Disclosed herein are embodiments for committing changes of an image of a virtual machine-based container running on a host computer system. A starting image for a container is obtained from a guest starting folder, and while the container runs the starting image changes to the image made by the running container are captured in a guest folder that is union mounted with the guest starting folder. Another union folder, which is the union of a new host folder and the starting folder, contains the changed image which can be used for the container or transferred to a different container.