Error: Debian/Ubuntu - ClamAV-clamd: Can't connect to UNIX socket /var/run/clamav/clamd.ctl

You get the following errors in your mail log (/var/log/mail.log) on Debian/Ubuntu:

Jul 28 22:04:28 server1 amavis[31819]: (31819-19) (!)ClamAV-clamd: Can't connect to UNIX socket /var/run/clamav/clamd.ctl: 2, retrying (2)
 Jul 28 22:04:34 server1 amavis[31819]: (31819-19) (!!)ClamAV-clamd av-scanner FAILED: run_av error: Too many retries to talk to /var/run/clamav/clamd.ctl (Can't connect to UNIX socket /var/run/clamav/clamd.ctl: No such file or directory) at (eval 88) line 309.
 Jul 28 22:04:34 server1 amavis[31819]: (31819-19) (!!)WARN: all primary virus scanners failed, considering backups

Solution

The package clamav-daemon is missing. Install it as follows:

apt-get install clamav-daemon

On Ubuntu you have to prepend the command with sudo if you are not logged in as root:

sudo apt-get install clamav-daemon