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davr
Asked: 2011-06-02 20:57:53 +0800 CST

Troubleshooting linux server reboots?

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I have a Linux server I've just set up, debian squeeze, 2.6.32-5-amd64, and over the past week it's rebooted three times, twice in one day. There was no power outage that I am aware of (and it's running on a UPS), and there are no errors in syslog, besides a few to-be-expected ones on bootup to do with clearing out entries in the ext4 journal due to the unclean shutdown.

What steps can I take to determine the cause of the reboots? Is there a way to get it to hang instead of rebooting, so I can copy stack traces or something off the screen? Any way to increase debug messages, or get it to dump things to disk, or something?

linux debian troubleshooting

3 Answers

  1. That may be some hardware problem; the most common are failed RAM and overheating. You could install mbmon to monitor motherboard and CPU temperature; and runmemtest86+ to check your RAM and CPU cache.

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  2. There is a chance it is a 'kernel panic' and a kernel 'oops' message is sent to the console before the reboot. The kernel can be configured to reboot on 'panic' or to stay on. Check:

    cat /proc/sys/kernel/panic

    If it is non-zero try putting 0 there (you can do it directly writting to the file, via /etc/sysctl.conf which is usually parsed on boot, or using the sysctl utility), this should stop rebooting. If it is already 0, then the reboots are not caused by kernel panics.

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  3. Check the output of last. Look for reboot. Try to correlate that with who was logged in if anyone and who has superuser privileges. If it is not a user, you may have power/heat issues or some type of kernel panic causing issues. Try to rule those out one by one.

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