How to share resource within 2 user group?

I have created a custom group for one of my user name. Meanwhile I have a folder contents need to share among this group and my default group.

Any hints how to do this?

Check out this DH wiki article on Unix groups, and note the section on Sharing FIles Between Groups

Not for the faint of heart, and IMHO, a real pain to manage effectively and with decent security, though YMMV! :wink: