Maybe you should check out Joerg Brauns live-CD . It's available at 
ftp://ftp.netbsd.org/pub/NetBSD/iso/1.5.2/i386live.iso.gz, there are 
also two readme-files README.FIRST-i386live and README.i386live in the 
same directory.
/Erik

Andy Ball wrote:

>Hello Erik,
>
>  EA> - A root device: if you don't have a hardrive you can use a
>    >   memory disk embeded in the kernel (like in the installation-
>    >   kernel) or NFS.
>
>I'm keen to try the memory disk idea.  I plan to build a firewall soon
>and would like it to have just a CD-ROM drive.  Some (which?) parts of
>the filesystem need to be read/write.  If they're small enough, I can
>have the rest mount read-only.
>
>  EA> - Your own statically linked /sbin/init on the root device. This
>    >   is the only userland process started by the kernel so if your
>    >   system only need to run one program call it init and place it
>    >   in /sbin. (Your program might have to do some of the things
>    >   that the original init does, e.g. if your program wants do
>    >   console io you will need a /dev/console and your init will
>    >   have to open that device and dup2 fd's 0, 1 and 2 to that fd).
>
>I think I get understand what you're saying, and where the application
>is simple and space is at a premium I can see the sense in that
>approach.  I'm not sure I'll try it just yet though ;-)
>
>  EA> You can of course use the standard init and instead creat your
>    > own /etc/rc.
>
>That sounds like the direction I'll take.
>
>  EA> If you want dynamically linked programs you will also need a
>    > /usr/lib filled with the libraries your programs use (running
>    > ldd on a binary will list does) and /usr/libexec/ld.elf_so is
>    > also needed.
>
>Hmm... can /usr/lib be read-only?
>
>  EA> Some programs (like netstat) need to lookup data in the kernel
>    > and for that they need the kernel symbol table. Normally the
>    > symbol-table is read from /netbsd but if you use a memory disk
>    > embeded in the kernel you might not want to put a kernel there
>
><grin>
>
>  EA> ...If that is the case you can use kvm_mkdb (8) to create a
>    > /var/db/kvm.db that will be used instead.
>
>I'll look that one up, I can see myself using it when I get to ROM or
>Flash based systems.  For the machines with CD-ROM drives, could
>/netbsd be a link to the kernel on the disc?
>
>  EA> If you use existing programs you will of course need to lookup
>    > what libraries they need (if dynamically linked), what config
>    > files they use, other directories (e.g. they might want to put a
>    > log file in /var/log) and if they exec other programs.
>
>It sounds as though I have plenty of homework to do!  :-)
>
>  EA> That's all I can think of for the moment.
>
>Thanks a lot, you've given me enough to get started and that is
>appreciated.
>
>Regards,
>  - Andy Ball.
>  
>