I know that many of the same programs run flawlessly on top of both kernels. I know that historically, the two kernels came from different origins. I know philosophically too that they stood for different things. My question is, today, in 2011, what makes a Unix kernel different from a Linux one, and vice versa?

  • 3
    There are probably more differences between Unix kernels, than between some of them and Linux.
    – vartec
    Dec 13, 2011 at 14:13

2 Answers 2


There is no unique thing named "the Unix kernel". There are multiple descendants of the original Unix kernel source code trunk that forked branches from it at different stages and that have evolved separately according to their own needs.

The mainstream ones these days are found in Operating Systems created either from System V source code: AIX, HPUX, Solaris or from BSD source code, OpenBSD, FreeBSD and Mac OS/X.

All of these kernels have their particular strengths and weaknesses, just like Linux and other "from scratch" Unix like kernels (minix, Gnu hurd, ...).

Here is a non exhaustive list of the areas where differences can be observed, in no particular order:

  • CPU architecture support
  • Availability of drivers
  • File systems supported
  • Virtualization capabilities
  • Scheduling features, (alternate scheduling classes, real-time, ...)
  • Modularity
  • Observability
  • Tunability
  • Reliability
  • Performance
  • Scalability
  • API stability between versions
  • Open/Close source, license used
  • Security (eg: privilege granularity)
  • Memory management
  • 1
    I dont know if this is a lot of work, but if its not too bad, can you elaborate on each of these catagories a little? Dec 14, 2011 at 0:32
  • Wow, had no idea Mac OS/X is a kernel...
    – Piper
    Aug 17, 2012 at 1:41
  • 1
    It is a full OS (like AIX, HP-UX, Solaris and the likes), not a kernel indeed. Answer updated.
    – jlliagre
    Aug 17, 2012 at 9:10

Here, first of all there is no unique thing named "the Unix kernel"

  1. Linux is open source and is developed by Linux community of developers.
  2. Unix was developed by AT&T Bell labs and is not open source.
  3. Linux is free to use.
  4. Unix is licensed OS.
  • A UNIX system is one that the Open Group certifies as meeting their standards. macOS is certified even though it does not have any AT&T code in it. Inspur-ux was at one point certified as UNIX and was open-source.
    – doneal24
    Dec 9, 2022 at 20:17

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