67 lines
2.1 KiB
Markdown
67 lines
2.1 KiB
Markdown
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---
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reviewers:
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- mikedanese
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- thockin
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title: Container Environment Variables
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content_template: templates/concept
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---
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{{% capture overview %}}
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This page describes the resources available to Containers in the Container environment.
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{{< toc >}}
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{{% capture body %}}
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## Container environment
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The Kubernetes Container environment provides several important resources to Containers:
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* A filesystem, which is a combination of an [image](/docs/concepts/containers/images/) and one or more [volumes](/docs/concepts/storage/volumes/).
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* Information about the Container itself.
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* Information about other objects in the cluster.
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### Container information
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The *hostname* of a Container is the name of the Pod in which the Container is running.
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It is available through the `hostname` command or the
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[`gethostname`](http://man7.org/linux/man-pages/man2/gethostname.2.html)
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function call in libc.
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The Pod name and namespace are available as environment variables through the
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[downward API](/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/).
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User defined environment variables from the Pod definition are also available to the Container,
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as are any environment variables specified statically in the Docker image.
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### Cluster information
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A list of all services that were running when a Container was created is available to that Container as environment variables.
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Those environment variables match the syntax of Docker links.
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For a service named *foo* that maps to a Container named *bar*,
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the following variables are defined:
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```shell
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FOO_SERVICE_HOST=<the host the service is running on>
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FOO_SERVICE_PORT=<the port the service is running on>
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```
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Services have dedicated IP addresses and are available to the Container via DNS,
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if [DNS addon](http://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/dns/) is enabled.
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{{% capture whatsnext %}}
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* Learn more about [Container lifecycle hooks](/docs/concepts/containers/container-lifecycle-hooks/).
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* Get hands-on experience
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[attaching handlers to Container lifecycle events](/docs/tasks/configure-pod-container/attach-handler-lifecycle-event/).
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{{% /capture %}}
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