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Applying template to Namespaces topic and moving to Tasks. (#2925) 

* Applying template to Namespaces topic and moving to Tasks.

* update links
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Ianeta Hutchinson 2017-08-01 02:34:55 -07:00 committed by Andrew Chen
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docs/tasks/administer-cluster/namespaces.md
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@ -5,42 +5,20 @@ assignees:
title: Share a Cluster with Namespaces
---
A Namespace is a mechanism to partition resources created by users into
a logically named group.
{% capture overview %}
This page shows how to view, work in, and delete namespaces. The page also shows how to use Kubernetes namespaces to subdivide your cluster.
{% endcapture %}
## Motivation
{% capture prerequisites %}
* Have an [existing Kubernetes cluster](/docs/getting-started-guides/).
* Have a basic understanding of Kubernetes _[Pods](/docs/concepts/workloads/pods/pod/)_, _[Services](/docs/concepts/services-networking/service/)_, and _[Deployments](/docs/concepts/workloads/controllers/deployment/)_.
{% endcapture %}
A single cluster should be able to satisfy the needs of multiple users or groups of users (henceforth a 'user community').
Each user community wants to be able to work in isolation from other communities.
Each user community has its own:
1. resources (pods, services, replication controllers, etc.)
2. policies (who can or cannot perform actions in their community)
3. constraints (this community is allowed this much quota, etc.)
A cluster operator may create a Namespace for each unique user community.
The Namespace provides a unique scope for:
1. named resources (to avoid basic naming collisions)
2. delegated management authority to trusted users
3. ability to limit community resource consumption
## Use cases
1. As a cluster operator, I want to support multiple user communities on a single cluster.
2. As a cluster operator, I want to delegate authority to partitions of the cluster to trusted users
in those communities.
3. As a cluster operator, I want to limit the amount of resources each community can consume in order
to limit the impact to other communities using the cluster.
4. As a cluster user, I want to interact with resources that are pertinent to my user community in
isolation of what other user communities are doing on the cluster.
{% capture steps %}
## Viewing namespaces
You can list the current namespaces in a cluster using:
1. List the current namespaces in a cluster using:
```shell
$ kubectl get namespaces
@ -64,16 +42,16 @@ Or you can get detailed information with:
```shell
$ kubectl describe namespaces <name>
Name: default
Labels: <none>
Status: Active
Name: default
Labels: <none>
Status: Active
No resource quota.
Resource Limits
Type Resource Min Max Default
---- -------- --- --- ---
Container cpu - - 100m
Type Resource Min Max Default
---- -------- --- --- ---
Container cpu - - 100m
```
Note that these details show both resource quota (if present) as well as resource limit ranges.
@ -95,7 +73,7 @@ See the [design doc](https://git.k8s.io/community/contributors/design-proposals/
## Creating a new namespace
To create a new namespace, first create a new YAML file called `my-namespace.yaml` with the contents:
1. Create a new YAML file called `my-namespace.yaml` with the contents:
```yaml
apiVersion: v1
@ -116,15 +94,9 @@ There's an optional field `finalizers`, which allows observables to purge resour
More information on `finalizers` can be found in the namespace [design doc](https://git.k8s.io/community/contributors/design-proposals/namespaces.md#finalizers).
### Working in namespaces
See [Setting the namespace for a request](/docs/user-guide/namespaces/#setting-the-namespace-for-a-request)
and [Setting the namespace preference](/docs/user-guide/namespaces/#setting-the-namespace-preference).
## Deleting a namespace
You can delete a namespace with
1. Delete a namespace with
```shell
$ kubectl delete namespaces <insert-some-namespace-name>
@ -134,16 +106,246 @@ $ kubectl delete namespaces <insert-some-namespace-name>
This delete is asynchronous, so for a time you will see the namespace in the `Terminating` state.
## Namespaces and DNS
## Subdividing your cluster using Kubernetes namespaces
When you create a [Service](/docs/user-guide/services), it creates a corresponding [DNS entry](/docs/admin/dns).
1. Understand the default namespace
By default, a Kubernetes cluster will instantiate a default namespace when provisioning the cluster to hold the default set of Pods,
Services, and Deployments used by the cluster.
Assuming you have a fresh cluster, you can introspect the available namespace's by doing the following:
```shell
$ kubectl get namespaces
NAME STATUS AGE
default Active 13m
```
2. Create new namespaces
For this exercise, we will create two additional Kubernetes namespaces to hold our content.
In a scenario where an organization is using a shared Kubernetes cluster for development and production use cases:
The development team would like to maintain a space in the cluster where they can get a view on the list of Pods, Services, and Deployments
they use to build and run their application. In this space, Kubernetes resources come and go, and the restrictions on who can or cannot modify resources
are relaxed to enable agile development.
The operations team would like to maintain a space in the cluster where they can enforce strict procedures on who can or cannot manipulate the set of
Pods, Services, and Deployments that run the production site.
One pattern this organization could follow is to partition the Kubernetes cluster into two namespaces: development and production.
Let's create two new namespaces to hold our work.
Use the file [`namespace-dev.json`](/docs/admin/namespaces/namespace-dev.json) which describes a development namespace:
{% include code.html language="json" file="namespace-dev.json" ghlink="/docs/admin/namespaces/namespace-dev.json" %}
Create the development namespace using kubectl.
```shell
$ kubectl create -f docs/admin/namespaces/namespace-dev.json
```
And then let's create the production namespace using kubectl.
```shell
$ kubectl create -f docs/admin/namespaces/namespace-prod.json
```
To be sure things are right, list all of the namespaces in our cluster.
```shell
$ kubectl get namespaces --show-labels
NAME STATUS AGE LABELS
default Active 32m <none>
development Active 29s name=development
production Active 23s name=production
```
3. Create pods in each namespace
A Kubernetes namespace provides the scope for Pods, Services, and Deployments in the cluster.
Users interacting with one namespace do not see the content in another namespace.
To demonstrate this, let's spin up a simple Deployment and Pods in the development namespace.
We first check what is the current context:
```shell
$ kubectl config view
apiVersion: v1
clusters:
- cluster:
certificate-authority-data: REDACTED
server: https://130.211.122.180
name: lithe-cocoa-92103_kubernetes
contexts:
- context:
cluster: lithe-cocoa-92103_kubernetes
user: lithe-cocoa-92103_kubernetes
name: lithe-cocoa-92103_kubernetes
current-context: lithe-cocoa-92103_kubernetes
kind: Config
preferences: {}
users:
- name: lithe-cocoa-92103_kubernetes
user:
client-certificate-data: REDACTED
client-key-data: REDACTED
token: 65rZW78y8HbwXXtSXuUw9DbP4FLjHi4b
- name: lithe-cocoa-92103_kubernetes-basic-auth
user:
password: h5M0FtUUIflBSdI7
username: admin
$ kubectl config current-context
lithe-cocoa-92103_kubernetes
```
The next step is to define a context for the kubectl client to work in each namespace. The value of "cluster" and "user" fields are copied from the current context.
```shell
$ kubectl config set-context dev --namespace=development --cluster=lithe-cocoa-92103_kubernetes --user=lithe-cocoa-92103_kubernetes
$ kubectl config set-context prod --namespace=production --cluster=lithe-cocoa-92103_kubernetes --user=lithe-cocoa-92103_kubernetes
```
The above commands provided two request contexts you can alternate against depending on what namespace you
wish to work against.
Let's switch to operate in the development namespace.
```shell
$ kubectl config use-context dev
```
You can verify your current context by doing the following:
```shell
$ kubectl config current-context
dev
```
At this point, all requests we make to the Kubernetes cluster from the command line are scoped to the development namespace.
Let's create some contents.
```shell
$ kubectl run snowflake --image=kubernetes/serve_hostname --replicas=2
```
We have just created a deployment whose replica size is 2 that is running the pod called snowflake with a basic container that just serves the hostname.
Note that `kubectl run` creates deployments only on Kubernetes cluster >= v1.2. If you are running older versions, it creates replication controllers instead.
If you want to obtain the old behavior, use `--generator=run/v1` to create replication controllers. See [`kubectl run`](/docs/user-guide/kubectl/v1.7/#run) for more details.
```shell
$ kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
snowflake 2 2 2 2 2m
$ kubectl get pods -l run=snowflake
NAME READY STATUS RESTARTS AGE
snowflake-3968820950-9dgr8 1/1 Running 0 2m
snowflake-3968820950-vgc4n 1/1 Running 0 2m
```
And this is great, developers are able to do what they want, and they do not have to worry about affecting content in the production namespace.
Let's switch to the production namespace and show how resources in one namespace are hidden from the other.
```shell
$ kubectl config use-context prod
```
The production namespace should be empty, and the following commands should return nothing.
```shell
$ kubectl get deployment
$ kubectl get pods
```
Production likes to run cattle, so let's create some cattle pods.
```shell
$ kubectl run cattle --image=kubernetes/serve_hostname --replicas=5
$ kubectl get deployment
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
cattle 5 5 5 5 10s
kubectl get pods -l run=cattle
NAME READY STATUS RESTARTS AGE
cattle-2263376956-41xy6 1/1 Running 0 34s
cattle-2263376956-kw466 1/1 Running 0 34s
cattle-2263376956-n4v97 1/1 Running 0 34s
cattle-2263376956-p5p3i 1/1 Running 0 34s
cattle-2263376956-sxpth 1/1 Running 0 34s
```
At this point, it should be clear that the resources users create in one namespace are hidden from the other namespace.
As the policy support in Kubernetes evolves, we will extend this scenario to show how you can provide different
authorization rules for each namespace.
{% endcapture %}
{% capture discussion %}
## Understanding the motivation for using namespaces
A single cluster should be able to satisfy the needs of multiple users or groups of users (henceforth a 'user community').
Kubernetes _namespaces_ help different projects, teams, or customers to share a Kubernetes cluster.
It does this by providing the following:
1. A scope for [Names](/docs/concepts/overview/working-with-objects/names/).
2. A mechanism to attach authorization and policy to a subsection of the cluster.
Use of multiple namespaces is optional.
Each user community wants to be able to work in isolation from other communities.
Each user community has its own:
1. resources (pods, services, replication controllers, etc.)
2. policies (who can or cannot perform actions in their community)
3. constraints (this community is allowed this much quota, etc.)
A cluster operator may create a Namespace for each unique user community.
The Namespace provides a unique scope for:
1. named resources (to avoid basic naming collisions)
2. delegated management authority to trusted users
3. ability to limit community resource consumption
Use cases include:
1. As a cluster operator, I want to support multiple user communities on a single cluster.
2. As a cluster operator, I want to delegate authority to partitions of the cluster to trusted users
in those communities.
3. As a cluster operator, I want to limit the amount of resources each community can consume in order
to limit the impact to other communities using the cluster.
4. As a cluster user, I want to interact with resources that are pertinent to my user community in
isolation of what other user communities are doing on the cluster.
## Understanding namespaces and DNS
When you create a [Service](/docs/concepts/services-networking/service/), it creates a corresponding [DNS entry](/docs/admin/dns).
This entry is of the form `<service-name>.<namespace-name>.svc.cluster.local`, which means
that if a container just uses `<service-name>` it will resolve to the service which
is local to a namespace. This is useful for using the same configuration across
multiple namespaces such as Development, Staging and Production. If you want to reach
across namespaces, you need to use the fully qualified domain name (FQDN).
## Design
{% endcapture %}
Details of the design of namespaces in Kubernetes, including a [detailed example](https://git.k8s.io/community/contributors/design-proposals/namespaces.md#example-openshift-origin-managing-a-kubernetes-namespace)
can be found in the [namespaces design doc](https://git.k8s.io/community/contributors/design-proposals/namespaces.md)
{% capture whatsnext %}
* Learn more about [setting the namespace preference](/docs/concepts/overview/working-with-objects/namespaces/#setting-the-namespace-preference).
* Learn more about [setting the namespace for a request](/docs/concepts/overview/working-with-objects/namespaces/#setting-the-namespace-for-a-request)
* See [namespaces design](https://github.com/kubernetes/community/blob/{{page.githubbranch}}/contributors/design-proposals/namespaces.md).
{% endcapture %}
{% include templates/task.md %}