What is GNU and how does it relate to Linux?
GNU ("GNU's Not Unix") is the free Unix-like OS that Richard Stallman started in 1983; it built everything except a working kernel, which Linux supplied in 1991 — together they form GNU/Linux.
The two projects fit together like two halves of a puzzle, started for opposite reasons. GNU had years of polished system tools but no finished kernel to run them on. Linux was a finished kernel with no surrounding tools. Combining them produced the first fully free, complete operating system.
| Project | Year | Founder | Had / needed |
|---|---|---|---|
| GNU | 1983 | Richard Stallman | All the tools (bash, gcc, coreutils) — needed a kernel |
| Linux | 1991 | Linus Torvalds | A working kernel — needed the tools |
GNU also gave us the philosophy, codified as the Four Freedoms that define what "free software" means:
- Run the program for any purpose.
- Study and modify it (which requires access to the source).
- Redistribute exact copies.
- Improve it and share your improved versions.
Note: "Free" here means freedom, not price — "free as in speech, not as in beer." You're allowed to sell free software; what you can't do is take away the recipient's four freedoms.
Go deeper:
What is Free Software? (GNU) — the FSF's own definition of free software and the philosophy behind GNU.