'su' command in Docker returns 'must be run from terminal'

Question

I'm developing a docker environment for teaching purposes and need to be able to switch users inside docker.

I set up the 'user' user with a password but when I try to switch to it with su, I get "su must be run from terminal".

I get this if I try to ssh into the docker and also by issuing commands through a php shell (an apache service is running on the Docker instance).

Any help is much appreciated.

Answer 1

When you are ssh-ing in or going in via php your session is not being allocated a pty. I have used each of the following solutions:

ANSWER 1: use ssh -t or ssh -tt to get pty allocated when logging in using ssh:

I had great fun getting commands to run right due to ptys when running sessions like this: jenkins shell -> ssh driver -> ssh test -> docker exec. Good answer here: https://unix.stackexchange.com/questions/105422/command-must-be-run-from-a-terminal

"Try the -t option to ssh. If that does not work try -tt."

"-t Force pseudo-tty allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple -t options force tty allocation, even if ssh has no local tty."

ANSWER 2: use docker run -t ... and docker exec -it

Use the -t and -it options to allocate pty in your docker exec session.

Also with docker exec you can simply use the -u option to login to container as different users and avoid using su. e.g.

$ docker exec -u root -it small_hypatia bash 

There is a good question and answer on this here: https://github.com/docker/docker/issues/8631

ANSWER 3: use python to spawn a pty in your shell

Quite a cute hack :)

jenkins@e9fbe94d4c89:~$ su - su: must be run from a terminal  $ echo "import pty; pty.spawn('/bin/bash')" > /tmp/asdf.py $ python /tmp/asdf.py  $ su - Password:   root@e9fbe94d4c89:~#