https://doc-stage.usersys.redhat.com/documentation/en-us/jboss_enterprise_application_platform_continuous_delivery/18/html-single/getting_started_with_jboss_eap_for_openshift_container_platform/#custom_scripts

7.13.5. Custom Scripts

• Mount a configmap to be executed as postconfigure.sh
  Use this option when you want any changes from the script to be implemented when the s2i image is built by the build controller.
• Add an install.sh script in the nominated installation directory
  Use this option when you want the script to run each time a pod is started after building the image.

I don't think that the above is correct.

• Both options "creates" script $JBOSS_HOME/extensions/postconfigure.sh.
• With both options the script is run each time a pod is started.
• with first option the config map is mounted to $JBOSS_HOME/extensions
• With second option the script is built into the image

7.13.5.1. Mounting a configmap to execute custom scripts

Note

Do not use this option when standalone-openshift.xml includes replacement XML comments (<!-REPLACEME→) that should be replaced at runtime. If you use this option, JBoss EAP reads and persists the configuration file, removing all of the XML comments that are expected to be replaced at runtime.

I'm not sure about this, as far I know placeholders should be already replaced when postconfigure.sh is run. I think it could be completely removed. There shouldn't be any difference in this between both methods.

The script is run when the image is built and any changes resulting from the script become part of the image.

The config map is mounted to pod and script is run when pod is started.

7.13.5.2. Using install.sh to execute custom scripts

Use this option when you want the script to run each time a pod is started after building the image.

As mentioned above, with both options the script is run each time a pod is started

Choose this option when standalone-openshift.xml includes replacement XML comments (<!-- ##REPLACEME## --> that should be replaced at runtime.

Mentioned above, placeholders should be already replaced. I think it can be removed.