Takuya Tokuda
0502832cbb
* ordering content by weight * fix weight of 'setup' contents * fix weight of 'concepts' contents * fix weight of 'tasks' contents * fix weight of 'tutorials' contents * fix weight of 'reference' contents * Revert "fix weight of 'tasks' contents" This reverts commit 4b6916bed07c92c5f9eed75fb0a7ef0244266623. * Revert "fix weight of 'tutorials' contents" This reverts commit a1f783314337b1eb40017aef47a6bf1453d8c840. * Revert "fix weight of 'setup' contents" This reverts commit 91c8de366587eed25c803f8e7d5a59005adb6025. * Revert "fix weight of 'reference' contents" This reverts commit cc95605f6a9863f8a4ffb636178c69a80d302c3e.
68 lines
2.2 KiB
Markdown
68 lines
2.2 KiB
Markdown
---
|
||
reviewers:
|
||
- mikedanese
|
||
- thockin
|
||
title: Container Environment Variables
|
||
content_template: templates/concept
|
||
weight: 20
|
||
---
|
||
|
||
{{% capture overview %}}
|
||
|
||
This page describes the resources available to Containers in the Container environment.
|
||
|
||
{{% /capture %}}
|
||
|
||
{{< toc >}}
|
||
|
||
{{% capture body %}}
|
||
|
||
## Container environment
|
||
|
||
The Kubernetes Container environment provides several important resources to Containers:
|
||
|
||
* A filesystem, which is a combination of an [image](/docs/concepts/containers/images/) and one or more [volumes](/docs/concepts/storage/volumes/).
|
||
* Information about the Container itself.
|
||
* Information about other objects in the cluster.
|
||
|
||
### Container information
|
||
|
||
The *hostname* of a Container is the name of the Pod in which the Container is running.
|
||
It is available through the `hostname` command or the
|
||
[`gethostname`](http://man7.org/linux/man-pages/man2/gethostname.2.html)
|
||
function call in libc.
|
||
|
||
The Pod name and namespace are available as environment variables through the
|
||
[downward API](/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/).
|
||
|
||
User defined environment variables from the Pod definition are also available to the Container,
|
||
as are any environment variables specified statically in the Docker image.
|
||
|
||
### Cluster information
|
||
|
||
A list of all services that were running when a Container was created is available to that Container as environment variables.
|
||
Those environment variables match the syntax of Docker links.
|
||
|
||
For a service named *foo* that maps to a Container named *bar*,
|
||
the following variables are defined:
|
||
|
||
```shell
|
||
FOO_SERVICE_HOST=<the host the service is running on>
|
||
FOO_SERVICE_PORT=<the port the service is running on>
|
||
```
|
||
|
||
Services have dedicated IP addresses and are available to the Container via DNS,
|
||
if [DNS addon](http://releases.k8s.io/{{< param "githubbranch" >}}/cluster/addons/dns/) is enabled.
|
||
|
||
{{% /capture %}}
|
||
|
||
{{% capture whatsnext %}}
|
||
|
||
* Learn more about [Container lifecycle hooks](/docs/concepts/containers/container-lifecycle-hooks/).
|
||
* Get hands-on experience
|
||
[attaching handlers to Container lifecycle events](/docs/tasks/configure-pod-container/attach-handler-lifecycle-event/).
|
||
|
||
{{% /capture %}}
|
||
|
||
|