trajano/centos-mounted-volume-plugin repository overview

⁠CentOS Mounted Volume Plugin

This is a managed Docker volume plugin to allow Docker containers to access any file system that can be mounted. It is based on CentOS and can utilize any package that CentOS along with EPEL provides.

⁠Caveats:

• This is a managed plugin only, no legacy support.
• This is VERY OPEN so please be careful when using this. If there is a specialized driver use that one if possible.
• This requires an INTERNET connection to download the additional packages. However http_proxy environment variable can be set.
• This slows down your start up as it will download packages before being able to create any mounts. The download starts off as another thread during initialization and the /Mount calls will wait till the download is finished.
• This will mount the /root and /sys/fs/cgroup folder of the host and expose it to the plugin as read only. /root is expected to contain files to be read by the mount command for credentials. /sys/fs/cgroup is needed for systemd integration to work.
• I had to choose one OS distro to start with, if there is a need for another distro just create an issue or PR.
• There is no facility to run systemctl or any additional commands, just the mount command. This would mean that NFS cannot be used with this plugin.
• In order to properly support versions use --alias when installing the plugin.
• There is no robust error handling. So garbage in -> garbage out

⁠How to use

In order to not make this a free-for-all, only the device option is recognized. Any mount options need to be set up as part of the plugin. Multiple copies of the plugin can co-exist with different options under different aliases.

The plugin supports the following settings:

• PACKAGES this is a comma separated list of packages that would be added.
• POSTINSTALL this will be executed after the packages have been installed
• MOUNT_OPTIONS this corresponds to the -o parameter of the mount command. It will be treated as a single string so it cannot inject the mount points or devices.
• MOUNT_TYPE the type of the mount, this corresponed to the -t parameter of the mount command
• http_options (note lower case) this sets the HTTP options as per https://www.centos.org/docs/5/html/yum/sn-yum-proxy-server.html⁠

When installinng, it is recommended that a PLUGINALIAS is specified so that you would know what it is for and can easily control multiple copies of it. This can be done in an automated fashion as:

docker plugin install --alias PLUGINALIAS \
  trajano/centos-mounted-volume-plugin \
  --grant-all-permissions --disable
docker plugin set PLUGINALIAS PACKAGES=nfs-utils
docker plugin set PLUGINALIAS MOUNT_TYPE=nfs
docker plugin set PLUGINALIAS MOUNT_OPTIONS=hard,proto=tcp,nfsvers=4,intr
docker plugin enable PLUGINALIAS

Example in docker-compose.yml:

volumes:
  sample:
    driver: PLUGINALIAS
    driver_opts:
      device: "server1:/share_name"
    name: "whatever_name_you_want"

Which yields the following command

mount -t nfs -o hard,proto=tcp,nfsvers=4,intr server1:/share_name /generated_mount_point

⁠Recipes

⁠NFS mount

docker plugin install \
  trajano/centos-mounted-volume-plugin \
  --grant-all-permissions --disable
docker plugin set trajano/centos-mounted-volume-plugin \
  PACKAGES=nfs-utils \
  POSTINSTALL="systemctl start rpcbind" \
  MOUNT_TYPE=nfs \
  MOUNT_OPTIONS=hard,proto=tcp,nfsvers=3,intr,nolock
docker plugin enable trajano/centos-mounted-volume-plugin
docker volume create -d trajano/centos-mounted-volume-plugin --opt device=192.168.1.1:/mnt/routerdrive/nfs nfsmountvolume
docker run -it -v nfsmountvolume:/mnt alpine