Initial checkin from CRI-O repo

Signed-off-by: Matthew Heon <matthew.heon@gmail.com>

1 files changed, 105 insertions, 0 deletions

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+# Running CRI-O on kubernetes cluster
+
+## Switching runtime from docker to CRI-O
+
+In standard docker kubernetes cluster, kubelet is running on each node as systemd service and is taking care of communication between runtime and api service.
+It is reponsible for starting microservices pods (such as `kube-proxy`, `kubedns`, etc. - they can be different for various ways of deploying k8s) and user pods.
+Configuration of kubelet determines which runtime is used and in what way.
+
+Kubelet itself is executed in docker container (as we can see in `kubelet.service`), but, what is important, **it's not** a kubernetes pod (at least for now), 
+so we can keep kubelet running inside container (as well as directly on the host), and regardless of this, run pods in chosen runtime.
+
+Below, you can find an instruction how to switch one or more nodes on running kubernetes cluster from docker to CRI-O.
+
+### Preparing crio
+
+You must prepare and install `crio` on each node you would like to switch. Here's the list of files that must be provided:
+
+| File path                                  | Description                | Location                                            |
+|--------------------------------------------|----------------------------|-----------------------------------------------------|
+| `/etc/crio/crio.conf`                      | crio configuration         | Generated on cri-o `make install`                   |
+| `/etc/crio/seccomp.conf`                   | seccomp config             | Example stored in cri-o repository                  |
+| `/etc/containers/policy.json`              | containers policy          | Example stored in cri-o repository                  |
+| `/bin/{crio, runc}`                        | `crio` and `runc` binaries | Built from cri-o repository                         |
+| `/usr/local/libexec/crio/conmon`           | `conmon` binary            | Built from cri-o repository                         |
+| `/opt/cni/bin/{flannel, bridge,...}`       | CNI plugins binaries       | Can be built from sources `containernetworking/cni` |
+| `/etc/cni/net.d/10-mynet.conf`             | Network config             | Example stored in [README file](README.md)          |
+
+`crio` binary can be executed directly on host, inside the container or in any way.
+However, recommended way is to set it as a systemd service.
+Here's the example of unit file:
+
+```
+# cat /etc/systemd/system/crio.service
+[Unit]
+Description=CRI-O daemon
+Documentation=https://github.com/kubernetes-incubator/cri-o
+
+[Service]
+ExecStart=/bin/crio --runtime /bin/runc --log /root/crio.log --log-level debug
+Restart=always
+RestartSec=10s
+
+[Install]
+WantedBy=multi-user.target
+```
+
+### Preparing kubelet
+At first, you need to stop kubelet service working on the node:
+```
+# systemctl stop kubelet
+```
+and stop all kubelet docker containers that are still runing.
+
+```
+# docker stop $(docker ps | grep k8s_ | awk '{print $1}')
+```
+
+We have to be sure that `kubelet.service` will start after `crio.service`.
+It can be done by adding `crio.service` to `Wants=` section in `/etc/systemd/system/kubelet.service`:
+
+```
+# cat /etc/systemd/system/kubelet.service | grep Wants
+Wants=docker.socket crio.service
+```
+
+If you'd like to change the way of starting kubelet (e.g. directly on host instead of docker container), you can change it here, but, as mentioned, it's not necessary.
+
+
+Kubelet parameters are stored in `/etc/kubernetes/kubelet.env` file.
+```
+# cat /etc/kubernetes/kubelet.env | grep KUBELET_ARGS
+KUBELET_ARGS="--pod-manifest-path=/etc/kubernetes/manifests 
+--pod-infra-container-image=gcr.io/google_containers/pause-amd64:3.0 
+--cluster_dns=10.233.0.3 --cluster_domain=cluster.local 
+--resolv-conf=/etc/resolv.conf --kubeconfig=/etc/kubernetes/node-kubeconfig.yaml
+--require-kubeconfig"
+```
+
+You need to add following parameters to `KUBELET_ARGS`:
+* `--experimental-cri=true` - Use Container Runtime Interface. Will be true by default from kubernetes 1.6 release.
+* `--container-runtime=remote` - Use remote runtime with provided socket.
+* `--container-runtime-endpoint=/var/run/crio.sock` - Socket for remote runtime (default `crio` socket localization).
+* `--runtime-request-timeout=10m` - Optional but useful. Some requests, especially pulling huge images, may take longer than default (2 minutes) and will cause an error. 
+
+Kubelet is prepared now.
+
+## Flannel network
+If your cluster is using flannel network, your network configuration should be like:
+```
+# cat /etc/cni/net.d/10-mynet.conf
+{
+    "name": "mynet",
+    "type": "flannel"
+}
+```
+Then, kubelet will take parameters from `/run/flannel/subnet.env` - file generated by flannel kubelet microservice.
+
+## Starting kubelet with CRI-O
+Start crio first, then kubelet. If you created `crio` service:
+```
+# systemctl start crio
+# systemctl start kubelet
+```
+
+You can follow the progress of preparing node using `kubectl get nodes` or `kubectl get pods --all-namespaces` on kubernetes master.