Technology · Ebook

urunc: Running Unikernels as Containers

by Shriira Press

urunc is a CNCF sandbox container runtime that aspires to be "runc for unikernels": a CRI-compatible runtime that packages unikernels as OCI images and boots them through a virtual machine or sandbox monitor, while presenting them to containerd and Kubernetes as ordinary containers. This book explains what unikernels are and why they never fit the cloud-native stack, then traces urunc's design — its containerd shim, runtime binary, and monitor abstraction over QEMU, Firecracker, and Solo5. It covers packaging images with com.urunc.unikernel annotations and the bunny tool, the boot flow from containerd through networking and storage to a live monitor, wiring urunc into Kubernetes via a RuntimeClass, and where the project fits among Unikraft, Rumprun, MirageOS, and Kata Containers.

Contents

1. 1Preface
2. 2Chapter 1 — runc for Unikernels
3. 3Chapter 2 — Unikernels and the Cloud-Native Mismatch
4. 4Chapter 3 — How urunc Is Built
5. 5Chapter 4 — Packaging Unikernels as OCI Images
6. 6Chapter 5 — From containerd to a Running Unikernel
7. 7Chapter 6 — urunc on Kubernetes
8. 8Chapter 7 — urunc in Practice