When running Clonezilla the program mounts the external HDD when "Informing the OS of partition table changes...". Why does it do that? It started doing that out of the blue. Commenting out the entry in /etc/fstab does nothing. Clonezilla is installed into Ubuntu.
I think the settings for automounting can found and modified in different locations (GUI tools) between standard Ubuntu and each of the community flavours.
In standard Ubuntu 16.04.x LTS you can try via