That /-a is a typo, it should be just -a (emerge --ask)
x y wrote
that is one command (cat /etc/…) or what?
Result of that cat is this
*/*::<name of layman>
This is how /etc/portage/package.mask/custom should look like, so if layman is named “foo” replace with “foo” so it will look like that
This is usefull to be sure that system updates from calculate won’t be disrupted (they shouldn’t). One caveat, if you do this you had to unmask dependencies for every package from certain overlay.
There is shortcut for emerge to automacally generate entries, later you had to accept it (emerge will print help on how to do that)
You can read emerge/calculate documentation and that https://oleeekchoff.blogspot.com/2012/06/use-overlay-for-specific-packages-only.html