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Created December 7, 2019 19:12
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How to init k8s cluster on Gentoo
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howto-k8s.md

Install Stuff

Emerge kubelet, kubeadm, kubectl, all the same version. For some reason, Gentoo stablized kubelet and kubectl but not kubeadm.

I'm using Calico, so also emerge net-misc/calico-cni-plugin.

Correct Stuff

Gentoo's kubelet package includes a systemd unit file that is 100% not going to work. We need to override it; place the following at /etc/systemd/system/kubelet.service:

# Note: This dropin only works with kubeadm and kubelet v1.11+
[Service]
Environment="KUBELET_KUBECONFIG_ARGS=--bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf"
Environment="KUBELET_CONFIG_ARGS=--config=/var/lib/kubelet/config.yaml"
# This is a file that "kubeadm init" and "kubeadm join" generate at runtime, populating the KUBELET_KUBEADM_ARGS variable dynamically
EnvironmentFile=-/var/lib/kubelet/kubeadm-flags.env
# This is a file that the user can use for overrides of the kubelet args as a last resort. Preferably, the user should use
# the .NodeRegistration.KubeletExtraArgs object in the configuration files instead. KUBELET_EXTRA_ARGS should be sourced from this file.
EnvironmentFile=-/etc/sysconfig/kubelet
ExecStart=
ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_CONFIG_ARGS $KUBELET_KUBEADM_ARGS $KUBELET_EXTRA_ARGS

Basically, the systemd unit Gentoo uses.

  1. does not supply the correct flags to kubelet
  2. does not pick up the correct flags that kubeadm will write out for it.

Init the Cluster

I'm doing Calico, as that's all I know how to do.

For Calico, you need to choose a network (CIDR) to operate your k8s cluster in. I'm choosing 10.128.0.0/10; the default 192.168.0.0/16 overlaps with my home LAN, so it will not work.

Download the Calico YAML file somewhere:

wget https://docs.projectcalico.org/v3.10/manifests/calico.yaml

Edit it; find 192.168.0.0/16 and replace it with whatever CIDR you desire to use.

The next steps are very quick, and we need to fulfill a race-condition to succeed; timing is important. You need two terminals, one to run kubeadm, one to correct for its shortcomings.

Terminal one: kubeadm init --pod-network-cidr=10.128.0.0/10 (again, change the CIDR here to whatever you want to use)

Terminal two:

kubeadm will start kubelet, but will do so prior to writing the CA cert to disk. If you journalctl -u kubelet, you should see it fail:

Dec 07 13:55:53 host kubelet[3012]: F1207 13:55:53.439570    3012 server.go:249] unable to load client CA file /etc/kubernetes/pki/ca.crt: open /etc/kubernetes/pki/ca.crt: no such file or directory
Dec 07 13:55:53 host systemd[1]: kubelet.service: Main process exited, code=exited, status=255/EXCEPTION
Dec 07 13:55:53 host systemd[1]: kubelet.service: Failed with result 'exit-code'.

Just restart it; by the time you get the command in, that file will be there: systemctl start kubelet Copy the config: cp /etc/kubernetes/admin.conf ~/.kube/config Apply Calico: kubectl apply -f calico.yaml Read the logs to verify that kubelet looks happy-ish, and follow the rest of the Calico tutorial as normal.

@ccokee
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ccokee commented Dec 8, 2020

Do you have etcd daemon running?

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