CernVM-FS in Docker Containers

There are two options to mount CernVM-FS in docker containers. The first option is to bind mount a mounted repository as a volume into the container. This has the advantage that the cvmfs cache is shared among multiple containers. The second option is to mount a repository inside a container, which requires a privileged container.

Volume Driver

There is an external package that provides a Docker Volume Driver for CernVM-FS. This package provides management of repositories in Docker and Kubernetes. It provides a convenient interface to handle CernVM-FS volume definitions.

Bind mount from the host

On Docker >= 1.10, the autofs managed area /cvmfs can be directly mounted into the container as a shared mount point like

docker run -i -t -v /cvmfs:/cvmfs:shared centos /bin/bash

In order to bind mount an individual repository from the host, turn off autofs on the host and mount the repository manually, like:

service autofs stop  # systemd: systemctl stop autofs
chkconfig autofs off  # systemd: systemctl disable autofs
mkdir -p /cvmfs/
mount -t cvmfs /cvmfs/

Start the docker container with the -v option to mount the cvmfs repository inside, like

docker run -i -t -v /cvmfs/ centos /bin/bash

The -v option can be used multiple times with different repositories.

Mount inside a container

In order to use mount inside a container, the container must be started in privileged mode, like

docker run --privileged -i -t centos /bin/bash

In such a container, CernVM-FS can be installed and used the usual way provided that autofs is turned off.

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