Managing Containerized GlusterFS

With the GlusterFS release, a GlusterFS service can be set up as a container on a Red Hat Enterprise Linux atomic host 7.2. Containers use the shared kernel concept and are much more efficient than hypervisors in system resource terms. Containers rest on top of a single Linux instance and allows applications to use the same Linux kernel as the system that they are running on. This improves the overall efficiency and reduces the space consumption considerably.

Note

For GlusterFS , Erasure Coding, NFS-Ganesha, BitRot, and Data Tiering are not supported with containerized GlusterFS.

Prerequisites

Before creating a container, execute the following steps.

  1. Create the directories in the atomic host for persistent mount by executing the following command:

    # mkdir -p /etc/glusterfs /var/lib/glusterd /var/log/glusterfs

  2. Ensure the bricks that are required are mounted on the atomic hosts. For more information see, Brick Configuration

  3. If Snapshot is required, then ensure that the dm-snapshot kernel module is loaded in Atomic Host system. If it is not loaded, then load it by executing the following command:

    # modprobe dm_snapshot

Starting a Container

Execute the following steps to start the container.

  1. Execute the following command to run the container:

    # docker run -d --privileged=true --net=host --name <container-name> -v /run -v /etc/glusterfs:/etc/glusterfs:z -v /var/lib/glusterd:/var/lib/glusterd:z -v /var/log/glusterfs:/var/log/glusterfs:z -v /sys/fs/cgroup:/sys/fs/cgroup:ro -v /mnt/brick1:/mnt/container_brick1:z <image name>

    where, * --net=host option ensures that the container has full access to the network stack of the host. * /mnt/brick1 is the mountpoint of the brick in the atomic host and :/mnt/container_brick1 is the mountpoint of the brick in the container. * -d option starts the container in the detached mode.

    + For example:

    +

    # docker run -d --privileged=true --net=host --name glusternode1 -v /run -v /etc/glusterfs:/etc/glusterfs:z -v /var/lib/glusterd:/var/lib/glusterd:z -v /var/log/glusterfs:/var/log/glusterfs:z -v /sys/fs/cgroup:/sys/fs/cgroup:ro -v /mnt/brick1:/mnt/container_brick1:z rhgs3/rhgs-server-rhel7

5ac864b5abc74a925aecc4fe9613c73e83b8c54a846c36107aa8e2960eeb97b4

    + Where, 5ac864b5abc74a925aecc4fe9613c73e83b8c54a846c36107aa8e2960eeb97b4 is the container ID.

    +

    Note

    • SELinux labels are automatically reset to svirt_sandbox_file_t so that the container can interact with the Atomic Host directory.

    • In the above command, the following ensures that the gluster configuration are persistent.

      -v /etc/glusterfs:/etc/glusterfs:z -v /var/lib/glusterd:/var/lib/glusterd -v /var/log/glusterfs:/var/log/glusterfs

  2. If you want to use snapshot then execute the following command:

    # docker run -d --privileged=true --net=host --name <container-name> -v /dev:/dev -v /run -v /etc/glusterfs:/etc/glusterfs:z -v /var/lib/glusterd:/var/lib/glusterd:z -v /var/log/glusterfs:/var/log/glusterfs:z -v /sys/fs/cgroup:/sys/fs/cgroup:ro -v /mnt/brick1:/mnt/container_brick1:z <image name>

    where, /mnt/brick1 is the mountpoint of the brick in the atomic host and :/mnt/container_brick1 is the mountpoint of the brick in the container.

    For example:

    # docker run -d --privileged=true --net=host --name glusternode1 -v /dev:/dev -v /run -v /etc/glusterfs:/etc/glusterfs:z -v /var/lib/glusterd:/var/lib/glusterd:z -v /var/log/glusterfs:/var/log/glusterfs:z -v /sys/fs/cgroup:/sys/fs/cgroup:ro -v /mnt/brick1:/mnt/container_brick1:z rhgs3/rhgs-server-rhel7

5da2bc217c0852d2b1bfe4fb31e0181753410071584b4e38bd77d7502cd3e92b

  3. To verify if the container is created, execute the following command:

    # docker ps

    For example:

    # docker ps

CONTAINER ID        IMAGE               COMMAND                CREATED             STATUS                      PORTS               NAMES
5da2bc217c08        891ea0584e94        "/usr/sbin/init"       10 seconds ago      Up 9 seconds                                    glusternode1

Creating a Trusted Storage Pool

Perform the following steps to create a Trusted Storage Pool:

  1. Access the container using the following command:

    # docker exec -it <container-name> /bin/bash

    For example:

    # docker exec -it glusternode1 /bin/bash

  2. To verify if glusterd is running, execute the following command:

    # systemctl status glusterd

  3. To verify if the bricks are mounted successfully, execute the following command:

    # mount |grep <brick_name>

  4. Peer probe the container to form the Trusted Storage Pool:

    # gluster peer probe <atomic host IP>

  5. Execute the following command to verify the peer probe status:

    # gluster peer status

Creating a Volume

Perform the following steps to create a volume.

  1. To create a volume execute the following command:

    # gluster volume create <vol-name> IP:/brickpath

  2. Start the volume by executing the following command:

    # gluster volume start <volname>

Mounting a Volume

Execute the following command to mount the volume created earlier:

# mount -t glusterfs <atomic host IP>:/<vol-name> /mount/point

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