161 lines
5.7 KiB
HTML
161 lines
5.7 KiB
HTML
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<html>
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<head>
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<title>frack</title>
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<link rel="stylesheet" type="text/css" media="all" href="../man.css">
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</head>
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<body bgcolor=#ffffff>
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<h2 align=center>frack</h2>
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<h4 align=center>OS/161 Reference Manual</h4>
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<h3>Name</h3>
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<p>
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frack - file system crack
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</p>
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<h3>Synopsis</h3>
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<p>
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<tt>/testbin/frack</tt> <tt>list</tt><br>
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<tt>/testbin/frack</tt> <tt>do</tt> <em>workload</em> [<em>arg</em>]<br>
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<tt>/testbin/frack</tt> <tt>check</tt> <em>workload</em> [<em>arg</em>]<br>
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</p>
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<h3>Description</h3>
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<p>
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<tt>frack</tt> is a general-purpose file system checker.
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It has a number of workloads built into it (currently 58, some of
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which are families of related workloads), each of which can be run in
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either <tt>do</tt> mode or <tt>check</tt> mode.
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</p>
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<p>
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In <tt>do</tt> mode, <tt>frack</tt> executes the chosen workload
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against the file system.
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</p>
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<p>
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In <tt>check</tt> mode, <tt>frack</tt> executes the chosen workload
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against an internal model of a file system, and builds a
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representation of all the successive states the file system reaches.
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Then it inspects the file system it is run on and matches its state
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against this representation.
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It finds the closest matching state, and then prints out the
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discrepancies it finds between that state and what it sees.
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</p>
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<p>
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Note that the <tt>check</tt> mode expects that the <tt>do</tt> mode
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was run on an empty (newly formatted) file system volume.
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Otherwise, any other stuff on the volume will appear as a discrepancy
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and may cause the state matching algorithm to fail.
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</p>
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<p>
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The intended use is for testing file system recovery: run a workload
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in <tt>do</tt> mode, crash during the workload (e.g. using the
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System/161 doom counter), run file system recovery, then run the same
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workload in <tt>check</tt> mode.
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Ideally, the <tt>check</tt> mode run will find the resulting on-disk
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state after recovery to exactly match some valid state the workload
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reached.
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In practice, some forms of discrepancy are often considered
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acceptable; your course staff should give you guidance on what you are
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and are not required to handle.
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</p>
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<p>
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Note that you probably want to get your recovery code to the point
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where it reliably produces a valid, self-consistent volume that
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<A HREF=../sbin/sfsck.html>sfsck</A> accepts before worrying about
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whether the <tt>frack check</tt> phase passes.
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</p>
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<p>
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<tt>frack</tt> can also be used for testing the general correctness of
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a file system, such as by running the <tt>do</tt> mode of a workload
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to completion and then immediately (or after shutting down cleanly and
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rebooting) running in <tt>check</tt> mode.
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</p>
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<p>
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Use <tt>frack list</tt> to see the available workloads.
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Some workloads take arguments; <em>size</em> arguments should be one
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of the keywords <tt>small</tt>, <tt>medium</tt>, or <tt>large</tt>,
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reflecting the size of the test file(s).
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<em>Seed</em> arguments are integer random seeds from 0 to
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2<sup>31</sup>-1.
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</p>
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<p>
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Some workloads contain an explicit <tt>sync</tt>; generally these are
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meant to be crashed after, not before (or during) the sync call.
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</p>
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<h3>Requirements</h3>
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<p>
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<tt>frack</tt> uses the following system calls:
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<ul>
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<li><A HREF=../syscall/open.html>open</A></li>
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<li><A HREF=../syscall/fstat>fstat</A></li>
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<li><A HREF=../syscall/ftruncate>ftruncate</A></li>
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<li><A HREF=../syscall/lseek.html>lseek</A></li>
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<li><A HREF=../syscall/getdirentry>getdirentry</A></li>
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<li><A HREF=../syscall/read>read</A></li>
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<li><A HREF=../syscall/write.html>write</A></li>
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<li><A HREF=../syscall/close.html>close</A></li>
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<li><A HREF=../syscall/link>link</A></li>
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<li><A HREF=../syscall/remove>remove</A></li>
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<li><A HREF=../syscall/chdir>chdir</A></li>
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<li><A HREF=../syscall/mkdir>mkdir</A></li>
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<li><A HREF=../syscall/rmdir>rmdir</A></li>
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<li><A HREF=../syscall/rename>rename</A></li>
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<li><A HREF=../syscall/sync>sync</A></li>
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<li><A HREF=../syscall/_exit.html>_exit</A></li>
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</ul>
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but note that it is intended to be able to exercise all the
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file-system-related calls and its exact requirements are
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workload-dependent.
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</p>
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<p>
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<tt>frack</tt> is most useful for testing file system recovery, by
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intentionally crashing during workload runs.
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But it is also useful for checking general correctness of a file
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system.
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</p>
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<h3>Bugs</h3>
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<p>
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Currently, none of the specific workloads are documented.
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</p>
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</body>
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</html>
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