Postgresql DB on a live cd

Hi,

I'am trying to create a demo cd (knoppix) with a jdbc application.

This application uses a static (read-only, no insert, modify or delete) 200MB
postgresql db, so can't put pgsql/data/base and pgsql/data/pg_xlog in ramdisk.

postmaster fails to start because can't open the files in these two dirs with
read and write access.

The question is : can postmaster start only with read access ?

Any alternative solutions ?

Thank in advance,
Lucio