How to Kill Inactive SSH Sessions
Sometimes you have a flaky internet connection and you may have been disconnected from your server a couple of times which resulted in inactive ssh sessions. When you look at details with w command, you see something like the following,
$ w
15:22:29 up 77 days, 5:40, 5 users, load average: 1.27, 0.88, 0.62
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root tty1 03Nov19 77days 0.00s 0.00s -bash
onuryilm pts/0 10.10.90.1 14:51 3:49 0.02s 0.02s -bash
onuryilm pts/1 10.10.90.1 15:19 1:57 1.03s 1.03s htop
onuryilm pts/2 10.10.90.3 15:22 23.00s 0.00s 0.00s -bash
onuryilm pts/3 10.10.90.1 15:22 2.00s 0.00s 0.00s w
Here one of the records, which starts with “onuryilm”, is active session but others are inactive SSH sessions.
By using pstree commmand, you can find inactive sessions. It shows the running processes as a tree. As all the sessions are SSH connections, all related processes are expected to be grouped under sshd process.
$ pstree -p
systemd(1)─┬─NetworkManager(4926)─┬─{NetworkManager}(4972)
│ └─{NetworkManager}(4974)
...
├─sshd(5180)─┬─sshd(404)───sshd(406)───bash(407)───pstree(2009)
│ ├─sshd(23390)───sshd(23392)───bash(23395)
│ ├─sshd(31851)───sshd(31853)───bash(31855)───htop(32199)
│ └─sshd(32640)───sshd(32646)───bash(32647)
...
Note: If your GNU/Linux distribution can’t find pstree command, please install psmisc package with your distribution’s package manager. For CentOS users below command should be fine,
sudo yum install psmisc
Now look for the parent PID of the session – PID from the line without the pstree command. The pstree line, would be the active SSH session that you’re using. To kill the idle sessions use kill command,
$ sudo kill 23390
$ sudo kill 31851
$ sudo kill 32640
Check afterwards with the w command,
$ w
15:28:29 up 77 days, 5:46, 2 users, load average: 0.71, 0.97, 0.76
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root tty1 03Nov19 77days 0.00s 0.00s -bash
onuryilm pts/3 10.10.90.1 15:22 5.00s 0.01s 0.00s w
Happy coding.