0bf070c33b
kata-container is not used by default even if enabling kata_containers_enabled. This updates the doc for writing how to do that.
102 lines
2.7 KiB
Markdown
102 lines
2.7 KiB
Markdown
# Kata Containers
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[Kata Containers](https://katacontainers.io) is a secure container runtime with lightweight virtual machines that supports multiple hypervisor solutions.
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## Hypervisors
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_Qemu_ is the only hypervisor supported by Kubespray.
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## Installation
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To enable Kata Containers, set the following variables:
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**k8s-cluster.yml**:
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```yaml
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container_manager: containerd
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kata_containers_enabled: true
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```
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**etcd.yml**:
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```yaml
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etcd_deployment_type: host
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```
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## Usage
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By default, runc is used for pods.
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Kubespray generates the runtimeClass kata-qemu, and it is necessary to specify it as
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the runtimeClassName of a pod spec to use Kata Containers:
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```shell
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$ kubectl get runtimeclass
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NAME HANDLER AGE
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kata-qemu kata-qemu 3m34s
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$
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$ cat nginx.yaml
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apiVersion: v1
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kind: Pod
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metadata:
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name: mypod
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spec:
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runtimeClassName: kata-qemu
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containers:
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- name: nginx
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image: nginx:1.14.2
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$
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$ kubectl apply -f nginx.yaml
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```
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## Configuration
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### Recommended : Pod Overhead
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[Pod Overhead](https://kubernetes.io/docs/concepts/configuration/pod-overhead/) is a feature for accounting for the resources consumed by the Runtime Class used by the Pod.
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When this feature is enabled, Kubernetes will count the fixed amount of CPU and memory set in the configuration as used by the virtual machine and not by the containers running in the Pod.
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Pod Overhead is mandatory if you run Pods with Kata Containers that use [resources limits](https://kubernetes.io/docs/concepts/configuration/manage-resources-containers/#requests-and-limits).
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**Set cgroup driver**:
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To enable Pod Overhead feature you have to configure Kubelet with the appropriate cgroup driver, using the following configuration:
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`cgroupfs` works best:
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```yaml
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kubelet_cgroup_driver: cgroupfs
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```
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... but when using `cgroups v2` (see <https://www.redhat.com/en/blog/world-domination-cgroups-rhel-8-welcome-cgroups-v2>) you can use systemd as well:
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```yaml
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kubelet_cgroup_driver: systemd
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```
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**Qemu hypervisor configuration**:
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The configuration for the Qemu hypervisor uses the following values:
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```yaml
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kata_containers_qemu_overhead: true
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kata_containers_qemu_overhead_fixed_cpu: 10m
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kata_containers_qemu_overhead_fixed_memory: 290Mi
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```
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### Optional : Select Kata Containers version
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Optionally you can select the Kata Containers release version to be installed. The available releases are published in [GitHub](https://github.com/kata-containers/kata-containers/releases).
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```yaml
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kata_containers_version: 2.2.2
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```
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### Optional : Debug
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Debug is disabled by default for all the components of Kata Containers. You can change this behaviour with the following configuration:
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```yaml
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kata_containers_qemu_debug: 'false'
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```
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