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Upgrading OpenShift configs

Occasionally, changes are made to OpenShift Butane configs (those that specify variant: openshift) that break backward compatibility. While this is not a concern for running machines, since Ignition only runs one time during first boot, it is a concern for those who maintain configuration files. This document serves to detail each of the breaking changes and tries to provide some reasoning for the change. This does not cover all of the changes to the spec - just those that need to be considered when migrating from one version to the next.

  1. Upgrading OpenShift configs
    1. From Version 4.11.0 to 4.12.0
    2. From Version 4.10.0 to 4.11.0
    3. From Version 4.9.0 to 4.10.0
      1. Resource compression
    4. From Version 4.8.0 to 4.9.0
    5. From rhcos Version 0.1.0 to openshift Version 4.8.0
      1. MachineConfig generation
      2. Removed config fields
      3. MachineConfig metadata fields
      4. MCO settings
      5. FIPS configuration for LUKS

From Version 4.11.0 to 4.12.0

There are no breaking changes between versions 4.11.0 and 4.12.0 of the openshift configuration specification. Any valid 4.11.0 configuration can be updated to a 4.12.0 configuration by changing the version string in the config.

From Version 4.10.0 to 4.11.0

There are no breaking changes between versions 4.10.0 and 4.11.0 of the openshift configuration specification. Any valid 4.10.0 configuration can be updated to a 4.11.0 configuration by changing the version string in the config.

From Version 4.9.0 to 4.10.0

There are no breaking changes between versions 4.9.0 and 4.10.0 of the openshift configuration specification. Any valid 4.9.0 configuration can be updated to a 4.10.0 configuration by changing the version string in the config.

Resource compression

Resource compression, which was disabled in all openshift specs in Butane 0.12.1, is re-introduced in this spec version. The compression field can be set to gzip to decompress gzip-compressed resources. In addition, Butane may automatically compress resources specified with inline or local.

variant: openshift
version: 4.10.0
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: config-openshift
storage:
  files:
    - path: /opt/file2
      contents:
        source: data:;base64,H4sIAAAAAAAC/zSQQY4bMQwE7/OKfsBgXpHccs0DGKntEJBIWSINP3+htfcmQECxq/74ZIeOlR3Vm08sDUhnnChuiyUYOSFVh66idgebxonFiuoHNVf3imAfPqFWtGpNC2SgyT+fBOONJrrcTSBNHykX8DcOmnZIRdf9eNJU+olH6oL5ipkVfHEWDQl1Q7YmvfgbreswXbpPfTN1gC9QULx3r/42eKTEBfzaTMkgdObkx1btmByT/2mVUwNqeHrLERLEc7uCaxFFW/tpRDBxy7tKHLYXYchUiZwX8PtVOIK5S1rASxEWCZQcWiUkYG4Y07XS4jzWjqWGkm3INoffblpUULk492/3tnfITqQVXJ+02a/jKwAA//+jjAk6wQEAAA==
        compression: gzip
      mode: 0644

From Version 4.8.0 to 4.9.0

There are no functionality changes between versions 4.8.0 and 4.9.0 of the openshift configuration specification. Any valid 4.8.0 configuration can be updated to a 4.9.0 configuration by changing the version string in the config.

From rhcos Version 0.1.0 to openshift Version 4.8.0

The new openshift config variant is intended to work both on the OpenShift Container Platform with RHEL CoreOS, and on OKD with Fedora CoreOS. The rhcos variant is no longer accepted by Butane.

The openshift 4.8.0 specification is not backward-compatible with the rhcos 0.1.0 specification. It adds new mandatory metadata fields and removes certain Ignition config fields. In addition, openshift configs are transpiled to an OpenShift MachineConfig rather than an Ignition config by default. A valid rhcos 0.1.0 configuration can be updated to an openshift 4.8.0 configuration by changing the variant and version strings and then correcting any errors reported during transpilation.

The following is a list of breaking changes and notable new features.

MachineConfig generation

By default, Butane transpiles an openshift Butane config into an OpenShift MachineConfig. Butane produces an Ignition config if the -r or --raw option is specified on the Butane command line.

Removed config fields

The config no longer allows certain Ignition config fields that are rejected or discouraged by the OpenShift Machine Config Operator.

In the storage section, directories and links are removed, along with append in files. Local file trees referenced in trees must not contain symlinks.

In the passwd section, groups is removed. All fields in users are removed except for name (which must be set to core) and ssh_authorized_keys.

MachineConfig metadata fields

The config gained a new top-level metadata section containing metadata for the generated MachineConfig. The mandatory name field specifies a name for the Kubernetes MachineConfig resource. The labels field specifies a map of key-value pairs to be applied to the MachineConfig resource as Kubernetes labels. The machineconfiguration.openshift.io/role label is required.

The metadata section is ignored when generating a raw Ignition config using the -r or --raw option.

variant: openshift
version: 4.8.0
metadata:
  name: minimal-config
  labels:
    machineconfiguration.openshift.io/role: worker

MCO settings

The config gained a new top-level openshift section specifying configuration for the Machine Config Operator. The extensions field lists RHCOS extension modules to be installed on the node. The fips field enables FIPS mode when set to true. The kernel_arguments field specifies a list of arguments to be added to the kernel command line. The kernel_type field can be set to realtime to use the real-time kernel on the node.

Fields in the openshift section are not included in a raw Ignition config generated using the -r or --raw option.

variant: openshift
version: 4.8.0
metadata:
  name: config-openshift
  labels:
    machineconfiguration.openshift.io/role: worker
openshift:
  extensions:
    - usbguard
  fips: true
  kernel_arguments:
    - console=ttyS1,115200
  kernel_type: realtime

FIPS configuration for LUKS

When the fips field in the openshift section is set to true, LUKS volumes specified in the config (but not in any referenced configs) are configured to use a cipher compatible with FIPS 140-2. This cipher is applied to LUKS volumes specified in the luks subsections of the storage and boot_device sections.

variant: openshift
version: 4.8.0
metadata:
  name: fips-luks
  labels:
    machineconfiguration.openshift.io/role: worker
openshift:
  fips: true
boot_device:
  luks:
    tpm2: true