90 lines
3.5 KiB
Markdown
90 lines
3.5 KiB
Markdown
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---
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reviewers:
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- derekwaynecarr
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- mikedanese
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- thockin
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title: Namespaces
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---
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Kubernetes supports multiple virtual clusters backed by the same physical cluster.
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These virtual clusters are called namespaces.
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## When to Use Multiple Namespaces
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Namespaces are intended for use in environments with many users spread across multiple
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teams, or projects. For clusters with a few to tens of users, you should not
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need to create or think about namespaces at all. Start using namespaces when you
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need the features they provide.
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Namespaces provide a scope for names. Names of resources need to be unique within a namespace, but not across namespaces.
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Namespaces are a way to divide cluster resources between multiple users (via [resource quota](/docs/concepts/policy/resource-quotas/)).
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In future versions of Kubernetes, objects in the same namespace will have the same
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access control policies by default.
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It is not necessary to use multiple namespaces just to separate slightly different
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resources, such as different versions of the same software: use [labels](/docs/user-guide/labels) to distinguish
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resources within the same namespace.
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## Working with Namespaces
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Creation and deletion of namespaces are described in the [Admin Guide documentation
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for namespaces](/docs/admin/namespaces).
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### Viewing namespaces
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You can list the current namespaces in a cluster using:
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```shell
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$ kubectl get namespaces
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NAME STATUS AGE
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default Active 1d
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kube-system Active 1d
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kube-public Active 1d
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```
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Kubernetes starts with three initial namespaces:
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* `default` The default namespace for objects with no other namespace
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* `kube-system` The namespace for objects created by the Kubernetes system
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* `kube-public` The namespace is created automatically and readable by all users (including those not authenticated). This namespace is mostly reserved for cluster usage, in case that some resources should be visible and readable publicly throughout the whole cluster. The public aspect of this namespace is only a convention, not a requirement.
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### Setting the namespace for a request
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To temporarily set the namespace for a request, use the `--namespace` flag.
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For example:
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```shell
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$ kubectl --namespace=<insert-namespace-name-here> run nginx --image=nginx
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$ kubectl --namespace=<insert-namespace-name-here> get pods
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```
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### Setting the namespace preference
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You can permanently save the namespace for all subsequent kubectl commands in that
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context.
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```shell
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$ kubectl config set-context $(kubectl config current-context) --namespace=<insert-namespace-name-here>
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# Validate it
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$ kubectl config view | grep namespace:
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```
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## Namespaces and DNS
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When you create a [Service](/docs/user-guide/services), it creates a corresponding [DNS entry](/docs/concepts/services-networking/dns-pod-service/).
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This entry is of the form `<service-name>.<namespace-name>.svc.cluster.local`, which means
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that if a container just uses `<service-name>`, it will resolve to the service which
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is local to a namespace. This is useful for using the same configuration across
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multiple namespaces such as Development, Staging and Production. If you want to reach
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across namespaces, you need to use the fully qualified domain name (FQDN).
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## Not All Objects are in a Namespace
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Most Kubernetes resources (e.g. pods, services, replication controllers, and others) are
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in some namespaces. However namespace resources are not themselves in a namespace.
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And low-level resources, such as [nodes](/docs/admin/node) and
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persistentVolumes, are not in any namespace.
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