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<title>sfsck</title>
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<h2 align=center>sfsck</h2>
<h4 align=center>OS/161 Reference Manual</h4>

<h3>Name</h3>
<p>
sfsck - check/repair an SFS filesystem
</p>

<h3>Synopsis</h3>
<p>
<tt>/sbin/sfsck</tt> <em>raw-device</em><br>
<tt>host-sfsck</tt> <em>disk-image-file</em>
</p>

<h3>Description</h3>
<p>
<tt>sfsck</tt> checks the SFS filesystem on the specified device for
correctness and consistency. Various possible errors and corrupt
states are detected and reported; some (but not all) can be corrected.
</p>

<p>
If <tt>sfsck</tt> is used under OS/161, the first form should be used,
where <em>raw-device</em> is a raw device name (such as "lhd1raw:").
Don't use a device that's currently mounted.
</p>

<p>
<tt>sfsck</tt> can also be used on the System/161 host OS, in which
case the second form should be used. The host-compiled version of
<tt>sfsck</tt> knows how to deal with the header on System/161 disk
images and does the right thing.
</p>

<h3>Requirements</h3>

<p>
<tt>sfsck</tt> uses the following system calls:
<ul>
<li> <A HREF=../syscall/open.html>open</A>
<li> <A HREF=../syscall/read.html>read</A>
<li> <A HREF=../syscall/write.html>write</A>
<li> <A HREF=../syscall/lseek.html>lseek</A>
<li> <A HREF=../syscall/fstat.html>fstat</A>
<li> <A HREF=../syscall/close.html>close</A>
<li> <A HREF=../syscall/sbrk.html>sbrk</A>
<li> <A HREF=../syscall/_exit.html>_exit</A>
</ul>
</p>

<p>
<tt>sfsck</tt> should function properly under OS/161 once you have
implemented the basic system calls, <tt>sbrk</tt> in the VM system,
and <tt>fstat</tt>.
</p>

<p>
The host version of <tt>sfsck</tt>, since it runs outside of OS/161,
should always work regardless of what you have and have not
implemented.
</p>

<p>
You will likely need to make some changes to <tt>sfsck</tt> in the
course of doing the file system assignment. If you are implementing
crash recovery for your file system, be sure to update <tt>sfsck</tt>
to know about any extra on-disk structures you add. You will want to
be able to use it to cross-check your recovery code... and so will the
course staff.
</p>

<h3>See Also</h3>
<p>
<A HREF=dumpsfs.html>dumpsfs</A>,
<A HREF=mksfs.html>mksfs</A>
</p>

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