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<TITLE>The Answer Guy 48: Maximal Mount Count Reached</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">
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<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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<!-- begin 53 -->
<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Maximal Mount Count Reached</H3>
<p><strong>From Marius Andreiana on Sat, 25 Sep 1999
</strong></p>
<!-- ::
Maximal Mount Count Reached
~~~~~~~~~~~~~~~~~~~~~~~~~~~
:: -->
<P><STRONG>
Dear Answer Guy,
</STRONG></P>
<P><STRONG>
I'm Marius and here is my problem :
</STRONG></P>
<P><STRONG>
From time to time ( seldom ), my RH Linux 6.0 says during booting
"<TT>/dev/hdaX</TT> had reached maximal mount count; check forced"
where X is 3 and 4. Here's my partition table :
</STRONG></P>
<Pre><STRONG><BlockQuote>
/dev/hda1, 170 MB, type= 6h (DOS 16-bit >=32)
/dev/hda2, 16 MB, type=82h (Linux swap)
/dev/hda3, 497 MB, type=83h (Linux native)
/dev/hda4, 129 MB, type=83h (Linux native)
</BlockQuote></STRONG></Pre>
<P><STRONG>
I always perform clean shutdowns. I suppose this is because all the
above 4 partitions are primary. But then why does it report
that message only from time to time ?
</STRONG></P>
<P><STRONG>
Thanks a lot for your time
<br>Marius
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
We call that "losing the lottery." It always seems to
happen when you're in a hurry to get the system back up and
running.
</BLOCKQUOTE>
<BLOCKQUOTE>
Don't worry about this message, though. It's perfectly
normal. Even if you do cleanly shutdown every time, there's
always that chance that some filesystem corruption has crept
in. So each filesystem stores the number of times you've
mounted it since you did an fsck (filesystem check) and
automatically forces one at those points.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you want to live dangerously you can change the
the maximal mount count value on a filesystem
using the 'tune2fs' command's -c option. You can also
manually set the mount value using the -C (upper case)
option. You can see the current values using a command
like:
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE><BlockQuote>
tune2fs -l <TT>/dev/hda1</TT>
</BlockQuote></CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
... This is the only command that you might run on any of
these devices while it is mounted. In my particular case it
shows a maximal mount count of 20. You should unmount any
filesystem before using tune2fs to write any new values unto
them using the other options from this command. (It should
be safe to change some values when you have a filesystem
mounted read-only; though it might be worth asking an
expert, so I've copied Ted T'so and Remy Card on this
message).
</BLOCKQUOTE>
<BLOCKQUOTE>
You can also set a volume label on any of your
ext2 filesystems using this command (BTW: 'tune2fs'
only works on ext2fs --- don't try to use it on
any other sorts of filesystems that you have). I
notice that the man page doesn't tell us anything
about these volume labels (like what characters
are allowed, and how long they can be). Glancing
at the source code to e2fsprogs I find that you can
have volume labels of up to 16 characters. I didn't
see any filtering on characters so I suppose any
string of non-NUL characters might be used ---
though I'd stick with simple alphanumerics and
printable punctuation to be safe.
</BLOCKQUOTE>
<BLOCKQUOTE>
As far as I know there is no way in which this
volume label is currently used. It seems to be a
wholly optional feature; I guess we can use these
to keep track of our removable media or something.
</BLOCKQUOTE>
<BLOCKQUOTE>
(Ted, Remy, is it safe to set some or all tune2fs
values on a filesystem while it's mounted read-only?
Are there any characters that should NOT be used
in the volume labels? Is there anything that uses
these volume labels, or are they just obscure
cosmetic options?)
</BLOCKQUOTE>
<!-- sig -->
<!-- end 53 -->
<p><hr width="40%"><p>
<!-- begin 53 -->
<H3 align="left"><img src="../../gx/dennis/qbubble.gif"
height="50" width="60" alt="(?) " border="0"
>Having been cc'd, Ted T'so adds...</H3>
<p><strong>From tytso on Mon, 27 Sep 1999
</strong></p>
<!-- ::
Having been cc'd, Ted T'so adds...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:: -->
<P><STRONG>
Date: Sat, 25 Sep 1999 01:14:42 -0700
From: Jim Dennis <<A HREF="mailto:jimd@starshine.org"
>jimd@starshine.org</A>>
</STRONG></P>
<P><STRONG>
We call that "losing the lottery." It always seems to
happen when you're in a hurry to get the system back up and
running.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Yup. Note that even once we have journalling support in ext2, you will
want to occasionally force an fsck over the filesystem just to make sure
there haven't been any errors caused by memory errors, disk errors,
cosmic rays, etc.
</BLOCKQUOTE>
<BLOCKQUOTE>
If you need your laptop to reboot quickly just before a demo (and your
laptop doesn't have a hiberate feature or some such), something you can
do is to sync your disks, make sure your system is quiscient (i.e.,
nothing is running), and then force a power cycle and let your system
reboot. Your system will then fsck all of your disks, and you can then
shutdown your system, confident that the dreaded "maximal mount count"
message won't appear during that critical demo.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
If you want to live dangerously you can change the
the maximal mount count value on a filesystem
using the 'tune2fs' command's -c option. You can also
manually set the mount value using the -C (upper case)
option. You can see the current values using a command
like:
</STRONG></P>
<P><STRONG><BlockQuote><Code>
tune2fs -l <TT>/dev/hda1</TT>
</Code></BlockQuote></STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
If you know that your system is fairly reliable --- you've been running
it for a while and you're not seeing wierd failures due to cheasy cheap
memory or overly long IDE or SCSI cables, etc. it's actually not so
dangerous to set a longer maximal count time.
</BLOCKQUOTE>
<BLOCKQUOTE>
One approach if your system is constantly getting shutdown and restarted
is to set the filesystem so it uses the time the filesystem was last
checked as a criteria instead of a maximal count. For example:
</BLOCKQUOTE>
<BLOCKQUOTE><BLOCKQUOTE><CODE>
tune2fs -c 100 -i 3m <TT>/dev/hda1</TT>
</CODE></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE>
This will cause the filesystem to be checked after 100 mounts, or 3
months, whichever comes first.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
(It should be safe to change some values when you have a
filesystem mounted read-only; though it might be worth asking
an expert, so I've copied Ted T'so and Remy Card on this
message).
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
Yes, it's safe these values if the filesystem is mounted read-only. If
you're ***sure*** that the filesystem is quiscent, and nothing is
changing on the filesystem, you can even get away with changing it while
the filesystem is mounted read-write. It's not something I'd really
recommend, but if you know what you're doing, you can get away from it.
It really depends on how much you like working without a safety net.
</BLOCKQUOTE>
<P><STRONG><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
As far as I know there is no way in which this
volume label is currently used. It seems to be a
wholly optional feature; I guess we can use these
to keep track of our removable media or something.
</STRONG></P>
<BLOCKQUOTE><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)"
HEIGHT="28" WIDTH="50" BORDER="0"
>
You can use the volume label in your <TT>/etc/fstab</TT> if you like: For
example:
</BLOCKQUOTE>
<BLOCKQUOTE><BlockQuote>
LABEL=temp <TT>/tmp</TT> ext2 defaults 1 2
</BlockQuote></BLOCKQUOTE>
<BLOCKQUOTE>
or
</BLOCKQUOTE>
<BLOCKQUOTE>
UUID=3a30d6b4-08a5-11d3-91c3-e1fc5550af17 <TT>/usr</TT> ext2 defaults 1 2
</BLOCKQUOTE>
<BLOCKQUOTE>
The advantage of doing this is that the filesystems are specified in a
device independent way. So for example, if your SCSI chain gets
reordered, the filesystems will get mounted correctly even though the
device names may have changed.
</BLOCKQUOTE>
<BLOCKQUOTE>
- Ted
</BLOCKQUOTE>
<!-- end 53 -->
<!--startcut ======================================================= -->
<P> <hr> <P>
<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
>Copyright ©</a> 1999, James T. Dennis
<BR>Published in <I>The Linux Gazette</I> Issue 48 December 1999</H5>
<H6 ALIGN="center">HTML transformation by
<A HREF="mailto:star@starshine.org">Heather Stern</a> of
Starshine Technical Services,
<A HREF="http://www.starshine.org/">http://www.starshine.org/</A>
</H6>
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