strace is a useful diagnostic, instructional, and debugging tool. System administrators, diagnosticians, and troubleshooters will find it invaluable for solving problems with programs for which the source is not readily available.
libutempter provides a library interface for terminal emulators such as screen and xterm to record user sessions to utmp and wtmp files.
A tool for securing DNS communications between a client and a DNS resolver.
A polyhedral extraction tool (PET).