Unable to enable the Fail2ban jail: Failed to reload following jails due to errors in configuration

Symptoms

• Unable to enable the Fail2ban jail with the errors below:

  # plesk bin ip_ban --enable-jails plesk-roundcube
  .....
  ERROR Found no accessible config files for 'action.d/iptables-multiport' under /etc/fail2ban
  ERROR Error in action definition iptables-multiport[name="plesk-roundcube", port="http,https,7080,7081"]
  ERROR Errors in jail 'plesk-roundcube'. Skipping...
  ERROR:f2bmng:Command '['/usr/bin/fail2ban-client', 'reload', 'plesk-roundcube']' returned non-zero exit status 255
  ERROR:f2bmng:Failed to reload following jails due to errors in configuration: plesk-roundcube

• Unable to start a Plesk migration, the following error is shown in the migration logs:

  CONFIG_TEXT: =|2020-06-28_17:11:46,741|D|MT|core.runners.base|||stderr: [2020-06-28 17:11:46.522] ERR [util_exec] proc_close() failed ['/opt/psa/admin/bin/f2bmng' '--reload'] with exit code [1]
  =|2020-06-28_17:11:46,741|D|MT|core.runners.base|||PHP Fatal error: Uncaught PleskUtilException: f2bmng failed: 2020-06-28 17:11:46,413 fail2ban.configreader [30092]: ERROR Found no accessible config files for 'filter.d/dropbear' under /etc/fail2ban
  =|2020-06-28_17:11:46,741|D|MT|core.runners.base|||2020-06-28 17:11:46,413 fail2ban.jailreader [30092]: ERROR Unable to read the filter 'dropbear'
  =|2020-06-28_17:11:46,741|D|MT|core.runners.base|||2020-06-28 17:11:46,413 fail2ban.jailsreader [30092]: ERROR Errors in jail 'dropbear'. Skipping...
  ...

Cause

The corrupted Fail2ban installation.

Resolution

1. Connect to the server via SSH

2. Create a backup for the Fail2ban jail rules:

   # cp /etc/fail2ban/jail.local /root/jail.local

3. Remove the Fail2ban component with the command:

   # plesk installer --select-release-current --remove-component fail2ban

4. Rename Fail2ban directory:

   # mv /etc/fail2ban /etc/fail2ban_old

5. Install Fail2ban component back:

   # plesk installer --select-release-current --install-component fail2ban

6. Move jail.local file back:

   # mv /root/jail.local /etc/fail2ban/