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OpenShift base images

This repository contains Dockerfiles for images which serve as base images with all the essential libraries and tools needed for OpenShift language images, for example:

This container image also installs several development libraries, that are often required in the builder images above. It also includes NPM package manager. Sharing those development packages in a common layer saves disk space and improves pulling speed.

NPM, a package manager for Node.js, offers a pleasant way to install JavaScript libraries, that are often needed as static files for various web applications. In order to offer good experience for web developers, the NPM package manager is also installed in the image.

For containers where the development libraries and NPM package manager are not necessary, users are advised to use the s2i-core variant of this container image.

Description

OpenShift S2I images use Software Collections packages to provide the latest versions of various software. 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 /bin/sh
  • PROMPT_COMMAND: enables the collection in interactive shell

Two examples:

  • If you specify BASH_ENV, then all your #!/bin/bash scripts do not need to call scl enable.
  • If you specify PROMPT_COMMAND, then on execution of the podman exec ... /bin/bash command, the collection will be automatically enabled.

Note: Executables in Software Collections packages (e.g., ruby) are not directly in a directory named in the PATH environment variable. This means that you cannot do:

$ podman exec <cid> ... ruby

but must instead do:

$ podman exec <cid> ... /bin/bash -c ruby

The /bin/bash -c, along with the setting the appropriate environment variable, ensures the correct ruby executable is found and invoked.

Note: while the examples in this README are calling podman, you can replace any such calls by docker with the same arguments

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 --recursive https://github.com/sclorg/s2i-base-container.git
$ cd s2i-base-container
$ make build VERSIONS=base TARGET=rhel7
  • CentOS7 base image

This image is available on DockerHub. To download it run:

podman pull sclorg/s2i-base-centos7

To build a Base image from scratch run:

$ git clone --recursive https://github.com/sclorg/s2i-base-container.git
$ cd s2i-base-container
$ make build VERSIONS=base

Notice: By omitting the VERSION parameter, the build/test action will be performed on all provided versions of s2i image.

See also

Dockerfile and other sources are available on https://github.com/sclorg/s2i-base-container. In that repository you also can find another variants of S2I base Dockerfiles. The Dockerfile for CentOS is called Dockerfile, the Dockerfile for RHEL7 is called Dockerfile.rhel7, the Dockerfile for RHEL8 is called Dockerfile.rhel8 and the Dockerfile for Fedora is Dockerfile.fedora.