There are several tools for indexing files on a computer to allow full text searches.

The classic of course is grep, but it doesn't generate any index, so it gets slow when searching through lots of files. In addition, it doesn't work well with non-ASCII files like OpenOffice documents, pdf or ps files and the like.

There is a list (not Debian specific) at http://www.antezeta.com/desktop-search.html .

Discussions and comparisons:

Debian package:

No Debian package yet: