I am running RH Linux 8 (kernel 2.2.18-14) on DELL POWEREDGE 400 sc machine. Most of my process will be ASIC tools (like synopsys, magma etc).. I find my machine getting logout automatically. When I leave a process running in the night, I find the machine in login screen the next day I come to office. There is nothing I could see in log. Sometimes even the machine gets restarted. When I go through the log file (/var/log/messages) I could find the machine restarted for no reason. How should I get rid of this? Hope I clearly specify the problem!!!!!

Please check the appropriate log files a bit more extensively you are bound to find out something as imperative as a system reboot occuring without your explicit knowledge. If not then I would start looking into maybe implementing some new or analyzing your current security measures. Maybe the machine is, was, or has been compromised.