Add systemd service

Deployment.md

@@ -1,4 +1,6 @@
-This page documents how to deploy ssh-chat using various methods
+This page documents how to deploy ssh-chat using various methods.
+
+You can run ssh-chat on port 22, but then you'll need to change the port of OpenSSH to something else like 2022. You can do this in `/etc/ssh/sshd_config`. Two services can't run on the same port like this.
 
 ## OpenRC
 
@@ -40,4 +42,26 @@ This page documents how to deploy ssh-chat using various methods
 
 # systemd
 
+(Replace `/PATH/TO/`)
+
+`/etc/systemd/system/ssh-chat.service`:
+
+```
+[Unit]
+Description=ssh-chat
+After=network.target
+
+[Service]
+Type=simple
+User=nobody
+ExecStart=/PATH/TO/ssh-chat --bind=":22" -i="/PATH/TO/host_key" --admin="/PATH/TO/authorized_keys"
+AmbientCapabilities=CAP_NET_BIND_SERVICE
+Restart=always
+
+[Install]
+WantedBy=multi-user.target
+```
+
+Additional resources:
+
 - https://impactcore.blogspot.ca/2017/09/ssh-chat-irc-like-chat-client-over-ssh.html