- Kernel
- Operating system
- Distribution
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# Kernel
- First Linux Kernel in 1991
- Linus Torvalds
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# Operating system
- GNU project in 1983 (1984)
- Richard Stallman
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# Distribution
- Debian
- Red Hat
- Slackware
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# Commercial distribution
- Red Hat Enterprise Linux (RHEL)
- SUSE Linux Enterprise
- Ubuntu Pro
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# Community
- A single operating system
- Distributions5
- A UNIX
- Mostly POSIX6 compliant in practice
- Difficult to use
- Many distributions are very user-friendly
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# References
1. [Unix Timeline](https://wiki.tuhs.org/doku.php?id=events:timeline) - Unix Heritage Wiki
2. [Overview of the GNU System](https://www.gnu.org/gnu/gnu-history.en.html) - GNU Project Homepage
3. [Linux - a free unix-386 kernel](https://github.com/oldlinux-web/oldlinux-files/blob/master/Linux-0.01/docs/Linux.pdf) - github.com/oldlinux-web
4. [Usage share of operating systems](https://en.wikipedia.org/wiki/Usage_share_of_operating_systems#Market_share_by_category) - wikipedia.org
5. [Linux distribution](https://en.wikipedia.org/wiki/Linux_distribution) - wikipedia.org
6. [POSIX](https://en.wikipedia.org/wiki/POSIX) - wikipedia.org