cli_docker_additional_registries=<registry_hostname> cli_docker_insecure_registries=<registry_hostname> cli_docker_blocked_registries=<registry_hostname>
This section explores some of the preparation required to install OKD as a set of services within containers. This applies to hosts using either Red Hat Enterprise Linux or Red Hat Atomic Host.
For the quick installation method, you can choose between the RPM or containerized method on a per host basis during the interactive installation, or set the values manually in an installation configuration file.
For the
advanced installation
method, you can set the Ansible variable containerized=true in an
inventory
file on a cluster-wide or per host basis.
The following sections detail the preparation for a containerized OKD installation.
Containerized installations make use of the following images:
openshift/origin
openshift/node (node + openshift-sdn + openvswitch RPM for client tools)
openshift/openvswitch (CentOS 7 + openvswitch RPM, runs ovsdb and ovsctl processes)
registry.access.redhat.com/rhel7/etcd
If you need to use a private registry to pull these images during the installation, you can specify the registry information ahead of time. For the advanced installation method, you can set the following Ansible variables in your inventory file, as required:
cli_docker_additional_registries=<registry_hostname> cli_docker_insecure_registries=<registry_hostname> cli_docker_blocked_registries=<registry_hostname>
The configuration of additional, insecure, and blocked Docker registries occurs at the beginning of the installation process to ensure that these settings are applied before attempting to pull any of the required images.
The installation process creates relevant systemd units which can be used to start, stop, and poll services using normal systemctl commands. For containerized installations, these unit names match those of an RPM installation, with the exception of the etcd service which is named etcd_container.
This change is necessary as currently RHEL Atomic Host ships with the etcd package installed as part of the operating system, so a containerized version is used for the OKD installation instead. The installation process disables the default etcd service. The etcd package is slated to be removed from RHEL Atomic Host in the future.
All OpenShift configuration files are placed in the same locations during containerized installation as RPM based installations and will survive os-tree upgrades.
However, the default image stream and template files are installed at /etc/origin/examples/ for containerized installations rather than the standard /usr/share/openshift/examples/, because that directory is read-only on RHEL Atomic Host.
RHEL Atomic Host installations normally have a very small root file system. However, the etcd, master, and node containers persist data in the /var/lib/ directory. Ensure that you have enough space on the root file system before installing OKD; see the System Requirements section for details.
OKD SDN initialization requires that the Docker bridge be reconfigured and that Docker is restarted. This complicates the situation when the node is running within a container. When using the Open vSwitch (OVS) SDN, you will see the node start, reconfigure Docker, restart Docker (which restarts all containers), and finally start successfully.
In this case, the node service may fail to start and be restarted a few times
because the master services are also restarted along with Docker. The current
implementation uses a workaround which relies on setting the Restart=always
parameter in the Docker based systemd units.