Unable to login to Plesk via SSH with root user after deleting Imunify360

Symptoms

• Unable to connect to Plesk server via SSH with root user:

  Access denied
  Permission denied

• The following error can be found in /var/log/messages (e.g. when connected not as root):

  hostname crond[30531]: PAM unable to dlopen(/usr/lib64/security/pam_imunify.so): /usr/lib64/security/pam_imunify.so: cannot open shared object file: No such file or directory

• Plesk notifications may not be sent after the execution of a Daily Maintenance task.

• Cron tasks are not executed at the required time. In the /var/log/cron log file the following errors may persist:

  crond[28816]: (root) PAM ERROR (Module is unknown)
  crond[28816]: (root) FAILED to authorize user with PAM (Module is unknown)

Cause

The Imunify360 extension has been recently deleted from the server, however, its leftovers are still present in the /etc/pam.d/system-auth and /etc/pam.d/password-auth configuration files.

Resolution

1. Log in to Plesk.

2. Install SSH Terminal extension and login to the server.

3. Comment out corresponding lines in /etc/pam.d/system-auth and /etc/pam.d/password-auth as follows, e.g. using Vi:

   #%PAM-1.0
   ...
   #auth required pam_imunify.so check_only
   ...
   #auth required pam_imunify.so
   ...