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Copy tasks/configure-pod-container/static-pod.md and glossary word files from en/ directory.

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TAKAHASHI Shuuji
2020-08-18 10:10:52 +09:00
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content/ja/docs/reference/glossary/docker.md
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---
title: Docker
id: docker
date: 2018-04-12
full_link: https://docs.docker.com/engine/
short_description: >
Docker is a software technology providing operating-system-level virtualization also known as containers.
aka:
tags:
- fundamental
---
Docker (specifically, Docker Engine) is a software technology providing operating-system-level virtualization also known as {{< glossary_tooltip text="containers" term_id="container" >}}.
<!--more-->
Docker uses the resource isolation features of the Linux kernel such as cgroups and kernel namespaces, and a union-capable file system such as OverlayFS and others to allow independent containers to run within a single Linux instance, avoiding the overhead of starting and maintaining virtual machines (VMs).
content/ja/docs/reference/glossary/mirror-pod.md
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---
title: Mirror Pod
id: mirror-pod
date: 2019-08-06
short_description: >
An object in the API server that tracks a static pod on a kubelet.
aka:
tags:
- fundamental
---
A {{< glossary_tooltip text="pod" term_id="pod" >}} object that a kubelet uses
to represent a {{< glossary_tooltip text="static pod" term_id="static-pod" >}}
<!--more-->
When the kubelet finds a static pod in its configuration, it automatically tries to
create a Pod object on the Kubernetes API server for it. This means that the pod
will be visible on the API server, but cannot be controlled from there.
(For example, removing a mirror pod will not stop the kubelet daemon from running it).
content/ja/docs/tasks/configure-pod-container/static-pod.md
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---
reviewers:
- jsafrane
title: Create static Pods
weight: 170
content_type: task
---
<!-- overview -->
*Static Pods* are managed directly by the kubelet daemon on a specific node,
without the {{< glossary_tooltip text="API server" term_id="kube-apiserver" >}}
observing them.
Unlike Pods that are managed by the control plane (for example, a
{{< glossary_tooltip text="Deployment" term_id="deployment" >}});
instead, the kubelet watches each static Pod (and restarts it if it fails).
Static Pods are always bound to one {{< glossary_tooltip term_id="kubelet" >}} on a specific node.
The kubelet automatically tries to create a {{< glossary_tooltip text="mirror Pod" term_id="mirror-pod" >}}
on the Kubernetes API server for each static Pod.
This means that the Pods running on a node are visible on the API server,
but cannot be controlled from there.
{{< note >}}
If you are running clustered Kubernetes and are using static
Pods to run a Pod on every node, you should probably be using a
{{< glossary_tooltip text="DaemonSet" term_id="daemonset" >}}
instead.
{{< /note >}}
## {{% heading "prerequisites" %}}
{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
This page assumes you're using {{< glossary_tooltip term_id="docker" >}} to run Pods,
and that your nodes are running the Fedora operating system.
Instructions for other distributions or Kubernetes installations may vary.
<!-- steps -->
## Create a static pod {#static-pod-creation}
You can configure a static Pod with either a [file system hosted configuration file](/docs/tasks/configure-pod-container/static-pod/#configuration-files) or a [web hosted configuration file](/docs/tasks/configure-pod-container/static-pod/#pods-created-via-http).
### Filesystem-hosted static Pod manifest {#configuration-files}
Manifests are standard Pod definitions in JSON or YAML format in a specific directory. Use the `staticPodPath: <the directory>` field in the [kubelet configuration file](/docs/tasks/administer-cluster/kubelet-config-file), which periodically scans the directory and creates/deletes static Pods as YAML/JSON files appear/disappear there.
Note that the kubelet will ignore files starting with dots when scanning the specified directory.
For example, this is how to start a simple web server as a static Pod:
1. Choose a node where you want to run the static Pod. In this example, it's `my-node1`.
```shell
ssh my-node1
```
2. Choose a directory, say `/etc/kubelet.d` and place a web server Pod definition there, for example `/etc/kubelet.d/static-web.yaml`:
```shell
# Run this command on the node where kubelet is running
mkdir /etc/kubelet.d/
cat <<EOF >/etc/kubelet.d/static-web.yaml
apiVersion: v1
kind: Pod
metadata:
name: static-web
labels:
role: myrole
spec:
containers:
- name: web
image: nginx
ports:
- name: web
containerPort: 80
protocol: TCP
EOF
```
3. Configure your kubelet on the node to use this directory by running it with `--pod-manifest-path=/etc/kubelet.d/` argument. On Fedora edit `/etc/kubernetes/kubelet` to include this line:
```
KUBELET_ARGS="--cluster-dns=10.254.0.10 --cluster-domain=kube.local --pod-manifest-path=/etc/kubelet.d/"
```
or add the `staticPodPath: <the directory>` field in the [kubelet configuration file](/docs/tasks/administer-cluster/kubelet-config-file).
4. Restart the kubelet. On Fedora, you would run:
```shell
# Run this command on the node where the kubelet is running
systemctl restart kubelet
```
### Web-hosted static pod manifest {#pods-created-via-http}
Kubelet periodically downloads a file specified by `--manifest-url=<URL>` argument
and interprets it as a JSON/YAML file that contains Pod definitions.
Similar to how [filesystem-hosted manifests](#configuration-files) work, the kubelet
refetches the manifest on a schedule. If there are changes to the list of static
Pods, the kubelet applies them.
To use this approach:
1. Create a YAML file and store it on a web server so that you can pass the URL of that file to the kubelet.
```yaml
apiVersion: v1
kind: Pod
metadata:
name: static-web
labels:
role: myrole
spec:
containers:
- name: web
image: nginx
ports:
- name: web
containerPort: 80
protocol: TCP
```
2. Configure the kubelet on your selected node to use this web manifest by running it with `--manifest-url=<manifest-url>`. On Fedora, edit `/etc/kubernetes/kubelet` to include this line:
```
KUBELET_ARGS="--cluster-dns=10.254.0.10 --cluster-domain=kube.local --manifest-url=<manifest-url>"
```
3. Restart the kubelet. On Fedora, you would run:
```shell
# Run this command on the node where the kubelet is running
systemctl restart kubelet
```
## Observe static pod behavior {#behavior-of-static-pods}
When the kubelet starts, it automatically starts all defined static Pods. As you have
defined a static Pod and restarted the kubelet, the new static Pod should
already be running.
You can view running containers (including static Pods) by running (on the node):
```shell
# Run this command on the node where the kubelet is running
docker ps
```
The output might be something like:
```
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
f6d05272b57e nginx:latest "nginx" 8 minutes ago Up 8 minutes k8s_web.6f802af4_static-web-fk-node1_default_67e24ed9466ba55986d120c867395f3c_378e5f3c
```
You can see the mirror Pod on the API server:
```shell
kubectl get pods
```
```
NAME READY STATUS RESTARTS AGE
static-web-my-node1 1/1 Running 0 2m
```
{{< note >}}
Make sure the kubelet has permission to create the mirror Pod in the API server. If not, the creation request is rejected by the API server. See
[PodSecurityPolicy](/docs/concepts/policy/pod-security-policy/).
{{< /note >}}
{{< glossary_tooltip term_id="label" text="Labels" >}} from the static Pod are
propagated into the mirror Pod. You can use those labels as normal via
{{< glossary_tooltip term_id="selector" text="selectors" >}}, etc.
If you try to use `kubectl` to delete the mirror Pod from the API server,
the kubelet _doesn't_ remove the static Pod:
```shell
kubectl delete pod static-web-my-node1
```
```
pod "static-web-my-node1" deleted
```
You can see that the Pod is still running:
```shell
kubectl get pods
```
```
NAME READY STATUS RESTARTS AGE
static-web-my-node1 1/1 Running 0 12s
```
Back on your node where the kubelet is running, you can try to stop the Docker
container manually.
You'll see that, after a time, the kubelet will notice and will restart the Pod
automatically:
```shell
# Run these commands on the node where the kubelet is running
docker stop f6d05272b57e # replace with the ID of your container
sleep 20
docker ps
```
```
CONTAINER ID IMAGE COMMAND CREATED ...
5b920cbaf8b1 nginx:latest "nginx -g 'daemon of 2 seconds ago ...
```
## Dynamic addition and removal of static pods
The running kubelet periodically scans the configured directory (`/etc/kubelet.d` in our example) for changes and adds/removes Pods as files appear/disappear in this directory.
```shell
# This assumes you are using filesystem-hosted static Pod configuration
# Run these commands on the node where the kubelet is running
#
mv /etc/kubelet.d/static-web.yaml /tmp
sleep 20
docker ps
# You see that no nginx container is running
mv /tmp/static-web.yaml /etc/kubelet.d/
sleep 20
docker ps
```
```
CONTAINER ID IMAGE COMMAND CREATED ...
e7a62e3427f1 nginx:latest "nginx -g 'daemon of 27 seconds ago
```