disk-utils/fsck.8

   1 .\" Copyright 1993, 1994, 1995 by Theodore Ts'o.  All Rights Reserved.
   2 .\" This file may be copied under the terms of the GNU Public License.
   3 .\"
   4 .TH FSCK 8 "February 2009" "util-linux" "System Administration"
   5 .SH NAME
   6 fsck \- check and repair a Linux filesystem
   7 .SH SYNOPSIS
   8 .B fsck
   9 .RB [ \-lsAVRTMNP ]
  10 .RB [ \-r
  11 .RI [ fd ]]
  12 .RB [ \-C
  13 .RI [ fd ]]
  14 .RB [ \-t
  15 .IR fstype ]
  16 .RI [ filesystem \&...\&]
  17 .RB [ \-\- ]
  18 .RI [ fs-specific-options ]
  19 .SH DESCRIPTION
  20 .B fsck
  21 is used to check and optionally repair one or more Linux filesystems.
  22 .I filesys
  23 can be a device name (e.g.,
  24 .IR /dev/hdc1 ", " /dev/sdb2 ),
  25 a mount point (e.g.,
  26 .IR / ", " /usr ", " /home ),
  27 or an filesystem label or UUID specifier (e.g.,
  28 UUID=8868abf6-88c5-4a83-98b8-bfc24057f7bd or LABEL=root).
  29 Normally, the
  30 .B fsck
  31 program will try to handle filesystems on different physical disk drives
  32 in parallel to reduce the total amount of time needed to check all of them.
  33 .PP
  34 If no filesystems are specified on the command line, and the
  35 .B \-A
  36 option is not specified,
  37 .B fsck
  38 will default to checking filesystems in
  39 .I /etc/fstab
  40 serially.  This is equivalent to the
  41 .B \-As
  42 options.
  43 .PP
  44 The exit status returned by
  45 .B fsck
  46 is the sum of the following conditions:
  47 .PP
  48 .RS
  49 .PD 0
  50 .TP
  51 .B 0
  52 No errors
  53 .TP
  54 .B 1
  55 Filesystem errors corrected
  56 .TP
  57 .B 2
  58 System should be rebooted
  59 .TP
  60 .B 4
  61 Filesystem errors left uncorrected
  62 .TP
  63 .B 8
  64 Operational error
  65 .TP
  66 .B 16
  67 Usage or syntax error
  68 .TP
  69 .B 32
  70 Checking canceled by user request
  71 .TP
  72 .B 128
  73 Shared-library error
  74 .PD
  75 .RE
  76 .PP
  77 The exit status returned when multiple filesystems are checked
  78 is the bit-wise OR of the exit statuses for each
  79 filesystem that is checked.
  80 .PP
  81 In actuality,
  82 .B fsck
  83 is simply a front-end for the various filesystem checkers
  84 (\fBfsck\fR.\fIfstype\fR) available under Linux.  The
  85 filesystem-specific checker is searched for in the
  86 PATH environment variable. If the PATH is undefined then
  87 fallback to "/sbin".
  88 .PP
  89 Please see the filesystem-specific checker manual pages for
  90 further details.
  91 .SH OPTIONS
  92 .TP
  93 .B \-l
  94 Create an exclusive
  95 .BR flock (2)
  96 lock file (/run/fsck/<diskname>.lock) for whole-disk device.
  97 This option can be used with one device only (this means that \fB\-A\fR and
  98 \fB\-l\fR are mutually exclusive).  This option is recommended when more
  99 .BR fsck (8)
 100 instances are executed in the same time.  The option is ignored when used for
 101 multiple devices or for non-rotating disks.  \fBfsck\fR does not lock underlying
 102 devices when executed to check stacked devices (e.g.\& MD or DM) \(en this feature is
 103 not implemented yet.
 104 .TP
 105 .BR \-r \ [ \fIfd\fR ]
 106 Report certain statistics for each fsck when it completes.  These statistics
 107 include the exit status, the maximum run set size (in kilobytes), the elapsed
 108 all-clock time and the user and system CPU time used by the fsck run.  For
 109 example:
 110
 111 /dev/sda1: status 0, rss 92828, real 4.002804, user 2.677592, sys 0.86186
 112
 113 GUI front-ends may specify a file descriptor
 114 .IR fd ,
 115 in which case the progress bar information will be sent to that file descriptor
 116 in a machine parsable format.  For example:
 117
 118 /dev/sda1 0 92828 4.002804 2.677592 0.86186
 119 .TP
 120 .B \-s
 121 Serialize
 122 .B fsck
 123 operations.  This is a good idea if you are checking multiple
 124 filesystems and the checkers are in an interactive mode.  (Note:
 125 .BR e2fsck (8)
 126 runs in an interactive mode by default.  To make
 127 .BR e2fsck (8)
 128 run in a non-interactive mode, you must either specify the
 129 .B \-p
 130 or
 131 .B \-a
 132 option, if you wish for errors to be corrected automatically, or the
 133 .B \-n
 134 option if you do not.)
 135 .TP
 136 .BI \-t " fslist"
 137 Specifies the type(s) of filesystem to be checked.  When the
 138 .B \-A
 139 flag is specified, only filesystems that match
 140 .I fslist
 141 are checked.  The
 142 .I fslist
 143 parameter is a comma-separated list of filesystems and options
 144 specifiers.  All of the filesystems in this comma-separated list may be
 145 prefixed by a negation operator
 146 .RB ' no '
 147 or
 148 .RB ' ! ',
 149 which requests that only those filesystems not listed in
 150 .I fslist
 151 will be checked.  If none of the filesystems in
 152 .I fslist
 153 is prefixed by a negation operator, then only those listed filesystems
 154 will be checked.
 155 .sp
 156 Options specifiers may be included in the comma-separated
 157 .IR fslist .
 158 They must have the format
 159 .BI opts= fs-option\fR.
 160 If an options specifier is present, then only filesystems which contain
 161 .I fs-option
 162 in their mount options field of
 163 .I /etc/fstab
 164 will be checked.  If the options specifier is prefixed by a negation
 165 operator, then only
 166 those filesystems that do not have
 167 .I fs-option
 168 in their mount options field of
 169 .I /etc/fstab
 170 will be checked.
 171 .sp
 172 For example, if
 173 .B opts=ro
 174 appears in
 175 .IR fslist ,
 176 then only filesystems listed in
 177 .I /etc/fstab
 178 with the
 179 .B ro
 180 option will be checked.
 181 .sp
 182 For compatibility with Mandrake distributions whose boot scripts
 183 depend upon an unauthorized UI change to the
 184 .B fsck
 185 program, if a filesystem type of
 186 .B loop
 187 is found in
 188 .IR fslist ,
 189 it is treated as if
 190 .B opts=loop
 191 were specified as an argument to the
 192 .B \-t
 193 option.
 194 .sp
 195 Normally, the filesystem type is deduced by searching for
 196 .I filesys
 197 in the
 198 .I /etc/fstab
 199 file and using the corresponding entry.
 200 If the type cannot be deduced, and there is only a single filesystem
 201 given as an argument to the
 202 .B \-t
 203 option,
 204 .B fsck
 205 will use the specified filesystem type.  If this type is not
 206 available, then the default filesystem type (currently ext2) is used.
 207 .TP
 208 .B \-A
 209 Walk through the
 210 .I /etc/fstab
 211 file and try to check all filesystems in one run.  This option is
 212 typically used from the
 213 .I /etc/rc
 214 system initialization file, instead of multiple commands for checking
 215 a single filesystem.
 216 .sp
 217 The root filesystem will be checked first unless the
 218 .B \-P
 219 option is specified (see below).  After that,
 220 filesystems will be checked in the order specified by the
 221 .I fs_passno
 222 (the sixth) field in the
 223 .I /etc/fstab
 224 file.
 225 Filesystems with a
 226 .I fs_passno
 227 value of 0 are skipped and are not checked at all.  Filesystems with a
 228 .I fs_passno
 229 value of greater than zero will be checked in order,
 230 with filesystems with the lowest
 231 .I fs_passno
 232 number being checked first.
 233 If there are multiple filesystems with the same pass number,
 234 .B fsck
 235 will attempt to check them in parallel, although it will avoid running
 236 multiple filesystem checks on the same physical disk.
 237 .sp
 238 .B fsck
 239 does not check stacked devices (RAIDs, dm-crypt, \&...\&) in parallel with any other
 240 device.  See below for FSCK_FORCE_ALL_PARALLEL setting.  The /sys filesystem is
 241 used to determine dependencies between devices.
 242 .sp
 243 Hence, a very common configuration in
 244 .I /etc/fstab
 245 files is to set the root filesystem to have a
 246 .I fs_passno
 247 value of 1
 248 and to set all other filesystems to have a
 249 .I fs_passno
 250 value of 2.  This will allow
 251 .B fsck
 252 to automatically run filesystem checkers in parallel if it is advantageous
 253 to do so.  System administrators might choose
 254 not to use this configuration if they need to avoid multiple filesystem
 255 checks running in parallel for some reason \(en for example, if the
 256 machine in question is short on memory so that
 257 excessive paging is a concern.
 258 .sp
 259 .B fsck
 260 normally does not check whether the device actually exists before
 261 calling a filesystem specific checker.  Therefore non-existing
 262 devices may cause the system to enter filesystem repair mode during
 263 boot if the filesystem specific checker returns a fatal error.  The
 264 .I /etc/fstab
 265 mount option
 266 .B nofail
 267 may be used to have
 268 .B fsck
 269 skip non-existing devices.
 270 .B fsck
 271 also skips non-existing devices that have the special filesystem type
 272 .BR auto .
 273 .TP
 274 .BR \-C \ [ \fIfd\fR ]
 275 Display completion/progress bars for those filesystem checkers (currently
 276 only for ext[234]) which support them.  \fBfsck\fR will manage the
 277 filesystem checkers so that only one of them will display
 278 a progress bar at a time.  GUI front-ends may specify a file descriptor
 279 .IR fd ,
 280 in which case the progress bar information will be sent to that file descriptor.
 281 .TP
 282 .B \-M
 283 Do not check mounted filesystems and return an exit status of 0
 284 for mounted filesystems.
 285 .TP
 286 .B \-N
 287 Don't execute, just show what would be done.
 288 .TP
 289 .B \-P
 290 When the
 291 .B \-A
 292 flag is set, check the root filesystem in parallel with the other filesystems.
 293 This is not the safest thing in the world to do,
 294 since if the root filesystem is in doubt things like the
 295 .BR e2fsck (8)
 296 executable might be corrupted!  This option is mainly provided
 297 for those sysadmins who don't want to repartition the root
 298 filesystem to be small and compact (which is really the right solution).
 299 .TP
 300 .B \-R
 301 When checking all filesystems with the
 302 .B \-A
 303 flag, skip the root filesystem.  (This is useful in case the root
 304 filesystem has already been mounted read-write.)
 305 .TP
 306 .B \-T
 307 Don't show the title on startup.
 308 .TP
 309 .B \-V
 310 Produce verbose output, including all filesystem-specific commands
 311 that are executed.
 312 .TP
 313 \fB\-?\fR, \fB\-\-help\fR
 314 Display help text and exit.
 315 .TP
 316 \fB\-\-version\fR
 317 Display version information and exit.
 318 .SH FILESYSTEM SPECIFIC OPTIONS
 319 .B Options which are not understood by fsck are passed to the filesystem-specific checker!
 320 .PP
 321 These options
 322 .B must
 323 not take arguments, as there is no
 324 way for
 325 .B fsck
 326 to be able to properly guess which options take arguments and which
 327 don't.
 328 .PP
 329 Options and arguments which follow the
 330 .B \-\-
 331 are treated as filesystem-specific options to be passed to the
 332 filesystem-specific checker.
 333 .PP
 334 Please note that \fBfsck\fR is not
 335 designed to pass arbitrarily complicated options to filesystem-specific
 336 checkers.  If you're doing something complicated, please just
 337 execute the filesystem-specific checker directly.  If you pass
 338 .B fsck
 339 some horribly complicated options and arguments, and it doesn't do
 340 what you expect,
 341 .B don't bother reporting it as a bug.
 342 You're almost certainly doing something that you shouldn't be doing
 343 with
 344 .BR fsck .
 345 Options to different filesystem-specific fsck's are not standardized.
 346 .SH ENVIRONMENT
 347 The
 348 .B fsck
 349 program's behavior is affected by the following environment variables:
 350 .TP
 351 .B FSCK_FORCE_ALL_PARALLEL
 352 If this environment variable is set,
 353 .B fsck
 354 will attempt to check all of the specified filesystems in parallel, regardless of
 355 whether the filesystems appear to be on the same device.  (This is useful for
 356 RAID systems or high-end storage systems such as those sold by companies such
 357 as IBM or EMC.)  Note that the fs_passno value is still used.
 358 .TP
 359 .B FSCK_MAX_INST
 360 This environment variable will limit the maximum number of filesystem
 361 checkers that can be running at one time.  This allows configurations
 362 which have a large number of disks to avoid
 363 .B fsck
 364 starting too many filesystem checkers at once, which might overload
 365 CPU and memory resources available on the system.  If this value is
 366 zero, then an unlimited number of processes can be spawned.  This is
 367 currently the default, but future versions of
 368 .B fsck
 369 may attempt to automatically determine how many filesystem checks can
 370 be run based on gathering accounting data from the operating system.
 371 .TP
 372 .B PATH
 373 The
 374 .B PATH
 375 environment variable is used to find filesystem checkers.
 376 .TP
 377 .B FSTAB_FILE
 378 This environment variable allows the system administrator
 379 to override the standard location of the
 380 .I /etc/fstab
 381 file.  It is also useful for developers who are testing
 382 .BR fsck .
 383 .TP
 384 .B LIBBLKID_DEBUG=all
 385 enables libblkid debug output.
 386 .TP
 387 .B LIBMOUNT_DEBUG=all
 388 enables libmount debug output.
 389 .SH FILES
 390 .I /etc/fstab
 391 .SH AUTHORS
 392 .nf
 393 Theodore Ts'o <tytso@mit.edu>
 394 Karel Zak <kzak@redhat.com>
 395 .fi
 396 .SH SEE ALSO
 397 .na
 398 .BR fstab (5),
 399 .BR mkfs (8),
 400 .BR fsck.ext2 (8)
 401 or
 402 .BR fsck.ext3 (8)
 403 or
 404 .BR e2fsck (8),
 405 .BR fsck.cramfs (8),
 406 .BR fsck.jfs (8),
 407 .BR fsck.nfs (8),
 408 .BR fsck.minix (8),
 409 .BR fsck.msdos (8),
 410 .BR fsck.vfat (8),
 411 .BR fsck.xfs (8),
 412 .BR reiserfsck (8)
 413 .ad
 414 .SH AVAILABILITY
 415 The fsck command is part of the util-linux package and is available from
 416 .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/
 417 Linux Kernel Archive
 418 .UE .