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33 .\" @(#)fsck.8 8.4 (Berkeley) 5/9/95
34 .\" $FreeBSD: src/sbin/fsck/fsck.8,v 1.14.2.3 2001/01/23 23:11:07 iedowse Exp $
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36 .Dd April 20, 2007
37 .Dt FSCK 8
38 .Os
39 .Sh NAME
40 .Nm fsck
41 .Nd UFS filesystem consistency check and interactive repair
42 .Sh SYNOPSIS
43 .Nm
44 .Fl p
45 .Op Fl f
46 .Op Fl m Ar mode
47 .Op Ar filesystem
48 .Ar ...
49 .Nm
50 .Op Fl Lny
51 .Op Fl b Ar block#
52 .Op Fl c Ar level
53 .Op Fl l Ar maxparallel
54 .Op Fl m Ar mode
55 .Op Ar filesystem
56 .Ar ...
57 .Sh DESCRIPTION
58 The first form of
59 .Nm
60 preens a standard set of filesystems or the specified filesystems.
61 It is normally used in the script
62 .Pa /etc/rc
63 during automatic reboot.
64 Here
65 .Nm
66 reads the table
67 .Pa /etc/fstab
68 to determine which filesystems to check.
69 Only partitions in fstab that are mounted ``rw,'' ``rq'' or ``ro''
70 and that have non-zero pass number are checked.
71 Filesystems with pass number 1 (normally just the root filesystem)
72 are checked one at a time.
73 When pass 1 completes, all remaining filesystems are checked,
74 running one process per disk drive.
75 The disk drive containing each filesystem is inferred from the longest prefix
76 of the device name that ends in a digit; the remaining characters are assumed
77 to be the partition designator.
78 .Pp
79 In "preen" mode the clean flag of each filesystem's superblock is examined
80 and only those filesystems that
81 are not marked clean are checked.
82 Filesystems are marked clean when they are unmounted,
83 when they have been mounted read-only, or when
84 .Nm
85 runs on them successfully.
86 If the
87 .Fl f
88 option is specified, the filesystems
89 will be checked regardless of the state of their clean flag.
90 .Pp
91 The kernel takes care that only a restricted class of innocuous filesystem
92 inconsistencies can happen unless hardware or software failures intervene.
93 These are limited to the following:
94 .Pp
95 .Bl -item -compact -offset indent
96 .It
97 Unreferenced inodes
98 .It
99 Link counts in inodes too large
100 .It
101 Missing blocks in the free map
102 .It
103 Blocks in the free map also in files
104 .It
105 Counts in the super-block wrong
106 .El
107 .Pp
108 These are the only inconsistencies that
109 .Nm
110 with the
111 .Fl p
112 option will correct; if it encounters other inconsistencies, it exits
113 with an abnormal return status and an automatic reboot will then fail.
114 For each corrected inconsistency one or more lines will be printed
115 identifying the filesystem on which the correction will take place,
116 and the nature of the correction. After successfully correcting a filesystem,
117 .Nm
118 will print the number of files on that filesystem,
119 the number of used and free blocks,
120 and the percentage of fragmentation.
121 .Pp
122 If sent a
123 .Dv QUIT
124 signal,
125 .Nm
126 will finish the filesystem checks, then exit with an abnormal
127 return status that causes an automatic reboot to fail.
128 This is useful when you want to finish the filesystem checks during an
129 automatic reboot,
130 but do not want the machine to come up multiuser after the checks complete.
131 .Pp
132 If
133 .Nm
134 receives a
135 .Dv SIGINFO
136 (see the
137 .Dq status
138 argument for
139 .Xr stty 1 )
140 signal, a line will be written to the standard output indicating
141 the name of the device currently being checked, the current phase
142 number and phase-specific progress information.
143 .Pp
144 Without the
145 .Fl p
146 option,
147 .Nm
148 audits and interactively repairs inconsistent conditions for filesystems.
149 If the filesystem is inconsistent the operator is prompted for concurrence
150 before each correction is attempted.
151 It should be noted that some of the corrective actions which are not
152 correctable under the
153 .Fl p
154 option will result in some loss of data.
155 The amount and severity of data lost may be determined from the diagnostic
156 output.
157 The default action for each consistency correction
158 is to wait for the operator to respond
159 .Li yes
160 or
161 .Li no .
162 If the operator does not have write permission on the filesystem
163 .Nm
164 will default to a
165 .Fl n
166 action.
167 .Pp
168 .Nm Fsck
169 has more consistency checks than
170 its predecessors
171 .Em check , dcheck , fcheck ,
172 and
173 .Em icheck
174 combined.
175 .Pp
176 The following flags are interpreted by
177 .Nm .
178 .Bl -tag -width indent
179 .It Fl b
180 Use the block specified immediately after the flag as
181 the super block for the filesystem. Block 32 is usually
182 an alternate super block.
183 .It Fl c
184 Convert the filesystem to the specified level.
185 Note that the level of a filesystem can only be raised.
186 .Pp
187 There are currently four levels defined:
188 .Bl -tag -width indent
189 .It 0
190 The filesystem is in the old (static table) format.
191 .It 1
192 The filesystem is in the new (dynamic table) format.
193 .It 2
194 The filesystem supports 32-bit uid's and gid's,
195 short symbolic links are stored in the inode,
196 and directories have an added field showing the file type.
197 .It 3
198 If maxcontig is greater than one,
199 build the free segment maps to aid in finding contiguous sets of blocks.
200 If maxcontig is equal to one, delete any existing segment maps.
201 .El
202 .Pp
203 In interactive mode,
204 .Nm
205 will list the conversion to be made
206 and ask whether the conversion should be done.
207 If a negative answer is given,
208 no further operations are done on the filesystem.
209 In preen mode,
210 the conversion is listed and done if
211 possible without user interaction.
212 Conversion in preen mode is best used when all the filesystems
213 are being converted at once.
214 The format of a filesystem can be determined from the
215 first line of output from
216 .Xr dumpfs 8 .
217 .It Fl f
218 Force
219 .Nm
220 to check
221 .Sq clean
222 filesystems when preening.
223 .It Fl l
224 Limit the number of parallel checks to the number specified in the following
225 argument.
226 By default, the limit is the number of disks, running one process per disk.
227 If a smaller limit is given, the disks are checked round-robin, one filesystem
228 at a time.
229 .It Fl L
230 Just print the "last mounted on" information and exit, do no other checking.
231 .It Fl m
232 Use the mode specified in octal immediately after the flag as the
233 permission bits to use when creating the
234 .Pa lost+found
235 directory rather than the default 1777.
236 In particular, systems that do not wish to have lost files accessible
237 by all users on the system should use a more restrictive
238 set of permissions such as 700.
239 .It Fl n
240 Assume a no response to all questions asked by
241 .Nm
242 except for
243 .Ql CONTINUE? ,
244 which is assumed to be affirmative;
245 do not open the filesystem for writing.
246 .It Fl p
247 Preen filesystems (see above).
248 .It Fl y
249 Assume a yes response to all questions asked by
250 .Nm ;
251 this should be used with great caution as this is a free license
252 to continue after essentially unlimited trouble has been encountered.
253 .El
254 .Pp
255 If no filesystems are given to
256 .Nm
257 then a default list of filesystems is read from
258 the file
259 .Pa /etc/fstab .
260 .Pp
261 Inconsistencies checked are as follows:
262 .Bl -enum -compact
263 .It
264 Blocks claimed by more than one inode or the free map.
265 .It
266 Blocks claimed by an inode outside the range of the filesystem.
267 .It
268 Incorrect link counts.
269 .It
270 Size checks:
271 .Bl -item -offset indent -compact
272 .It
273 Directory size not a multiple of DIRBLKSIZ.
274 .It
275 Partially truncated file.
276 .El
277 .It
278 Bad inode format.
279 .It
280 Blocks not accounted for anywhere.
281 .It
282 Directory checks:
283 .Bl -item -offset indent -compact
284 .It
285 File pointing to unallocated inode.
286 .It
287 Inode number out of range.
288 .It
289 Directories with unallocated blocks (holes).
290 .It
291 Dot or dot-dot not the first two entries of a directory
292 or having the wrong inode number.
293 .El
294 .It
295 Super Block checks:
296 .Bl -item -offset indent -compact
297 .It
298 More blocks for inodes than there are in the filesystem.
299 .It
300 Bad free block map format.
301 .It
302 Total free block and/or free inode count incorrect.
303 .El
304 .El
305 .Pp
306 Orphaned files and directories (allocated but unreferenced) are,
307 with the operator's concurrence, reconnected by
308 placing them in the
309 .Pa lost+found
310 directory.
311 The name assigned is the inode number.
312 If the
313 .Pa lost+found
314 directory does not exist, it is created.
315 If there is insufficient space its size is increased.
316 .Pp
317 Because of inconsistencies between the block device and the buffer cache,
318 the raw device should always be used.
319 .Sh FILES
320 .Bl -tag -width /etc/fstab -compact
321 .It Pa /etc/fstab
322 contains default list of filesystems to check.
323 .El
324 .Sh DIAGNOSTICS
325 The diagnostics produced by
326 .Nm
327 are fully enumerated and explained in Appendix A of
328 .Rs
329 .%T "Fsck \- The UNIX File System Check Program"
330 .Re
331 .Sh SEE ALSO
332 .Xr fs 5 ,
333 .Xr fstab 5 ,
334 .Xr UFS 5 ,
335 .Xr fsdb 8 ,
336 .Xr newfs 8 ,
337 .Xr reboot 8