How customized can an mfsroot be?

[perryh at pluto.rain.com]

Peter Steele <psteele at maxiscale.com> wrote:
> In my read-only CD-ROM boot case, /var is created as a MFS device
> automatically and populated, but a basic directory layout only is
> used. Nothing from the CD-ROM /var is copied into the MFS /var
> that is created.
>
> I cannot figure out how BSD can do this automagically, so I'll
> have to have a duplicate copy of /var on the CD and populate it
> from that. What I've tried that works well is when I'm about to
> run mkisofs to create the .iso from, I rename my /var to /var2 and
> create an empty /var. When the iso is booted, a default MFS based
> /var is created with a specific collection of directories. I have
> a startup script that copies my /var2 contents into /var and that
> does the trick.

You might be able to reduce the iso size some by making a tarball
of /var (using tar -y or tar -z) instead of keeping /var2 as a tree.
Granted you would then need to have tar(1) in the iso, which may
cancel out much of the savings if you would not otherwise have
needed it.