Time of disconnection in Ubuntu Server

Question

In Ubuntu server (with ssh protocol), how I can change the time of disconnection for inactivity?

Answer 1

If, perhaps you want the other way around (disconnecting inactive clients from the server), the respective options are ClientAliveCountMax and ClientAliveInterval, located in sshd_config.

Use man 5 sshd_config for more details.

Answer 2

Edit your /etc/ssh/ssh_config file and set appropriate values for ServerAliveCountMax and ServerAliveInterval.

From man ssh_config:

ServerAliveCountMax
Sets the number of server alive messages (see below) which may be sent without ssh(1) receiving any messages back from the server. If this threshold is reached while server alive messages are being sent, ssh will disconnect from the server, terminating the session. It is important to note that the use of server alive messages is very different from TCPKeepAlive (below). The server alive messages are sent through the encrypted channel and there‐ fore will not be spoofable. The TCP keepalive option enabled by TCPKeepAlive is spoofable. The server alive mechanism is valu‐ able when the client or server depend on knowing when a connec‐ tion has become inactive.

The default value is 3. If, for example, ServerAliveInterval (see below) is set to 15 and ServerAliveCountMax is left at the default, if the server becomes unresponsive, ssh will disconnect after approximately 45 seconds. This option applies to protocol version 2 only; in protocol version 1 there is no mechanism to request a response from the server to the server alive messages, so disconnection is the responsibility of the TCP stack.

ServerAliveInterval
Sets a timeout interval in seconds after which if no data has been received from the server, ssh(1) will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server, or 300 if the BatchMode option is set. This option applies to protocol version 2 only. ProtocolKeepAlives and SetupTimeOut are Debian-specific compatibility aliases for this option.