Fail2ban jails not activated on Plesk server: NOK: ('database disk image is malformed')

Symptoms

• Activation of fail2ban jails / Re-reading IP addresses / Adding IP address to trusted fails with the following error in Plesk:

  PLESK_ERROR: ERROR NOK: ('database disk image is malformed',)
  ERROR NOK: ('columns jail, path, firstlinemd5 are not unique',)
  ERROR NOK: ('database or disk is full',)
  ERROR:f2bmng:Command '['/usr/bin/fail2ban-client', 'reload', 'plesk-wordpress']' returned non-zero exit status 255
  ERROR:f2bmng:Failed to reload following jails due to errors in configuration: plesk-wordpress

• /var/log/plesk/panel.log contains the following error:

  CONFIG_TEXT: fail2ban.transmitter [2431]: WARNING Command ['set', 'plesk-wordpress', 'addlogpath', '/var/www/vhosts/system/example.com/logs/access_log', 'head'] has failed. Received DatabaseError('database disk image is malformed',)

Cause

fail2ban sqlite database file is corrupted.

Resolution

Repair fail2ban sqlite database as below:

1. Log into the server via SSH;

   Note: If direct SSH access to the server is not possible, contact server administrator for further assistance.

2. Enter Fail2Ban sqlite database:

   # sqlite3 /var/lib/fail2ban/fail2ban.sqlite3

3. Execute the following commands:

   MYSQL_LIN: sqlite> .mode insert
   sqlite> .output fixed.sql
   sqlite> .dump
   sqlite> .exit

4. Open fixed.sql with any text editor and remove the lines described below:

   CONFIG_TEXT: BEGIN TRANSACTION;
   ...
   /**** ERROR: (11) database disk image is malformed *****/
   /**** ERROR: (11) database disk image is malformed
   ...
   *****/ ROLLBACK; -- due to errors

5. Create a new sqlite database:

   # sqlite3 fai2ban.fixed.sqlite3

6. Import the content of fixed file:

   MYSQL_LIN: sqlite> .read fixed.sql

7. Create a backup of /var/lib/fail2ban/fail2ban.sqlite3 database and replace it with the fixed one:

   # cp -a /var/lib/fail2ban/fail2ban.sqlite3{,.bkp}
   # yes | cp -a fai2ban.fixed.sqlite3 /var/lib/fail2ban/fail2ban.sqlite3

 If repair is not possible then re-install fail2ban component How to install / uninstall Plesk components?