Machine Config

Machine Config Operator Documentation

Creating a Machine Configuration File

1. Base64 encode the content for inclusion in a MachineConfig:

   echo -n "mysecretvalue" | base64
   

2. Place the encoded value after base64, in the MachineConfig (the base64 string bXlzZWNyZXR2YWx1ZQ== decodes to mysecretvalue):

   apiVersion: machineconfiguration.openshift.io/v1
   kind: MachineConfig
   metadata:
     name: 99-worker-example
     labels:
       machineconfiguration.openshift.io/role: worker
   spec:
     config:
       ignition:
         version: 3.5.0
       storage:
         files:
         - path: /etc/file.conf
           mode: 0644
           overwrite: true
           contents:
             source: data:text/plain;charset=utf-8;base64,bXlzZWNyZXR2YWx1ZQ==
   

3. Apply:

   Warning

   Applying a MachineConfig that changes file content, systemd units, or other non-SSH configuration will cause the Machine Config Operator to drain and reboot every node in the target pool. Ensure the cluster has sufficient capacity. To defer the reboot, pause the pool first: oc patch mcp worker --type merge -p '{"spec":{"paused":true}}'. Unpause after: oc patch mcp worker --type merge -p '{"spec":{"paused":false}}'.

   oc apply -f 99-worker-example.yaml
   

Use a File

base64 -w0 myfile.txt

CONTENT=$(base64 -w0 /path/to/myfile.conf)

cat <<EOF
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: 99-worker-myfile
spec:
  config:
    ignition:
      version: 3.5.0
    storage:
      files:
      - path: /etc/myfile.conf
        mode: 0644
        overwrite: true
        contents:
          source: data:text/plain;base64,${CONTENT}
EOF

To decode/verify:

echo "$CONTENT" | base64 -d

Creating a Machine Configuration File with Butane

Butane transpiles human-readable configs into MachineConfig resources, avoiding manual base64 encoding.

1. Install Butane:

   curl -LO https://mirror.openshift.com/pub/openshift-v4/clients/butane/latest/butane
   chmod +x butane
   sudo mv butane /usr/local/bin/
   

2. Write a Butane config — create 99-worker-example.bu:

   variant: openshift
   version: 4.22.0  # Must match your OCP minor version (e.g., 4.23.0 for OCP 4.23)
   metadata:
     name: 99-worker-example
     labels:
       machineconfiguration.openshift.io/role: worker
   storage:
       files:
         - path: /etc/file.conf
           mode: 0644
           overwrite: true
           contents:
             inline: |
               mysecretvalue
   

3. Transpile to MachineConfig:

   butane 99-worker-example.bu -o 99-worker-example.yaml
   

4. Apply:

   oc apply -f 99-worker-example.yaml
   

Using a Local File

Instead of inline, reference a local file:

variant: openshift
version: 4.22.0  # Must match your OCP minor version
metadata:
  name: 99-worker-example
  labels:
    machineconfiguration.openshift.io/role: worker
storage:
  files:
    - path: /etc/file.conf
      mode: 0644
      overwrite: true
      contents:
        local: file.conf

butane 99-worker-example.bu --files-dir . -o 99-worker-example.yaml