% starter-systemd-SYSTEMD (1) Container Image Pages % Tommy Hughes % October 13, 2016
starter-systemd-systemd - starter-systemd container image
The starter-systemd image provides an example of how a RHEL-based image build could start.
The starter-systemd image is designed to be run by the atomic command with one of these options:
run
Starts the installed container with selected privileges to the host.
stop
Stops the installed container
uninstall
Removes the installed container, not the image
The container itself consists of: - RHEL7 base image - systemd - crond - Apache/2.x - Atomic help file
Files added to the container during docker build include: /help.1.
To use the starter-systemd container, you can run the atomic command with run, stop, or uninstall options:
To run the starter-systemd container:
atomic run acme/starter-systemd
To stop the starter-systemd container (after it is installed), run:
atomic stop acme/starter-systemd
To remove the starter-systemd container (not the image) from your system, run:
atomic uninstall acme/starter-systemd
The starter-systemd container includes the following LABEL settings:
That atomic command runs the docker command set in this label:
RUN=
LABEL RUN='docker run -tdi --name ${NAME}
-u 123456
-p 8080:80
${IMAGE}' \
The contents of the RUN label tells an atomic run acme/starter-systemd command to demonstrate arbitrary uid (-u) capabilities, open hostPort 8080 to containerPort 80, and set the name of the container.
Name=
The registry location and name of the image. For example, Name="acme/starter-systemd".
Version=
The Red Hat Enterprise Linux version from which the container was built. For example, Version="7.2".
Release=
The specific release number of the container. For example, Release="12.1.a":
When the atomic command runs the starter-systemd container, it reads the command line associated with the selected option from a LABEL set within the Docker container itself. It then runs that command. The following sections detail each option and associated LABEL:
THESE IMPLICATIONS DO NOT APPLY TO THIS IMAGE - this is only an example of what documentation might look like:
Below is an example of what is referred to as a super-privileged container. It is designed to have almost complete access to the host system as root user. The following docker command options open selected privileges to the host:
-d
Runs continuously as a daemon process in the background
--privileged
Turns off security separation, so a process running as root in the container would have the same access to the host as it would if it were run directly on the host.
--net=host
Allows processes run inside the container to directly access host network interfaces
--pid=host
Allows processes run inside the container to see and work with all processes in the host process table
--restart=always
If the container should fail or otherwise stop, it would be restarted
Similar to a Changelog of sorts which can be as detailed as the maintainer wishes.
Tommy Hughes