Building a Base Image Containing COBOL Server

This topic outlines the steps that a Dockerfile must carry out to create a base image for COBOL Server.

By far the easiest, and the recommended, way to create a base image for COBOL Server is to use the container demonstration as described in The Container Demonstration for the COBOL Server Base Image. If you do use the container demonstration, you do not need to perform any of the steps described in this topic because the container demonstration does them all for you. The information in this topic is provided if you choose to write your own Dockerfile to create a COBOL Server base image.

Note: A separate document, Best Practices for Moving Your COBOL Applications to Containers, is available that describes best practices that Micro Focus recommends you adopt when moving an existing COBOL application to run in a containerized environment. See Micro Focus: Best Practices for Moving Your COBOL Applications to Containers for more information.

Once you have built your COBOL Server base image you can then build additional images, based on the base image, that include your COBOL applications as well as COBOL Server. For more information on creating those additional images see Building an Image Containing an Application to Run under COBOL Server.

Prerequisites
Building a base image
Creating a custom JRE image
Adding .NET support to an image

Prerequisites

Before building a base image for COBOL Server you need to ensure that you have available the following:

The installable executable file for COBOL Server. This is setup_cobol_server_for_docker_8.0_platform.gz and is supplied in the container demonstration for the COBOL Server base image.
The appropriate license (.mflic or .xml) file for COBOL Server.

Building a base image

To build a base image that includes COBOL Server your Dockerfile needs to perform the following steps:

Specify a base image to work from. This will typically be rhel7/rhel:latest or suse/sles12sp3 depending on whether you are using Red Hat Linux or SUSE Linux.
Define metadata for your image. This will make it easier to establish significant details of the image when you use the docker inspect or podman inspect command.
Define any variables for filenames and folder locations.
Install any packages that are required for COBOL Server to install successfully. See Software Requirements for more information.
Copy the installable executable file for COBOL Server (setup_cobol_server_for_docker_8.0_platform.gz) from your host machine to a temporary folder in the image's filesystem.
Create the user and groups whose details will be used when installing COBOL Server.
Ensure that the installable executable file for COBOL Server has execute permissions, then execute it.
When running setup_cobol_server_for_docker_8.0_platform.gz you need to specify the following parameters:

-IacceptEULA

to indicate that you accept the terms of the Micro Focus End User License Agreement (EULA).

-ESadminID=user-name

to set the Enterprise Server System Administrator Process User ID.
Configure the dynamic linker run-time bindings to include the shared objects supplied with COBOL Server.
Doing this avoids the need to update the LD_LIBRARY_PATH environment variable.
Perform any required clean-up. This includes tasks such as resetting variables and deleting temporary folders.
Install a license for COBOL Server then remove the license file.

Note: You might also want to create an image that you can log in to and execute shell or COBOL Server commands. This option is useful if you are not adding any application files to a base image but want to be able to use COBOL Server commands from it.

All of the container demonstrations offer the option to create such a login image, and those images are tagged with the suffix "_login". See Running the Container Demonstration for the COBOL Server Base Image for information on how to specify that you want to create a _login image. For details on the commands required to build such an image, see the bld.sh script in any of the container demonstrations.

Creating a custom JRE image

The build tool for image creation, bld.sh, enables you to create a custom Java Run-Time image from the downloaded Adopt OpenJDK. Using a custom JRE runtime helps reduce the size of the image, typically saving 70% on the size of the included Java component.

Support for custom Java runtimes is provided only for Java versions 11 and newer.

To create a custom JRE:

When you are creating a new COBOL Server image, specify the java argument in order to enable the use of java. This automatically specifies the use of a custom JRE, by default.
Note: Use java nojre if you do not want to use a custom JRE. The Adopt OpenJDK with be included as is without any modifications. For example:
```
./bld.sh java nojre
```

You can customize the image further by changing the modules and locales to be included in the image. To do this, use the following options in addition to the java jre with the product bld.sh file:

jre - create a custom JRE using jlink.
jre=slim - create custom JRE with a 'slim' set of modules - for example, java.base, java.management, java.logging, java.desktop,jdk.localedata.
jremodules=mod1,mod2,...- specify java modules for the JRE.
jreincludelocale=l1,l2,... - specify locales to include in the JRE.
jreextraarg=--verbose - specify any extra arguments for jlink.

Example:

The following command-line example helps create an image with some specific modules and with English, French and German locales:

 ./bld.sh java jre
jremodules=java.base,java.management,java.logging,java.desktop,jdk.localedata,jdk.attach
jreextraarg=--verbose jreincludelocale=en,fr,de

Adding .NET 6 support to an image

Note: This option is supported on the following platforms:

AmazonLinux 2
RHEL 8
SLES/OpenSUSE Leap 15
Ubuntu 18.04, 20.04, 21.04, 21.10

The build tool for image creation, bld.sh, supports an optional argument, dotnet, that adds .NET 6 support to an image.

Specify dotnet when you create the image, and either the .NET 6 SDK or .NET 6 Runtime will be included in your image. bld.sh uses the dotnet NuGet tool to register the products' NuGet repository and templates. In this way, the image is ready for use by you or your CI/CD system.

For Visual COBOL, bld.sh installs the .NET SDK. The NuGet package path is adjusted, and templates are registered. The installation is completed by a secondary script, dotnet_install.sh.

For COBOL ServerCOBOL Server, the .NET Runtime is used.