You can do this via m2ee:
loglevel SysLogSubscriber ConnectionBus_Update DEBUG
(replacing ConnectionBus_Update with your lognode, note that everything is case sensitive)
Assuming you're running in the Mendix private cloud, you can then view the logs via:
tail -f -n100 /var/log/xas2/yourappname.log
(replacing yourappname with your appname)
To get a list of available lognodes, simply issue the "loglevel" command. Note that lognodes only show up after the first time they've logged something.
You can change the loglevels by using the m2ee loglevel command