Checkpointing

Checkpoints currently work with root containers only. Therefore, you have to run the example container as root. Instead of prefixing each command with sudo, you can also switch to the root user beforehand via sudo -i.

$ sudo podman run -dt -p 8080:80/tcp docker.io/library/httpd
$ sudo podman ps

Checkpointing the container

Checkpointing a container stops the container while writing the state of all processes in the container to disk. With this a container can later be restored and continue running at exactly the same point in time as the checkpoint. This capability requires CRIU 3.11 or later installed on the system.

To checkpoint the container use:

$ sudo podman container checkpoint <container_id>

Restoring the container

Restoring a container is only possible from a previously checkpointed container. The restored container will continue to run at exactly the same point in time it was checkpointed.

To restore the container use:

$ sudo podman container restore <container_id>

After being restored, the container will answer requests again as it did before checkpointing.

$ curl http://<IP_address>:8080

Migrating the container

To live migrate a container from one host to another the container is checkpointed on the source system of the migration, transferred to the destination system and then restored on the destination system. When transferring the checkpoint, it is possible to specify an output-file.

On the source system:

$ sudo podman container checkpoint <container_id> -e /tmp/checkpoint.tar.gz
$ scp /tmp/checkpoint.tar.gz <destination_system>:/tmp

On the destination system:

$ sudo podman container restore -i /tmp/checkpoint.tar.gz

After being restored, the container will answer requests again as it did before checkpointing. This time the container will continue to run on the destination system.

$ curl http://<IP_address>:8080