In many Linux distributions, the locate command has been replaced by slocate. There is typically a symbolic link to "locate" so that you don't need to remember which you have. slocate stands for "secure locate". It stores permissions information in the database so that normal users can't pry into directories they wouldn't otherwise be able to read. The usage information for slocate is essentially the same as for locate, although the output might be different depending on the user running the command.