Merge pull request #13300 from chrisnegus/create-modify-images-4.0

Did 3 assembly, 21 mods for new 4.0 image content

Author: bmcelvee

images/s2i-flow.png

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+// Module included in the following assemblies:
+// * assembly/openshift_images
+
+[id='containers-about_{context}']
+= What is a container?
+
+The basic units of {product-title} applications are called _containers_.
+link:https://access.redhat.com/articles/1353593[Linux container technologies]
+are lightweight mechanisms for isolating running processes so that they are
+limited to interacting with only their designated resources.
+The word "container" is defined as a specific running or paused instance of a container image.
+
+Many application instances can be running in containers on a single host without
+visibility into each others' processes, files, network, and so on. Typically,
+each container provides a single service (often called a "micro-service"), such
+as a web server or a database, though containers can be used for arbitrary
+workloads.
+
+The Linux kernel has been incorporating capabilities for container technologies
+for years. The Docker project developed a convenient
+management interface for Linux containers on a host.
+More recently, the link:https://github.com/opencontainers/[Open Container Initiative]
+has developed open standards for container formats and container runtimes.
+{product-title} and
+Kubernetes add the ability to orchestrate OCI- and Docker-formatted containers across
+multi-host installations.
+
+Though you do not directly interact with container runtimes when using
+{product-title}, understanding their capabilities and terminology is
+important for understanding their role in {product-title} and how your
+applications function inside of containers.
+
+Tools such as link:https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux_atomic_host/7/html-single/managing_containers/#using_podman_to_work_with_containers[podman] can be used to replace `docker` command-line
+tools for running and managing containers directly.
+Using `podman`, you can experiment with containers separately from {product-title}.

modules/containers-about.adoc

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+// Module included in the following assemblies:
+// * assembly/openshift_images
+
+[id='image-id-about_{context}']
+= What is a container image id?
+
+A container image id is a SHA (Secure Hash Algorithm) code that can be used to pull an image.
+A SHA image ID cannot change. A specific SHA identifier always references the exact same container image content.
+Here is an example:
+
+----
+registry.access.redhat.com/openshift3/jenkins-2-rhel7@sha256:a7ca0569fb2b04f424043e44f8ab1c836acdd943d87701dcf143021ee66ad0a6
+----