How to ensure sshd is the last service to be stopped during shutdown?

I have noticed that when I issue a reboot command, my SSH connection is immediately closed on CentOS 7. It does not mean the server has rebooted, as I can still ping it.

It seems systemd is killing sshd too early. Sometimes a service will get stuck shutting down or just be slow, and I can't login anymore to verify what is wrong even though the server is up.

Is there a way to tell systemd to only kill sshd after all other service are down?

Solution 1:

Even if you could ensure that SSH is the last service to be shut down, it would be pointless, because you will lose connection as soon as network services are stopped.

A Linux machine that boots starts all services in a pre-determined order: first the most vital services, the syslog, the firewall, then the network, and eventually the applications requiring network access (server web, server SSH, etc.). When shutting down, these services are stopped in reverse order. So you will lose SSH connection almost immediately.

The fact that SSH is already down while you can still ping the remote machine is normal.