CernVM-FS Graph Driver for Docker
Docker is a popular containerization technology both in industry and in science because it makes containers easy to create, manage and share. Docker images are composed of shared layers to save space and bandwidth, but the price for obtaining image is very high. For instance, to start a cluster of 1000 nodes using an image of 1 GB your network has to transfer 1 TB at once and as quickly as possible.
On average only 6% of the image is required [1]. We developed a Docker plugin [2] to refine data reuse granularity from layers to files. Additionally, the download is delayed until the file is accessed for the first time. Using this approach and CernVM-FS [3], only a fraction of the image is initially transferred and containers start instantly.
This project is presented at ACAT 2017 in Seattle. You can get the poster in PDF here: Making Containers Lazy with Docker and CernVM-FS.
You can obtain and test this plugin this way:
$ docker plugin install cvmfs/overlay2-graphdriver
$ docker plugin enable cvmfs/overlay2-graphdriver
# Restart Docker daemon with flags --experimental -s cvmfs/overlay2-graphdriver
$ docker run -it cvmfs/thin_ubuntu echo "Hello ACAT 2017"
Notice: make sure that the overlay Linux kernel module is available and loaded
(sudo modprobe overlay).
This project is in an early experimental phase. It can be used in realistic scenarios but it hasn't yet reached production quality.
If you have any questions or need help with testing, please to write to nikola.hardi@cern.ch (link sends e-mail).