Wale: A solution to share libraries in Docker containers

This paper presents an approach to avoid disk space duplication which occurs when a same library or package is employed in several Docker containers. The approach, called Wale, relies on the deployment of a single Docker image called Core Image, aiming at collecting all the libraries shared among the various Docker images. The management of the Docker images is made by means of the automatic manipulation of the related Dockerfile performed by the Wale tool. The user is asked to describe the characteristics of her/his container in a proper “Wale file” that is then processed by the Wale tool thus creating the proper Docker image. In this way, common libraries and files are moved into the Core Image, which is rebuilt again along with the new image containers. Even if Wale extends the original sharing degree of Docker, it does not violate the isolation level provided by Docker itself, and thus is able to guarantee security and privacy. A description of a realistic case-study, which proves the effectiveness of the approach in terms of saved disk space, is also included in the paper.