Usage: /usr/bin/gdaladdo [--help] [--long-usage] [--help-general]
                         [-r nearest|average|rms|gauss|bilinear|cubic|cubicspline|lanczos|average_magphase|mode]
                         [-ro] [--quiet] [-b <band>]... [-oo <NAME=VALUE>]...
                         [-minsize <val>]
                         [[-clean]|[--partial-refresh-from-source-timestamp]|
                         [--partial-refresh-from-projwin <ulx> <uly> <lrx> <lry>]|
                         [--partial-refresh-from-source-extent <filename1>[,<filenameN>]...]]
                         filename [<level>]...

Note: /usr/bin/gdaladdo --long-usage for full help.