Red Hat Enterprise Linux Always Ready config option scheme
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Historically, the RHEL kernel is forked from a Fedora kernel.
Today, the Always Ready Kernel (ARK) is constantly rebased as new kernel
releases come out. New configuration options are reviewed and set
with each release.
The config options are split out into a hierarchical
tree structure, with one file per config option at each level of the
hierarchy. The config options are merged and properly layered according to
the file "priority" in the same directory as this README to generate the
final kernel-$VERSION-<arch>-<variant>.config files we need for building the
actual kernels.
The configuration is broken down into several directories:
ark - This contains all configuration options that have been fully
reviewed by kernel developers and are suitable for inclusion at branch time.
pending-common - This directory contains all configuration options that have
not yet been fully reviewed for inclusion. Because of the rate at which
kernel options come out, we can't guarantee everything has been reviewed
by the time a build needs to happen. In the interest of letting the build
proceed for other testing, configuration options are staged in the
pending directory. It is expected that this directory will be empty
at branch time.
In each directory (ark etc.), we have generic/CONFIG_* and debug/CONFIG_*, then
generic/<arch>/CONFIG_* and generic/<arch>/<variant>/CONFIG_*, as well as
debug/<arch>/CONFIG_*. While this may seem overly complex compared with
past RHEL kernel config setups at first glance, its actually quite
straight-forward and should be less error-prone. There's no potential
for configuration options getting out of order or conflicts when changing
adjacent configuraiton options.
pending-fedora - This directory contains configuration options that have not
been reviewed by Fedora kernel maintainers. Since the Fedora kernel turns on
more configuration options than ARK, there are often settings that are not set
to default in pending-common. These settings are moved to the fedora/
configuration directory after community review. Options are populated with
"make FLAVOR=fedora dist-commit-configs".
custom-overrides - This directory contains an empty set of the generic and debug
arch-specific directory tree. Any config option set here is applied last and
therefore will override anything set in the ark, fedora, or pending directories.
This allows users to easily override a config option without altering the
standard directories. Users can even maintain their own branch with a full set
of custom configuration options that can be easily be rebased on top of
os-build without worrying about conflicts.
All the configuration options for each arch and variant can be found
in the "priority" file.
If you want to make a change that applies to all kernels, debug and
non-debug alike, add a config option file under ark/generic/. If it should
only apply to all debug kernels, add it under ark/debug/. Arch-specific
options go under ark/generic/<arch>/ and so on. Each layer's individual config
option files are concatenated together with all other options at the same
level, then stacked atop the lower layers until reaching the highest
precedence layer for the given config option.
Send any questions, comments or concerns to rhkernel-list@redhat.com.
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