default, but future versions of
 412 .B fsck
 413 may attempt to automatically determine how many filesystem checks can
 414 be run based on gathering accounting data from the operating system.
 415 .TP
 416 .B PATH
 417 The
 418 .B PATH
 419 environment variable is used to find filesystem checkers.  A set of
 420 system directories are searched first:
 421 .BR /sbin ,
 422 .BR /sbin/fs.d ,
 423 .BR /sbin/fs ,
 424 .BR /etc/fs ,
 425 and
 426 .BR /etc .
 427 Then the set of directories found in the
 428 .B PATH
 429 environment are searched.
 430 .TP
 431 .B FSTAB_FILE
 432 This environment variable allows the system administrator
 433 to override the standard location of the
 434 .B /etc/fstab
 435 file.  It is also useful for developers who are testing
 436 .BR fsck .
 437 .TP
 438 .B LIBBLKID_DEBUG=0xffff
 439 enables debug output.
 440 .TP
 441 .B LIBMOUNT_DEBUG=0xffff
 442 enables debug output.
 443 .SH SEE ALSO
 444 .BR fstab (5),
 445 .BR mkfs (8),
 446 .BR fsck.ext2 (8)
 447 or
 448 .BR fsck.ext3 (8)
 449 or
 450 .BR e2fsck (8),
 451 .BR cramfsck (8),
 452 .BR fsck.minix (8),
 453 .BR fsck.msdos (8),
 454 .BR fsck.jfs (8),
 455 .BR fsck.nfs (8),
 456 .BR fsck.vfat (8),
 457 .BR fsck.xfs (8),
 458 .BR fsck.xiafs (8),
 459 .BR reiserfsck (8).
 460 .SH AUTHOR
 461 .MT tytso@mit.edu
 462 Theodore Ts'o
 463 .ME
 464 .SH AVAILABILITY
 465 The fsck command is part of the util-linux package and is available from
 466 .UR ftp://\:ftp.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 467 Linux Kernel Archive
 468 .UE .