The MODE determines which part of the NUT is to be started, and which configuration files must be modified.
The values of MODE can be:
none: NUT is not configured, or use the Integrated Power Management, or use some external system to startup NUT components. So nothing is to be started.
standalone: This mode address a local only configuration, with 1 UPS protecting the local system. This implies to start the 3 NUT layers (driver, upsd and upsmon) and the matching configuration files. This mode can also address UPS redundancy.
netserver: same as for the standalone configuration, but also need some more ACLs and possibly a specific LISTEN directive in upsd.conf. Since this MODE is opened to the network, a special care should be applied to security concerns.
netclient: this mode only requires upsmon.
one of "none", "standalone", "netserver", "netclient""standalone"