dspinellis/unix-history-repo

unix-history-repo is a Git repository that reconstructs the complete history of the Unix operating system as a single, browsable commit timeline spanning from 1970 to the present. Unix is the ancestor of nearly every major operating system in use today, including Linux, macOS, and Android. This repository makes it possible to trace that lineage through actual code. The repository was built by combining 22 historical snapshots of Unix source code: early research versions from Bell Labs (where Unix was created by Ken Thompson and Dennis Ritchie), later versions developed at the University of California Berkeley, an early open-source port called 386BSD, and the ongoing FreeBSD project. Custom software was used to stitch these snapshots into a coherent commit sequence with roughly 850,000 commits and more than 8,000 merges. About 2,700 individual contributors are attributed, including the original researchers identified through primary historical research. Because it uses Git, standard Git commands work across the entire history. You can run git log to see a timeline of changes going back to 1972, use git blame on a source file to see which version of Unix each line came from and who wrote it, or check out a specific historical release by branch name. The README demonstrates: tracing the evolution of the Unix pipe command across decades, or finding that code written by Dennis Ritchie in 1979 is still present unchanged in FreeBSD 15.0 in 2025. The repository is intended for research in software engineering and software history. It weighs about 2 GB. Contributions are not accepted here directly, a companion repository called unix-history-make contains the scripts and metadata used to build it, and that is where contributions are welcomed.