upgrade

• Upgrades the following components

• APi Server

• Controller Manager
• Scheduler
• KubeProxy
• CoreDNS

• Etcd

• kubeadm updates the components of only the node in which it is running, not all the components of the cluster

• kubeadm does not upgrade kubelet. It must be upgraded manually
• The version shown in kubectl get no is the version of the kubelet of each node

Master nodes

• Control Plane

# upgrade kubeadm cli
apt-get upgrade -y "kubeadm=1.21.0-00"
kubeadm version

# check which versions are available to upgrade to and validate whether your current cluster is upgradeable
kubeadm upgrade plan

# upgrade cluster to a specified version
kubeadm upgrade apply "1.21.0"

• Kubelet

# Drain pods in the node
kubectl drain "master-node" --ignore-daemonsets

# upgrade kubeadm, kubelet and kubectl
apt-get upgrade -y "kubelet=1.21.0=00"
apt-get upgrade -y "kubectl=1.21.0=00"
systemctl daemon-reload
systemctl restart kubelet

# Uncodon the drained node
kubectl uncordon "master-node"

Worker nodes

• Kubelet

# Drain node (must be run from the master node!)
kubectl drain "worker-node" --ignore-daemonsets

# upgrade kubeadm cli
apt-get upgrade -y "kubeadm=1.21.0-00"

# upgrade commands for the node (kubelet version)
kubeadm upgrade node

# upgrade kubelet and kubectl
apt-get upgrade -y "kubelet=1.21.0=00"
apt-get upgrade -y "kubectl=1.21.0=00"
systemctl daemon-reload
systemctl restart kubelet

# Uncodon the drained node (must be run from the master node!)
kubectl uncordon "worker-node"