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About the kernel in Hyperscale

We try to follow the kernel build from CentOS Stream 9 as closely as possible.


Links can be found on the CI/CD page.

Contributing to the Hyperscale kernel code

All of the patches we backport for the Hyperscale build of the kernel are first merged to redhat/centos-stream/src/kernel/centos-stream-9, a Git repo where the RHEL kernel is developed and maintained. This allows us to leverage the testing and maintenance by the RHEL kernel team and share efforts with the broader CentOS community that also contribute to the kernel.

We try to maintain as few patches as possible for each release, but we are open to including new features or bug fixes that are not yet available. We follow the practices documented by the RHEL kernel team.


  • Get a Fedora account if you don't have one already.
    • Make sure to follow this part and set up your ~/.fedora.upn to tell our tooling your FAS username if it differs from your Unix name.
  • Get a account if you don't have one already.
    • Make sure your display name matches your actual name used in Git commits.
    • Make sure the email address you use for Git commits is attached to your account.
  • Set your account username in your Fedora account.
  • Set your Red Hat Bugzilla account and make sure your Fedora account email address matches your Bugzilla account email address.
  • Install git-backport into ~/.local/bin.
  • Fork redhat/centos-stream/src/kernel/centos-stream-9.
  • In your local clone of your fork, add redhat/centos-stream/src/kernel/centos-stream-9 as a remote by the name upstream.
  • In your local clone of your fork, add torvalds/linux as a remote by the name mainline.
  • Run git fetch --all to fetch all the refs from all the remotes.
  • Create a new branch based on upstream/main for the patches to be applied: git checkout --no-track -b <branchname> upstream/main
  • Generate a list of commits to backport and save it to a file to use with git-backport.
    • For example, for backporting zstd from v5.16, do: git log --pretty=oneline v5.14..v5.16 lib/zstd | tac > git-backport-zstd-v5.16-patchset
  • Create a bug for the RHEL kernel for your backport.
    • Note: the link above might not select kernel as a component for you automatically. If it doesn't, just do so manually and select the correct subcomponent when the menu shows up.
    • As an example, here's the one done for the zstd backport from v5.16.
  • Use git-backport to generate the patch set to apply as commits: git-backport -a -b <RHBZ> -d $PWD/backport-stage-diffs/ -f <git-backport-file>
  • Use git am to apply the patch set: git am $PWD/backport-stage-diffs/
  • Push your branch to your fork on
  • Open a merge request (MR) against redhat/centos-stream/src/kernel/centos-stream-9 with your change.
  • Once merged and the RHEL kernel folks make a release, one of the Hyperscale kernel maintainers will update the RPM spec and publish a new version of the kernel for Hyperscale with the patches included.

Contributing to the RPM spec

Not yet available

kernel Hyperscale RPM sources

Build Commands

For CBS you will need to be onboarded to the SIG.

From inside the fork of the kernel Hyperscale RPM sources repo:

# Local build with mock; You can skip these steps and use cbs directly
mock -r centos-stream-9-x86_64 -D '%dist .hsx.el9' --sources SOURCES --spec SPECS/*.spec

# Create src.rpm for CBS
rpmbuild --define "%_topdir $PWD" --define "%dist .hsx.el9" -bs SPECS/kernel.spec

# CBS scratch builds
cbs build --scratch hyperscale9s-packages-experimental-el9s <path to src.rpm>

Once the specfile changes are pushed you can do a real build:

# CBS builds for CentOS Stream 8
git checkout c8s-sig-hyperscale
cbs build hyperscale8s-packages-experimental-el8 "git+$(git rev-parse HEAD)"

# CBS builds for CentOS Stream 9
git checkout c9s-sig-hyperscale
cbs build hyperscale9s-packages-experimental-el9s "git+$(git rev-parse HEAD)"

# Tag it for testing
cbs tag-build hyperscale8s-packages-experimental-testing kernel-<version num>.hsx.el8
cbs tag-build hyperscale9s-packages-experimental-testing kernel-<version num>.hsx.el9

# Tag for release; This will let it go to the mirrors
cbs tag-build hyperscale8s-packages-experimental-release kernel-<version num>.hsx.el8
cbs tag-build hyperscale9s-packages-experimental-release kernel-<version num>.hsx.el9
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