From UnrealIRCd documentation wiki
Upgrading from a 4.0.X version to 4.0.Y or 4.2.Y is very simple. You can upgrade from any 4.0.X version to any newer version. So you can upgrade from 4.0.1 straight to 4.2.0.
- Backup your existing /home/xxx/unrealircd directory:
cp -Rav /home/xxx/unrealircd /home/xxx/unrealircd.bak
- Download and install latest version of UnrealIRCd. See Installing from source and stop before Creating a configuration file.
- Double check: make sure you ran make install as this will install all new files in /home/xxx/unrealircd.
- Restart the IRCd to make the changes effective:
- cd /home/xxx/unrealircd
- ./unrealircd restart
- Just in case, make a backup of your UnrealIRCd directory (C:\Program Files (x86)\UnrealIRCd 4).
- Surf to https://www.unrealircd.org/ and click Downloads. Pick your branch, download the installer
- Run the installer
- Now restart your IRC Server (Stop UnrealIRCd, then Start UnrealIRCd)