How to disconnect idle (after few minutes of inactivity) SSH sessions automatically

Uncomments the following two lines under /etc/ssh/sshd_config and restart the SSH services.

# vi /etc/ssh/sshd_config

ClientAliveInterval 300             

ClientAliveCountMax 0

ClientAliveCountMax – This indicates the total number of checkalive message sent by the SSH server without getting any response from the SSH client. Default is 3 but I’m going to set zero (0) to check this experiment.

ClientAliveInterval – This indicates the time-out in 5 seconds. After x number of seconds, ssh server will send a message to the client asking for response. Default is 0. If any response received from client, the session was killed automatically.

Restart the SSH services

# service sshd restart

Stopping sshd:                                             [  OK  ]

Starting sshd:                                             [  OK  ]

#

TEST:

Open new putty session for any user and wait for 5 min, you will get the following message:

Server sent disconnect message type 2 (protocol error): “Timeout, your session not responding.”