Set Kubelet image via kubelet.service KUBELET_IMAGE

* Write the systemd kubelet.service to use `KUBELET_IMAGE`
as the Kubelet. This provides a nice way to use systemd
dropins to temporarily override the image (e.g. during a
registry outage)

Note: Only Typhoon Kubelet images and registries are supported.

digital-ocean/container-linux/kubernetes/cl/controller.yaml

@@ -62,6 +62,7 @@ systemd:
         After=coreos-metadata.service
         Wants=rpc-statd.service
         [Service]
+        Environment=KUBELET_IMAGE=docker://quay.io/poseidon/kubelet:v1.18.2
         EnvironmentFile=/run/metadata/coreos
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/cni/net.d
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/manifests
@@ -101,7 +102,7 @@ systemd:
           --mount volume=var-log,target=/var/log \
           --volume opt-cni-bin,kind=host,source=/opt/cni/bin \
           --mount volume=opt-cni-bin,target=/opt/cni/bin \
-          docker://quay.io/poseidon/kubelet:v1.18.2 -- \
+          $${KUBELET_IMAGE} -- \
           --anonymous-auth=false \
           --authentication-token-webhook \
           --authorization-mode=Webhook \

digital-ocean/container-linux/kubernetes/cl/worker.yaml

@@ -35,6 +35,7 @@ systemd:
         After=coreos-metadata.service
         Wants=rpc-statd.service
         [Service]
+        Environment=KUBELET_IMAGE=docker://quay.io/poseidon/kubelet:v1.18.2
         EnvironmentFile=/run/metadata/coreos
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/cni/net.d
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/manifests
@@ -74,7 +75,7 @@ systemd:
           --mount volume=var-log,target=/var/log \
           --volume opt-cni-bin,kind=host,source=/opt/cni/bin \
           --mount volume=opt-cni-bin,target=/opt/cni/bin \
-          docker://quay.io/poseidon/kubelet:v1.18.2 -- \
+          $${KUBELET_IMAGE} -- \
           --anonymous-auth=false \
           --authentication-token-webhook \
           --authorization-mode=Webhook \

digital-ocean/fedora-coreos/kubernetes/fcc/controller.yaml

@@ -55,6 +55,7 @@ systemd:
         After=afterburn.service
         Wants=rpc-statd.service
         [Service]
+        Environment=KUBELET_IMAGE=quay.io/poseidon/kubelet:v1.18.2
         EnvironmentFile=/run/metadata/afterburn
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/cni/net.d
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/manifests
@@ -81,7 +82,7 @@ systemd:
           --volume /var/log:/var/log \
           --volume /var/run/lock:/var/run/lock:z \
           --volume /opt/cni/bin:/opt/cni/bin:z \
-          quay.io/poseidon/kubelet:v1.18.2 \
+          $${KUBELET_IMAGE} \
           --anonymous-auth=false \
           --authentication-token-webhook \
           --authorization-mode=Webhook \

digital-ocean/fedora-coreos/kubernetes/fcc/worker.yaml

@@ -26,6 +26,7 @@ systemd:
         After=afterburn.service
         Wants=rpc-statd.service
         [Service]
+        Environment=KUBELET_IMAGE=quay.io/poseidon/kubelet:v1.18.2
         EnvironmentFile=/run/metadata/afterburn
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/cni/net.d
         ExecStartPre=/bin/mkdir -p /etc/kubernetes/manifests
@@ -52,7 +53,7 @@ systemd:
           --volume /var/log:/var/log \
           --volume /var/run/lock:/var/run/lock:z \
           --volume /opt/cni/bin:/opt/cni/bin:z \
-          quay.io/poseidon/kubelet:v1.18.2 \
+          $${KUBELET_IMAGE} \
           --anonymous-auth=false \
           --authentication-token-webhook \
           --authorization-mode=Webhook \