# ./drivers/upsdrvctl -DD -d start nutdev1
Network UPS Tools - UPS driver controller 2.7.4-4656-g0007056
   0.000000     [D1] Starting UPS: nutdev1
   0.000680     [D2] 1 remaining attempts
   0.001258     [D2] exec:  /usr/local/ups/bin/usbhid-ups -DD -a nutdev1
Network UPS Tools - Generic HID driver 0.45 (2.7.4-4652-gb559cc4)
USB communication driver (libusb 1.0) 0.42
   0.000000     [D1] debug level is '2'
...

# ./drivers/upsdrvctl -DDDDDDDD -d start nutdev1
Network UPS Tools - UPS driver controller 2.7.4-4656-g0007056
   0.000000     [D1] Starting UPS: nutdev1
   0.000752     [D1] Requested debugging level 8 is too high for pass-through args, truncated to 6
   0.001410     [D2] 1 remaining attempts
   0.002004     [D2] exec:  /usr/local/ups/bin/usbhid-ups -DDDDDD -a nutdev1
Network UPS Tools - Generic HID driver 0.45 (2.7.4-4652-gb559cc4)
USB communication driver (libusb 1.0) 0.42
   0.000000     [D5] send_to_all: SETINFO driver.parameter.port "auto"
   0.000749     [D5] send_to_all: SETINFO driver.parameter.vendorid "0463"
   0.001376     [D5] send_to_all: SETINFO driver.parameter.productid "FFFF"
   0.001995     [D5] send_to_all: SETINFO driver.parameter.product "Protection Station"
   0.002633     [D5] send_to_all: SETINFO driver.parameter.serial "AN2E49008"
   0.003255     [D5] send_to_all: SETINFO driver.parameter.vendor "EATON"
   0.003853     [D5] send_to_all: SETINFO driver.parameter.bus "003"
   0.004633     [D1] debug level is '6'
...

# ./drivers/upsdrvctl -DD start nutdev1
Network UPS Tools - UPS driver controller 2.7.4-4656-g0007056
   0.000000     [D2]
If you're not a NUT core developer, chances are that you're told to enable debugging
to see why a driver isn't working for you. We're sorry for the confusion, but this is
the 'upsdrvctl' wrapper, not the driver you're interested in.

Below you'll find one or more lines starting with 'exec:' followed by an absolute
path to the driver binary and some command line option. This is what the driver
starts and you need to copy and paste that line and append the debug flags to that
line (less the 'exec:' prefix).

Alternately, provide an additional '-d' (lower-case) parameter to 'upsdrvctl' to
pass its current debug level to the launched driver.

   0.004182     [D1] Starting UPS: nutdev1
   0.004980     [D2] 1 remaining attempts
   0.005226     [D2] exec:  /usr/local/ups/bin/usbhid-ups -a nutdev1
Network UPS Tools - Generic HID driver 0.45 (2.7.4-4652-gb559cc4)
USB communication driver (libusb 1.0) 0.42
...

# ./drivers/upsdrvctl start nutdev1
Network UPS Tools - UPS driver controller 2.7.4-4652-gb559cc4
Network UPS Tools - Generic HID driver 0.45 (2.7.4-4652-gb559cc4)
USB communication driver (libusb 1.0) 0.42
...