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4 Replies Latest reply: Mar 21, 2013 6:44 PM by Dude! RSS

Confused about all these different kernel versions

Dude! Guru
Currently Being Moderated
Hello,

Wikipedia at http://en.wikipedia.org/wiki/Linux_kernel#Maintenance outlines, that 2.6.39 is the last stable release of the 2.6 kernel series. From what I understand, this does not apply to the Oracle UEK kernel, which still uses the 2.6.39 notation for compatibility reasons.

Reading the OL 6.4 release notes at https://oss.oracle.com/ol6/docs/RELEASE-NOTES-U4-en.html#ol_uek2_64rn the UEK2 Release 2 kernel 2.6.39-400 is based on the upstream kernel 3.0.36. The UEK2 R1 kernel was based on the mainline 3.0.16 kernel. Does upstream and mainline kernel mean the same? I read that each mainline build is named by the base upstream version. What does that mean?

The link https://www.kernel.org shows an interesting view, listing various kernels, including a 3.9 mainline kernel. So it seems there is a lot of parallel development going on with versions 2.6, 3.0 and 3.2 and later. Searching around, I found the Oracle Linux playground repository https://blogs.oracle.com/wim/entry/oracle_linux_playground_channel_sample which already provides kernel 3.8.

Why are there so many different kernel versions? Why is the Oracle UEK kernel based on 3.0 and not 3.5, for instance? Will the next release of the UEK kernel be based on the 3.9, which is a mainline kernel?

Thanks.
  • 1. Re: Confused about all these different kernel versions
    Avi Miller Guru
    Currently Being Moderated
    Dude wrote:
    Reading the OL 6.4 release notes at https://oss.oracle.com/ol6/docs/RELEASE-NOTES-U4-en.html#ol_uek2_64rn the UEK2 Release 2 kernel 2.6.39-400 is based on the upstream kernel 3.0.36. The UEK2 R1 kernel was based on the mainline 3.0.16 kernel. Does upstream and mainline kernel mean the same? I read that each mainline build is named by the base upstream version. What does that mean?
    No, UEK2 was based on 3.0.x -- UEK1 was based on 2.6.32.x
    Why are there so many different kernel versions? Why is the Oracle UEK kernel based on 3.0 and not 3.5, for instance? Will the next release of the UEK kernel be based on the 3.9, which is a mainline kernel?
    1. Because people don't like upgrading production servers very often.
    2. Because 3.5 hadn't been released yet when we started building UEK Release 2.
    3. No, mainline 3.9 hasn't been released yet. UEK3 will be based on 3.7 or 3.8.
  • 2. Re: Confused about all these different kernel versions
    Dude! Guru
    Currently Being Moderated
    According to the OL 6.4 release notes: The Unbreakable Enterprise Kernel Release 2 (UEK R2) is based on the upstream kernel 3.0.36 stable source tree.

    I actually did not have the UEK (2.6.32) kernel in mind. Since OL 6.4 uses UEK R2 and not UEK2 I thought it meant UEK2 Release 2 and concluded:

    UEK1 = 2.6.32
    UEK2 Release 1 = 3.0.16 (mainline)
    UEK2 Release 2 = 3.0.36 (upstream, stable)

    So this means there is no UEK2 Release 1 and 2, just:

    UEK1 = 2.6.32
    UEK2 = 3.0.x
    UEK3 = 3.?
  • 3. Re: Confused about all these different kernel versions
    Avi Miller Guru
    Currently Being Moderated
    Dude wrote:
    So this means there is no UEK2 Release 1 and 2, just UEK1 and UEK2?
    We refer to them as "Quarterly Updates" -- so 2.6.39-100, 2.6.39-200, 2.6.39-300, 2.6.39-400 are all "UEK2", but different quarterly updates (and a different kABI, which is why we incremented the -XXX value). The next quarterly update will still be 2.6.39-400 (because kABI remains the same), but it'll be a bumped version. Essentially, UEK1 (2.6.32-anything) is based on 2.6.32 and UEK2 (2.6.39-anything) is based on 3.0.something.
  • 4. Re: Confused about all these different kernel versions
    Dude! Guru
    Currently Being Moderated
    The notation "UEK R2" vs. "UEK2" was part of the confusion and question. Thanks for clearing!

    I forgot to consider the time and effort it obviously takes to test the release of a stable kernel, e.g. 3.5 until the release of a new UEK version, e.g. UEK3 with the Oracle kernel drivers and software.

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