Merge branch 'custom-base-more2' into 'wip-baseimage-rework'

Draft: Rework build system further

See merge request fedora/bootc/base-images!89

.gitlab-ci.yml

@@ -16,8 +16,10 @@ build:
     set -xeuo pipefail
     curl -L --fail -o /etc/yum.repos.d/coreos-continuous.repo https://copr.fedorainfracloud.org/coprs/g/CoreOS/continuous/repo/fedora-42/group_CoreOS-continuous-fedora-42.repo
     dnf -y install rpm-ostree
-    buildah build "${hostbuildopts[@]}" -f Containerfile.base --no-cache --security-opt=label=disable --cap-add=all --device /dev/fuse -t ${IMAGE_PREFIX}-base:tmp .
+    cd base
+    buildah build "${hostbuildopts[@]}" -f Containerfile --no-cache --security-opt=label=disable --cap-add=all --device /dev/fuse -t ${IMAGE_PREFIX}-base:tmp .
     # Rechunk
     rpm-ostree experimental compose build-chunked-oci --bootc --format-version=1 \
            --from=${IMAGE_PREFIX}-base:tmp --output containers-storage:${IMAGE_PREFIX}-base
+    cd ..
     buildah build "${hostbuildopts[@]}" -f Containerfile --no-cache --from ${IMAGE_PREFIX}-base -t ${IMAGE_PREFIX}-standard:tmp .

Containerfile

@@ -1,42 +1,18 @@
-# This generates the default base image.
+# This generates the "standard" base image, deriving from the minimal base.
 
 # This is a local reference by default because we haven't shipped this image yet.
 FROM localhost/fedora-bootc:base
-# Drop our package sets into /usr/share/doc, so that other things can parse it
+# Copy in our configuration and build scripts. Most of the heavy lifting
-COPY packages*.txt /usr/share/doc/fedora-bootc/
+# is in `stage-install` which we emit into /usr/share/doc so it can be
-# Overlay our defaults
+# used as a reference in other images.
 COPY usr/ /usr/
 RUN <<EORUN
-set -euo pipefail
+set -xeuo pipefail
-dnf_args=()
+# This script installs our default packages. These scripts
-echo "Loading packages-excluded"
+# are not a stable API, but may become one in the future.
-basedir=/usr/share/doc/fedora-bootc/
+/usr/share/doc/bootc-image-standard/stage-install
-for x in $(grep -E -v '^#' ${basedir}/packages-excluded.txt); do
+# Cleanup
-  dnf_args+=(--exclude ${x})
+/usr/share/doc/bootc-image-standard/stage-clean
-done
+# And lint.
-echo "Loading packages"
-package_files=(${basedir}/packages-recommended-minimal.txt ${basedir}/packages.txt)
-pkgfile_for_arch=/usr/share/doc/fedora-bootc/packages-$(arch).txt
-if test -f ${pkgfile_for_arch}; then
-  echo "Loading ${pkgfile_for_arch}"
-  package_files+=(${pkgfile_for_arch})
-fi
-base_pkgs=$(grep -hE -v '^#' ${package_files[@]})
-dnf -y ${dnf_args[@]} install $base_pkgs
-
-# Ensure we regenerate the initramfs with new content
-# https://docs.fedoraproject.org/en-US/bootc/initramfs/
-kver=$(cd /usr/lib/modules && echo *); dracut -vf /usr/lib/modules/$kver/initramfs.img $kver
-
-# Undo RPM scripts enabling units; we want the presets to be canonical for the base image.
-# https://github.com/projectatomic/rpm-ostree/issues/1803
-rm -rf /etc/systemd/system/*
-systemctl preset-all
-rm -rf /etc/systemd/user/*
-systemctl --user --global preset-all
-
-dnf clean all
-# Lots of cleaning
-rm -vrf /var/log /var/cache /var/lib/dnf
 bootc container lint
 EORUN

base/Containerfile

@@ -8,26 +8,26 @@
 # If you want to configure the input rpm-md repositories, just override this
 # container image.
 FROM quay.io/fedora/fedora:rawhide as repos
-# See https://github.com/coreos/rpm-ostree/issues/3397
-RUN ln -sr /usr/lib/sysimage/rpm /usr/share/rpm
 
-# BOOTSTRAPPING: This can be any image that has the following packages.
+# We use stream10 to demonstrate that we support "cross builds".
-FROM registry.gitlab.com/fedora/bootc/base-images-dev/fedora-bootc-dev:rawhide as builder
+FROM quay.io/centos/centos:stream10 as builder
-RUN dnf -y install rpm-ostree selinux-policy-targeted sqlite
+RUN <<EORUN
+set -xeuo pipefail
+# For rpm-ostree v2025.5
+curl -L -o /etc/yum.repos.d/coreos-continuous.repo https://copr.fedorainfracloud.org/coprs/g/CoreOS/continuous/repo/centos-stream-10/group_CoreOS-continuous-centos-stream-10.repo
+dnf -y install rpm-ostree selinux-policy-targeted sqlite
+EORUN
 # Copy in our source code.
 COPY . /src
 WORKDIR /src
-RUN --mount=type=bind,from=repos,src=/,dst=/repos <<EORUN
+RUN --mount=type=bind,from=repos,src=/,dst=/repos,rw <<EORUN
 set -xeuo pipefail
-# Synchronize the dnf/rpm configs from the repos container.
+# Copy the build configuration into the builder image, as if it's the final image
-for x in etc/dnf etc/yum.repos.d etc/pki/rpm-gpg; do
+cp -a . /usr/lib/sysimage/base-image-manifest
-  rm -rf /"$x" && cp -a /repos/${x} /$x
+# And embed the rebuild script
-done
+install -m 0755 -t /usr/libexec ./bootc-base-image-rebuild-self
-# And copy to the workdir; TODO fix this in rpm-ostree
+# Finally, run the build script in the same way we expect custom images to do.
-cp /etc/yum.repos.d/*.repo base
+/usr/libexec/bootc-base-image-rebuild-self /repos /target-rootfs
-rpm-ostree experimental compose rootfs --source-root=/repos base/manifest.yaml /target-rootfs
-# Embed the configuration in the image itself, so that it can be used by later builds as well
-cp -a base /target-rootfs/usr/lib/sysimage/base-image-manifests
 EORUN
 
 # This pulls in the rootfs generated in the previous step

base/Makefile

@@ -0,0 +1,2 @@
+install:
+	install -m 0755 -t $(DESTDIR)/usr/libexec bootc-base-image-rebuild-self

base/bootc-base-image-rebuild-self

@@ -0,0 +1,17 @@
+#!/bin/bash
+# This script regenerates this base image using a build
+# configuration (list of packages, scripts) embedded in this current image.
+# The actual *content* packages will come from the source root.
+set -xeuo pipefail
+source_root=$1
+shift
+target=$1
+shift
+if ! test -x /usr/bin/rpm-ostree; then
+    dnf -y install rpm-ostree
+fi
+rpm-ostree experimental compose rootfs --source-root-rw=$source_root /usr/lib/sysimage/base-image-manifest/manifest.yaml $target
+# Finally, propagate the configuration and build script into the target root.
+for f in /usr/lib/sysimage/base-image-manifest /usr/libexec/bootc-base-image-rebuild-self; do
+    cp -a $f $target/$f
+done

base/bootc-base-image-rebuild-self.md

@@ -0,0 +1,83 @@
+# bootc-base-image-rebuild-self
+
+A core premise of the bootc model is that rich
+control over Linux system customization can be accomplished
+with a "default" container build:
+
+```
+FROM <base image>
+RUN ...
+```
+
+As of recently, it is possible to e.g. swap the kernel
+and other fundamental components as part of default derivation.
+
+## Understanding the base image content
+
+Most, but not all content from the base image comes from RPMs.
+There is some additional non-RPM content, as well as postprocessing
+that operates on the filesystem root. At the current
+time the implementation of the base image build uses `rpm-ostree`,
+but this is considered an implementation detail subject to change.
+
+## Rebuilding from externally controlled content
+
+Some use cases want even more control - for example,
+as an organization deploying a bootc system, I may want to ensure
+the base image version carries a set of packages at
+exactly specific versions (perhaps defined by a lockfile,
+or an rpm-md repository). There are many tools which
+manage snapshots of yum (rpm-md) repositories.
+
+The `/usr/libexec/bootc-base-image-rebuild-self` which is
+included in the base image is designed to enable this
+level of control.
+
+## Using bootc-base-image-rebuild-self
+
+This tool takes just two arguments:
+
+- A "repository configuration root" which should have an `/etc/yum.repos.d`
+  that defines the input RPM content.
+- A path to the target root filesystem which will be generated
+
+### Implementation
+
+The current implementation uses `rpm-ostree` on a manifest (treefile)
+embedded in the container image itself. The set of packages installed
+is currently not configurable; however it is quite minimal and can
+easily be customized further as we will see below.
+
+The build tooling is designed to support "cross builds"; the
+repository root could e.g. be CentOS Stream 10, while the
+builder root is Fedora or RHEL, etc. In other words, one given
+base image can be used as a "builder" to produce another
+using different RPMs.
+
+### Example: Generate a new image using CentOS Stream 10 content from RHEL
+
+FROM quay.io/centos/centos:stream10 as repos
+
+FROM registry.redhat.io/rhel10/rhel-bootc:10 as builder
+RUN --mount=type=bind,from=repos,src=/,dst=/repos,rw /usr/libexec/bootc-base-image-rebuild-self /repos /target-rootfs
+
+# This container image uses the "artifact pattern"; it has some
+# basic configuration we expect to apply to multiple container images.
+FROM quay.io/exampleos/baseconfig@sha256:.... as baseconfig
+
+FROM scratch
+COPY --from=builder /target-rootfs/ /
+# Now we make other arbitrary changes. Copy our systemd units and
+# other tweaks from the baseconfig container image.
+COPY --from=baseconfig /usr/ /usr/
+RUN <<EORUN
+set -xeuo pipefail
+# Install critical components
+dnf -y install linux-firmware NetworkManager cloud-init cowsay
+dnf clean all
+bootc container lint
+EORUN
+LABEL containers.bootc 1
+ENV container=oci
+STOPSIGNAL SIGRTMIN+3
+CMD ["/sbin/init"]

usr/share/doc/bootc-image-standard/stage-clean

@@ -0,0 +1,5 @@
+#!/bin/bash
+set -xeuo pipefail
+dnf clean all
+# Lots of cleaning
+rm -vrf /var/log /var/cache /var/lib/dnf

usr/share/doc/bootc-image-standard/stage-install

@@ -0,0 +1,29 @@
+#!/bin/bash
+set -euo pipefail
+dn=$(dirname $0)
+cd ${dn}
+dnf_args=()
+echo "Loading packages-excluded"
+for x in $(grep -E -v '^#' packages-excluded.txt); do
+  dnf_args+=(--exclude ${x})
+done
+echo "Loading packages"
+package_files=(packages-recommended-minimal.txt packages.txt)
+pkgfile_for_arch=packages-$(arch).txt
+if test -f ${pkgfile_for_arch}; then
+  echo "Loading ${pkgfile_for_arch}"
+  package_files+=(${pkgfile_for_arch})
+fi
+base_pkgs=$(grep -hE -v '^#' ${package_files[@]})
+dnf -y ${dnf_args[@]} install $base_pkgs
+
+# Ensure we regenerate the initramfs with new content
+# https://docs.fedoraproject.org/en-US/bootc/initramfs/
+kver=$(cd /usr/lib/modules && echo *); dracut -vf /usr/lib/modules/$kver/initramfs.img $kver
+
+# Undo RPM scripts enabling units; we want the presets to be canonical for the base image.
+# https://github.com/projectatomic/rpm-ostree/issues/1803
+rm -rf /etc/systemd/system/*
+systemctl preset-all
+rm -rf /etc/systemd/user/*
+systemctl --user --global preset-all