Chapter 3. Using configuration snippets

If you want to configure one or two settings, such as adding subject alternative names (SANs), you can use the /etc/microshift/config.d/ configuration directory to drop in configuration snippet YAML files. You must restart MicroShift for new configurations to apply.

To return to previous values, you can delete a configuration snippet and restart MicroShift.

At runtime, the YAML files inside /etc/microshift/config.d are merged into the existing MicroShift configuration, whether that configuration is a result of default values or a user-created config.yaml file. You do not need to create a config.yaml file to use a configuration snippet.

Files in the snippet directory are sorted in lexicographical order and run sequentially. You can use numerical prefixes for snippets so that each is read in the order you want. The last-read file takes precedence when there is more than one YAML for the same parameter.

Lists, or arrays, are not merged, they are overwritten. For example, you can replace a SAN or list of SANs by creating an additional snippet for the same field that is read after the first:

If you want to add a value to an existing list, you can add it to an existing snippet. For example, to add hostZ to an existing list of SANs, edit the snippet you have instead of creating a new one:

apiServer:
  subjectAltNames:
    - host1
    - host2
    - hostZ

apiServer:
  subjectAltNames:
    - host1
    - host2
    - hostZ

apiServer:
  subjectAltNames:
    - host1
    - host2
    - hostZ

apiServer:
  subjectAltNames:
    - host1
    - host2
    - hostZ

Objects are merged together when you use a configuration snippet.

apiServer:
  advertiseAddress: "microshift-example"

apiServer:
  advertiseAddress: "microshift-example"

apiServer:
  auditLog:
    maxFileAge: 12

apiServer:
  auditLog:
    maxFileAge: 12

apiServer:
  advertiseAddress: "microshift-example"
  auditLog:
    maxFileAge: 12

apiServer:
  advertiseAddress: "microshift-example"
  auditLog:
    maxFileAge: 12

In this example, the values of both advertiseAddress and auditLog.maxFileAge fields merge into the configuration, but only the c.com and d.com subjectAltNames values are retained. This happens because the numbering in the filename indicates that the c.com and d.com values are higher priority.

apiServer:
  advertiseAddress: "microshift-example"

apiServer:
  advertiseAddress: "microshift-example"

apiServer:
  auditLog:
    maxFileAge: 12

apiServer:
  auditLog:
    maxFileAge: 12

apiServer:
  subjectAltNames:
    - a.com
    - b.com

apiServer:
  subjectAltNames:
    - a.com
    - b.com

apiServer:
  subjectAltNames:
    - c.com
    - d.com

apiServer:
  subjectAltNames:
    - c.com
    - d.com

apiServer:
  advertiseAddress: "microshift-example"
  auditLog:
    maxFileAge: 12
  subjectAltNames:
    - c.com
    - d.com

apiServer:
  advertiseAddress: "microshift-example"
  auditLog:
    maxFileAge: 12
  subjectAltNames:
    - c.com
    - d.com