Exploring the New Container Checkpointing Feature

The new Container Checkpointing feature, recently introduced as an alpha feature in Kubernetes 1.25, enables the checkpointing of running containers, allowing their current state to be saved and potentially resumed later without data or process loss. This feature, integrated with several container engines, enhances forensic analysis capabilities and addresses use cases such as speeding up container startup, migrating containers without losing state, and maintaining containers during host updates. While Kubernetes currently supports only checkpointing, and not restoring, at the container engine level, the feature is expected to evolve, potentially allowing direct restoration in Kubernetes and extending capabilities to pods. The Checkpoint/Restore In Userspace (CRIU) project underpins this functionality, enabling the freezing and snapshotting of container states. Despite its promise, the feature presents challenges such as increased disk usage and potential security risks from checkpointed secrets, and it contrasts with the stateless container paradigm. Podman, another container engine, has offered similar functionality since 2018, supporting advanced checkpointing and restoring capabilities, including converting checkpointed states into local images for registry storage and cross-environment restoration.