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<TITLE>The Answer Guy 43: Floppy Failure: mdir Works; mount Fails</TITLE>
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<H4>"The Linux Gazette...<I>making Linux just a little more fun!</I>"</H4>
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<H1><A NAME="answer">
<img src="../../gx/dennis/qbubble.gif" alt="(?)"
border="0" align="middle">
<font color="#B03060">The Answer Guy</font>
<img src="../../gx/dennis/bbubble.gif" alt="(!)"
border="0" align="middle">
</A></H1>
<BR>
<H4>By James T. Dennis,
<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a><BR>
LinuxCare,
<A HREF="http://www.linuxcare.com/">http://www.linuxcare.com/</A>
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<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Floppy Failure: mdir Works; mount Fails</H3>
<p><strong>From Tim Baverstock on Fri, 25 Jun 1999
</strong></p>
<!-- ::
Floppy Failure: mdir Works; mount Fails
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:: -->
<P><STRONG>
Hi.
</STRONG></P>
<P><STRONG>
I came across this page where someone'd asked you a question,
apparently identical to something a (non-techie) friend of mine is
now experiencing, except that his Linux is a vanilla RedHat 5.1
install (although with Star Office, and RedHat 5.2 Ghostscript and
ppp).
</STRONG></P>
<P><STRONG>
He has a PCI PnP soundcard in his machine, which he's not managed
to get working with W95 or with Linux, but the rest of the machine
worked fine for both OSs, including the floppy.
</STRONG></P>
<P><STRONG>
All of a sudden, about a month ago, the floppy stopped mounting on
Linux (works fine on W95).
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Does writing to the floppy work under MS Windows?
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
I can `<TT>less -f /dev/fd0</TT>', to see the data on the floppy, and
<tt>mdir</tt>/<tt>mcopy</tt> work fine.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Does '<tt>mcopy</tt>' work in both directions (copying to
the floppy as well as from it)?
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
The machine mounts his W95 <tt>C:</tt> drive as <TT>/mnt/dosC</TT>, and
that works perfectly as well.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
So we know that this kernel is compiled with
FAT fs support (linked in directly or the
loadable module support is working).
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
When I try `<TT>mount -t msdos /dev/fd0 /tmp/floppy</TT>', the mount
command goes into `<tt>D</tt>' wait in the `<tt>ps axf</tt>' output, as
does the update demon. The floppy lights, spins, then stops, but no
failure messages appear, and I can't kill the mount. Subsequent
attepts to mount also block, and if I recall correctly, <tt>mcopy</tt> says
it can't write to the device.
</STRONG></P>
<P><STRONG>
Nothing appears in <TT>/var/log/messages</TT>.
</STRONG></P>
<P><STRONG>
During shutdown, the <tt>umount -a</tt> line in
<TT>/etc/rc.d/init.d/halt</TT> hangs too.
</STRONG></P>
<P><STRONG>
If you're interested in whether fiddling with the soundcard fixes
the problem, I'll be happy to let you know, but since mcopy and
mdir work, this seems unlikely.
</STRONG></P>
<P><STRONG>
Nothing's been added or removed within the machine's case, so I
think the only thing that could have changed, which persists over
powerdowns, is the CMOS, and hence (presumably) some aspect of PnP
that W95 was fiddling around with.
</STRONG></P>
<P><STRONG>
I've only ever had <tt>isapnp</tt> work under RedHat 6.0, when Redhat did
it all for me!
<IMG SRC="../../gx/dennis/smily.gif" ALT=":)"
height="24" width="20" align="middle">
For my earlier kernels, I used the <tt>cmgr</tt> patch.
</STRONG></P>
<P><STRONG>
Cheers,
<br>Tim Baverstock.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
What happens if you try mounting it in read-only mode?
</BLOCKQUOTE>
<BLOCKQUOTE>
It sure sounds like a hardware failure. I'd buy an
extra floppy drive (about $20 US in most computer parts
stores). I've asked questions to see if the problem
is limited to the write functionality (since a careful
reading of your messages seems to correlate to read-only
vs. read/write access). When you mount a filesystem
in rw mode under Linux --- I think the atime on the
root of that filesystem will be updated (involving
a write to the media). If it works when you try the
'<tt>mount -o ro</tt>' variation on the command --- that
suggests that it is related to the write functions.
</BLOCKQUOTE>
<!-- sig -->
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<hr width="40%" align="center">
<!-- begin 4 -->
<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Found The Culprit!</H3>
<p><strong>From Tim Baverstock on Sun, 27 Jun 1999
</strong></p>
<p><strong>
Hi Jim.
</strong></p>
<p><strong>
Ach! Rats!
</strong></p>
<p><strong>
I forgot to email you the solution I discovered!
</strong></p>
<p><strong>
The drive wrote perfectly well under Windows, and worked without difficulty in
both directions with <tt>mcopy</tt>. I should have made this clearer in my
first email; my apologies for this.
</strong></p>
<p><strong>
The functionality of the drive, and the evident integrity of the msdos filing
system module eliminated those subsystems from the problem, which was why I was
so perplexed, and why I wrote to you.
<IMG SRC="../../gx/dennis/smily.gif" ALT=":)"
height="24" width="20" align="middle">
</strong></p>
<p><strong>
The next day, I used <tt>strace</tt> on `<tt>mount</tt>' to try and find out
where it hung. It hung on the actual <tt>mount()</tt> system call itself.
</strong></p>
<p><strong>
I noticed that the automounter was in `<tt>D</tt>' discwait on the process
list during its own mount attempt, so I disabled it in the boot sequence
while trying to find out what was going on (I wanted to strace the very
first attempt to mount the floppydrive) but that cured the problem!
</strong></p>
<p><strong>
Further investigation (with <tt>strace</tt>) revealed that I'd earlier changed
<TT>/etc/resolv.conf</TT> to include a domain search path while trying to set
my friend up with an ISP account, and the DNS hang was causing automount to
hang while trying to finagle those strange pseudo-NFS mounts of the local
host it does (by the host's internet name, not as `localhost') for the floppy
drive!
</strong></p>
<p><strong>
I fixed <tt>resolv.conf</tt>, and the problem went away, although I've left
AMD disabled, because autofs does the same job, and was installed alongside
it on RedHat; and because one day I'll get my friend's ISP working on Linux
as well as Windows. I don't want this to repeat.
<IMG SRC="../../gx/dennis/smily.gif" ALT=":)"
height="24" width="20" align="middle">
</strong></p>
<p><strong>
Many thanks for your response, and my apologies once more for not writing
sooner,
</strong></p>
<p><strong>
Tim Baverstock.
</strong></p>
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<P> <hr> <P>
<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
>Copyright &copy;</a> 1999, James T. Dennis
<BR>Published in <I>The Linux Gazette</I> Issue 43 July 1999</H5>
<H6 ALIGN="center">HTML transformation by
<A HREF="mailto:star@starshine.org">Heather Stern</a> of
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<A HREF="http://www.starshine.org/">http://www.starshine.org/</A>
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