Unable to access RoundCube webmail with the 500 error: the /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18 symlink is missing

Symptoms

• Unable to access RoundCube webmail on a Plesk server with the error:

  500 external Server Error

• The errors below can be found in /var/log/plesk-roundcube/errors file:

  PHP Fatal error: Undefined class constant 'MYSQL_ATTR_FOUND_ROWS' in /usr/share/psa-roundcube/program/lib/Roundcube/rcube_db_mysql.php on line 144

Cause

The /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18 symlink is missing.

Resolution

1. Log into the server via SSH.

2. Using the command below create the missing symlink:

   # ln -s libmariadb.so.3 /usr/lib/x86_64-linux-gnu/libmysqlclient.so.18