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This commit is contained in:
Tim Bannister
2022-01-17 21:38:22 +00:00
parent 62905feb8e
commit 000536e52c
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content/en/docs/setup/production-environment/tools/kubeadm/high-availability.md
+212 -208
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@@ -12,9 +12,9 @@ This page explains two different approaches to setting up a highly available Kub
cluster using kubeadm: cluster using kubeadm:
- With stacked control plane nodes. This approach requires less infrastructure. The etcd members - With stacked control plane nodes. This approach requires less infrastructure. The etcd members
and control plane nodes are co-located. and control plane nodes are co-located.
- With an external etcd cluster. This approach requires more infrastructure. The - With an external etcd cluster. This approach requires more infrastructure. The
control plane nodes and etcd members are separated. control plane nodes and etcd members are separated.
Before proceeding, you should carefully consider which approach best meets the needs of your applications Before proceeding, you should carefully consider which approach best meets the needs of your applications
and environment. [This comparison topic](/docs/setup/production-environment/tools/kubeadm/ha-topology/) outlines the advantages and disadvantages of each. and environment. [This comparison topic](/docs/setup/production-environment/tools/kubeadm/ha-topology/) outlines the advantages and disadvantages of each.
@@ -60,147 +60,146 @@ There are many configurations for load balancers. The following example is only
option. Your cluster requirements may need a different configuration. option. Your cluster requirements may need a different configuration.
{{< /note >}} {{< /note >}}
1. Create a kube-apiserver load balancer with a name that resolves to DNS. 1. Create a kube-apiserver load balancer with a name that resolves to DNS.
- In a cloud environment you should place your control plane nodes behind a TCP - In a cloud environment you should place your control plane nodes behind a TCP
forwarding load balancer. This load balancer distributes traffic to all forwarding load balancer. This load balancer distributes traffic to all
healthy control plane nodes in its target list. The health check for healthy control plane nodes in its target list. The health check for
an apiserver is a TCP check on the port the kube-apiserver listens on an apiserver is a TCP check on the port the kube-apiserver listens on
(default value `:6443`). (default value `:6443`).
- It is not recommended to use an IP address directly in a cloud environment. - It is not recommended to use an IP address directly in a cloud environment.
- The load balancer must be able to communicate with all control plane nodes - The load balancer must be able to communicate with all control plane nodes
on the apiserver port. It must also allow incoming traffic on its on the apiserver port. It must also allow incoming traffic on its
listening port. listening port.
- Make sure the address of the load balancer always matches - Make sure the address of the load balancer always matches
the address of kubeadm's `ControlPlaneEndpoint`. the address of kubeadm's `ControlPlaneEndpoint`.
- Read the [Options for Software Load Balancing](https://git.k8s.io/kubeadm/docs/ha-considerations.md#options-for-software-load-balancing) - Read the [Options for Software Load Balancing](https://git.k8s.io/kubeadm/docs/ha-considerations.md#options-for-software-load-balancing)
guide for more details. guide for more details.
1. Add the first control plane nodes to the load balancer and test the 1. Add the first control plane node to the load balancer, and test the
connection: connection:
```sh ```shell
nc -v LOAD_BALANCER_IP PORT nc -v <LOAD_BALANCER_IP> <PORT>
``` ```
- A connection refused error is expected because the apiserver is not yet A connection refused error is expected because the API server is not yet
running. A timeout, however, means the load balancer cannot communicate running. A timeout, however, means the load balancer cannot communicate
with the control plane node. If a timeout occurs, reconfigure the load with the control plane node. If a timeout occurs, reconfigure the load
balancer to communicate with the control plane node. balancer to communicate with the control plane node.
1. Add the remaining control plane nodes to the load balancer target group. 1. Add the remaining control plane nodes to the load balancer target group.
## Stacked control plane and etcd nodes ## Stacked control plane and etcd nodes
### Steps for the first control plane node ### Steps for the first control plane node
1. Initialize the control plane: 1. Initialize the control plane:
```sh ```sh
sudo kubeadm init --control-plane-endpoint "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT" --upload-certs sudo kubeadm init --control-plane-endpoint "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT" --upload-certs
``` ```
- You can use the `--kubernetes-version` flag to set the Kubernetes version to use. - You can use the `--kubernetes-version` flag to set the Kubernetes version to use.
It is recommended that the versions of kubeadm, kubelet, kubectl and Kubernetes match. It is recommended that the versions of kubeadm, kubelet, kubectl and Kubernetes match.
- The `--control-plane-endpoint` flag should be set to the address or DNS and port of the load balancer. - The `--control-plane-endpoint` flag should be set to the address or DNS and port of the load balancer.
- The `--upload-certs` flag is used to upload the certificates that should be shared - The `--upload-certs` flag is used to upload the certificates that should be shared
across all the control-plane instances to the cluster. If instead, you prefer to copy certs across across all the control-plane instances to the cluster. If instead, you prefer to copy certs across
control-plane nodes manually or using automation tools, please remove this flag and refer to [Manual control-plane nodes manually or using automation tools, please remove this flag and refer to [Manual
certificate distribution](#manual-certs) section below. certificate distribution](#manual-certs) section below.
{{< note >}} {{< note >}}
The `kubeadm init` flags `--config` and `--certificate-key` cannot be mixed, therefore if you want The `kubeadm init` flags `--config` and `--certificate-key` cannot be mixed, therefore if you want
to use the [kubeadm configuration](/docs/reference/config-api/kubeadm-config.v1beta3/) to use the [kubeadm configuration](/docs/reference/config-api/kubeadm-config.v1beta3/)
you must add the `certificateKey` field in the appropriate config locations you must add the `certificateKey` field in the appropriate config locations
(under `InitConfiguration` and `JoinConfiguration: controlPlane`). (under `InitConfiguration` and `JoinConfiguration: controlPlane`).
{{< /note >}} {{< /note >}}
{{< note >}} {{< note >}}
Some CNI network plugins require additional configuration, for example specifying the pod IP CIDR, while others do not. Some CNI network plugins require additional configuration, for example specifying the pod IP CIDR, while others do not.
See the [CNI network documentation](/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#pod-network). See the [CNI network documentation](/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#pod-network).
To add a pod CIDR pass the flag `--pod-network-cidr`, or if you are using a kubeadm configuration file To add a pod CIDR pass the flag `--pod-network-cidr`, or if you are using a kubeadm configuration file
set the `podSubnet` field under the `networking` object of `ClusterConfiguration`. set the `podSubnet` field under the `networking` object of `ClusterConfiguration`.
{{< /note >}} {{< /note >}}
- The output looks similar to: The output looks similar to:
```sh ```sh
... ...
You can now join any number of control-plane node by running the following command on each as a root: You can now join any number of control-plane node by running the following command on each as a root:
kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866 --control-plane --certificate-key f8902e114ef118304e561c3ecd4d0b543adc226b7a07f675f56564185ffe0c07 kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866 --control-plane --certificate-key f8902e114ef118304e561c3ecd4d0b543adc226b7a07f675f56564185ffe0c07
Please note that the certificate-key gives access to cluster sensitive data, keep it secret! Please note that the certificate-key gives access to cluster sensitive data, keep it secret!
As a safeguard, uploaded-certs will be deleted in two hours; If necessary, you can use kubeadm init phase upload-certs to reload certs afterward. As a safeguard, uploaded-certs will be deleted in two hours; If necessary, you can use kubeadm init phase upload-certs to reload certs afterward.
Then you can join any number of worker nodes by running the following on each as root: Then you can join any number of worker nodes by running the following on each as root:
kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866 kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866
``` ```
- Copy this output to a text file. You will need it later to join control plane and worker nodes to the cluster. - Copy this output to a text file. You will need it later to join control plane and worker nodes to
- When `--upload-certs` is used with `kubeadm init`, the certificates of the primary control plane the cluster.
are encrypted and uploaded in the `kubeadm-certs` Secret. - When `--upload-certs` is used with `kubeadm init`, the certificates of the primary control plane
- To re-upload the certificates and generate a new decryption key, use the following command on a control plane are encrypted and uploaded in the `kubeadm-certs` Secret.
node that is already joined to the cluster: - To re-upload the certificates and generate a new decryption key, use the following command on a
control plane
node that is already joined to the cluster:
```sh ```sh
sudo kubeadm init phase upload-certs --upload-certs sudo kubeadm init phase upload-certs --upload-certs
``` ```
- You can also specify a custom `--certificate-key` during `init` that can later be used by `join`. - You can also specify a custom `--certificate-key` during `init` that can later be used by `join`.
To generate such a key you can use the following command: To generate such a key you can use the following command:
```sh ```sh
kubeadm certs certificate-key kubeadm certs certificate-key
``` ```
{{< note >}} {{< note >}}
The `kubeadm-certs` Secret and decryption key expire after two hours. The `kubeadm-certs` Secret and decryption key expire after two hours.
{{< /note >}} {{< /note >}}
{{< caution >}} {{< caution >}}
As stated in the command output, the certificate key gives access to cluster sensitive data, keep it secret! As stated in the command output, the certificate key gives access to cluster sensitive data, keep it secret!
{{< /caution >}} {{< /caution >}}
1. Apply the CNI plugin of your choice: 1. Apply the CNI plugin of your choice:
[Follow these instructions](/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#pod-network) [Follow these instructions](/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#pod-network)
to install the CNI provider. Make sure the configuration corresponds to the Pod CIDR specified in the kubeadm configuration file if applicable. to install the CNI provider. Make sure the configuration corresponds to the Pod CIDR specified in the
kubeadm configuration file (if applicable).
{{< note >}} {{< note >}}
You must pick a network plugin that suits your use case and deploy it before you move on to next step. You must pick a network plugin that suits your use case and deploy it before you move on to next step.
If you don't do this, you will not be able to launch your cluster properly. If you don't do this, you will not be able to launch your cluster properly.
{{< /note >}} {{< /note >}}
1. Type the following and watch the pods of the control plane components get started: 1. Type the following and watch the pods of the control plane components get started:
```sh ```sh
kubectl get pod -n kube-system -w kubectl get pod -n kube-system -w
``` ```
### Steps for the rest of the control plane nodes ### Steps for the rest of the control plane nodes
{{< note >}}
Since kubeadm version 1.15 you can join multiple control-plane nodes in parallel.
Prior to this version, you must join new control plane nodes sequentially, only after
the first node has finished initializing.
{{< /note >}}
For each additional control plane node you should: For each additional control plane node you should:
1. Execute the join command that was previously given to you by the `kubeadm init` output on the first node. 1. Execute the join command that was previously given to you by the `kubeadm init` output on the first node.
It should look something like this: It should look something like this:
```sh ```sh
sudo kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866 --control-plane --certificate-key f8902e114ef118304e561c3ecd4d0b543adc226b7a07f675f56564185ffe0c07 sudo kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866 --control-plane --certificate-key f8902e114ef118304e561c3ecd4d0b543adc226b7a07f675f56564185ffe0c07
``` ```
- The `--control-plane` flag tells `kubeadm join` to create a new control plane. - The `--control-plane` flag tells `kubeadm join` to create a new control plane.
- The `--certificate-key ...` will cause the control plane certificates to be downloaded - The `--certificate-key ...` will cause the control plane certificates to be downloaded
from the `kubeadm-certs` Secret in the cluster and be decrypted using the given key. from the `kubeadm-certs` Secret in the cluster and be decrypted using the given key.
You can join multiple control-plane nodes in parallel.
## External etcd nodes ## External etcd nodes
@@ -210,60 +209,64 @@ in the kubeadm config file.
### Set up the etcd cluster ### Set up the etcd cluster
1. Follow [these instructions](/docs/setup/production-environment/tools/kubeadm/setup-ha-etcd-with-kubeadm/) to set up the etcd cluster. 1. Follow these [instructions](/docs/setup/production-environment/tools/kubeadm/setup-ha-etcd-with-kubeadm/) to set up the etcd cluster.
1. Setup SSH as described [here](#manual-certs). 1. Setup SSH as described [here](#manual-certs).
1. Copy the following files from any etcd node in the cluster to the first control plane node: 1. Copy the following files from any etcd node in the cluster to the first control plane node:
```sh ```sh
export CONTROL_PLANE="ubuntu@10.0.0.7" export CONTROL_PLANE="ubuntu@10.0.0.7"
scp /etc/kubernetes/pki/etcd/ca.crt "${CONTROL_PLANE}": scp /etc/kubernetes/pki/etcd/ca.crt "${CONTROL_PLANE}":
scp /etc/kubernetes/pki/apiserver-etcd-client.crt "${CONTROL_PLANE}": scp /etc/kubernetes/pki/apiserver-etcd-client.crt "${CONTROL_PLANE}":
scp /etc/kubernetes/pki/apiserver-etcd-client.key "${CONTROL_PLANE}": scp /etc/kubernetes/pki/apiserver-etcd-client.key "${CONTROL_PLANE}":
``` ```
- Replace the value of `CONTROL_PLANE` with the `user@host` of the first control-plane node. - Replace the value of `CONTROL_PLANE` with the `user@host` of the first control-plane node.
### Set up the first control plane node ### Set up the first control plane node
1. Create a file called `kubeadm-config.yaml` with the following contents: 1. Create a file called `kubeadm-config.yaml` with the following contents:
apiVersion: kubeadm.k8s.io/v1beta3
kind: ClusterConfiguration
kubernetesVersion: stable
controlPlaneEndpoint: "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT"
etcd:
external:
endpoints:
- https://ETCD_0_IP:2379
- https://ETCD_1_IP:2379
- https://ETCD_2_IP:2379
caFile: /etc/kubernetes/pki/etcd/ca.crt
certFile: /etc/kubernetes/pki/apiserver-etcd-client.crt
keyFile: /etc/kubernetes/pki/apiserver-etcd-client.key
{{< note >}} ```yaml
The difference between stacked etcd and external etcd here is that the external etcd setup requires ---
a configuration file with the etcd endpoints under the `external` object for `etcd`. apiVersion: kubeadm.k8s.io/v1beta3
In the case of the stacked etcd topology this is managed automatically. kind: ClusterConfiguration
{{< /note >}} kubernetesVersion: stable
controlPlaneEndpoint: "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT" # change this (see below)
etcd:
external:
endpoints:
- https://ETCD_0_IP:2379 # change ETCD_0_IP appropriately
- https://ETCD_1_IP:2379 # change ETCD_1_IP appropriately
- https://ETCD_2_IP:2379 # change ETCD_2_IP appropriately
caFile: /etc/kubernetes/pki/etcd/ca.crt
certFile: /etc/kubernetes/pki/apiserver-etcd-client.crt
keyFile: /etc/kubernetes/pki/apiserver-etcd-client.key
```
- Replace the following variables in the config template with the appropriate values for your cluster: {{< note >}}
The difference between stacked etcd and external etcd here is that the external etcd setup requires
a configuration file with the etcd endpoints under the `external` object for `etcd`.
In the case of the stacked etcd topology, this is managed automatically.
{{< /note >}}
- `LOAD_BALANCER_DNS` - Replace the following variables in the config template with the appropriate values for your cluster:
- `LOAD_BALANCER_PORT`
- `ETCD_0_IP` - `LOAD_BALANCER_DNS`
- `ETCD_1_IP` - `LOAD_BALANCER_PORT`
- `ETCD_2_IP` - `ETCD_0_IP`
- `ETCD_1_IP`
- `ETCD_2_IP`
The following steps are similar to the stacked etcd setup: The following steps are similar to the stacked etcd setup:
1. Run `sudo kubeadm init --config kubeadm-config.yaml --upload-certs` on this node. 1. Run `sudo kubeadm init --config kubeadm-config.yaml --upload-certs` on this node.
1. Write the output join commands that are returned to a text file for later use. 1. Write the output join commands that are returned to a text file for later use.
1. Apply the CNI plugin of your choice. 1. Apply the CNI plugin of your choice.
{{< note >}} {{< note >}}
You must pick a network plugin that suits your use case and deploy it before you move on to next step. You must pick a network plugin that suits your use case and deploy it before you move on to next step.
@@ -276,7 +279,7 @@ The steps are the same as for the stacked etcd setup:
- Make sure the first control plane node is fully initialized. - Make sure the first control plane node is fully initialized.
- Join each control plane node with the join command you saved to a text file. It's recommended - Join each control plane node with the join command you saved to a text file. It's recommended
to join the control plane nodes one at a time. to join the control plane nodes one at a time.
- Don't forget that the decryption key from `--certificate-key` expires after two hours, by default. - Don't forget that the decryption key from `--certificate-key` expires after two hours, by default.
## Common tasks after bootstrapping control plane ## Common tasks after bootstrapping control plane
@@ -296,79 +299,80 @@ If you choose to not use `kubeadm init` with the `--upload-certs` flag this mean
you are going to have to manually copy the certificates from the primary control plane node to the you are going to have to manually copy the certificates from the primary control plane node to the
joining control plane nodes. joining control plane nodes.
There are many ways to do this. In the following example we are using `ssh` and `scp`: There are many ways to do this. The following example uses `ssh` and `scp`:
SSH is required if you want to control all nodes from a single machine. SSH is required if you want to control all nodes from a single machine.
1. Enable ssh-agent on your main device that has access to all other nodes in 1. Enable ssh-agent on your main device that has access to all other nodes in
the system: the system:
``` ```
eval $(ssh-agent) eval $(ssh-agent)
```
1. Add your SSH identity to the session:
```
ssh-add ~/.ssh/path_to_private_key
```
1. SSH between nodes to check that the connection is working correctly.
- When you SSH to any node, add the `-A` flag. This flag allows the node that you
have logged into via SSH to access the SSH agent on your PC.
```
ssh -A 10.0.0.7
```
- When using sudo on any node, make sure to preserve the environment so SSH
forwarding works:
```
sudo -E -s
```
1. After configuring SSH on all the nodes you should run the following script on the first
control plane node after running `kubeadm init`. This script will copy the certificates from
the first control plane node to the other control plane nodes:
In the following example, replace `CONTROL_PLANE_IPS` with the IP addresses of the
other control plane nodes.
```sh
USER=ubuntu # customizable
CONTROL_PLANE_IPS="10.0.0.7 10.0.0.8"
for host in ${CONTROL_PLANE_IPS}; do
scp /etc/kubernetes/pki/ca.crt "${USER}"@$host:
scp /etc/kubernetes/pki/ca.key "${USER}"@$host:
scp /etc/kubernetes/pki/sa.key "${USER}"@$host:
scp /etc/kubernetes/pki/sa.pub "${USER}"@$host:
scp /etc/kubernetes/pki/front-proxy-ca.crt "${USER}"@$host:
scp /etc/kubernetes/pki/front-proxy-ca.key "${USER}"@$host:
scp /etc/kubernetes/pki/etcd/ca.crt "${USER}"@$host:etcd-ca.crt
# Quote this line if you are using external etcd
scp /etc/kubernetes/pki/etcd/ca.key "${USER}"@$host:etcd-ca.key
done
``` ```
1. Add your SSH identity to the session: {{< caution >}}
Copy only the certificates in the above list. kubeadm will take care of generating the rest of the certificates
``` with the required SANs for the joining control-plane instances. If you copy all the certificates by mistake,
ssh-add ~/.ssh/path_to_private_key the creation of additional nodes could fail due to a lack of required SANs.
``` {{< /caution >}}
1. SSH between nodes to check that the connection is working correctly.
- When you SSH to any node, make sure to add the `-A` flag:
```
ssh -A 10.0.0.7
```
- When using sudo on any node, make sure to preserve the environment so SSH
forwarding works:
```
sudo -E -s
```
1. After configuring SSH on all the nodes you should run the following script on the first control plane node after
running `kubeadm init`. This script will copy the certificates from the first control plane node to the other
control plane nodes:
In the following example, replace `CONTROL_PLANE_IPS` with the IP addresses of the
other control plane nodes.
```sh
USER=ubuntu # customizable
CONTROL_PLANE_IPS="10.0.0.7 10.0.0.8"
for host in ${CONTROL_PLANE_IPS}; do
scp /etc/kubernetes/pki/ca.crt "${USER}"@$host:
scp /etc/kubernetes/pki/ca.key "${USER}"@$host:
scp /etc/kubernetes/pki/sa.key "${USER}"@$host:
scp /etc/kubernetes/pki/sa.pub "${USER}"@$host:
scp /etc/kubernetes/pki/front-proxy-ca.crt "${USER}"@$host:
scp /etc/kubernetes/pki/front-proxy-ca.key "${USER}"@$host:
scp /etc/kubernetes/pki/etcd/ca.crt "${USER}"@$host:etcd-ca.crt
# Quote this line if you are using external etcd
scp /etc/kubernetes/pki/etcd/ca.key "${USER}"@$host:etcd-ca.key
done
```
{{< caution >}}
Copy only the certificates in the above list. kubeadm will take care of generating the rest of the certificates
with the required SANs for the joining control-plane instances. If you copy all the certificates by mistake,
the creation of additional nodes could fail due to a lack of required SANs.
{{< /caution >}}
1. Then on each joining control plane node you have to run the following script before running `kubeadm join`. 1. Then on each joining control plane node you have to run the following script before running `kubeadm join`.
This script will move the previously copied certificates from the home directory to `/etc/kubernetes/pki`: This script will move the previously copied certificates from the home directory to `/etc/kubernetes/pki`:
```sh ```sh
USER=ubuntu # customizable USER=ubuntu # customizable
mkdir -p /etc/kubernetes/pki/etcd mkdir -p /etc/kubernetes/pki/etcd
mv /home/${USER}/ca.crt /etc/kubernetes/pki/ mv /home/${USER}/ca.crt /etc/kubernetes/pki/
mv /home/${USER}/ca.key /etc/kubernetes/pki/ mv /home/${USER}/ca.key /etc/kubernetes/pki/
mv /home/${USER}/sa.pub /etc/kubernetes/pki/ mv /home/${USER}/sa.pub /etc/kubernetes/pki/
mv /home/${USER}/sa.key /etc/kubernetes/pki/ mv /home/${USER}/sa.key /etc/kubernetes/pki/
mv /home/${USER}/front-proxy-ca.crt /etc/kubernetes/pki/ mv /home/${USER}/front-proxy-ca.crt /etc/kubernetes/pki/
mv /home/${USER}/front-proxy-ca.key /etc/kubernetes/pki/ mv /home/${USER}/front-proxy-ca.key /etc/kubernetes/pki/
mv /home/${USER}/etcd-ca.crt /etc/kubernetes/pki/etcd/ca.crt mv /home/${USER}/etcd-ca.crt /etc/kubernetes/pki/etcd/ca.crt
# Quote this line if you are using external etcd # Quote this line if you are using external etcd
mv /home/${USER}/etcd-ca.key /etc/kubernetes/pki/etcd/ca.key mv /home/${USER}/etcd-ca.key /etc/kubernetes/pki/etcd/ca.key
``` ```