Not counting the reserved space by root (usually 5%), if the /tmp is really 100% full, so 0 bytes free, why couldn't we log in to the machine via ssh? We only got the error message cannot fork. Are there any parameters to the ssh client so that we could still log in to a machine when it has a 100% full /tmp? UPDATE: reboot is not really an option :\
SSH login and /tmp on 100%
ssh