docs: Add Section about Kubeconfig

Author: Jan-Schuppik

doc/02-Installation.md

@@ -70,15 +70,15 @@ All available settings can be found under [Configuration](03-Configuration.md).
 
 ## Running Icinga for Kubernetes
 
-With locally accessible kubeconfig and `config.yml` files, `icinga-kubernetes` can be executed by running:
+With locally accessible [kubeconfig](04-Kubeconfig.md) and `config.yml` files, `icinga-kubernetes` can be executed by running:
 
 ```bash
 icinga-kubernetes -config /path/to/config.yml
 ```
 
 ## Using a Container
 
-With locally accessible kubeconfig and `config.yml` files,
+With locally accessible [kubeconfig](04-Kubeconfig.md) and `config.yml` files,
 run the `icinga/icinga-kubernetes` image using a container runtime of you choice, e.g. Docker:
 
 ```bash

doc/04-Kubeconfig.md

@@ -0,0 +1,69 @@
+# Kubeconfig
+
+Kubernetes uses a configuration file, typically referred to as **kubeconfig**,
+to manage cluster access details and user credentials. It is created when you create a new cluster or
+when you create a new user for an existing cluster.
+
+## Purpose of the Kubeconfig
+
+This file enables the `kubectl` command-line tool to interact with the
+Kubernetes cluster, allowing users to perform various operations such as deploying applications, inspecting cluster
+resources, and managing cluster configurations.
+
+Like `kubectl`, Icinga for Kubernetes requires a kubeconfig file to access the Kubernetes API.
+
+## Managing Kubeconfig
+
+### Location of Kubeconfig File
+
+By default, the kubeconfig file is located at `~/.kube/config` on most systems.
+
+
+#### Changing the Location
+You can specify a different location for the kubeconfig file by setting the KUBECONFIG environment variable.
+This allows you to use a configuration file stored in another location.
+
+
+```shell
+export KUBECONFIG=/path/to/your/kubeconfig
+````
+
+### Structure of the Kubeconfig File
+
+A typical kubeconfig file is a YAML file with the following main sections:
+
+- **apiVersion:** Specifies the version of the Kubernetes API.
+- **kind:** Defines the type of Kubernetes resource being described.
+- **clusters:** Defines the clusters that kubectl can connect to.
+- **users:** Contains the authentication information for different users.
+- **contexts:** Represents a combination of a cluster, a user, and a namespace.
+- **current-context:** Indicates the default context that kubectl uses for commands.
+
+
+#### Example kubeconfig file
+
+The following example of a kubeconfig file illustrates the values that must be replaced by user-specific values.
+
+```yml
+apiVersion: v1
+kind: Config
+clusters:
+  - cluster:
+      server: https://your-cluster-api-server:8443
+      certificate-authority: /path/to/ca.crt
+    name: your-cluster
+users:
+  - name: your-user
+    user:
+      client-certificate: /path/to/client.crt
+      client-key: /path/to/client.key
+contexts:
+  - context:
+      cluster: your-cluster
+      user: your-user
+      namespace: default
+    name: your-context
+current-context: your-context
+```
+
+For a more detailed explanation of the kubeconfig file, see the [official Kubernetes documentation](https://kubernetes.io/docs/concepts/configuration/organize-cluster-access-kubeconfig/).