All versions of fog currently put only one storage node’s config into /etc/exports, normally, this is just /images
so the first thing is to check the exports file: /etc/exports. If an entry for your eternal drive isn’t there, just copy/paste the two existing lines and change the paths to point to the external drive.
Note that inside the external drive’s “images” directory, you need a “dev” directory.
also, in both /images and in /images/dev, you need a hidden file, named .mntcheck
you can create this file using the touch command, like this: touch .mntcheck