Re: shared NFS systems

[Matt Zimmerman <mdz@debian.org>]

On Tue, Nov 28, 2000 at 02:13:07PM +1100, Brian May wrote:

> I think it should be an important goal of Debian to work properly,
> without resorting to hacks, on systems which share one or more files
> using something like NFS (from sharing /usr all the way through to
> sharing / for nfsroot systems).
> 
> [...]
> 
> If you spot any mistakes or possible improvements, please send me a
> patch file for the *.xml file, and I will consider applying it ASAP.
> Alternatively, if somebody else wants to maintain this file, go
> ahead...

I don't have a working XML docbook environment to test whether this is correct,
but my editor likes it.  A patch is attached which discusses how a possible
kernel extension (union mounts) could simplify the situation.

-- 
 - mdz

*** nfs-dpkg.xml.old	Mon Nov 27 22:05:40 2000
--- nfs-dpkg.xml	Mon Nov 27 22:50:05 2000
***************
*** 164,169 ****
--- 164,190 ----
  	think some of the details are too different from how it is currently
  	done.</para>
        </listitem>
+ 
+       <listitem>
+ 	<para>
+ 	  Some of these problems would go away if the kernel supported
+ 	some kind of union filesystem layer.  For example:
+ 	</para>
+ 
+ 	  <screen>
+ 	    $ mount -o union /tmp/scratch /usr $ mount -o union
+ 	    ...same for other shared mount points...
+ 	  </screen>
+ 
+ 	<para>
+ 	  Then, a package could be installed, and modifications to
+ 	  /usr would be written to a scratch filesystem (which would
+ 	  eventually be thrown away).  Local modifications to /etc,
+ 	  /var, etc. would still take place, but files installed to
+ 	  /usr would be ignored in favor of the shared versions once
+ 	  the scratch filesystem was unmounted.
+ 	</para>
+       </listitem>
      </orderedlist>
    </section>