mirror of https://github.com/k3s-io/k3s
153 lines
6.3 KiB
Markdown
153 lines
6.3 KiB
Markdown
# kubeconfig files
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In order to easily switch between multiple clusters, a kubeconfig file was defined. This file contains a series of authentication mechanisms and cluster connection information associated with nicknames. It also introduces the concept of a tuple of authentication information (user) and cluster connection information called a context that is also associated with a nickname.
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Multiple kubeconfig files are allowed. At runtime they are loaded and merged together along with override options specified from the command line (see rules below).
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## Related discussion
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https://github.com/GoogleCloudPlatform/kubernetes/issues/1755
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## Example kubeconfig file
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```
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apiVersion: v1
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clusters:
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- cluster:
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api-version: v1
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server: http://cow.org:8080
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name: cow-cluster
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- cluster:
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certificate-authority: path/to/my/cafile
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server: https://horse.org:4443
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name: horse-cluster
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- cluster:
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insecure-skip-tls-verify: true
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server: https://pig.org:443
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name: pig-cluster
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contexts:
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- context:
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cluster: horse-cluster
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namespace: chisel-ns
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user: green-user
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name: federal-context
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- context:
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cluster: pig-cluster
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namespace: saw-ns
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user: black-user
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name: queen-anne-context
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current-context: federal-context
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kind: Config
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preferences:
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colors: true
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users:
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- name: blue-user
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user:
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token: blue-token
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- name: green-user
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user:
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client-certificate: path/to/my/client/cert
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client-key: path/to/my/client/key
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```
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## Loading and merging rules
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The rules for loading and merging the kubeconfig files are straightforward, but there are a lot of them. The final config is built in this order:
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1. Get the kubeconfig from disk. This is done with the following hierarchy and merge rules:
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If the CommandLineLocation (the value of the `kubeconfig` command line option) is set, use this file only. No merging. Only one instance of this flag is allowed.
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Else, if EnvVarLocation (the value of $KUBECONFIG) is available, use it as a list of files that should be merged.
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Merge files together based on the following rules.
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Empty filenames are ignored. Files with non-deserializable content produced errors.
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The first file to set a particular value or map key wins and the value or map key is never changed.
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This means that the first file to set CurrentContext will have its context preserved. It also means that if two files specify a "red-user", only values from the first file's red-user are used. Even non-conflicting entries from the second file's "red-user" are discarded.
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Otherwise, use HomeDirectoryLocation (~/.kube/config) with no merging.
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1. Determine the context to use based on the first hit in this chain
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1. command line argument - the value of the `context` command line option
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1. current-context from the merged kubeconfig file
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1. Empty is allowed at this stage
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1. Determine the cluster info and user to use. At this point, we may or may not have a context. They are built based on the first hit in this chain. (run it twice, once for user, once for cluster)
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1. command line argument - `user` for user name and `cluster` for cluster name
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1. If context is present, then use the context's value
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1. Empty is allowed
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1. Determine the actual cluster info to use. At this point, we may or may not have a cluster info. Build each piece of the cluster info based on the chain (first hit wins):
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1. command line arguments - `server`, `api-version`, `certificate-authority`, and `insecure-skip-tls-verify`
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1. If cluster info is present and a value for the attribute is present, use it.
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1. If you don't have a server location, error.
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1. Determine the actual user info to use. User is built using the same rules as cluster info, EXCEPT that you can only have one authentication technique per user.
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1. Load precedence is 1) command line flag, 2) user fields from kubeconfig
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1. The command line flags are: `client-certificate`, `client-key`, `username`, `password`, and `token`.
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1. If there are two conflicting techniques, fail.
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1. For any information still missing, use default values and potentially prompt for authentication information
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## Manipulation of kubeconfig via `kubectl config <subcommand>`
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In order to more easily manipulate kubeconfig files, there are a series of subcommands to `kubectl config` to help.
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See [docs/kubectl_config.md](kubectl_config.md) for help.
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### Example
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```
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$kubectl config set-credentials myself --username=admin --password=secret
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$kubectl config set-cluster local-server --server=http://localhost:8080
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$kubectl config set-context default-context --cluster=local-server --user=myself
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$kubectl config use-context default-context
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$kubectl config set contexts.default-context.namespace the-right-prefix
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$kubectl config view
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```
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produces this output
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```
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clusters:
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local-server:
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server: http://localhost:8080
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contexts:
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default-context:
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cluster: local-server
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namespace: the-right-prefix
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user: myself
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current-context: default-context
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preferences: {}
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users:
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myself:
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username: admin
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password: secret
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```
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and a kubeconfig file that looks like this
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```
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apiVersion: v1
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clusters:
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- cluster:
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server: http://localhost:8080
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name: local-server
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contexts:
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- context:
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cluster: local-server
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namespace: the-right-prefix
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user: myself
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name: default-context
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current-context: default-context
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kind: Config
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preferences: {}
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users:
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- name: myself
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user:
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username: admin
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password: secret
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```
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#### Commands for the example file
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```
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$kubectl config set preferences.colors true
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$kubectl config set-cluster cow-cluster --server=http://cow.org:8080 --api-version=v1
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$kubectl config set-cluster horse-cluster --server=https://horse.org:4443 --certificate-authority=path/to/my/cafile
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$kubectl config set-cluster pig-cluster --server=https://pig.org:443 --insecure-skip-tls-verify=true
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$kubectl config set-credentials blue-user --token=blue-token
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$kubectl config set-credentials green-user --client-certificate=path/to/my/client/cert --client-key=path/to/my/client/key
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$kubectl config set-context queen-anne-context --cluster=pig-cluster --user=black-user --namespace=saw-ns
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$kubectl config set-context federal-context --cluster=horse-cluster --user=green-user --namespace=chisel-ns
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$kubectl config use-context federal-context
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```
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[]()
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