Red Hat SummitChapter 1. Understanding image mode for RHEL with MicroShift
You can embed MicroShift into an operating system image using image mode for Red Hat Enterprise Linux (RHEL).
1.1. About image mode for Red Hat Enterprise Linux (RHEL)
By using image mode for RHEL, you can use the same tools and techniques for the operating system that you use with application containers. Image mode for RHEL is a deployment method that uses a container-native approach to build, deploy, and manage the operating system as a rhel-bootc image.
- This container image uses standard OCI or Docker containers as a transport and delivery format for base operating system updates.
- A bootc image includes a Linux kernel that is used to start the operating system.
- By using bootc containers, developers, operations administrators, and solution providers can all use the same container-native tools and techniques.
Image mode for RHEL splits the creation and installation of software changes into two steps: one on a build system and one on a running target system.
- In the build-system step, a Podman build inspects the RPM files available for installation, determines any dependencies, and creates an ordered list of chained steps to complete. Along with any other system configuration steps taking place, the end result is a new operating system available to install.
- In the running-target-system step, a bootc update downloads, unpacks, and prepares the new operating system to be started alongside the currently running system. Local configuration changes are carried forward to the new operating system. These changes take effect only when the system is restarted and the new operating system image replaces the previously running one.
1.2. Preparing for bootc image building
Use the image builder tool to compose customized MicroShift bootc images optimized for edge deployments. You can run a MicroShift node with your applications on a image mode for RHEL virtual machine for development and testing first, then use your whole solution in edge production environments.
Use the following RHEL documentation to understand the full details of using image mode for RHEL:
Follow the instructions at the following link:
For offline or disconnected configurations, embed all container image dependencies as part of the system image. When container images are downloaded without being embedded into the system image, CRI-O wipes them off during unclean shutdowns, such as when a power loss occurs. In this case, you can only restore those container images when the system is online.
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