OpenShift base images
This repository contains Dockerfiles which serve as base images with all the
essential libraries and tools needed for OpenShift language images, namely:
Installation and Usage
Choose either the CentOS7 or RHEL7 base image:
- RHEL7 base image
To build a RHEL7 based image, you need to build it on properly subscribed RHEL machine.
$ git clone https://github.com/openshift/s2i-base.git $ cd s2i-base $ make build TARGET=rhel7
- CentOS7 base image
This image is available on DockerHub. To download it run:
docker pull openshift/base-centos7
To build a Base image from scratch run:
$ git clone https://github.com/openshift/s2i-base.git $ cd s2i-base $ make build
Software Collections in S2I images
OpenShift S2I images use Software Collections
packages to provide the latest versions of various language environments.
The SCL packages are released more frequently than the RHEL or CentOS systems,
which are unlikely to change for several years.
We rely on RHEL and CentOS for base images, on the other hand,
because those are stable, supported, and secure platforms.
Normally, SCL requires manual operation to enable the collection you want to use.
This is burdensome and can be prone to error.
The OpenShift S2I approach is to set Bash environment variables that
serve to automatically enable the desired collection:
BASH_ENV: enables the collection for all non-interactive Bash sessions
ENV: enables the collection for all invocations of
PROMPT_COMMAND: enables the collection in interactive shell
- If you specify
BASH_ENV, then all your
do not need to call
- If you specify
PROMPT_COMMAND, then on execution of the
docker exec ... /bin/bashcommand, the collection will be automatically enabled.
The language interpreter executables in the collection (e.g.,
are not directly in a directory named in the
PATH environment variable.
This means that you cannot do:
$ docker exec <cid> ... ruby
but must instead do:
$ docker exec <cid> ... /bin/bash -c ruby
/bin/bash -c, along with the setting the appropriate environment variable,
ensures the correct
ruby executable is found and invoked.