There were previously attempts to arrange debugability of "production-mode" start-up of NUT daemons vs. their forced foregrounding in case of -D options present in command line. As I recently needed to inspect how driver services start and why they failed in my case, I took another attempt in this area, and came up with the proposed solution (just for drivers so far) to:

• separate the -D CLI option vs. explicit option to foreground -F or background -B the daemon; if neither of the latter options is set, defaults are as before (go background unless debugged);

  ** Names/shortcuts/help-text of the options can be subject to peer review, to have some values acceptable for consistently named options across the board, if we extend this approach to other NUT daemons;

• allow to set the default (driver) debugging level in either global or driver-level section of ups.conf; if both are set, the driver-level setting takes precedence; either of these may be set to a zero or positive integer;

  ** unlike command-line -D this setting does not require foregrounding (-F can be explicitly passed if desired) so the service daemons stay backgrounded by default as before;

  ** this allows to see debug messages in original service log, with the service units (access rights, environment, etc.) otherwise not modified - which often corrupts or complicates command-line troubleshooting;

  ** a more arguable corollary: since we do not currently have a way to disable debugging (set 0 level) I chose to require that the valid option in ups.conf (global section, or preferably driver-level value) specifies the minimum debugging level applied to the daemon -- if the command-line invocation specifies less -D flags, the practically applied level would be the one in the config.

  *** Per peer review, this design choice (and config option name) can be amended; at the very least with current implementation a CLI caller can easily set a minimum of -D (== 1) level instead, and something in CLI processing would need to be invented to reset a "-D == 0" level.

(see also #123 and #821 and #349)