scmi.md

SCMI

Service Container Manager Interface (SCMI) is an embedded installer that has been included in the image since release tags 1.7.2 and 2.1.2.

SCMI installation examples

The following example uses docker to run the scmi install command to create and start a container named ssh.1. To use SCMI it requires the use of the --privileged docker run parameter and the docker host's root directory mounted as a volume with the container's mount directory also being set in the scmi --chroot option. The --setopt option is used to add extra parameters to the default docker run command template; in the following example a named configuration volume is added which allows the SSH host keys to persist after the first container initialisation.

Note: The placeholder {{NAME}} can be used in options and is replaced with the container's name.

Note: In the following examples replace {{latest-release-tag}} with the latest release tag

SCMI install

$ docker run \
  --rm \
  --privileged \
  --volume /:/media/root \
  jdeathe/centos-ssh:{{latest-release-tag}} \
  /usr/sbin/scmi install \
    --chroot=/media/root \
    --tag={{latest-release-tag}} \
    --name=ssh.1 \
    --setopt="--volume {{NAME}}.config-ssh:/etc/ssh"

SCMI uninstall

To uninstall the previous example simply run the same docker run command with the scmi uninstall command.

$ docker run \
  --rm \
  --privileged \
  --volume /:/media/root \
  jdeathe/centos-ssh:{{latest-release-tag}} \
  /usr/sbin/scmi uninstall \
    --chroot=/media/root \
    --tag={{latest-release-tag}} \
    --name=ssh.1 \
    --setopt="--volume {{NAME}}.config-ssh:/etc/ssh"

SCMI systemd support

If your docker host has systemd (and optionally etcd) installed then scmi provides a method to install the container as a systemd service unit. This provides some additional features for managing a group of instances on a single docker host and has the option to use an etcd backed service registry. Using a systemd unit file allows the System Administrator to use a Drop-In to override the settings of a unit-file template used to create service instances. To use the systemd method of installation use the -m or --manager option of scmi and to include the optional etcd register companion unit use the --register option.

$ docker run \
  --rm \
  --privileged \
  --volume /:/media/root \
  jdeathe/centos-ssh:{{latest-release-tag}} \
  /usr/sbin/scmi install \
    --chroot=/media/root \
    --tag={{latest-release-tag}} \
    --name=ssh.1 \
    --manager=systemd \
    --register \
    --env='SSH_SUDO="ALL=(ALL) NOPASSWD:ALL"' \
    --env='SSH_USER="centos"' \
    --setopt='--volume {{NAME}}.config-ssh:/etc/ssh'

SCMI image information

Since release tags 1.7.2 and 2.1.2 the install template has been added to the image metadata. Using docker inspect, you can access scmi to perform install/uninstall tasks.

Note: A prerequisite of the following examples is that the image has been pulled (or loaded from the release package).

$ docker pull jdeathe/centos-ssh:{{latest-release-tag}}

To see detailed information about the image run scmi with the --info option. To see all available scmi options run with the --help option.

$ eval "sudo -E $(
    docker inspect \
    -f "{{.ContainerConfig.Labels.install}}" \
    jdeathe/centos-ssh:{{latest-release-tag}}
  ) --info"

To perform an installation using the docker name ssh.2 simply use the --name or -n option.

$ eval "sudo -E $(
    docker inspect \
    -f "{{.ContainerConfig.Labels.install}}" \
    jdeathe/centos-ssh:{{latest-release-tag}}
  ) --name=ssh.2"

To uninstall use the same command that was used to install but with the uninstall Label.

$ eval "sudo -E $(
    docker inspect \
    -f "{{.ContainerConfig.Labels.uninstall}}" \
    jdeathe/centos-ssh:{{latest-release-tag}}
  ) --name=ssh.2"

SCMI on Atomic Host

With the addition of install/uninstall image labels it is possible to use Project Atomic's atomic install command to simplify install/uninstall tasks on CentOS Atomic Hosts.

To see detailed information about the image run scmi with the --info option. To see all available scmi options run with the --help option.

$ sudo -E atomic install \
  -n ssh.3 \
  jdeathe/centos-ssh:{{latest-release-tag}} \
  --info

To perform an installation using the docker name ssh.3 simply use the -n option of the atomic install command.

$ sudo -E atomic install \
  -n ssh.3 \
  jdeathe/centos-ssh:{{latest-release-tag}}

Alternatively, you could use the scmi options --name or -n for naming the container.

$ sudo -E atomic install \
  jdeathe/centos-ssh:{{latest-release-tag}} \
  --name ssh.3

To uninstall use the same command that was used to install but with the uninstall Label.

$ sudo -E atomic uninstall \
  -n ssh.3 \
  jdeathe/centos-ssh:{{latest-release-tag}}