jails; sharing parts of file system; mounting pieces of file system in other positions, etc.

[Rob]

Chad Leigh asked on Wednesday January 07, 2004:


>
> On linux you can do a
>
> % mount -bind olddir newdir
>
> to remount a piece of the FS somewhere else.  The NullFS on FBSD seems
> to allow similar things.  However, as much as I could find on NullFS
in
> Google seems to indicate that it is pretty much broken and shouldn't
be
> used.
>
> What I want to do is run several jails that would share the "read
only"
> pieces of a system like / /bin /sbin /usr/bin /usr/sbin and stuff like
> that.  Each jail would have their own /etc and other places that would
> need to be different and writable.  This way I only have to update the
> system once when I upgrade and not do all my various jails one at a
> time. Of course, some things would need to be done for each jail (etc
> updates etc) but this would minimize it...
>
> Is this a possible thing to do under FBSD?  How are others doing it?
>
> Thanks for your input
>
> Chad
>

I'm currently setting up my 4.9-RELEASE webserver to do something
similar - each jail gets a root filesystem, but /usr is shared readonly
by all of them. The exception is /usr/local/etc, which is symlinked to
/etc/local (in the jail).

My impression, though I don't have much to back this up with, is that
nullfs is reliable enough in read-only mode. Other folks may have a
different opinion.