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https://github.com/pyveci/racker
Racker is an experimental harness tool for provisioning and running operating system containers.
https://github.com/pyveci/racker
docker docker-image harness harness-framework machinectl oci oci-image oci-images skopeo systemd systemd-container systemd-nspawn systemd-run test-environment test-harness testing testing-tool umoci
Last synced: 20 days ago
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Racker is an experimental harness tool for provisioning and running operating system containers.
- Host: GitHub
- URL: https://github.com/pyveci/racker
- Owner: pyveci
- License: agpl-3.0
- Created: 2022-05-02T19:08:14.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2024-03-29T05:09:53.000Z (7 months ago)
- Last Synced: 2024-09-03T22:48:14.503Z (2 months ago)
- Topics: docker, docker-image, harness, harness-framework, machinectl, oci, oci-image, oci-images, skopeo, systemd, systemd-container, systemd-nspawn, systemd-run, test-environment, test-harness, testing, testing-tool, umoci
- Language: Python
- Homepage:
- Size: 251 KB
- Stars: 5
- Watchers: 2
- Forks: 1
- Open Issues: 8
-
Metadata Files:
- Readme: README.rst
- Changelog: CHANGES.rst
- License: LICENSE
Awesome Lists containing this project
README
.. highlight:: sh
######
Racker
######
.. container::
*Operating system containers for humans and machines.*
- **Documentation**: https://github.com/cicerops/racker
- **Source code**: https://github.com/cicerops/racker
- **PyPI**: https://pypi.org/project/racker/
|
.. image:: https://img.shields.io/badge/systemd-239%20and%20newer-blue.svg
:target: https://github.com/systemd/systemd
:alt: systemd System and Service Manager
.. image:: https://img.shields.io/pypi/pyversions/racker.svg
:target: https://pypi.org/project/racker/
:alt: Python version
.. image:: https://img.shields.io/pypi/v/racker.svg
:target: https://pypi.org/project/racker/
:alt: Version
.. image:: https://img.shields.io/pypi/status/racker.svg
:target: https://pypi.org/project/racker/
:alt: Maturity status
.. image:: https://github.com/cicerops/racker/workflows/Tests/badge.svg
:target: https://github.com/cicerops/racker/actions?workflow=Tests
:alt: Test suite status
.. image:: https://codecov.io/gh/cicerops/racker/branch/main/graph/badge.svg
:target: https://codecov.io/gh/cicerops/racker
:alt: Test suite code coverage
.. image:: https://img.shields.io/pypi/l/racker.svg
:target: https://pypi.org/project/racker/
:alt: License
.. image:: https://pepy.tech/badge/racker/month
:target: https://pepy.tech/project/racker
:alt: PyPI downloads / month
----
*****
About
*****
Introduction
============
Racker is an experimental harness tool for provisioning and launching
containers, with a focus on `operating system containers `_.
By a "harness tool", we mean a combination of image bakery and payload
launcher.
- The image bakery is based on modern and generic tools for creating machine
images like `mkosi`_ and `Packer`_, as well `OCI-compliant container images
`_. Container images can be acquired from both vendor-
specific and standardized distribution channels like `OCI-compliant image
registries `_.
- A payload is any of an interactive command prompt (shell), a single program
invocation, or a long-running daemon.
Details
=======
Racker is ...
-------------
- A lightweight wrapper around ``systemd-nspawn`` to provide and launch
container environments for/with ``systemd``.
- A lightweight wrapper around ``vagrant`` to provide convenient access to all
things needing a full VM, like running Windows on Linux or macOS.
- A tribute to the authors and contributors of GNU, Linux, systemd, Python,
VirtualBox, Vagrant, Docker, Windows, Windows Docker Machine and countless
others.
With Racker, you can ...
------------------------
- Launch interactive command prompts or invoke programs non-interactively
within a isolated and volatile Linux and Windows environments.
- Build upon the runtime harness framework to build solutions for running and
testing software packages in different environments, mostly run headless and
non-interactively.
Runner backends
---------------
Racker has two different subsystems / runner backends, one for Linux and
another one for Windows.
- For running Linux operating system containers, Racker uses `systemd`_ and
`systemd-nspawn`_. Provisioning of additional software is performed using the
native package manager of the corresponding Linux distribution.
Operating system coverage
-------------------------
On the host side, Racker can run on Linux, macOS, and Windows. On the container
side, the following list of operating systems has been verified to work
well.
Linux
.....
- AmazonLinux 2022
- Arch Linux 20220501
- CentOS 7-9
- Debian 9-12 and unstable (stretch, buster, bullseye, bookworm, sid)
- Fedora 35-37
- openSUSE 15 and latest (leap, tumbleweed)
- Oracle Linux 8
- Red Hat RHEL 8 and 9
- Rocky Linux 8
- SUSE SLES 15 and BCI:latest
- Ubuntu LTS 20 and 22 (focal, jammy)
Prior art
---------
The aims of Racker are very similar to `Docker`_, `Podman`_, `Distrobox`_ and
`Toolbox`_. However, there are also some differences.
Most people running Linux probably want to use `Podman`_ these days. For more
background, enjoy reading `Container wars`_ and `Container Tools Guide`_.
- Racker is currently based on `systemd-nspawn`_ and `Vagrant`_ instead of
`Docker`_ or `Podman`_.
- Racker's focus is to provide easy provisioning and launching `OS containers`_
aka. `OS-level virtualization`_, using `systemd`_ as init process.
- The acquisition and provisioning of operating system images does not need any
special preparation steps, those are handled by Racker on the fly.
- Racker aims to provide concise usability by folding its usage into a single
command.
- Racker is written in Python instead of Golang or Bash.
See also `Comparison with similar tools - more details`_.
About ``systemd-nspawn``
========================
``systemd-nspawn`` may be used to run a command or OS in a light-weight
namespace container. In many ways it is similar to ``chroot``, but more
powerful since it fully virtualizes the file system hierarchy, as well as
the process tree, the various IPC subsystems and the host and domain name.
It is primarily intended for use in development, experimenting, debugging,
instrumentation, testing and building of software.
It can easily be used to start containers capable of booting up a complete
and unmodified Linux distribution inside as normal system services.
For learning more details about ``systemd-nspawn``, we strongly recommend to
read the more extensive `systemd-nspawn in a nutshell`_.
*****
Setup
*****
Install prerequisites::
apt-get update
apt-get install --yes systemd-container skopeo umoci python3-pip python3-venv
Install Racker::
python3 -m venv .venv
source .venv/bin/activate
pip install racker --upgrade
To install the latest development version, use this command instead::
pip install git+https://github.com/cicerops/racker --upgrade
.. note::
If you are not running Linux on your workstation, the documentation about
the `Racker sandbox installation`_ outlines how to run this program within
a virtual machine using Vagrant.
*****
Usage
*****
Racker
======
The ``racker`` program aims to resemble the semantics of Docker by providing a
command line interface compatible with the ``docker`` command.
::
# Invoke the vanilla Docker `hello-world` image.
# FIXME: Does not work yet.
# racker run -it --rm hello-world /hello
# racker run -it --rm quay.io/podman/hello
# Acquire rootfs images.
racker pull debian:bullseye-slim
racker pull fedora:37
# Launch an interactive shell.
racker run -it --rm debian:bullseye-slim bash
racker run -it --rm fedora:37 bash
racker run -it --rm docker://registry.access.redhat.com/ubi8/ubi-minimal /bin/bash
racker run -it --rm docker://quay.io/centos/centos:stream9 bash
# Launch a single command.
racker run -it --rm debian:11-slim hostnamectl
racker run -it --rm opensuse/tumbleweed hostnamectl
racker run -it --rm ubuntu:jammy /bin/cat /etc/os-release
racker run -it --rm registry.suse.com/suse/sle15 /bin/cat /etc/os-release
racker run -it --rm registry.suse.com/bci/bci-base:15.4 /bin/cat /etc/os-release
racker run -it --rm docker://ghcr.io/jpmens/mqttwarn-standard /usr/bin/hostnamectl
# Verbose mode.
racker --verbose run -it --rm fedora:37 hostnamectl
# Use stdin and stdout, with timing.
time echo "hello world" | racker run -it --rm fedora:37 cat /dev/stdin > hello
cat hello
Postroj
=======
The idea behind ``postroj`` is to provide an entrypoint to a command line
interface implementing actions that don't fit into ``racker``, mostly having a
more high-level character.
Currently, ``postroj pkgprobe`` implements a flavor of *full system
integration/acceptance testing* in order to test the soundness of actual
installed binary distribution packages, in the spirit of `autopkgtest`_.
To do so, it implements the concept of *curated* operating system images,
whose labels have a different layout than labels of Docker filesystem images.
Getting started::
# List available images.
postroj list-images
# Acquire images for curated operating systems.
postroj pull debian-bullseye
postroj pull fedora-37
# Acquire rootfs images for all available distributions.
postroj pull --all
# Run a self test procedure, invoking `hostnamectl` on all containers.
postroj selftest hostnamectl
Package testing::
# Run a self test procedure, invoking example probes on all containers.
postroj selftest pkgprobe
# Run two basic probes on different operating systems.
postroj pkgprobe --image=debian-bullseye --check-unit=systemd-journald
postroj pkgprobe --image=fedora-37 --check-unit=systemd-journald
postroj pkgprobe --image=archlinux-20220501 --check-unit=systemd-journald
# Run probes that need to install a 3rd party package beforehand.
postroj pkgprobe \
--image=debian-stretch \
--package=http://ftp.debian.org/debian/pool/main/w/webfs/webfs_1.21+ds1-12_amd64.deb \
--check-unit=webfs \
--check-network=http://localhost:8000
postroj pkgprobe \
--image=debian-bullseye \
--package=https://dl.grafana.com/oss/release/grafana_8.5.1_amd64.deb \
--check-unit=grafana-server \
--check-network=http://localhost:3000
postroj pkgprobe \
--image=centos-8 \
--package=https://dl.grafana.com/oss/release/grafana-8.5.1-1.x86_64.rpm \
--check-unit=grafana-server \
--check-network=http://localhost:3000
***********
Performance
***********
A SuT which just uses a dummy probe ``/bin/systemctl is-active systemd-journald``
on Debian 10 "buster" cycles quite fast, essentially demonstrating that the
overhead of environment setup/teardown is insignificant.
::
time postroj pkgprobe --image=debian-buster --check-unit=systemd-journald
real 0m0.589s
user 0m0.161s
sys 0m0.065s
On a cold system, where the filesystem image would need to be acquired before
spawning the container, it's still fast enough::
time postroj pkgprobe --image=debian-bookworm --check-unit=systemd-journald
real 0m22.582s
user 0m8.572s
sys 0m3.136s
*********************
Questions and answers
*********************
- | Q: How does it work?
| A: Directly quoting the `machinectl`_ documentation here:
Note that `systemd-run`_ with its ``--machine=`` switch may be used in place of the
``machinectl shell`` command, and allows non-interactive operation, more detailed and
low-level configuration of the invoked unit, as well as access to runtime and exit
code/status information of the invoked shell process.
In particular, use ``systemd-run``'s ``--wait`` switch to propagate exit status information
of the invoked process. Use ``systemd-run``'s ``--pty`` switch for acquiring an interactive
shell, similar to ``machinectl shell``. In general, ``systemd-run`` is preferable for
scripting purposes.
- | Q: How does it work, really?
| A: Roughly speaking...
- `skopeo`_ and `umoci`_ are used to acquire root filesystem images from Docker image registries.
- `systemd-nspawn`_ is used to run commands on root filesystems for provisioning them.
- Containers are started with ``systemd-nspawn --boot``.
- `systemd-run`_ is used to interact with running containers.
- `machinectl`_ is used to terminate containers.
- | Q: How is this project related with Docker?
| A: The runtime is completely independent of Docker, it is solely based on
``systemd-nspawn`` containers instead. However, root filesystem images can be
pulled from Docker image registries in the spirit of `machinectl pull-dkr`_.
Other than this, the ``racker`` command aims to be a drop-in replacement for
its corresponding ``docker`` counterpart.
- | Q: Do I need to have Docker installed on my machine?
| A: No, Racker works without Docker.
- | Q: How are machine names assigned?
| A: Machine names for spawned containers are automatically assigned.
The name will be assembled from the distribution's ``fullname`` attribute,
prefixed with ``postroj-``.
Examples: ``postroj-debian-buster``, ``postroj-centos-8``.
- | Q: Does the program need root privileges?
| A: Yes, the program currently must be invoked with ``root`` or corresponding
``sudo`` privileges. However, it would be sweet to enable unprivileged
operations soon. ``systemd-nspawn`` should be able to do it, using
``--private-users`` or ``--user``?
- | Q: Where does the program store its data?
| A: Data is stored at ``/var/lib/postroj``.
In this manner, it completely gets out of the way of any other images, for
example located at ``/var/lib/machines``. Thus, any images created or managed
by Racker will not be listed by ``machinectl list-images``.
| A: The download cache is located at ``/var/cache/postroj/downloads``.
- | Q: Where are the filesystem images stored?
| A: Activated filesystem images are located at ``/var/lib/postroj/images``.
- | Q: How large are curated filesystem images?
| A: The preference for curated filesystem images is to use their corresponding
"slim" variants where possible, aiming to only use artefacts with download
sizes < 100 MB.
- | Q: Are container disks ephemeral?
| A: Yes, by default, all container images will be ephemeral, i.e. all changes to
them are volatile.
***************
Troubleshooting
***************
*It's always the cable. ;]*
1. If you see that your container might not have network access, make sure to
provide a valid DNS configuration in your host's ``/etc/resolv.conf``.
When in doubt, please add ``nameserver 9.9.9.9`` as the first entry.
2. Sometimes, configuring an arbitrary name server is not permitted. An indicator
could be this configuration within ``/etc/resolv.conf``::
nameserver 127.0.0.53
options edns0 trust-ad
If that is the case, you can look up the trusted DNS servers by running
``resolvectl status`` or ``resolvectl dns``. Then, use the DNS server listed
there to announce per ``nameserver `` entry to your container's
``/etc/resolv.conf``.
.. _autopkgtest: https://www.freedesktop.org/wiki/Software/systemd/autopkgtest/
.. _Chocolatey: https://chocolatey.org/
.. _Comparison with similar tools - more details: https://github.com/cicerops/racker/blob/main/doc/comparison.rst
.. _Container Tools Guide: https://github.com/containers/buildah/tree/main/docs/containertools
.. _Container wars: https://github.com/cicerops/racker/blob/main/doc/research/container-wars.rst
.. _Distrobox: https://github.com/89luca89/distrobox
.. _Docker: https://github.com/docker/
.. _machinectl: https://www.freedesktop.org/software/systemd/man/machinectl.html
.. _machinectl pull-dkr: https://github.com/cicerops/racker/blob/main/doc/research/machinectl-pull-dkr.rst
.. _nerdctl: https://github.com/containerd/nerdctl
.. _Microsoft Container Registry: https://mcr.microsoft.com/
.. _mkosi: https://github.com/systemd/mkosi
.. _OCI Distribution Specification: https://github.com/opencontainers/distribution-spec
.. _OCI Image Format: https://github.com/opencontainers/image-spec
.. _OS containers: http://0pointer.net/blog/systemd-for-administrators-part-xxi.html
.. _OS-level virtualization: https://wiki.debian.org/SystemVirtualization#OS-level_virtualization
.. _Packer: https://www.packer.io/
.. _Podman: https://podman.io/
.. _Racker sandbox installation: https://github.com/cicerops/racker/blob/main/doc/sandbox.rst
.. _skopeo: https://github.com/containers/skopeo
.. _systemd: https://www.freedesktop.org/wiki/Software/systemd/
.. _systemd-nspawn: https://www.freedesktop.org/software/systemd/man/systemd-nspawn.html
.. _systemd-nspawn in a nutshell: https://github.com/cicerops/racker/blob/main/doc/systemd-nspawn.rst
.. _systemd-run: https://www.freedesktop.org/software/systemd/man/systemd-run.html
.. _Toolbox: https://containertoolbx.org/
.. _umoci: https://github.com/opencontainers/umoci
.. _Vagrant: https://www.vagrantup.com/
.. _Vagrant Cloud: https://app.vagrantup.com/
.. _Windows Docker Machine: https://github.com/StefanScherer/windows-docker-machine