XML-RPC Command Interface.:
xcmd <xmlrpc method> <optional arguments>
For debbuging the following command can help:
bcfg2-admin xcmd Metadata.toggle_debug
Those two examples can alos be found in the Package section.
To rebuild the packages plugin cache:
bcfg2-admin xcmd Packages.Refresh
To perform a soft reload to reread the configuration file and download only missing sources.:
bcfg2-admin xcmd Packages.Reload