Build RHEL 8 kernel via rocky linux container

Dockerfile

FROM rockylinux:8 AS builder

RUN dnf install -y 'dnf-command(builddep)' 'dnf-command(config-manager)'
RUN dnf config-manager --set-enabled powertools
RUN dnf builddep -y kernel

FROM builder

WORKDIR /tmp
RUN dnf download --source kernel && rpm -ivh kernel*.src.rpm

WORKDIR /root/rpmbuild/SPECS
RUN rpmbuild -bp kernel.spec --with baseonly

RUN ln -s /root/rpmbuild/BUILD/kernel-*/linux-* /tmp/source
WORKDIR /tmp/source

# Emulate InitBuildVars() from kernel.spec
RUN make -s mrproper

# Remove modules
RUN sed -E -e 's/^(CONFIG_[^=]+)=m/# \1 is not set/' configs/kernel-*-$(uname -m)-debug.config > .config
RUN make olddefconfig

# TODO: Apply custom config

RUN make -j 8