gVisor has the ability to checkpoint a process, save its current state in a state file, and restore into a new container using the state file.
Checkpoint/restore functionality is currently available via raw
commands. To use the checkpoint command, first run a container.
runsc run <container id>
To checkpoint the container, the
--image-path flag must be provided. This is
the directory path within which the checkpoint state-file will be created. The
file will be called
checkpoint.img and necessary directories will be created
if they do not yet exist.
Note: Two checkpoints cannot be saved to the same directory; every image-path provided must be unique.
runsc checkpoint --image-path=<path> <container id>
There is also an optional
--leave-running flag that allows the container to
continue to run after the checkpoint has been made. (By default, containers stop
their processes after committing a checkpoint.)
Note: All top-level runsc flags needed when calling run must be provided to checkpoint if –leave-running is used.
Note: –leave-running functions by causing an immediate restore so the container, although will maintain its given container id, may have a different process id.
runsc checkpoint --image-path=<path> --leave-running <container id>
To restore, provide the image path to the
checkpoint.img file created during
the checkpoint. Because containers stop by default after checkpointing, restore
needs to happen in a new container (restore is a command which parallels start).
runsc create <container id> runsc restore --image-path=<path> <container id>
Currently checkpoint/restore through
runsc is not entirely compatible with
Docker, although there has been progress made from both gVisor and Docker to
enable compatibility. Here, we document the ideal workflow.
Run a container:
docker run [options] --runtime=runsc <image>`
Checkpoint a container:
docker checkpoint create <container> <checkpoint_name>`
Create a new container into which to restore:
docker create [options] --runtime=runsc <image>
Restore a container:
docker start --checkpoint --checkpoint-dir=<directory> <container>
--leave-runningflag. This issue is fixed in newer releases.
--checkpoint-dirflag but this will be required when restoring from a checkpoint made in another container.