# CRI-O [CRI-O] is a lightweight container runtime for Kubernetes. Kubespray supports basic functionality for using CRI-O as the default container runtime in a cluster. * Kubernetes supports CRI-O on v1.11.1 or later. * etcd: configure either kubeadm managed etcd or host deployment _To use the CRI-O container runtime set the following variables:_ ## all/all.yml ```yaml download_container: false skip_downloads: false etcd_kubeadm_enabled: true ``` ## k8s_cluster/k8s_cluster.yml ```yaml container_manager: crio ``` ## etcd.yml ```yaml etcd_deployment_type: host # optionally and mutually exclusive with etcd_kubeadm_enabled ``` ## all/crio.yml Enable docker hub registry mirrors ```yaml crio_registries: - prefix: docker.io insecure: false blocked: false location: registry-1.docker.io mirrors: - location: 192.168.100.100:5000 insecure: true - location: mirror.gcr.io insecure: false ``` ## Note about pids_limit For heavily mult-threaded workloads like databases, the default of 1024 for pids-limit is too low. This parameter controls not just the number of processes but also the amount of threads (since a thread is technically a process with shared memory). See [cri-o#1921] In order to increase the default `pids_limit` for cri-o based deployments you need to set the `crio_pids_limit` for your `k8s_cluster` ansible group or per node depending on the use case. ```yaml crio_pids_limit: 4096 ``` [CRI-O]: https://cri-o.io/ [cri-o#1921]: https://github.com/cri-o/cri-o/issues/1921 ## Note about user namespaces CRI-O has support for user namespaces. This feature is optional and can be enabled by setting the following two variables. ```yaml crio_runtimes: - name: runc path: /usr/bin/runc type: oci root: /run/runc allowed_annotations: - "io.kubernetes.cri-o.userns-mode" crio_remap_enable: true ``` The `allowed_annotations` configures `crio.conf` accordingly. The `crio_remap_enable` configures the `/etc/subuid` and `/etc/subgid` files to add an entry for the **containers** user. By default, 16M uids and gids are reserved for user namespaces (256 pods * 65536 uids/gids) at the end of the uid/gid space.