Squashfs is a highly compressed read-only filesystem for Linux. It uses zlib to compress files, inodes, and directories. All blocks are packed to minimize the data overhead, and block sizes of between 4K and 1M are supported. It is intended to be used for archival use, for live CDs, and for embedded systems where low overhead is needed.
PostgreSQL File Finder is an alternative to the locate/updatedb commands found in most Linux environments. It searches the filesystem for all files and directories and stores that information in a PostgreSQL database. It can also collect file lists from other hosts, giving you the opportunity to search for files on several hosts using the same command.
fsdb speeds the creation of slocate's database files by keeping its own database and updating only those parts that need to be updated. It connects to a daemon to receive the updated inodes. In turn, the daemon interfaces with a kernel module which hooks into Linux's dnotify mechanism.