Sysbox on Flatcar Preview Repo

July 6, 2021 · View on GitHub

This is a preview repository for running the Sysbox container runtime on Kinvolk's Flatcar OS.

The repo contains Sysbox binaries built specifically for Flatcar, as well as the Container Linux configuration yaml needed to install Sysbox on Flatcar.

NOTE: This is a preview repo while Nestybox tests Sysbox on Flatcar. Once testing completes, this repo will be removed and the information here will be transferred to the main Sysbox repo.

Contents

Why Sysbox on Flatcar?

Flatcar is a container-optimized Linux distro, meaning that the OS is designed to run workloads inside containers efficiently and securely.

Running Sysbox on Flatcar further increases container security and flexibility, as Sysbox enables containers deployed by Docker or Kubernetes to run with stronger isolation (Linux user-namespace, procfs and sysfs virtualization, initial mount locking, etc.). In addition, Sysbox enables containers to run most workloads that run in virtual machines (including systemd, Docker, and even Kubernetes), thus enabling new powerful use cases for containers beyond microservice deployment.

Supported Flatcar Releases

  • 2765.2.6 (Oklo)

Installing Sysbox on Flatcar

The method of installation depends on whether Sysbox is installed on a Docker host or a Kubernetes node.

Installing Sysbox on Flatcar Docker Hosts

To install Sysbox on a host machine (physical or VM) running Flatcar, simply use this Container Linux configuration file. This config installs the Sysbox components on the Flatcar host.

NOTE: Add to the config file any other configurations you need for the machine (e.g., users, ssh keys, etc.)

For example, the steps below deploy Sysbox on a Google Compute Engine (GCE) virtual machine:

  1. Add the ssh authorized key to the config.yaml:
passwd:
  users:
    - name: core
      ssh_authorized_keys:
        - "ssh-rsa AAAAB3NzaC1yc..."
  1. Convert the config to the Ignition format. This is done using the ct tool, as described in this Kinvolk doc:
$ ct --platform=gce < config.yaml > config.ign
  1. Provision the GCE VM and pass the config.ign generated in the prior step as "user-data".
$ gcloud compute instances create flatcar-vm --image-project kinvolk-public --image-family flatcar-stable --zone us-central1-a --machine-type n2-standard-4 --metadata-from-file user-data=config.ign
Created [https://www.googleapis.com/compute/v1/projects/predictive-fx-309900/zones/us-central1-a/instances/flatcar-vm].
NAME        ZONE           MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP    EXTERNAL_IP    STATUS
flatcar-vm  us-central1-a  n2-standard-4               10.128.15.196  34.132.170.36  RUNNING

When the VM boots, Sysbox will already be installed and running. You can verify this as follows:

core@flatcar-vm ~ $ systemctl status sysbox
● sysbox.service - Sysbox container runtime
     Loaded: loaded (/etc/systemd/system/sysbox.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2021-07-05 19:35:41 UTC; 3h 10min ago
       Docs: https://github.com/nestybox/sysbox
   Main PID: 1064 (sh)
      Tasks: 2 (limit: 19154)
     Memory: 704.0K
     CGroup: /system.slice/sysbox.service
             ├─1064 /bin/sh -c /opt/bin/sysbox/sysbox-runc --version && /opt/bin/sysbox/sysbox-mgr --version && /opt/bin/sysbox/sysbox-fs --version && /bin/sleep infinity
             └─1084 /bin/sleep infinity

You can now deploy containers with Docker + Sysbox as follows:

core@flatcar-vm ~ $ docker run --runtime=sysbox-runc -it --rm <some-image>

This will create a container that is strongly secured and is capable of running microservices as well as full OS environments (similar to a VM, but with the efficiency and speed of containers).

For example, to deploy a "VM-like" container that runs Ubuntu Focal + systemd + Docker inside:

core@flatcar-vm ~ $ docker run --runtime=sysbox-runc -it --rm nestybox/ubuntu-focal-systemd-docker

Please refer the Sysbox Quickstart Guide and Nestybox blog site for may more usage examples.

NOTE: If you exclude the --runtime=sysbox-runc flag, Docker will launch containers with it's default runtime (aka runc). You can have regular Docker containers live side-by-side and communicate with Docker + Sysbox containers without problem.

Installing Sysbox on Flatcar Kubernetes Nodes

Though Sysbox supports installation on K8s nodes, this is not yet supported on K8s nodes using Flatcar.

If you are interested in running Sysbox on Flatcar K8s nodes, please contact us and let us know.

Sysbox Components

The config.yaml performs the following configurations on a Flatcar host:

  • Places the Sysbox binaries in a directory called /opt/bin/sysbox. The binaries include:

    • sysbox-mgr, sysbox-runc, sysbox-fs, the shiftfs module, and fusermount.

  • Loads the shiftfs module into the kernel.

    • This module is present in Ubuntu kernels, but typically not present on other distros. It brings multiple functional benefits, such as giving Sysbox the ability to isolate containers with the Linux user-namespace without changes in Docker's configuration. More on shiftfs here.

  • Configures some kernel sysctl parameters (the config.yaml has the details).

  • Installs and starts the Sysbox systemd units.

  • Configures Docker to learn about Sysbox and restarts Docker.

The result is that the host is fully configured to run Docker containers with Sysbox.

Contact

Slack: Nestybox Slack Workspace

Email: contact@nestybox.com

We are available from Monday-Friday, 9am-5pm Pacific Time.

Thank You!

We thank you very much for using Sysbox on Flatcar! We hope you find it interesting and that it helps you use containers in new and more secure and powerful ways.