How do I switch user without any references to the old one?

Question

A while back, when playing with unprivileged LXC, I discovered that the command to create a container failed if I used su to switch to the user, but it worked if I used ssh user@localhost to login.

This is not a LXC related question, but it made me wonder how to best switch user without leaving references or bringing variables from the old one?

Thanks!

Answer 1

A difference between su and ssh is that the latter actually involves a login shell, whereas the former does not by default -- although it does create a new interactive shell (see INVOCATION at the top of man bash for the significance of interactive and login shells). From man su:

For backward compatibility su defaults to not change the current directory and to only set the environment variables HOME and SHELL (plus USER and LOGNAME if the target user is not root). It is recommended to always use the --login option (instead of its shortcut -) to avoid side effects caused by mixing environments.

So, you could try su --login and see if that does what you want.

I'm presuming you're using a GUI, which is why you don't simply exit and log in again. However, that may be possible anyway (depending, I believe, on your init system), by simply running login from whatever terminal you are using. If it works, you should see the normal login: prompt, and when done you can exit from that as per su.