[rpdillon]

It's crazy man, you can get full text search for any concept you want. Here goes:

    C-h r (open Emacs manual)
    C-s "line numbers"

That's it. Just keep pressing C-s and it will search through every section of the entire manual for the keyword you mentioned. After 5 tries, it lands on "16.24 Customization of Display", and you can read how that works.

Also apropos works.

[Jtsummers]

Some distros used to (still do?) drop some of the manuals, it was really annoying to discover this on Ubuntu a few years back. As someone who knew the manuals should be there it was easy to get the right google search to find out how to install them, someone new or inexperienced with emacs would likely not recognize that anything was missing in the first place.

[bogomog]

I was mildly disappointed the other day when I did a <C-h a>, and instead of "apropos" I saw "search for command". Apropos was one of those killer features that was, as far as I know, unique to emacs (until the "command palette" appeared in one of the newer editors).