kubernetes: Configuration of kubelet via file

This allows cri-containerd and docker based systems to pass the correct options
via composition of yml files, while keeping the kubelet service stanza common.

Since bind mounts are not conditional on the presence of the source we need to
create an empty file in the docker case.

Signed-off-by: Ian Campbell <ijc@docker.com>

projects/kubernetes/kube-master.yml

@@ -65,6 +65,8 @@ services:
 files:
   - path: /etc/kubernetes
     symlink: "/var/lib/kubeadm"
+  - path: /etc/kubelet.conf
+    contents: ""
   - path: /etc/sysctl.d/01-kubernetes.conf
     contents: 'net.ipv4.ip_forward = 1'
   - path: /opt/cni

projects/kubernetes/kube-node.yml

@@ -63,6 +63,8 @@ services:
 files:
   - path: /etc/kubernetes
     symlink: "/var/lib/kubeadm"
+  - path: /etc/kubelet.conf
+    contents: ""
   - path: /etc/sysctl.d/01-kubernetes.conf
     contents: 'net.ipv4.ip_forward = 1'
   - path: /opt/cni

projects/kubernetes/kubernetes/Dockerfile

@@ -45,4 +45,4 @@ WORKDIR /
 ENTRYPOINT ["/usr/bin/kubelet.sh"]
 COPY --from=build /out /
 ENV KUBECONFIG "/etc/kubernetes/admin.conf"
-LABEL org.mobyproject.config='{"binds": ["/dev:/dev", "/etc/resolv.conf:/etc/resolv.conf", "/run:/run:rshared,rbind", "/var:/var:rshared,rbind", "/var/lib/kubeadm:/etc/kubernetes"], "mounts": [{"type": "cgroup", "options": ["rw","nosuid","noexec","nodev","relatime"]}], "capabilities": ["all"], "rootfsPropagation": "shared", "pid": "host", "runtime": {"mkdir": ["/var/lib/kubeadm", "/var/lib/cni/etc", "/var/lib/cni/opt"], "mounts": [{"type": "bind", "source": "/var/lib/cni/opt", "destination": "/opt/cni", "options": ["rw", "bind"]}, {"type": "bind", "source": "/var/lib/cni/etc", "destination": "/etc/cni", "options": ["rw", "bind"]}]}}'
+LABEL org.mobyproject.config='{"binds": ["/dev:/dev", "/etc/resolv.conf:/etc/resolv.conf", "/run:/run:rshared,rbind", "/var:/var:rshared,rbind", "/var/lib/kubeadm:/etc/kubernetes", "/etc/kubelet.conf:/etc/kubelet.conf"], "mounts": [{"type": "cgroup", "options": ["rw","nosuid","noexec","nodev","relatime"]}], "capabilities": ["all"], "rootfsPropagation": "shared", "pid": "host", "runtime": {"mkdir": ["/var/lib/kubeadm", "/var/lib/cni/etc", "/var/lib/cni/opt"], "mounts": [{"type": "bind", "source": "/var/lib/cni/opt", "destination": "/opt/cni", "options": ["rw", "bind"]}, {"type": "bind", "source": "/var/lib/cni/etc", "destination": "/etc/cni", "options": ["rw", "bind"]}]}}'

projects/kubernetes/kubernetes/kubelet.sh

@@ -4,6 +4,9 @@ if [ ! -e /var/lib/cni/.opt.defaults-extracted ] ; then
     tar -xzf /root/cni.tgz -C /var/lib/cni/opt/bin
     touch /var/lib/cni/.opt.defaults-extracted
 fi
+if [ -e /etc/kubelet.conf ] ; then
+    . /etc/kubelet.conf
+fi
 until kubelet --kubeconfig=/var/lib/kubeadm/kubelet.conf \
 	      --require-kubeconfig=true \
 	      --pod-manifest-path=/var/lib/kubeadm/manifests \
@@ -15,7 +18,7 @@ until kubelet --kubeconfig=/var/lib/kubeadm/kubelet.conf \
 	      --network-plugin=cni \
 	      --cni-conf-dir=/var/lib/cni/etc/net.d \
 	      --cni-bin-dir=/var/lib/cni/opt/bin \
-	      $@; do
+	      $KUBELET_ARGS $@; do
     if [ ! -f /var/config/userdata ] ; then
 	sleep 1
     else