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researchv10 Dan Cross

.TH FSCK 8
.CT 1 sa_nonmortals
.SH NAME
fsck \- file system consistency check and interactive repair
.SH SYNOPSIS
.B /etc/fsck
.B -p
[
.I special ...
]
.br
.B /etc/fsck
[
.B -y
]
[
.B -n
]
[
.BI -s X
]
[
.BI -S X
]
[
.B -t
.I filename
] [
.I special ...
]
.SH DESCRIPTION
.I Fsck
inspects the disk filesystems
in the named
.I special
files
and repairs inconsistencies.
If no files are named,
every file system listed in
.IR fstab (5)
with type 0
and a nonzero pass number
is checked.
.PP
Under option
.BR -p ,
.I fsck
runs without intervention,
repairing minor inconsistencies
and aborting on major ones.
This form is usually called from
.IR rc (8).
If no special files are named,
file systems in
.I fstab
are checked in parallel passes:
all file systems with pass number 1
are checked simultaneously,
then all file systems with pass number 2,
and so on until
.I fstab
is exhausted.
.PP
Here are the minor ailments
repaired automatically
under
.BR -p :
.RS
unreferenced inodes;
.br
wrong link counts in inodes;
.br
missing blocks in the free list;
.br
blocks in the free list also in files; and
.br
counts wrong in the super-block.
.RE
.PP
Other inconsistencies
cause
.I fsck
to abandon the inconsistent file system,
and exit with a nonzero status
when the current pass finishes.
.PP
Without the
.B -p
option,
.I fsck
inspects one file system at a time,
interactively.
Each inconsistency causes
.I fsck
to print a message
and ask permission to fix the problem.
The operator may require arcane knowledge
to guide
.I fsck
safely through repair of a badly damaged file system.
.PP
Here are the remaining options.
They are allowed only if
.B -p
is absent.
.TP
.B  -y
Assume a yes response to all questions.
This should be used with great caution.
.TP
.B  -n
Assume a no response to all questions;
do not open the file system for writing.
This option is assumed if the file system cannot be opened for writing.
.TP
.BI -s X
Ignore the actual free list and (unconditionally) reconstruct a new
one by rewriting the super-block of the file system.
The file system should be unmounted while this is done; if this
is not possible, care should be taken that the system is quiescent
and that it is rebooted immediately afterwards.
This precaution is necessary so that the old, bad, in-core copy
of the superblock will not continue to be used, or written on the file system.
If the file system has a bitmap free list (see
.IR filsys (5)),
the free list is always reconstructed unless the
.B -n
option is enabled.
.IP
Parameter
.I X
allows free-list parameters to be specified:
.BI -s blocks-per-cylinder : blocks-to-skip\c
\&.
If
.I X
is not given,
the values used when the file system was created
are used; see
.IR mkfs (8).
If these values were not specified, 
.I X
is assumed to be
.BR 400:9 .
.TP
.BI -S X
Conditionally reconstruct the free list.
This option
is like
.BI -s X
except that the free list is rebuilt only
if no discrepancies were found.
.B -S
implies
.BR -n .
.TP
.B -t
If
.I fsck
cannot obtain enough memory to keep its tables,
it uses a scratch file.
If the
.B -t
option is
specified, the file named in the next argument
is used as the scratch file, if needed.
Without
.BR -t ,
.I fsck
will prompt the operator for the name of the
scratch file.
The file chosen should not be on the
file system being checked.
If it did not already exist,
it is removed when
.I fsck
completes.
.PD
.br
.ne 6
.PP
Inconsistencies checked are:
.IP
.nf
Blocks claimed more than once.
Blocks designated outside the file system.
Incorrect link counts.
Directory size not 16-byte aligned.
Bad inode format.
Blocks not accounted for anywhere.
Directory entry pointing to unallocated inode.
Inode number out of range.
More than 65536 inodes.
More blocks for inodes than there are in the file system.
Bad free block list format.
Total free block and/or free inode count incorrect.
.fi
.PP
Orphaned files and directories (allocated but unreferenced) are
reconnected by
placing them in the directory
.F lost+found
in the root of the file system being checked.
The name assigned is the inode number,
prefixed by
.LR # .
.PP
Checking the raw device is almost always faster,
but
.I fsck
distinguishes bitmapped from non-bitmapped file systems
by examining the minor device number,
so the block device is safer.
.SH FILES
.F /etc/fstab
.SH "SEE ALSO"
.IR fstab (5), 
.IR filsys (5), 
.IR mkfs (8),
.IR reboot (8)
.br
T. J. Kowalski,
`Fsck\(emthe
.SM UNIX
File System Check Program',
this manual, Volume 2
.SH BUGS
Inode numbers for
.B .
and
.B ..
in each directory should be checked for validity.
.PP
Some systems save core images after a crash
in the swap area;
on such machines,
checking many large file systems in parallel
may cause swapping, overwriting the crash dump.
It is best just to write crash dumps in a a safer place.
If disk space for dumps and swapping is scarce,
avoid checking more than three 120-megabyte file systems
in parallel on a machine with four megabytes of physical memory.
.PP
Examining the minor device number is a botch;
there should be an explicit flag somewhere.
.PP
.I Fsck
does not have supernatural powers.

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