I spent a decent portion of one day this week angrily screaming at the screen. I couldn’t do anything. I was logged into a switch, and I could type commands that don’t actually do anything. I could enter configure mode, I could even stage changes, but I just couldn’t seem to commit them. The Junos shell would hang every time. Obviously, this can create all sorts of problems, such as exhausting the number of SSH connections allowed. I couldn’t even force logout a user via the Junos shell! To continue troubleshooting, this is what I did:

  1. Login as root.
  2. Type cli to start the Junos shell.
  3. Attempt to troubleshoot.
  4. When the shell inevitably locks during the troubleshooting process:
    1. Press ^z (control-z) to suspend the shell process.
    2. Once in the shell, enter the following:
sh
kill -9 $(ps aux | grep [c]li | awk '{print $2}')

That’s a bit verbose, so I made it into a script that I dropped into root’s directory on all of my devices. Now, I just type sh kill_cli and POOF! Magic!

Here’s the script I drop into the root folder:

Just make it executable (chmod 700 kill_cli) and then execute it by typing sh kill_cli.

Be warned that this method will kill all of the Junos shells, including your peers’! You’ll need to be a bit more selective if you just want to kill your own (i.e., type ps aux | grep cli | grep -v grep [which can be done from the csh BSD shell that root uses by default] and hunt down the PIDs [number in the second column] for your user)

Extra Tip

Remember I mentioned that you can exhaust SSH connections? Here’s how you can force a user to disconnect from the FreeBSD shell:

sh
SSH_USER=tyler
kill -9 $(ps aux | egrep [s]shd.*$SSH_USER)

Replace tyler above with the login name of the user you wish to disconnect. You can also just omit SSH_USER and replace $(SSH_USER) above with the user name (tyler, in our example).

This is another good candidate for a script!

First, scp the script to the root user’s $HOME directory. Make it executable:

chmod 700 logout_user

Finally, execute it with sh logout_user $SSH_USER, replacing $SSH_USER with the user you want to kick out (such as tyler).

This post is part of the #30in30 challenge.