named high CPU usage under Ubuntu resolved

When running Ubuntu you might encounter a strange behaviour where the named process, which is part of BIND, is taking up a large amount of CPU. In my case this was more then 120% due to the fact it was using more then a single core. Normally named would take only a very small amount of the CPU cycles available so this can be seen as strange behaviour. Reason for this behaviour turned out to be a wrongly set permission on the /var/cache/bind directory.

Due to some reason the default Ubuntu distribution is shipping with only root permissions on /var/cache/bind while named is running as the user bind. The named process is trying to write to the /var/cache/bind directory however fails due to the fact that this can only be done by the root user. This in turn results in retries which take a lot of your CPU away from other processes.

To resolve this, one of, the solution is to reset the permissions on /var/cache/bind which can be done with the commands below;

chown root:bind /var/cache/bind
chmod g+w /var/cache/bind

After this you will have to stop and start bind which can be done with the below command.

service bind9 restart

This should result in a lot less CPU usage from the named process.