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I have a VPS server running CentOS - it's been great for about a year but has just got a little flaky, going down every couple of days and requiring a reboot.

I was hoping you could offer me any basic troubleshooting steps that I might otherwise miss to locate what could be causing this.

I know I'm going to do a lot of hunting through log files, which ones would be the best to start with?

All advice appreciated.

I'm not sure if I should mark this community wiki since it's kind of an open ended question. I still don't quite get what community wiki mode is about. (But I assume I can edit and check the box if I need to)

Update: Problem was being caused by emergency maintenance being performed by my provider, so crisis averted. However, I am still very hungry to learn so feel free to leave more tips. I'll stay active in this question and upvote the ones that help me learn or are otherwise awesome.

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Check /var/log/messages – Rob Olmos Sep 13 '10 at 1:57
These are the kind of tips I'm looking for. Now I just have to figure out what's "normal" in that log file, and what everything means. It's mostly xinetd starting and exiting smtp connections, with an occasional pure-ftpd making a connection from – Syntax Error Sep 14 '10 at 16:44
up vote 0 down vote accepted

If you have a managed VPS, your first step should be to contact your provider for support.

If you have an unmanaged VPS and you cannot identify anything in the logs, you've confirmed the security of your server to the best of your ability, and you cannot identify any installed software which is due for an upgrade, you may want to bring the issue to the attention of your service provider as it could be indicative of a problem on their end (be it incoming DDoS attacks, a bad neighbor, faulty hardware, or otherwise).

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I'm looking more for troubleshooting tips on my end, although that is still good advice. In fact, in my current situation, the problem was in fact being caused by emergency maintenance on their end, so your tip should never be over looked. I'll accept your answer since you guessed what was causing it, but hopefully people will still leave more tips so I can learn. – Syntax Error Sep 14 '10 at 16:48
To paraphrase the excellent guide which comes up first for "linux os troubleshooting" at Google: df -H; tail -f /var/log/messages; dmesg | less -… – danlefree Sep 14 '10 at 17:55
Very useful commands. I'll read the full article as well. – Syntax Error Sep 14 '10 at 21:17

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