Enabling ClamAV in Plesk Email Security fails: Cannot allocate memory

Symptoms

• Enabling ClamAV in the Plesk Email Security extension fails:

  Execution filemng has failed with exit code 1, stdout: , stderr: Job for clamd@scan.service failed because the control process exited with error code. See "systemctl status clamd@scan.service" and "journalctl -xe" for details.

• Manually enabling the service clamd in the server's console also fails:

  # systemctl status clamd@scan.service
  * clamd@scan.service - clamd scanner (scan) daemon
  Loaded: loaded (/usr/lib/systemd/system/clamd@.service; enabled; vendor preset: disabled)
  Active: activating (start) 
  ...
  clamd[17834]: daemonize() failed: Cannot allocate memory
  clamd[17834]: Socket file removed.

Cause

There is not enough RAM memory to initialize the service. The server should have at least 4 GB of overall RAM and 2 GB free RAM.

Resolution

Allocate more RAM to the server either on your own or by contacting the administrator/provider of the server.