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29 .\" @(#)fsck.8 8.4 (Berkeley) 5/9/95
38 .Nd file system consistency check and interactive repair
48 The specified disk partitions and/or file systems are checked.
49 In "preen" or "check clean" mode the clean flag of each file system's
50 superblock is examined and only those file systems that are not marked clean
52 File systems are marked clean when they are unmounted,
53 when they have been mounted read-only, or when
55 runs on them successfully.
58 option is specified, the file systems
59 will be checked regardless of the state of their clean flag.
61 The kernel takes care that only a restricted class of innocuous file system
62 inconsistencies can happen unless hardware or software failures intervene.
63 These are limited to the following:
65 .Bl -item -compact -offset indent
69 Link counts in inodes too large
71 Missing blocks in the free map
73 Blocks in the free map also in files
75 Counts in the super-block wrong
78 These are the only inconsistencies that
82 option will correct; if it encounters other inconsistencies, it exits
83 with an abnormal return status and an automatic reboot will then fail.
84 For each corrected inconsistency one or more lines will be printed
85 identifying the file system on which the correction will take place,
86 and the nature of the correction.
87 After successfully correcting a file system,
89 will print the number of files on that file system,
90 the number of used and free blocks,
91 and the percentage of fragmentation.
97 will finish the file system checks, then exit with an abnormal
98 return status that causes an automatic reboot to fail.
99 This is useful when you want to finish the file system checks during an
101 but do not want the machine to come up multiuser after the checks complete.
111 signal, a line will be written to the standard output indicating
112 the name of the device currently being checked, the current phase
113 number and phase-specific progress information.
119 audits and interactively repairs inconsistent conditions for file systems.
120 If the file system is inconsistent the operator is prompted for concurrence
121 before each correction is attempted.
122 It should be noted that some of the corrective actions which are not
123 correctable under the
125 option will result in some loss of data.
126 The amount and severity of data lost may be determined from the diagnostic
128 The default action for each consistency correction
129 is to wait for the operator to respond
133 If the operator does not have write permission on the file system
139 The following flags are interpreted by
141 .Bl -tag -width indent
143 Determine whether the file system needs to be cleaned immediately
144 in foreground, or if its cleaning can be deferred to background.
145 To be eligible for background cleaning it must have been running
146 with soft updates, not have been marked as needing a foreground check,
147 and be mounted and writable when the background check is to be done.
148 If these conditions are met, then
150 exits with a zero exit status.
151 Otherwise it exits with a non-zero exit status.
152 If the file system is clean,
153 it will exit with a non-zero exit status so that the clean status
154 of the file system can be verified and reported during the foreground
156 Note that when invoked with the
158 flag, no cleanups are done.
161 does is to determine whether a foreground or background
162 check is needed and exit with an appropriate status code.
164 A check is done on the specified and possibly active file system.
165 The set of corrections that can be done is limited to those done
166 when running in preen mode (see the
169 If unexpected errors are found,
170 the file system is marked as needing a foreground check and
172 exits without attempting any further cleaning.
174 Use the block specified immediately after the flag as
175 the super block for the file system.
176 An alternate super block is usually located at block 32 for UFS1,
177 and block 160 for UFS2.
179 Check if file system was dismouted cleanly.
180 If so, skip file system checks (like "preen").
181 However, if the file system was not cleanly dismounted, do full checks,
187 Convert the file system to the specified level.
188 Note that the level of a file system can only be raised.
189 There are currently four levels defined:
190 .Bl -tag -width indent
192 The file system is in the old (static table) format.
194 The file system is in the new (dynamic table) format.
196 The file system supports 32-bit uid's and gid's,
197 short symbolic links are stored in the inode,
198 and directories have an added field showing the file type.
200 If maxcontig is greater than one,
201 build the free segment maps to aid in finding contiguous sets of blocks.
202 If maxcontig is equal to one, delete any existing segment maps.
207 will list the conversion to be made
208 and ask whether the conversion should be done.
209 If a negative answer is given,
210 no further operations are done on the file system.
212 the conversion is listed and done if
213 possible without user interaction.
214 Conversion in preen mode is best used when all the file systems
215 are being converted at once.
216 The format of a file system can be determined from the
217 first line of output from
222 in 'damaged recovery' mode, which will enable certain aggressive
223 operations that can make
225 to survive with file systems that has very serious data damage, which
226 is an useful last resort when on disk data damage is very serious
229 to crash otherwise. Be
231 using this flag, it is dangerous if there are data transmission hazards
232 because a false positive cylinder group magic number mismatch could
234 .Em irrevertible data loss!
236 This option implies the
244 file systems when preening.
246 Use the mode specified in octal immediately after the flag as the
247 permission bits to use when creating the
249 directory rather than the default 1777.
250 In particular, systems that do not wish to have lost files accessible
251 by all users on the system should use a more restrictive
252 set of permissions such as 700.
254 Assume a no response to all questions asked by
258 which is assumed to be affirmative;
259 do not open the file system for writing.
261 Preen file systems (see above).
263 Assume a yes response to all questions asked by
265 this should be used with great caution as this is a free license
266 to continue after essentially unlimited trouble has been encountered.
269 Inconsistencies checked are as follows:
273 Blocks claimed by more than one inode or the free map.
275 Blocks claimed by an inode outside the range of the file system.
277 Incorrect link counts.
280 .Bl -item -offset indent -compact
282 Directory size not a multiple of DIRBLKSIZ.
284 Partially truncated file.
289 Blocks not accounted for anywhere.
292 .Bl -item -offset indent -compact
294 File pointing to unallocated inode.
296 Inode number out of range.
298 Directories with unallocated blocks (holes).
300 Dot or dot-dot not the first two entries of a directory
301 or having the wrong inode number.
305 .Bl -item -offset indent -compact
307 More blocks for inodes than there are in the file system.
309 Bad free block map format.
311 Total free block and/or free inode count incorrect.
315 Orphaned files and directories (allocated but unreferenced) are,
316 with the operator's concurrence, reconnected by
320 The name assigned is the inode number.
323 directory does not exist, it is created.
324 If there is insufficient space its size is increased.
326 .Bl -tag -width /etc/fstab -compact
328 contains default list of file systems to check.
333 The diagnostics produced by
335 are fully enumerated and explained in Appendix A of
337 .%T "Fsck \- The UNIX File System Check Program"