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Compose server
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Using higher level build tooling
Originally rpm-ostree compose tree was intended to be a "high level" tool,
but that didn't work out very well in practice. Today, you should consider
it as a low level tool. For example, most people that want to generate
OSTree commits also want to generate bootable disk images, and rpm-ostree
has nothing to do with that.
One example higher level tool that takes care of both OSTree commit generation and bootable disk images is coreos-assembler.
Background on managing an OSTree repository
Before you get started, it's recommended to read (at least) these two sections of the OSTree manual:
Generating OSTree commits from a CentOS base
First, you'll need a copy of rpm-ostree. The current recommendation is to use
a privileged container, but you can also install rpm-ostree directly to a
physical or virtual machine.
It's included in the package collection for Fedora, and there are CentOS Core packages as well as bleeding edge CentOS builds.
You can create a privileged container with e.g. podman via: podman run --privileged registry.fedoraproject.org/fedora:27 .... However you create the
environment, run yum -y install rpm-ostree.
A good first thing to try would be using the CentOS Atomic Host metadata to generate a custom host.
One time setup, where we clone the git repository, then make two OSTree repos, one for doing builds, one for export via HTTP:
# mkdir /srv/centos-atomic
# cd /srv/centos-atomic
# git clone https://github.com/CentOS/sig-atomic-buildscripts -b downstream
# mkdir build-repo
# ostree --repo=build-repo init --mode=bare-user
# mkdir repo
# ostree --repo=repo init --mode=archive
We'll also want to cache downloaded RPMs:
# mkdir cache
Running rpm-ostree compose tree
This program takes as input a manifest file that describes the target system, and commits the result to an OSTree repository.
The input format is a JSON "treefile". See examples in
api-doc/treefile-examples. More real-world examples include the manifest
for
Fedora Atomic and
CentOS Atomic.
If you're doing this multiple times, it's strongly recommended to create a cache directory:
# rpm-ostree compose tree --unified-core --cachedir=cache --repo=/srv/centos-atomic/build-repo sig-atomic-buildscripts/centos-atomic-host.json
This will download RPMs from the referenced repos, and commit the result to the
OSTree repository, using the ref named by ref.
Once we have that commit, let's export it:
# ostree --repo=repo pull-local build-repo centos-atomic-host/7/x86_64/standard
You can tell client systems to rebase to it by combining ostree remote add,
and rpm-ostree rebase on the client side.