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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 $
35 .\" $DragonFly: src/sbin/fsck/fsck.8,v 1.7 2008/05/01 23:36:43 swildner Exp $
36 .\"
37 .Dd April 20, 2007
38 .Dt FSCK 8
39 .Os
40 .Sh NAME
41 .Nm fsck
42 .Nd filesystem consistency check and interactive repair
43 .Sh SYNOPSIS
44 .Nm
45 .Fl p
46 .Op Fl f
47 .Op Fl m Ar mode
48 .Op Ar filesystem
49 .Ar ...
50 .Nm
51 .Op Fl Lny
52 .Op Fl b Ar block#
53 .Op Fl c Ar level
54 .Op Fl l Ar maxparallel
55 .Op Fl m Ar mode
56 .Op Ar filesystem
57 .Ar ...
58 .Sh DESCRIPTION
59 The first form of
60 .Nm
61 preens a standard set of filesystems or the specified filesystems.
62 It is normally used in the script
63 .Pa /etc/rc
64 during automatic reboot.
65 Here
66 .Nm
67 reads the table
68 .Pa /etc/fstab
69 to determine which filesystems to check.
70 Only partitions in fstab that are mounted ``rw,'' ``rq'' or ``ro''
71 and that have non-zero pass number are checked.
72 Filesystems with pass number 1 (normally just the root filesystem)
73 are checked one at a time.
74 When pass 1 completes, all remaining filesystems are checked,
75 running one process per disk drive.
76 The disk drive containing each filesystem is inferred from the longest prefix
77 of the device name that ends in a digit; the remaining characters are assumed
78 to be the partition designator.
79 .Pp
80 In "preen" mode the clean flag of each filesystem's superblock is examined
81 and only those filesystems that
82 are not marked clean are checked.
83 Filesystems are marked clean when they are unmounted,
84 when they have been mounted read-only, or when
85 .Nm
86 runs on them successfully.
87 If the
88 .Fl f
89 option is specified, the filesystems
90 will be checked regardless of the state of their clean flag.
91 .Pp
92 The kernel takes care that only a restricted class of innocuous filesystem
93 inconsistencies can happen unless hardware or software failures intervene.
94 These are limited to the following:
95 .Pp
96 .Bl -item -compact -offset indent
97 .It
98 Unreferenced inodes
99 .It
100 Link counts in inodes too large
101 .It
102 Missing blocks in the free map
103 .It
104 Blocks in the free map also in files
105 .It
106 Counts in the super-block wrong
107 .El
108 .Pp
109 These are the only inconsistencies that
110 .Nm
111 with the
112 .Fl p
113 option will correct; if it encounters other inconsistencies, it exits
114 with an abnormal return status and an automatic reboot will then fail.
115 For each corrected inconsistency one or more lines will be printed
116 identifying the filesystem on which the correction will take place,
117 and the nature of the correction. After successfully correcting a filesystem,
118 .Nm
119 will print the number of files on that filesystem,
120 the number of used and free blocks,
121 and the percentage of fragmentation.
122 .Pp
123 If sent a
124 .Dv QUIT
125 signal,
126 .Nm
127 will finish the filesystem checks, then exit with an abnormal
128 return status that causes an automatic reboot to fail.
129 This is useful when you want to finish the filesystem checks during an
130 automatic reboot,
131 but do not want the machine to come up multiuser after the checks complete.
132 .Pp
133 If
134 .Nm
135 receives a
136 .Dv SIGINFO
137 (see the
138 .Dq status
139 argument for
140 .Xr stty 1 )
141 signal, a line will be written to the standard output indicating
142 the name of the device currently being checked, the current phase
143 number and phase-specific progress information.
144 .Pp
145 Without the
146 .Fl p
147 option,
148 .Nm
149 audits and interactively repairs inconsistent conditions for filesystems.
150 If the filesystem is inconsistent the operator is prompted for concurrence
151 before each correction is attempted.
152 It should be noted that some of the corrective actions which are not
153 correctable under the
154 .Fl p
155 option will result in some loss of data.
156 The amount and severity of data lost may be determined from the diagnostic
157 output.
158 The default action for each consistency correction
159 is to wait for the operator to respond
160 .Li yes
161 or
162 .Li no .
163 If the operator does not have write permission on the filesystem
164 .Nm
165 will default to a
166 .Fl n
167 action.
168 .Pp
169 .Nm Fsck
170 has more consistency checks than
171 its predecessors
172 .Em check , dcheck , fcheck ,
173 and
174 .Em icheck
175 combined.
176 .Pp
177 The following flags are interpreted by
178 .Nm .
179 .Bl -tag -width indent
180 .It Fl b
181 Use the block specified immediately after the flag as
182 the super block for the filesystem. Block 32 is usually
183 an alternate super block.
184 .It Fl c
185 Convert the filesystem to the specified level.
186 Note that the level of a filesystem can only be raised.
187 .Pp
188 There are currently four levels defined:
189 .Bl -tag -width indent
190 .It 0
191 The filesystem is in the old (static table) format.
192 .It 1
193 The filesystem is in the new (dynamic table) format.
194 .It 2
195 The filesystem supports 32-bit uid's and gid's,
196 short symbolic links are stored in the inode,
197 and directories have an added field showing the file type.
198 .It 3
199 If maxcontig is greater than one,
200 build the free segment maps to aid in finding contiguous sets of blocks.
201 If maxcontig is equal to one, delete any existing segment maps.
202 .El
203 .Pp
204 In interactive mode,
205 .Nm
206 will list the conversion to be made
207 and ask whether the conversion should be done.
208 If a negative answer is given,
209 no further operations are done on the filesystem.
210 In preen mode,
211 the conversion is listed and done if
212 possible without user interaction.
213 Conversion in preen mode is best used when all the filesystems
214 are being converted at once.
215 The format of a filesystem can be determined from the
216 first line of output from
217 .Xr dumpfs 8 .
218 .It Fl f
219 Force
220 .Nm
221 to check
222 .Sq clean
223 filesystems when preening.
224 .It Fl l
225 Limit the number of parallel checks to the number specified in the following
226 argument.
227 By default, the limit is the number of disks, running one process per disk.
228 If a smaller limit is given, the disks are checked round-robin, one filesystem
229 at a time.
230 .It Fl L
231 Just print the "last mounted on" information and exit, do no other checking.
232 .It Fl m
233 Use the mode specified in octal immediately after the flag as the
234 permission bits to use when creating the
235 .Pa lost+found
236 directory rather than the default 1777.
237 In particular, systems that do not wish to have lost files accessible
238 by all users on the system should use a more restrictive
239 set of permissions such as 700.
240 .It Fl n
241 Assume a no response to all questions asked by
242 .Nm
243 except for
244 .Ql CONTINUE? ,
245 which is assumed to be affirmative;
246 do not open the filesystem for writing.
247 .It Fl p
248 Preen filesystems (see above).
249 .It Fl y
250 Assume a yes response to all questions asked by
251 .Nm ;
252 this should be used with great caution as this is a free license
253 to continue after essentially unlimited trouble has been encountered.
254 .El
255 .Pp
256 If no filesystems are given to
257 .Nm
258 then a default list of filesystems is read from
259 the file
260 .Pa /etc/fstab .
261 .Pp
262 Inconsistencies checked are as follows:
263 .Bl -enum -compact
264 .It
265 Blocks claimed by more than one inode or the free map.
266 .It
267 Blocks claimed by an inode outside the range of the filesystem.
268 .It
269 Incorrect link counts.
270 .It
271 Size checks:
272 .Bl -item -offset indent -compact
273 .It
274 Directory size not a multiple of DIRBLKSIZ.
275 .It
276 Partially truncated file.
277 .El
278 .It
279 Bad inode format.
280 .It
281 Blocks not accounted for anywhere.
282 .It
283 Directory checks:
284 .Bl -item -offset indent -compact
285 .It
286 File pointing to unallocated inode.
287 .It
288 Inode number out of range.
289 .It
290 Directories with unallocated blocks (holes).
291 .It
292 Dot or dot-dot not the first two entries of a directory
293 or having the wrong inode number.
294 .El
295 .It
296 Super Block checks:
297 .Bl -item -offset indent -compact
298 .It
299 More blocks for inodes than there are in the filesystem.
300 .It
301 Bad free block map format.
302 .It
303 Total free block and/or free inode count incorrect.
304 .El
305 .El
306 .Pp
307 Orphaned files and directories (allocated but unreferenced) are,
308 with the operator's concurrence, reconnected by
309 placing them in the
310 .Pa lost+found
311 directory.
312 The name assigned is the inode number.
313 If the
314 .Pa lost+found
315 directory does not exist, it is created.
316 If there is insufficient space its size is increased.
317 .Pp
318 Because of inconsistencies between the block device and the buffer cache,
319 the raw device should always be used.
320 .Sh FILES
321 .Bl -tag -width /etc/fstab -compact
322 .It Pa /etc/fstab
323 contains default list of filesystems to check.
324 .El
325 .Sh DIAGNOSTICS
326 The diagnostics produced by
327 .Nm
328 are fully enumerated and explained in Appendix A of
329 .Rs
330 .%T "Fsck \- The UNIX File System Check Program"
331 .Re
332 .Sh SEE ALSO
333 .Xr fs 5 ,
334 .Xr fstab 5 ,
335 .Xr fsdb 8 ,
336 .Xr newfs 8 ,
337 .Xr reboot 8