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kubeadm: update HA etcd guide for clarity and fix an issue

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There were a couple of reported problems with this guide:

- The introductory paragraph talks about single control plane nodes
and does not mention the different options for HA etcd. Clear the
language to reduce the confusion and cross-link to the ha-topology
page.
- The hostname / IP detection in kubeadm can end
up with values not suitable for the certificates that kubeadm
generates for all etcd instances. Ensure that the hostnames / IPs
are pinned by the user in the example script.

Side cleanup related to the dockershim removal:
- Use containerd in the setup example and don't mention docker as
a requirement.
This commit is contained in:
Lubomir I. Ivanov
2022-01-11 15:48:00 +02:00
parent aae389ad73
commit 0acf0e98ee
1 changed files with 36 additions and 16 deletions
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content/en/docs/setup/production-environment/tools/kubeadm/setup-ha-etcd-with-kubeadm.md
+36 -16
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@@ -16,19 +16,20 @@ or upgrades for such nodes. The long term plan is to empower the tool
aspects.
{{< /note >}}
Kubeadm defaults to running a single member etcd cluster in a static pod managed
by the kubelet on the control plane node. This is not a high availability setup
as the etcd cluster contains only one member and cannot sustain any members
becoming unavailable. This task walks through the process of creating a high
availability etcd cluster of three members that can be used as an external etcd
when using kubeadm to set up a kubernetes cluster.
By default, kubeadm runs a local etcd instance on each control plane node.
It is also possible to treat the etcd cluster as external and provision
etcd instances on separate hosts. The differences between the two approaches are covered in the
[Options for Highly Available topology][/docs/setup/production-environment/tools/kubeadm/ha-topology] page.
This task walks through the process of creating a high availability external
etcd cluster of three members that can be used by kubeadm during cluster creation.
## {{% heading "prerequisites" %}}
* Three hosts that can talk to each other over ports 2379 and 2380. This
* Three hosts that can talk to each other over TCP ports 2379 and 2380. This
document assumes these default ports. However, they are configurable through
the kubeadm config file.
* Each host must [have docker, kubelet, and kubeadm installed](/docs/setup/production-environment/tools/kubeadm/install-kubeadm/).
* Each host must have systemd and a bash compatible shell installed.
* Each host must [have a container runtime, kubelet, and kubeadm installed](/docs/setup/production-environment/tools/kubeadm/install-kubeadm/).
* Each host should have access to the Kubernetes container image registry (`k8s.gcr.io`) or list/pull the required etcd image using
`kubeadm config images list/pull`. This guide will setup etcd instances as
[static pods](/docs/tasks/configure-pod-container/static-pod/) managed by a kubelet.
@@ -48,6 +49,11 @@ the certificates described below; no other cryptographic tooling is required for
this example.
{{< /note >}}
{{< note >}}
The examples below use IPv4 addresses but you can also configure kubeadm, the kubelet and etcd
to use IPv6 addresses. Dual-stack is supported by some Kubernetes options, but not by etcd. For more details
on Kubernetes dual-stack support see [Dual-stack support with kubeadm](/docs/setup/production-environment/tools/kubeadm/dual-stack-support/).
{{< /note >}}
1. Configure the kubelet to be a service manager for etcd.
@@ -59,8 +65,9 @@ this example.
cat << EOF > /etc/systemd/system/kubelet.service.d/20-etcd-service-manager.conf
[Service]
ExecStart=
# Replace "systemd" with the cgroup driver of your container runtime. The default value in the kubelet is "cgroupfs".
ExecStart=/usr/bin/kubelet --address=127.0.0.1 --pod-manifest-path=/etc/kubernetes/manifests --cgroup-driver=systemd
# Replace "systemd" with the cgroup driver of your container runtime. The default value in the kubelet is "cgroupfs".
# Replace the value of "--container-runtime-endpoint" for a different container runtime if needed.
ExecStart=/usr/bin/kubelet --address=127.0.0.1 --pod-manifest-path=/etc/kubernetes/manifests --cgroup-driver=systemd --container-runtime=remote --container-runtime-endpoint=unix:///var/run/containerd/containerd.sock
Restart=always
EOF
@@ -80,21 +87,34 @@ this example.
member running on it using the following script.
```sh
# Update HOST0, HOST1, and HOST2 with the IPs or resolvable names of your hosts
# Update HOST0, HOST1 and HOST2 with the IPs of your hosts
export HOST0=10.0.0.6
export HOST1=10.0.0.7
export HOST2=10.0.0.8
# Update NAME0, NAME1 and NAME2 with the hostnames of your hosts
export NAME0="infra0"
export NAME1="infra1"
export NAME2="infra2"
# Create temp directories to store files that will end up on other hosts.
mkdir -p /tmp/${HOST0}/ /tmp/${HOST1}/ /tmp/${HOST2}/
ETCDHOSTS=(${HOST0} ${HOST1} ${HOST2})
NAMES=("infra0" "infra1" "infra2")
HOSTS=(${HOST0} ${HOST1} ${HOST2})
NAMES=(${NAME0} ${NAME1} ${NAME2})
for i in "${!ETCDHOSTS[@]}"; do
HOST=${ETCDHOSTS[$i]}
for i in "${!HOSTS[@]}"; do
HOST=${HOSTS[$i]}
NAME=${NAMES[$i]}
cat << EOF > /tmp/${HOST}/kubeadmcfg.yaml
---
apiVersion: "kubeadm.k8s.io/v1beta3"
kind: InitConfiguration
nodeRegistration:
name: ${NAME}
localAPIEndpoint:
advertiseAddress: ${HOST}
---
apiVersion: "kubeadm.k8s.io/v1beta3"
kind: ClusterConfiguration
etcd:
@@ -104,7 +124,7 @@ this example.
peerCertSANs:
- "${HOST}"
extraArgs:
initial-cluster: ${NAMES[0]}=https://${ETCDHOSTS[0]}:2380,${NAMES[1]}=https://${ETCDHOSTS[1]}:2380,${NAMES[2]}=https://${ETCDHOSTS[2]}:2380
initial-cluster: ${NAMES[0]}=https://${HOSTS[0]}:2380,${NAMES[1]}=https://${HOSTS[1]}:2380,${NAMES[2]}=https://${HOSTS[2]}:2380
initial-cluster-state: new
name: ${NAME}
listen-peer-urls: https://${HOST}:2380