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Everyday at 4am my linode graphs shows a huge spike in CPU, Network, and Disk IO. The CPU spikes to 45%.

How can I find out what is causing this? I took a look in /etc/cron.daily/ but there are a lot of items in there, and I'm not sure how to see which one(s) are running at that time. I am a little worried because the Networking is spiking huge as well, and I don't know what is going on.

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You can look into /etc/cron.daily/* and in /var/spool/cron/* to locate the cron.

My first guess, however, would be for you to look at 'updatedb' from the slocate package (which scan the whole filesystem and create files lists), and for LogRotate which generally generate VERY high load on a highly used system (because it copy files, rotate them, reload processes). Those 2 scripts are programmed to run at 4AM by default. Try moving them to 3h30 and check if there's an impact.

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And if you have anyremote filesystems mounted, it also explains the network IO :) – Dennis Kaarsemaker Nov 21 '12 at 21:00
Haaa. Nice catch! I was wondering about that one... – CloudWeavers Nov 22 '12 at 15:54

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