1. Find messages.xml
It's in your mission's db folder, next to types.xml: mpmissions, then your map's mission folder, then db. Download a copy before you change it.
2. Know the kinds of message
Each message in the file is one of these:
- On join: shown to each player a set number of minutes after they connect, ideal for a welcome and rules
- Repeating: shown to everyone on a timer, such as every 60 minutes, ideal for your Discord link
- Once: shown a single time, a set number of minutes after the server starts
- Countdown: counts down to a deadline, and #tmin in the text is replaced with the minutes left
3. Set up the restart
Add a countdown message with a deadline in minutes, such as 240 for four hours, and switch shutdown on. When the deadline arrives the server stops, and Nitrado starts it again. Players see something like "Server restarts in #tmin minutes" as it approaches.
You only need one countdown with shutdown on. The earliest deadline is the one that restarts the server, so a second one is easy to set by mistake.
4. Save and restart
Upload the file to the same db folder and restart. DayZ reads messages.xml when it starts, so the new schedule begins after that restart.
The free Server Messages editor shows each message as a card, previews it in game chat, draws the schedule across a restart cycle and catches mistakes like a shutdown with no deadline. On the Server and Pro plans it saves straight to Nitrado with a backup.