Sysbox

What Sysbox is

Sysbox is a free, open-source container runtime for running system workloads in rootless containers on Linux. It is designed for software such as systemd, Docker, and Kubernetes that commonly expects a VM-like environment. Sysbox works with OCI-compatible container managers and orchestrators, including Docker and Kubernetes, and supports Systemd-in-Docker, Docker-in-Docker, Kubernetes-in-Docker, K3s-in-Docker, and Buildx/Buildkit workflows. It supports image building and uses the OCI image format.

For isolation, Sysbox uses Linux user namespaces so root inside a container has no privileges on the host. It also virtualizes parts of procfs and sysfs. Its security controls include Linux namespaces, seccomp, cgroups resource limits, and restrictions on initial mounts. Containers still share the host’s Linux kernel, so isolation is weaker than with VM-based runtimes. The project describes uses in CI/CD, development and local testing, legacy application hosting, and isolated compute environments. Installation is for supported Linux hosts and architectures such as amd64 and arm64; the README recommends at least 4 CPUs and 4 GB RAM. Sysbox Community Edition is free under the Apache License 2.0.

Who it suits

Sysbox suits Linux users who need to run system-level workloads such as Docker or Kubernetes inside rootless containers, including for CI/CD, development, testing, or legacy application hosting. It is a fit when the host uses a supported Linux distribution and architecture and the workload can share the Linux kernel.

Limits

Sysbox Community Edition is free, but its isolation is weaker than VM-based runtimes because containers share the Linux kernel. It does not support exposing host devices inside system containers or reducing the allowed syscall set through a Docker seccomp profile.

Getting started

1. Open the Sysbox project website at https://github.com/nestybox/sysbox.
2. Check that the host uses a supported Linux distribution and architecture.
3. Plan for the recommended minimum of 4 CPUs and 4 GB RAM.
4. Install Sysbox on the Linux host using the applicable distribution instructions.
5. Use it with an OCI-compatible container manager such as Docker or Kubernetes.

Verdict

Choose Sysbox if you need a free Linux runtime for rootless system workloads, containerized development, or CI/CD. Look elsewhere if you need VM-level isolation, host-device access inside system containers, or Docker seccomp profiles to restrict allowed syscalls.