cvmfs

Docker image with CVMFS client.

The image only comes with the software. Configuration files for cvmfs are not provided in the Docker image;
Consider using in combination with Helm charts (or similar tools for container configuration) to create the expected configuration files -- See ScienceBox CVMFS chart

Provide the configuration file /etc/cvmfs/default.local with relevant configuration parameters (e.g., cache size, http proxy, ...)
Repository-specific configuration should be provided by creating configuration files at /etc/cvmfs/config.d/<repo_name>.local
Official documentation for the CVMFS client is at https://cvmfs.readthedocs.io/en/stable/cpt-configure.html
To mount a repoitory, use the command mount -t cvmfs <repo_name> /cvmfs/<repo_name>. The folder /cvmfs/<repo_name> must exist and be empty;

Alternatively, use /etc/fstab to specify the repositories to be mounted (and mount them with mount -a. Example:

sft.cern.ch /cvmfs/sft.cern.ch cvmfs defaults,_netdev,nodev 0 0
sft-nightlies.cern.ch /cvmfs/sft-nightlies.cern.ch cvmfs defaults,_netdev,nodev 0 0

The last option is to start the cvmfs2 process directly:

/usr/bin/cvmfs2 -o rw,nodev,_netdev,system_mount,fsname=cvmfs2,allow_other,grab_mountpoint,uid=998,gid=996 sft.cern.ch /cvmfs/sft.cern.ch

The CVMFS container requires a privileged security context and access to the fuse device on the host.

For Docker, add the following options to the docker run command:
```
--cap-add SYS_ADMIN --device /dev/fuse 
```
For Kubernetes:

In the container spec:

securityContext:
  privileged: true
  capabilities:
    add: ["SYS_ADMIN"]

volumeMounts:
- name: fuse-device
  mountPath: /dev/fuse

In the volume spec:

volumes:
- name: fuse-device
  hostPath:
    path: /dev/fuse

The CVMFS repositories mounted using the client in the container can be exposed to the host system and to other containers;
To do so, use bind mount with the host and use 'shared' bind propagation: --volume /cvmfs:/cvmfs:shared. Other containers will be able to mount the folder /cvmfs from the host.
Docker documentation on bind propagation: https://docs.docker.com/storage/bind-mounts/#configure-bind-propagation
Similarly for Kubernetes: https://kubernetes.io/docs/concepts/storage/volumes/#mount-propagation

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