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I have new brand new Dell with Ubuntu 16.04.02 LTS pre-installed. I've done updates, setup a local account and installed ssh.

When I try to ssh into the machine it asks for my password, prints "Welcome to Ubuntu", "last login: Thu..." and then "Connection closed".

This happens from remote systems, or locally when I run 

ssh 127.0.0.1

The problem is just login sessions, it works if I give it a command like

ssh 127.0.0.1 /bin/date

I can even get a minimally working shell but it isn't attached to a tty so lots of things don't work.

ssh 127.0.0.1 /bin/bash -i

The account uses bash. The startup scripts are unchanged from the ones in /etc/skel, just .bashrc and .profile. I've tried moving them aside. Based on an old answer I have verified that they don't have an exit in them.

I'm using a normal user account; not root.

muru
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J Prescott
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  • Try ssh -t 127.0.0.1 /bin/bash -i. The -t asks for a TTY allocation. – muru May 26 '17 at 02:18
  • For fun, grep your_username /etc/passwd and see if anything is funky there. Unless the VAR or you changed something, what you are trying to do should work swell. Also, you could try ssh -l localhost using a different username. If this works that would eliminate a lot of possibilities. Lastly, after you ssh localhost, cat /HOME/.bash_history and see if there is an unexpected exit or quit at the end of it. – jones0610 May 26 '17 at 04:06
  • muru, thanks for the ssh -t tip. It does successfully work around the current problem and would have been great to know countless times in my past when trying to login to partially wedged systems. – J Prescott Jun 01 '17 at 14:57

1 Answers1

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I was able to isolate the problem by adding debugging statements to /etc/profile to trace early startup.

Dell has added a file /etc/profile.d/display-toggle-keybinding.sh to fiddle with some keybindings. That file starts with: 

if [ -z "$DISPLAY" ]; then  
   exit 0  
fi

Since things in /etc/profile.d are sourced, they run in the current shell rather that a subshell, so when they exit it kills off the whole session.

Once I saw the problem it was easily verified by trying 

ssh -X 127.0.0.1

which worked fine. The -X enables X11 forwarding which means that DISPLAY is set. The problem only occurs when DISPLAY is not set.

You can correct the problem by editing /etc/profile.d/display-toggle-keybinding.sh and changing the "exit 0" to "return 0". "return" is a slightly less powerful version of "exit" which only exits the file currently being executed.

The comment in the file indicates that it is from package "dell-wmi-aio" so it may be unique to AIO systems. I'm using an Optiplex 7450 AIO.

I found the answer to this question to be very helpful in describing how the various types of bash shells (interactive, login, graphical etc) differ and what their startup sequences are:
Scripts in /etc/profile.d Being Ignored?

J Prescott
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