There are several places in Mac OS X, that don't get indexed by spotlight or the terminal locate command.
Is there a way to change that?
How can I search in places like /private?
locate should include system files (if you enable database creation -- it's turned off by default, at least in Snow Leopard -- with the command sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.locate.plist).
Spotlight does index system files, but normally leaves them out of the search results because most users want to search their files, not the OS internals. If you want to see system files in the results, you have to enable them:
(Kind) is (Any). Select "Other" from the attribute ("Kind") pop-up menu.Note that including these options in the pop-up menu is permanent, but actually selecting them has to be re-done for each search (i.e. next time you search, you only get to skip steps 3 and 4).