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I have an Ubuntu 10.04 server that's going a bit slow. It's very slow to log in via SSH, and it's very slow when making edits via a Mediawiki instance installed on there.

For normal read access to the hosted website, it's fast (I have APC installed, FWIW), and it's also fast with SSH once I'm actually logged in.

What sort of things should I be checking as possible sources of this problem? I need to diagnose it remotely.

Cheers JP

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1 Answer 1

  1. There's a problem with the account at the server that slows down logins - stale NFS mount, some prompt that waits and waits, etc. Try ssh -v ... and check your startup files (do man bash and look at the INVOCATION section).
  2. There's an unexpected load on the remote system, use uptime, and ps to investigate.
  3. Something else is wrong, do your ssh login, then immediately do /bin/ls -lrt /var/log, followed by tail -n 100 on the most recently modified log files - they'll tell what the system logged as you connected.
  4. Something else is wrong, do your Mediawiki edits, then immediately do /bin/ls -lrt /var/log, followed by tail -n 100 on the most recently modified log files - they'll tell what's what.
  5. If I, or anyone else, tell you "do somecommand", don't blindly do it! Use the man, man -k, and info commands to understand both the intent and the particular example of "somecommand".
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thanks for the tips. 'UseDNS no' was the solution for the SSH login issue. That indicates a reverse DNS problem (which is not surprising; I am unable to set a reverse DNS entry for the host in question). I need to find out if the resulting Mediawiki delays are due to database write delays or else some DNS/reverse DNs delay that is occurring. I will try looking at the log files as you suggested. –  jdpipe Feb 29 '12 at 5:26
    
You could use wireshark to capture packets leaving the server, while you do your slow Wikimedia stuff. Then, look at the packets wireshark captured, and see if there's a DNS conversation that's taking a long time. –  waltinator Mar 2 '12 at 18:23

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