How to Kill or Terminate an Inactive or Idle SSH Session on Linux

Lets imagine that you are working on a remote Linux machine via ssh, for some reason your session is disconnected, such as an internet problem or power outage or your local PC is restarted, etc,.

You may or mayn’t log in to the server again for work, but you have left the previous ssh session with out logout.

If so, how to kill them?

To do so, you need to find the process id (PID) of the idle ssh session.

You can easily identify inactive ssh session with the help of the W command.

Once you know the session information using the w command, use the pstree command to find the process id (PID) of the idle ssh session.

These are the steps you need to take to achieve this.

The following articles may help you to learn more about SSH related stuff.

1) How to Identify Idle SSH Session on Linux

Verify how many users are currently logged in by logging into the system and issuing the w command. If you find your own session, isolate the idle ssh session information.

In my situation, two users are currently logged in, one is my new ssh session, which is currently running the w command and the other is my inactive session.

# w

 10:36:39 up 26 days, 20:29,  2 users,  load average: 0.00, 0.02, 0.00
USER     TTY      FROM              [email protected]   IDLE   JCPU   PCPU WHAT
root     pts/0    219.91.219.14    10:34   28.00s  0.00s  0.00s -bash
root     pts/2    219.91.219.14    10:36    0.00s  0.00s  0.00s w

2) How to Get an SSH Session Parent Process ID (PID)

In order to kill the idle ssh session, you need the parent process ID (PPID) of the idle session. To get it, run the pstree command to see a tree map of all processes.

You will also get an output like the one below. But the structure and PIDs of the tree can vary.

# pstree -p | grep sshd
        |-sshd(2023)-+-sshd(10132)---bash(10136)
        |            `-sshd(10199)---bash(10208)---pstree(10226)

From the above output, you can see the parent ID of the sshd process and their branches. The parent ID of the sshd process is sshd (2023) and the branches are sshd (10132) and sshd (10199).

As I said at the beginning of the article, one is my new session shd (10199) because it shows the command I am currently running pstree, so the other inactive session is sshd (10132).

3) How to Kill an Inactive SSH Session

We got all the information about the inactive session. Now, I’m going to kill the inactive session using the kill command. Be sure to replace your PID instead us.

  					 
# kill -9 10132

4) How to Check If the Idle Session is Killed or not?

This can be verified using the w command and the pstree command. The other session was successfully killed as I could only see one session of my own.

# w

 10:40:18 up 26 days, 20:33,  1 user,  load average: 0.11, 0.04, 0.01
USER     TTY      FROM              [email protected]   IDLE   JCPU   PCPU WHAT
root     pts/2    219.91.219.14    10:36    0.00s  0.00s  0.00s w

Verify using the pstree command.

# pstree -p
        |-sshd(2023)---sshd(10199)---bash(10208)---pstree(10431)

Magesh Maruthamuthu

Love to play with all Linux distribution

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