Bug#705649: Document solutions for re-enabling static mtab
tags 705649 + patch
On Tue, Apr 16, 2013 at 10:37:37PM +0100, Roger Leigh wrote:
> I've not made any changes as yet. Given that this will only affect
> users who are using e.g. nbd as their rootfs, and not any regular
> use of network nfsroot etc., the best option may be to simply
> document how to re-enable a static mtab in the release notes, for
> users who are dependent upon _netdev working. This would
> essentially be to
> - comment out the mtab_migrate conditional in /etc/init.d/checkroot.sh
> - rm /etc/mtab
> - cat /proc/mounts > /etc/mtab
> and to reboot; the _netdev flag will then be stored in mtab correctly.
Patch for the release notes attached. I've gone through the process
locally and confirmed that this all works as documented.
Regards,
Roger
--
.''`. Roger Leigh
: :' : Debian GNU/Linux http://people.debian.org/~rleigh/
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Index: en/issues.dbk
===================================================================
--- en/issues.dbk (revision 9741)
+++ en/issues.dbk (working copy)
@@ -186,6 +186,73 @@
</section>
+<section id="mtab">
+<title><filename>/etc/mtab</filename> and <literal>_netdev</literal></title>
+
+<para>
+The file <filename>/etc/mtab</filename>, used to store the list of
+currently mounted filesystems, has been changed to be a symbolic link
+to <filename>/proc/mounts</filename>. For almost every case, this
+change will result in a more robust system since the list can never
+become inconsistent with reality. However, if you use the
+<literal>_netdev</literal> option in <filename>/etc/fstab</filename>
+to indicate that a filesystem is a network filesystem requiring
+special handling, this will no longer be set in
+<filename>/proc/mounts</filename> after rebooting. This will
+<emphasis>not</emphasis> cause problems for standard network
+filesystems such as <acronym>NFS</acronym>, which do not rely on the
+<literal>_netdev</literal> option. Filesystems which are
+<emphasis>unaffected</emphasis> by this issue are
+<literal>ceph</literal>, <literal>cifs</literal>,
+<literal>coda</literal>, <literal>gfs</literal>,
+<literal>ncp</literal>, <literal>ncpfs</literal>,
+<literal>nfs</literal>, <literal>nfs4</literal>,
+<literal>ocfs2</literal> and <literal>smbfs</literal>. For
+filesystems which <emphasis>do</emphasis> rely on
+<literal>_netdev</literal> for correct unmounting at shutdown, for
+example when using an <acronym>NBD</acronym>, a static mtab will be
+the only way to use <literal>_netdev</literal> in wheezy. If you have
+such a setup, then after completing the upgrade to wheezy restore a
+static <filename>/etc/mtab</filename> by doing the following:
+</para>
+<itemizedlist>
+<listitem>
+<para>
+Edit <filename>/etc/init.d/checkroot.sh</filename>, and comment out
+these lines:
+</para>
+<screen>
+ if [ "$rootmode" != "ro" ]; then
+ mtab_migrate
+ fi
+</screen>
+<para>
+</para>
+</listitem>
+<listitem>
+<para>
+If you have rebooted the system, and <filename>/etc/mtab</filename> is
+now a symbolic link:
+</para>
+<screen>
+# rm /etc/mtab
+# cp /proc/mounts /etc/mtab
+</screen>
+<para>
+Re-add the <literal>_netdev</literal> option by remounting the
+affected filesystems:
+</para>
+<screen>
+# mount -o remount <replaceable>filesystem</replaceable>
+</screen>
+<para>
+<filename>/etc/mtab</filename> will be recreated fully next time you
+reboot the system.
+</para>
+</listitem>
+</itemizedlist>
+</section>
+
<!--Wheezy-->
<section id="mksh">
<title>The pdksh to mksh transition</title>
Index: en/release-notes.dbk
===================================================================
--- en/release-notes.dbk (revision 9741)
+++ en/release-notes.dbk (working copy)
@@ -394,6 +394,10 @@
<glossdef><para>Mail Transport Agent</para></glossdef>
</glossentry>
<glossentry>
+ <glossterm>NBD</glossterm>
+ <glossdef><para>Network Block Device</para></glossdef>
+ </glossentry>
+ <glossentry>
<glossterm>NFS</glossterm>
<glossdef><para>Network File System</para></glossdef>
</glossentry>
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