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Add section on pause containers for pods (#534)

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Jim Galasyn
2018-03-01 12:53:41 -08:00
parent 7b0afccc80
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@@ -95,20 +95,20 @@ persist the state of UCP. These are the UCP services running on manager nodes:
| ucp-metrics | Used to collect and process metrics for a node, like the disk space available. |
| ucp-proxy | A TLS proxy. It allows secure access to the local Docker Engine to UCP components. |
| ucp-swarm-manager | Used to provide backwards-compatibility with Docker Swarm. |
| ucp-kubelet | The kubernetes node agent running on every node, which is responsible for running kubernetes pods, reporting the health of the node, and monitoring resource usage. |
| ucp-kubelet | The Kubernetes node agent running on every node, which is responsible for running Kubernetes pods, reporting the health of the node, and monitoring resource usage. |
| ucp-kube-apiserver | A master component that serves the Kubernetes API. It persists its state in `etcd` directly, and all other components communicate with API server directly. |
| ucp-kube-controller-manager | A master component that manages the desired state of controllers and other Kubernetes objects. It monitors the API server and performs background tasks when needed. |
| ucp-kube-proxy | The networking proxy running on every node, which enables pods to contact Kubernetes services and other pods, via cluster IP addresses. |
| ucp-kube-scheduler | A master component that handles scheduling of pods. It communicates with the API server only to obtain workloads that need to be scheduled. |
| k8s_ucp-kubedns | The main Kubernetes DNS Service, used by pods to [resolve service names](https://v1-8.docs.kubernetes.io/docs/concepts/services-networking/dns-pod-service/). Part of the `kube-dns` deployment. Runs on one manager node only. Provides service discovery for Kubernetes services and pods. A set of three containers deployed via Kubernetes as a single pod. |
| k8s_POD_kube-dns | "Pause" container for the `kube-dns` pod. By default, this container is hidden, but you can see it by running `docker ps -a`. |
| k8s_ucp-kube-compose | A custom kubernetes resource component that's responsible for translating Compose files into Kubernetes constructs. Part of the `compose` deployment. Runs on one manager node only. |
| k8s_POD_compose | "Pause" container for the Compose pod. By default, this container is hidden, but you can see it by running `docker ps -a`. |
| k8s_calico-kube-controllers | A cluster-scoped Kubernetes controller used to coordinate calico networking. Runs on one manager node only. |
| k8s_POD_calico-kube-controllers | "Pause" container for the `calico-kube-controllers` pod. By default, this container is hidden, but you can see it by running `docker ps -a`. |
| k8s_POD_kube-dns | Pause container for the `kube-dns` pod. |
| k8s_ucp-kube-compose | A custom Kubernetes resource component that's responsible for translating Compose files into Kubernetes constructs. Part of the `compose` deployment. Runs on one manager node only. |
| k8s_POD_compose | Pause container for the `compose` pod. |
| k8s_calico-kube-controllers | A cluster-scoped Kubernetes controller used to coordinate Calico networking. Runs on one manager node only. |
| k8s_POD_calico-kube-controllers | Pause container for the `calico-kube-controllers` pod. |
| k8s_install-cni_calico-node | A container that's responsible for installing the Calico CNI plugin binaries and configuration on each host. Part of the `calico-node` daemonset. Runs on all nodes. |
| k8s_calico-node | The Calico node agent, which coordinates networking fabric according to the cluster-wide Calico configuration. Part of the `calico-node` daemonset. Runs on all nodes. Configure the CNI plugin by using the `--cni-installer-url` flag. If this flag isn't set, UCP uses Calico as the default CNI plugin. |
| k8s_POD_calico-node | "Pause" container for the Calico-node pod. By default, this container is hidden, but you can see it by running `docker ps -a`. |
| k8s_POD_calico-node | Pause container for the `calico-node` pod. |
| k8s_ucp-kubedns-sidecar | Health checking and metrics daemon of the Kubernetes DNS Service. Part of the `kube-dns` deployment. Runs on one manager node only. |
| k8s_ucp-dnsmasq-nanny | A dnsmasq instance used in the Kubernetes DNS Service. Part of the `kube-dns` deployment. Runs on one manager node only. |
@@ -123,11 +123,31 @@ services running on worker nodes:
| ucp-dsinfo | Docker system information collection script to assist with troubleshooting |
| ucp-reconcile | When ucp-agent detects that the node is not running the right UCP components, it starts the ucp-reconcile container to converge the node to its desired state. It is expected for the ucp-reconcile container to remain in an exited state when the node is healthy. |
| ucp-proxy | A TLS proxy. It allows secure access to the local Docker Engine to UCP components |
| ucp-kubelet | The kubernetes node agent running on every node, which is responsible for running Kubernetes pods, reporting the health of the node, and monitoring resource usage |
| ucp-kubelet | The Kubernetes node agent running on every node, which is responsible for running Kubernetes pods, reporting the health of the node, and monitoring resource usage |
| ucp-kube-proxy | The networking proxy running on every node, which enables pods to contact Kubernetes services and other pods, via cluster IP addresses |
| k8s_install-cni_calico-node | A container that's responsible for installing the Calico CNI plugin binaries and configuration on each host. Part of the `calico-node` daemonset. Runs on all nodes. |
| k8s_calico-node | The Calico node agent, which coordinates networking fabric according to the cluster-wide Calico configuration. Part of the `calico-node` daemonset. Runs on all nodes. |
| k8s_POD_calico-node | "Pause" container for the Calico-node pod. By default, this container is hidden, but you can see it by running `docker ps -a`. |
| k8s_POD_calico-node | Pause container for the `calico-node` pod. |
## Pause containers
Every pod in Kubernetes has a _pause_ container, which is an "empty" container
that bootstraps the pod to establish all of the namespaces. Pause containers
hold the cgroups, reservations, and namespaces of a pod before its individual
containers are created. The pause container's image is always present, so the
allocation of the pod's resources is instantaneous.
By default, pause containers are hidden, but you can see them by running
`docker ps -a`.
```
docker ps -a | grep -I pause
8c9707885bf6 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_calico-kube-controllers-559f6948dc-5c84l_kube-system_d00e5130-1bf4-11e8-b426-0242ac110011_0
258da23abbf5 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_kube-dns-6d46d84946-tqpzr_kube-system_d63acec6-1bf4-11e8-b426-0242ac110011_0
2e27b5d31a06 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_compose-698cf787f9-dxs29_kube-system_d5866b3c-1bf4-11e8-b426-0242ac110011_0
5d96dff73458 dockereng/ucp-pause:3.0.0-6d332d3 "/pause" 47 hours ago Up 47 hours k8s_POD_calico-node-4fjgv_kube-system_d043a0ea-1bf4-11e8-b426-0242ac110011_0
```
## Volumes used by UCP