BUG?! primary key in inherited table

Hi,

Is primary key similar to 'not null columns with indices'? The reason I

am asking because I found that when you inherit table B from table A,
the primary key in A won't be inherited to B, but only the columns.

I was wondering how do you inherit a primary key or, even, a foreign
key? If it's not possible, what are the ways going around it? (not
null index or...???)

Thanks for your help!

- Bernie