How to start, restart and stop SSH service

SSH service by OpenSSH is normally provided by the sshd daemon. In most Unix-based operating systems the daemon process can be managed by systemd, System V. Init scripts or the service command.

You can use all three methods to manage your SSH server on most platforms. Common options include the ability to start, stop and restart the SSH. You can also view detailed status of the running sshd daemon and set to whether or not to automatically start sshd during system startup.

1. Stop SSH service using service command.

   $ sudo service ssh stop

2. Start SSH service using systemd.

   $ sudo systemctl start ssh

3. Configure SSH to automatically start during system boot.

   $ sudo systemctl enable ssh
   Synchronizing state of ssh.service with SysV service script with /lib/systemd/systemd-sysv-install.
   Executing: /lib/systemd/systemd-sysv-install enable ssh
   Created symlink /etc/systemd/system/sshd.service → /lib/systemd/system/ssh.service.
   Created symlink /etc/systemd/system/multi-user.target.wants/ssh.service → /lib/systemd/system/ssh.service.

4. Configure SSH service to not automatically start during system boot.

   $ sudo systemctl disable ssh
   Synchronizing state of ssh.service with SysV service script with /lib/systemd/systemd-sysv-install.
   Executing: /lib/systemd/systemd-sysv-install disable ssh
   Removed /etc/systemd/system/multi-user.target.wants/ssh.service.
   Removed /etc/systemd/system/sshd.service.

5. Restart SSH service using System V. Init scripts.

   $ sudo /etc/init.d/ssh restart
   Restarting ssh (via systemctl): ssh.service.

6. View SSH status using systemd.

   $ sudo systemctl status ssh
   ● ssh.service - OpenBSD Secure Shell server
        Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: >
        Active: active (running) since Sun 2020-07-12 08:33:28 +08; 1s ago
          Docs: man:sshd(8)
                man:sshd_config(5)
       Process: 3608 ExecStartPre=/usr/sbin/sshd -t (code=exited, status=0/SUCCES>
      Main PID: 3629 (sshd)
         Tasks: 1 (limit: 4624)
        Memory: 1.3M
        CGroup: /system.slice/ssh.service
                └─3629 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups
   
   Jul 12 08:33:27 host systemd[1]: Starting OpenBSD Secure Shell server...
   Jul 12 08:33:28 host sshd[3629]: Server listening on 0.0.0.0 port 22.
   Jul 12 08:33:28 host sshd[3629]: Server listening on :: port 22.
   Jul 12 08:33:28 host systemd[1]: Started OpenBSD Secure Shell server.