After creating a few new users on the RN312, using the web interface provided with the device, I noted that none of the users could ssh into the NAS.
Turns out the new users are created without a default shell, resulting in a successful ssh login, followed by a terminated connection. No good.
For example, a user named charlie would have something like the following entry in the /etc/passwd file. Note the final bold characters:
Change this to
Charlie should now be able to ssh into the NAS. By the way, you HAVE set up ssh keys for your users, right… Way more secure than plan text passwords, and a lot more convenient…