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Commit c306367

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sohankunkerkarhaircommander
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docs: Update KubeletConfigDropinDir doc information
Signed-off-by: Sohan Kunkerkar <sohank2602@gmail.com> Signed-off-by: Peter Hunt <pehunt@redhat.com>
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‎content/en/docs/reference/node/kubelet-config-directory-merging.md

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---
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content_type: "reference"
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title: Kubelet Configuration Directory Merging
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weight: 50
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---
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When using the kubelet's `--config-dir` flag to specify a drop-in directory for
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configuration, there is some specific behavior on how different types are
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merged.
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Here are some examples of how different data types behave during configuration merging:
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### Structure Fields
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There are two types of structure fields in a YAML structure: singular (or a
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scalar type) and embedded (structures that contain scalar types).
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The configuration merging process handles the overriding of singular and embedded struct fields to create a resulting kubelet configuration.
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For instance, you may want a baseline kubelet configuration for all nodes, but you may want to customize the `address` and `authorization` fields.
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This can be done as follows:
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Main kubelet configuration file contents:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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port: 20250
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authorization:
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mode: Webhook
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webhook:
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cacheAuthorizedTTL: "5m"
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cacheUnauthorizedTTL: "30s"
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serializeImagePulls: false
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address: "192.168.0.1"
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```
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Contents of a file in `--config-dir` directory:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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authorization:
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mode: AlwaysAllow
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webhook:
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cacheAuthorizedTTL: "8m"
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cacheUnauthorizedTTL: "45s"
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address: "192.168.0.8"
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```
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The resulting configuration will be as follows:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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port: 20250
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serializeImagePulls: false
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authorization:
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mode: AlwaysAllow
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webhook:
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cacheAuthorizedTTL: "8m"
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cacheUnauthorizedTTL: "45s"
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address: "192.168.0.8"
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```
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### Lists
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You can overide the slices/lists values of the kubelet configuration.
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However, the entire list gets overridden during the merging process.
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For example, you can override the `clusterDNS` list as follows:
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Main kubelet configuration file contents:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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port: 20250
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serializeImagePulls: false
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clusterDNS:
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- "192.168.0.9"
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- "192.168.0.8"
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```
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Contents of a file in `--config-dir` directory:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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clusterDNS:
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- "192.168.0.2"
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- "192.168.0.3"
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- "192.168.0.5"
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```
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The resulting configuration will be as follows:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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port: 20250
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serializeImagePulls: false
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clusterDNS:
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- "192.168.0.2"
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- "192.168.0.3"
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- "192.168.0.5"
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```
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### Maps, including Nested Structures
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Individual fields in maps, regardless of their value types (boolean, string, etc.), can be selectively overridden.
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However, for `map[string][]string`, the entire list associated with a specific field gets overridden.
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Let's understand this better with an example, particularly on fields like `featureGates` and `staticPodURLHeader`:
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Main kubelet configuration file contents:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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port: 20250
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serializeImagePulls: false
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featureGates:
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AllAlpha: false
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MemoryQoS: true
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staticPodURLHeader:
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kubelet-api-support:
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- "Authorization: 234APSDFA"
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- "X-Custom-Header: 123"
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custom-static-pod:
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- "Authorization: 223EWRWER"
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- "X-Custom-Header: 456"
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```
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Contents of a file in `--config-dir` directory:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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featureGates:
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MemoryQoS: false
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KubeletTracing: true
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DynamicResourceAllocation: true
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staticPodURLHeader:
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custom-static-pod:
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- "Authorization: 223EWRWER"
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- "X-Custom-Header: 345"
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```
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The resulting configuration will be as follows:
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```yaml
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apiVersion: kubelet.config.k8s.io/v1beta1
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kind: KubeletConfiguration
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port: 20250
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serializeImagePulls: false
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featureGates:
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AllAlpha: false
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MemoryQoS: false
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KubeletTracing: true
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DynamicResourceAllocation: true
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staticPodURLHeader:
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kubelet-api-support:
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- "Authorization: 234APSDFA"
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- "X-Custom-Header: 123"
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custom-static-pod:
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- "Authorization: 223EWRWER"
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- "X-Custom-Header: 345"
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```

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