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I installed munin on my ubuntu server. It's showing my 'inode table usage' spiking every morning at 8am. It then rapidly curves down and settles over the course of several hours. What might cause this?

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I thought it might be something running in /etc/cron.daily but this was set to run at 6a.m. and I've changed it to 4am. The spike remains at 8am. I also enabled cron logging, but can't see anything getting launched at 8a.m.

It's a virtual server hosted by memset. Could it be caused by something happening on the virtual host?

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On a default ubuntu/debian set-up, some things will run via 'anacron'. The timing of this can depend on a number of factors, particularly when the machine started up, but on a server machine it will trigger at 7:30 a.m. every morning by default.

This is configured in the file /etc/cron.d/anacron , so a simple solution is to edit that file and and set the configured time to something more convenient (e.g. middle of the night if you are concerned about the tasks impacting day time performance) There is no need to restart anything.

The cron log which I enabled, was in fact showing the initiation of anacron at 7:30. Anacron delays for a little while before doing anything and also presumably queued up several jobs, the result being that one job was starting up at about 8a.m. each day and causing a lot of inode table usage (people have suggested the mlocate db re-index) I don't know that it was causing any performance problems, but it seems healthier now to see it doing this in the middle of the night.

There is some brief documentation specific to ubuntu here: https://help.ubuntu.com/community/CronHowto#How_Anacron_is_Arranged

...and much more detailed explanation of the interplay between cron and anacron here: http://tuxradar.com/content/automate-linux-cron-and-anacron

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Look for cronjobs running at about that time. In Ubuntu check the files in /etc/cron.daily first, as well as root's crontab ("sudo crontab -l"). Most likely it is something like log rotation, or log analysis that is creating many temporary file.

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It certainly looks like something scheduled, but I can't see anything in the root or my user crontab. I even tried this bash script: stackoverflow.com/questions/134906/… to check if there was some cron stuff I was missing. Any other schedule mechanisms I could check (beyond cron) ? I wondered about postgres autovacuum, but I think that's more regular than daily –  Harry Wood Nov 14 '11 at 13:21
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Or trying logging in at 8am, and running top :-) –  nickgrim Nov 15 '11 at 11:21
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