[Voyage-linux] No change to /dev/sda during shutdown

[(spam-protected)]

All,

One of the significant differences between Debian Linux and Voyage Linux
is the support for using Compact Flash instead of a hard drive.
(http://wiki.voyage.hk/rw_ro.txt)

The way I understand it, /var/log and /var/tmp are kept in RAM and saved
to their original locations on shutdown.

My question is: (How) can I disable this? I basically want the OS never
to make any changes to /dev/sda, also during shutdown and boot-up,
unless I manually re-mount read-writable.

Thanks a lot -