kubeadm init

kubeadm init to bootstrap a Kubernetes control-plane node

• kubeadm init --pod-network-cidr=10.244.0.0/16
• kubeadm init --ignore-preflight-errors=All

Dependencies:

• kubeadm config images pull
• apt install socat conntrack
• snap install kubectl --classic
• snap install kubelet --classic && snap start kubelet.daemon
• crictl-tools

Play-with-K8s

• kubeadm init --apiserver-advertise-address $(hostname -i) --pod-network-cidr 10.5.0.0/16
• kubectl apply -f https://raw.githubusercontent.com/cloudnativelabs/kube-router/master/daemonset/kubeadm-kuberouter.yaml

With errors

kubeadm init --pod-network-cidr=10.244.0.0/16
W0419 17:17:35.020389   29884 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io 
kubeproxy.config.k8s.io]
[init] Using Kubernetes version: v1.18.2
[preflight] Running pre-flight checks
[preflight] WARNING: Couldn't create the interface used for talking to the container runtime: docker is required for container runtime: exec: "docker": 
executable file not found in $PATH
	[WARNING FileExisting-socat]: socat not found in system path 
	[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
 error execution phase preflight: [preflight] Some fatal errors occurred: 
	[ERROR NumCPU]: the number of available CPUs 1 is less than the required 2
	[ERROR FileExisting-crictl]: crictl not found in system path
	[ERROR FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables does not exist
	[ERROR FileExisting-conntrack]: conntrack not found in system path
	[ERROR KubeletVersion]: couldn't get kubelet version: cannot execute 'kubelet --version': executable file not found in $PATH
 [preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
 To see the stack trace of this error execute with --v=5 or higher

[ERROR NumCPU]: the number of available CPUs 1 is less than the required 2

• If using multipass: Multipass: Modify number of CPU on an existing instance

kubeadm init --pod-network-cidr=10.244.0.0/16 --ignore-preflight-errors=All

With errors: docker not installed

kubeadm init

 W0823 18:18:03.055636   30827 configset.go:202] WARNING: kubeadm cannot validate component configs for API groups [kubelet.config.k8s.io kubeproxy.config.k8s.io]
 [init] Using Kubernetes version: v1.18.8
 [preflight] Running pre-flight checks
 [preflight] WARNING: Couldn't create the interface used for talking to the container runtime: docker is required for 
 container runtime: exec: "docker": executable file not found in $PATH
 	[WARNING FileExisting-socat]: socat not found in system path 
	[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
 error execution phase preflight: [preflight] Some fatal errors occurred:
	[ERROR NumCPU]: the number of available CPUs 1 is less than the required 2
	[ERROR FileExisting-crictl]: crictl not found in system path
	[ERROR FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables does 
 not exist
	[ERROR FileContent--proc-sys-net-ipv4-ip_forward]: /proc/sys/net/ipv4/ip_forward contents are not set to 1
	[ERROR FileExisting-conntrack]: conntrack not found in system path
 [preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
 To see the stack trace of this error execute with --v=5 or higher

v1.25.4

[init] Using Kubernetes version: v1.25.4
[preflight] Running pre-flight checks
W1203 13:22:13.289185  159684 checks.go:1019] [preflight] WARNING: Couldn't create the interface used for talking to the container 
runtime: crictl is required by the container runtime: executable file not found in $PATH 
	[WARNING SystemVerification]: missing optional cgroups: blkio
	[WARNING Service-Kubelet]: kubelet service is not enabled, please run 'systemctl enable kubelet.service'
error execution phase preflight: [preflight] Some fatal errors occurred:
	[ERROR FileContent--proc-sys-net-bridge-bridge-nf-call-iptables]: /proc/sys/net/bridge/bridge-nf-call-iptables does not exist
	[ERROR FileContent--proc-sys-net-ipv4-ip_forward]: /proc/sys/net/ipv4/ip_forward contents are not set to 1
	[ERROR FileExisting-crictl]: crictl not found in system path
	[ERROR KubeletVersion]: couldn't get kubelet version: cannot execute 'kubelet --version': executable file not found in $PATH
[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
To see the stack trace of this error execute with --v=5 or higher

Related terms

• conntrack (command) Netfilter (apt install conntrack)
• socat: apt install socat
• kubeadm config images pull
• Kubernetes (snap install)
• kubeadm join
• kind: ClusterConfiguration
• snap install kubelet --classic
• /etc/kubernetes/manifests/

See also

• Play with Kubernetes: kubeadm init
• kubeadm [ init | token | config | reset | version | upgrade | join | --help ]
• Kubernetes installation, Deploy EKS cluster using Terraform, Create your first EKS Cluster using AWS Management Console, kubeadm init, eksctl create cluster