My server is restarted by itself tonight. How can I determine waht caused this? I checked in /var/log/messages but I can't understand from there.
Is there any other way/option ?
I use Red Hat Enterprise Linux AS release 3 (Taroon Update 5)
Your server is restarting because some piece of hardware in it is failing. It is, after all, an antique that should have been decommissioned years ago. The symptom you describe is also strongly correlated with failed hardware components, regardless of the age of the system.