Systemd service (on linux)

In order to have ttyd launch on startup and restart automatically on error, you can create and enable a service file running its binary. Say we've downloaded a binary from the releases page and moved it to /opt (so its full path is now /opt/ttyd). paste the following content into /etc/systemd/system/ttyd.service:

[Unit]
Description=TTYD
After=syslog.target
After=network.target

[Service]
ExecStart=/opt/ttyd login
Type=simple
Restart=always
User=root
Group=root

[Install]
WantedBy=multi-user.target

Now, to start the service and make sure it starts on boot:

sudo systemctl start ttyd && sudo systemctl enable ttyd

MAKE SURE YOU DON'T RUN ANY COMMAND OTHER THAN login AS ROOT, AND THAT YOUR ROOT ACCOUNT HAS A PASSWORD. IF YOU CHOOSE TO RUN A DIFFERENT COMMAND, USE ANY NON-ROOT USER.