I found, that I could use symlinks for that directories, I had such a config on a server running without problems. Sometimes /var has it's own partition, and so /tmp. Another way seems to put symlinks /tmp and /var pointing to a "own" (r/w of course) partition, which at least decreases problems at system crashes, what do you think?
Certainly it is also a solution. In fact for production servers I always split the system into various filesystems, not only for security reasons, but also for integrity. It's a good idea to _always_ put at least the following directories on their own filesystem: /boot /home /var /tmp /usr /opt This way you can still bring your machine up if you have a corrupted filesystem. Also consider using LIDS, as Kurt already sugested. Regards, Bráulio Gergull