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Note that Red Hat, SUSE, and Canonical all don't use them. They maintain their own kernel trees with their modifications. These kernel teams have different prio

Note that Red Hat, SUSE, and Canonical all don't use them. They maintain their own kernel trees with their modifications. These kernel teams have different priorities: * stable ABI within a timespan (RH, SUSE) * feature backports based on customer demand (all three) * out of tree goop (Canonical) I've also heard from others (though notably, not folks specifically at these companies) that longterm kernels are iffier than regular stable kernels because people come out of the woodwork to push weird stuff for longterm kernels, which destabilizes things more than with regular stable kernels.

bluedays 6y ago
Seems like even Arch maintains it's own kernel. Not uncommon for distros to do it at all.
- artistsvoid 6y ago
  Wrong, or at the least misleading. What do you mean by 'maintain' here? Because Arch is trying to stay on the bleeding edge side of things in a reasonable manner and is rolling release, they almost stay 1:1 with upstream, "maintains its own kernel" makes it sound like they would do some heavy patching and do active maintenance with certain kernel versions, et cetera. You can have a look yourself if you want to https://git.archlinux.org/linux.git/commit/?h=v5.7.5-arch1&id=35f8fcadda6fd6d6eb582a7750ee307b2b822686 https://git.archlinux.org/linux.git/commit/?h=v5.7.5-arch1&i...
  - bluedays 6y ago
    They have their own kernel as can be seen here: https://i.imgur.com/jP6Pdvq.png https://i.imgur.com/jP6Pdvq.png Also if you look at the diffstat you can see that there were a number of changes here: https://i.imgur.com/J2em78v.png https://i.imgur.com/J2em78v.png It may be align with the majority of the kernel, but these patches exist in every version of the kernel that is released by Arch. What else could that be called aside from maintaining your own kernel? These changes are extremely small within scope which is the nature of Arch, but they still exist. A more hands-on distro will see many more changes than Arch, naturally. However, as evidenced from the above you can see that Arch does have it's own kernel and I cited Arch as an example because it strives so hard to maintain 1:1 with upstream. Btw, I use Arch.
    - phh 6y ago
      "maintaining your own kernel" in this context means that you're bringing bugfixes (including security) independently from the mainline Linux kernel, which would usually involve cherry-picking commits from the mainline. Archlinux doesn't do that, and straight merges Linux mainline.
    - bonzini 6y ago
      The RHEL8 kernel has a few tens of thousands of commits on top of 4.18. That's a bit more than Arch. :)
baggy_trough 6y ago
What is the difference between a "longterm kernel" and a "regular stable kernel"?
- gregkh 6y ago
  "regular stable kernel" lives only about 3-4 months, just long enough for the next release from Linus to feel "good enough". "longterm kernel" lives for 2+ years. I pick one each year (usually the last one released in a year) for that. See the releases page on kernel.org for details on what the longterm kernels are, and for how long they are being maintained and by whom.
iforgotpassword 6y ago
Not in my experience. LTS never seems to break any compatibility, even internal kernel structs, function names, etc.
- phh 6y ago
  Actually LTS does break ABI, but gregkh is working with Android to make a partially ABI-stable LTS (I assume it would be a fork of the real LTS though?). I know they are also working with RH and Suse, but I don't know if RH and Suse will only share the tools, or will also have the same LTS source tree. When I say "partially-ABI" stable, their goal is to list acceptable symbols and automatically verify that vendor modules use those symbols, and only those accceptable symbols are ABI-stable.
  - gregkh 6y ago
    That "partially-ABI stable" is the same exact thing that Red Hat and SUSE and Debian have been doing for 20+ years now. Nothing major and exciting there, but see the presentations at the Linux Plumbers conferences for details on the tools being used if people are curious (hint this time everyone is working together on the same set of tools...)
fomine3 6y ago
Because release schedule doesn't match to LTS release schedule? Distributors may want to ship OS with latest kernel than latest LTS.

bluedays 6y ago

Seems like even Arch maintains it's own kernel. Not uncommon for distros to do it at all.

artistsvoid 6y ago
Wrong, or at the least misleading. What do you mean by 'maintain' here? Because Arch is trying to stay on the bleeding edge side of things in a reasonable manner and is rolling release, they almost stay 1:1 with upstream, "maintains its own kernel" makes it sound like they would do some heavy patching and do active maintenance with certain kernel versions, et cetera. You can have a look yourself if you want to https://git.archlinux.org/linux.git/commit/?h=v5.7.5-arch1&id=35f8fcadda6fd6d6eb582a7750ee307b2b822686 https://git.archlinux.org/linux.git/commit/?h=v5.7.5-arch1&i...
- bluedays 6y ago
  They have their own kernel as can be seen here: https://i.imgur.com/jP6Pdvq.png https://i.imgur.com/jP6Pdvq.png Also if you look at the diffstat you can see that there were a number of changes here: https://i.imgur.com/J2em78v.png https://i.imgur.com/J2em78v.png It may be align with the majority of the kernel, but these patches exist in every version of the kernel that is released by Arch. What else could that be called aside from maintaining your own kernel? These changes are extremely small within scope which is the nature of Arch, but they still exist. A more hands-on distro will see many more changes than Arch, naturally. However, as evidenced from the above you can see that Arch does have it's own kernel and I cited Arch as an example because it strives so hard to maintain 1:1 with upstream. Btw, I use Arch.
  - phh 6y ago
    "maintaining your own kernel" in this context means that you're bringing bugfixes (including security) independently from the mainline Linux kernel, which would usually involve cherry-picking commits from the mainline. Archlinux doesn't do that, and straight merges Linux mainline.
  - bonzini 6y ago
    The RHEL8 kernel has a few tens of thousands of commits on top of 4.18. That's a bit more than Arch. :)

baggy_trough 6y ago

What is the difference between a "longterm kernel" and a "regular stable kernel"?

gregkh 6y ago
"regular stable kernel" lives only about 3-4 months, just long enough for the next release from Linus to feel "good enough". "longterm kernel" lives for 2+ years. I pick one each year (usually the last one released in a year) for that. See the releases page on kernel.org for details on what the longterm kernels are, and for how long they are being maintained and by whom.

iforgotpassword 6y ago

Not in my experience. LTS never seems to break any compatibility, even internal kernel structs, function names, etc.

phh 6y ago
Actually LTS does break ABI, but gregkh is working with Android to make a partially ABI-stable LTS (I assume it would be a fork of the real LTS though?). I know they are also working with RH and Suse, but I don't know if RH and Suse will only share the tools, or will also have the same LTS source tree. When I say "partially-ABI" stable, their goal is to list acceptable symbols and automatically verify that vendor modules use those symbols, and only those accceptable symbols are ABI-stable.
- gregkh 6y ago
  That "partially-ABI stable" is the same exact thing that Red Hat and SUSE and Debian have been doing for 20+ years now. Nothing major and exciting there, but see the presentations at the Linux Plumbers conferences for details on the tools being used if people are curious (hint this time everyone is working together on the same set of tools...)

fomine3 6y ago

Because release schedule doesn't match to LTS release schedule? Distributors may want to ship OS with latest kernel than latest LTS.