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<font size="-1"><a href="http://user-mode-linux.sourceforge.net/sdotm.html">Disaster of the Month</a></font>
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<td valign="top" align="left">
<center>
<h3>The Sysadmin Disaster of the Month</h3>
</center>
Each month, we will introduce a disaster scenario and accept
submissions of recovery procedures from them. For examples of good
disasters, see my O'Reilly article
<a href="http://www.oreillynet.com/pub/a/linux/2001/11/29/UserModeLinux.html">
here</a>.
<p>
If you're new to UML, you'll probably want to read the following pages
before starting to solve this month's problem:
<ul>
<li><a href="dl-sf.html">Downloading UML</a></li>
<li><a href="run.html">Running it</a></li>
<li>
<a href="shared_fs.html">Using COW block devices</a>
</li>
<li><a href="mconsole.html">Using the UML
management console </a>
</li>
</ul>
<a name="The December 2001 Disaster"/><table width="100%" bgcolor="#e0e0e0">
<tr>
<td>
<b>
<font color="black">The December 2001 Disaster</font>
</b>
</td>
</tr>
</table>
<blockquote head="The December 2001 Disaster">
This month's disaster involves a trashed filesystem. To create the
disaster, boot up UML with a COW-ed or copied root filesystem, and
zero out the root filesystem's superblock:
<blockquote>
<tt>
<font color="#000000">dd if=/dev/zero of=/dev/ubd/0 seek=1 bs=1024 count=1</font>
</tt>
</blockquote>
You will then get all kinds of nasty-loooking stuff in the kernel log
such as:
<tt>
<pre>
<font size="-1">
EXT2-fs error (device ubd(98,0)): ext2_write_inode: bad inode number: 50571
EXT2-fs error (device ubd(98,0)): ext2_write_inode: bad inode number: 33108
EXT2-fs error (device ubd(98,0)): ext2_write_inode: bad inode number: 32987
EXT2-fs error (device ubd(98,0)): ext2_write_inode: bad inode number: 33165
EXT2-fs error (device ubd(98,0)): ext2_write_inode: bad inode number: 33112
EXT2-fs error (device ubd(98,0)): ext2_write_inode: bad inode number: 34175
EXT2-fs error (device ubd(98,0)): ext2_new_block: block(1006) >= blocks count(0) - block_group = 0, es == a0a8c400
EXT2-fs error (device ubd(98,0)): ext2_new_block: block(1116) >= blocks count(0) - block_group = 0, es == a0a8c400
</font>
</pre>
</tt>
You can try running halt, but it probably won't work, so shut it down
with the mconsole instead:
<tt>
<pre>
<font size="-1">
(debian) sysrq u
OK
(debian) halt
OK
</font>
</pre>
</tt>
Your mission, should you choose to accept it, is to restore this
filesystem to health.
</blockquote>
<a name="Submit your solution"/><table width="100%" bgcolor="#e0e0e0">
<tr>
<td>
<b>
<font color="black">Submit your solution</font>
</b>
</td>
</tr>
</table>
<blockquote head="Submit your solution">
If you have a solution to this month's problem and you want it to be
immortalized on this very site, submit it here.
<p>
I will pick one or more winning solutions based on criteria such as
<ul>
<li>originality - all else being equal, I like non-obvious solutions
</li>
<li>subtlety - if applicable, small fixes are better than big ones
</li>
<li>brevity - short and sweet is better than long and involved
</li>
<li>parsimony - the fewer external resources you need, the better
</li>
</ul>
<p>
<form method="POST" action="http://user-mode-linux.sourceforge.net/cgi-bin/sdotm_submit.pl">
Who you are (any identification is OK, including none at all)
<br>
<input name="submitter" type="text">
<p>
Your billiant recovery:
<br>
<textarea name="answer" cols="60" rows="20"></textarea>
<br>
<input value="Submit your solution" type="submit">
<input value="recovery" name="form" type="hidden">
</form>
</blockquote>
<a name="Propose a disaster"/><table width="100%" bgcolor="#e0e0e0">
<tr>
<td>
<b>
<font color="black">Propose a disaster</font>
</b>
</td>
</tr>
</table>
<blockquote head="Propose a disaster">
If you have a scenario which you think would make a good Disaster of
the Month, please submit it here. If you have a good solution,
include it as well. Disasters which have actually happened in real
life are especially good, but anything which can happen on a physical
box is fine.
<p>
Each month, I will look over the submissions and choose an interesting
one to feature as that month's disaster of the month.
<p>
<form method="POST" action="http://user-mode-linux.sourceforge.net/cgi-bin/sdotm_submit.pl">
Who you are (any identification is OK, including none at all)
<br>
<input name="submitter" type="text">
<p>
Your disaster:
<br>
<textarea name="answer" cols="60" rows="20"></textarea>
<br>
<input value="Submit your disaster" type="submit">
<input value="disaster" name="form" type="hidden">
</form>
</blockquote>
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</tr>
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