用*nix的Terminal远程连接VPS的时候，长时间不操作，就会掉，这时候可以通过修改ssh_config，来使得长时间不操作，也不会掉线。
Linux桌面系统下，可以通过修改 /etc/ssh/ssh_config文件（注意：不是修改/etc/ssh/sshd_config文件)，添加
ServerAliveInterval 300
ServerAliveCountMax 5
而OS X桌面系统的此文件为/etc/ssh_config(注意：不是修改/etc/sshd_config文件)，修改内容同上。
添加的内容意思为，每隔300秒向服务器请求一次心跳，超过5次没响应就认为掉线。
注:以上修改均在客户端机器修改，而不是在VPS上修改.
参考：https://patrickmn.com/aside/how-to-keep-alive-ssh-sessions/ （此文最详细。它还顺便提到了服务器上如何修改,服务器上是修改sshd_config文件：
You can also make your OpenSSH server keep alive all connections with clients by adding the following to
In your session properties, go to Connection and under Sending of null packets to keep session active, set Seconds between keepalives (0 to turn off) to e.g. 300(5 minutes). ）
注:以上修改均在客户端机器修改，而不是在VPS上修改.
参考：https://patrickmn.com/aside/how-to-keep-alive-ssh-sessions/ （此文最详细。它还顺便提到了服务器上如何修改,服务器上是修改sshd_config文件：
You can also make your OpenSSH server keep alive all connections with clients by adding the following to
/etc/ssh/sshd_config:ClientAliveInterval 300 ClientAliveCountMax 5
These settings will make the SSH client or server send a null packet to the other side every 300 seconds (5 minutes), and give up if it doesn’t receive any response after 5 tries。建议在服务器上也进行相应的修改！
我测试了，两边都修改后，好像真的长时间不操作而不掉线了。
我测试了，两边都修改后，好像真的长时间不操作而不掉线了。
以及在windows桌面系统的putty中如何设置：
On PuTTY
In your session properties, go to Connection and under Sending of null packets to keep session active, set Seconds between keepalives (0 to turn off) to e.g. 300(5 minutes). ）
https://www.a2hosting.com/kb/getting-started-guide/accessing-your-account/keeping-ssh-connections-alive
http://www.howtogeek.com/howto/linux/keep-your-linux-ssh-session-from-disconnecting/
https://www.maketecheasier.com/keep-ssh-connections-alive-in-linux/
