Fail2ban service fails to start on a server with Plesk

Symptoms

• Fail2Ban in Plesk fails to start with any of the following errors:

  PLESK_ERROR: Internal error: f2bmng failed: ln -s ‘/usr/lib/systemd/system/fail2ban.service’ ‘/etc/systemd/system/multi-user.target.wants/fail2ban.service’
  Job for fail2ban.service failed. See ‘systemctl status fail2ban.service’ and ‘journalctl -n’ for details.
  ERROR:f2bmng:Failed to start fail2ban serviceMessage: f2bmng failed: ln -s ‘/usr/lib/systemd/system/fail2ban.service’ ‘/etc/systemd/system/multi-user.target.wants/fail2ban.service’
  Job for fail2ban.service failed. See ‘systemctl status fail2ban.service’ and ‘journalctl -n’ for details.
  ERROR:f2bmng:Failed to start fail2ban serviceFile Agent.phpLine 243Type PleskUtilException

  ---

  # service fail2ban start
  * Starting authentication failure monitor fail2ban
  Traceback (most recent call last):
  File “/usr/bin/fail2ban-client”, line 472, in <module>
  if client.start(sys.argv):
  File “/usr/bin/fail2ban-client”, line 442, in start
  return self.__processCommand(args)
  File “/usr/bin/fail2ban-client”, line 216, in __processCommand
  if self.__ping():
  File “/usr/bin/fail2ban-client”, line 153, in __ping
  return self.__processCmd([[“ping”]], False)
  File “/usr/bin/fail2ban-client”, line 185, in __processCmd
  client.close()
  File “/usr/lib/python2.7/dist-packages/fail2ban/client/csocket.py”, line 55, in close
  self.__csock.sendall(CSPROTO.CLOSE + CSPROTO.END)
  File “/usr/lib/python2.7/socket.py”, line 224, in meth
  return getattr(self._sock,name)(*args)
  socket.error: [Errno 32] Broken pipe

Cause

fail2ban service was started manually with –x option.

Resolution

1. Connect to the server using SSH.

2. Kill fail2ban service on the server and remove its socket:

   # kill `ps afvvx | grep -v grep | grep fail2ban-server | awk ‘{print $1}’ | xargs`
   # rm -f /var/run/fail2ban/fail2ban.sock

   Note: In case of missing fail2ban process, incorrect command usage message will be shown.

3. Start Fail2Ban service from Tools & Settings -> Services Management -> IP Address Banning (Fail2ban) in Plesk GUI:

   

4. In case of steps above did not help – reinstall Fail2Ban components: How to install/uninstall Plesk components?