We want to use systemd as cgroup driver for docker and kubelet, let's see how to achieve that.
Configure docker
After you install and start docker, by default it will use cgroupfs as the cgroup driver, check by running:
docker info | grep Cgroup Cgroup Driver: cgroupfs
Edit /usr/lib/systemd/system/docker.service file:
ExecStart=/usr/bin/dockerd --exec-opt native.cgroupdriver=systemd
Then reload daemon and restart docker
systemctl daemon-reload systemctl restart docker
Verify the change
docker info | grep Cgroup Cgroup Driver: systemd
Configure kubelet
Currently, the kubelet cannot automatically detects the cgroup driver used by the CRI runtime, but the value of --cgroup-driver must match the cgroup driver used by the CRI runtime to ensure the health of the kubelet.
Note: interesting thing is kubeadm init now can automatically detect and set kubelet with the same cgroup driver as docker (I use version 1.13.x).
There is a file: /var/lib/kubelet/kubeadm-flags.env, that kubeadm init and kubeadm join generates at runtime, populating the KUBELET_KUBEADM_ARGS variable dynamically, in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf you can see it:
you will see systemd resides in /var/lib/kubelet/kubeadm-flags.env:
KUBELET_KUBEADM_ARGS=--cgroup-driver=systemd --network-plugin=cni --pod-infra-container-image=k8s.gcr.io/pause:3.1
Anyway let's see how to do the configuration manually. After install kubelet, go to edit /etc/systemd/system/kubelet.service.d/10-kubeadm.conf file, add this line:
Environment="KUBELET_CGROUP_ARGS=--cgroup-driver=systemd"
Append $KUBELET_CGROUP_ARGS at end of ExecStart=/usr/bin/kubelet statement:
Then when you complete kubeadm init, verify the change:
ps aux | grep kubelet root 19864 4.5 0.6 2326996 104192 ? Ssl 01:21 32:49 /usr/bin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --config=/var/lib/kubelet/config.yaml --cgroup-driver=systemd --network-plugin=cni --pod-infra-container-image=k8s.gcr.io/pause:3.1 --cgroup-driver=systemd
You see, there are 2 --cgroup-driver=systemd options, so I think manually configure kubelet service file is needless.