By default Serv-U stores all of its settings in the ServUDaemon.ini and ServUAdmin.ini files. (If you are running Serv-U 2.5n or below this is called the Serv-U.ini file.) Make a copy of these files and store it on a remote drive or disk. Then you can always download a fresh copy of Serv-U and add these .INI files back into the install directory to restore your settings.
If you have selected to store any of your domains in the Windows registry then also export the registry key "HKEY_LOCAL_MACHINE\SOFTWARE\Cat Soft\" for backup. To move Serv-U to a new PC import this registry branch in the new PC's registry.
NOTE: before backing up the file open it and making sure that your settings are there. This confirms what settings you are backing up. You will see all the server settings stored here.
== 簽名檔 ==