I installed Ubuntu core on my raspberry pi3. After configuring it I have now ssh access to the pi using my ubuntu account and a private key. Now I want to create an additional user, to simplify the ssh process (since I don't always have that private key around and simply want to login in with username + pass).
So I tried
sudo useradd myusername
But that results in this error , but I get the error:
Cannot lock /etc/password; try again later
When I for example try to create a directory in the root of the file system, I get an error:
cannot create directory ‘test’: Read-only file system
When I the different partions with df, I see also that the partion of root (/) is 100% in use.
What is going on? How can I create that additional user?