I have CentOs server 5.4 , I usually remote by ssh.
My problem is server usually restart but I don't reason. I check log in file /var/log/messages: I don't see "signal 15" which kernel have to receive before restart. Everyone can see in attach.
I try to restart with command "init 6", of course in logfile /var/log/messages, I see "signal 15".
I guess My server have error in power or hardware.
"last | egrep reboot"
reboot system boot 2.6.18-164.el5 Mon Jun 6 16:40 (17:03)
reboot system boot 2.6.18-164.el5 Mon Jun 6 12:35 (04:00)
reboot system boot 2.6.18-164.el5 Sat Jun 4 15:45 (2+00:50)
reboot system boot 2.6.18-164.el5 Sat Jun 4 00:51 (2+15:44)
reboot system boot 2.6.18-164.el5 Fri Jun 3 17:46 (2+22:49)
reboot system boot 2.6.18-164.el5 Fri Jun 3 11:09 (3+05:26)
reboot system boot 2.6.18-164.el5 Mon May 30 09:52 (7+06:43)
reboot system boot 2.6.18-164.el5 Sat May 28 04:01 (9+12:34)
reboot system boot 2.6.18-164.el5 Sat May 28 03:25 (9+13:10)
reboot system boot 2.6.18-164.el5 Fri May 27 06:02 (10+10:33)
reboot system boot 2.6.18-164.el5 Thu May 19 15:10 (18+01:25)
reboot system boot 2.6.18-164.el5 Wed May 18 14:36 (1+00:30)
reboot system boot 2.6.18-164.el5 Wed May 18 14:15 (00:16)
reboot system boot 2.6.18-164.el5 Wed May 18 12:15 (01:56)
reboot system boot 2.6.18-164.el5 Wed May 18 11:33 (00:37)
reboot system boot 2.6.18-164.el5 Wed May 18 11:14 (00:14)
reboot system boot 2.6.18-164.el5 Tue May 17 22:32 (12:38)
reboot system boot 2.6.18-164.el5 Thu May 27 23:40 (354+22:47)
reboot system boot 2.6.18-164.el5 Thu May 27 23:26 (00:07)
reboot system boot 2.6.18-164.el5 Thu May 27 22:34 (00:11)
reboot system boot 2.6.18-164.el5 Thu May 27 21:55 (00:12)
reboot system boot 2.6.18-164.el5 Thu May 27 21:48 (00:03)
Nothing related in this log, except that there was a logged user before the reboot?
Jun 4 00:06:39 <name_sever> gconfd (root-7195): starting (version 2.14.0), pid 7195 user 'root'
I`m not very familiar with gnome and its logs, but you can check if the box was not rebooted by user(if gnome logs that) and who was logged before the reboot with last. Other wise look trought the logs and ask if you find something fishy. If this don`t result in anything check hardware(memory, CPU, storage, motherboard etc) and enable auditing.