website/content/en/docs/concepts/configuration/configmap.md

---
title: ConfigMaps
content_template: templates/concept
weight: 20
---

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{{< glossary_definition term_id="configmap" prepend="A ConfigMap is" length="all" >}}

{{< caution >}}
ConfigMap does not provide secrecy or encryption.  
If the data you want to store are confidential, use a
{{< glossary_tooltip text="Secret" term_id="secret" >}} rather than a ConfigMap,
or use additional (third party) tools to keep your data private.
{{< /caution >}}

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## Motivation

Use a ConfigMap for setting configuration data separately from application code.

For example, imagine that you are developing an application that you can run on your
own computer (for development) and in the cloud (to handle real traffic).
You write the code to
look in an environment variable named `DATABASE_HOST`. Locally, you set that variable
to `localhost`. In the cloud, you set it to refer to a Kubernetes
{{< glossary_tooltip text="Service" term_id="service" >}} that exposes the database
component to your cluster.

This lets you fetch a container image running in the cloud and
debug the exact same code locally if needed.

## ConfigMap object

A ConfigMap is an API [object](/docs/concepts/overview/working-with-objects/kubernetes-objects/)
that lets you store configuration for other objects to use. Unlike most
Kubernetes objects that have a `spec`, a ConfigMap has a `data` section to
store items (keys) and their values.

The name of a ConfigMap must be a valid
[DNS subdomain name](/docs/concepts/overview/working-with-objects/names#dns-subdomain-names).

## ConfigMaps and Pods

You can write a Pod `spec` that refers to a ConfigMap and configures the container(s)
in that Pod based on the data in the ConfigMap. The Pod and the ConfigMap must be in
the same {{< glossary_tooltip text="namespace" term_id="namespace" >}}.

Here's an example ConfigMap that has some keys with single values,
and other keys where the value looks like a fragment of a configuration
format.

```yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: game-demo
data:
  # property-like keys; each key maps to a simple value
  player_initial_lives: 3
  ui_properties_file_name: "user-interface.properties"
  #
  # file-like keys
  game.properties: |
    enemy.types=aliens,monsters
    player.maximum-lives=5    
  user-interface.properties: |
    color.good=purple
    color.bad=yellow
    allow.textmode=true    
```

There are four different ways that you can use a ConfigMap to configure
a container inside a Pod:

1. Command line arguments to the entrypoint of a container
1. Environment variables for a container
1. Add a file in read-only volume, for the application to read
1. Write code to run inside the Pod that uses the Kubernetes API to read a ConfigMap

These different methods lend themselves to different ways of modeling
the data being consumed.
For the first three methods, the
{{< glossary_tooltip text="kubelet" term_id="kubelet" >}} uses the data from
the Secret when it launches container(s) for a Pod.

The fourth method means you have to write code to read the Secret and its data.
However, because you're using the Kubernetes API directly, your application can
subscribe to get updates whenever the ConfigMap changes, and react
when that happens. By accessing the Kubernetes API directly, this
technique also lets you access a ConfigMap in a different namespace.

Here's an example Pod that uses values from `game-demo` to configure a Pod:
```yaml
apiVersion: v1
kind: Pod
metadata:
  name: configmap-demo-pod
spec:
  containers:
    - name: demo
      image: game.example/demo-game
      env:
        # Define the environment variable
        - name: PLAYER_INITIAL_LIVES # Notice that the case is different here
                                     # from the key name in the ConfigMap.
          valueFrom:
            configMapKeyRef:
              name: game-demo           # The ConfigMap this value comes from.
              key: player_initial_lives # The key to fetch.
        - name: UI_PROPERTIES_FILE_NAME
          valueFrom:
            configMapKeyRef:
              name: game-demo
              key: ui_properties_file_name
      volumeMounts:
      - name: config
        mountPath: "/config"
        readOnly: true
  volumes:
    # You set volumes at the Pod level, then mount them into containers inside that Pod
    - name: config
      configMap:
        # Provide the name of the ConfigMap you want to mount.
        name: game-demo
```


A ConfigMap doesn't differentiate between single line property values and
multi-line file-like values.
What matters how Pods and other objects consume those values.
For this example, defining a volume and mounting it inside the `demo`
container as `/config` creates four files:

- `/config/player_initial_lives`
- `/config/ui_properties_file_name`
- `/config/game.properties`
- `/config/user-interface.properties`

If you want to make sure that `/config` only contains files with a
`.properties` extension, use two different ConfigMaps, and refer to both
ConfigMaps in the `spec` for a Pod. The first ConfigMap defines
`player_initial_lives` and `ui_properties_file_name`. The second
ConfigMap defines the files that the kubelet places into `/config`.

{{< note >}}
The most common way to use ConfigMaps is to configure settings for
containers running in a Pod in the same namespace. You can also use a
ConfigMap separately.

For example, you
might encounter {{< glossary_tooltip text="addons" term_id="addons" >}}
or {{< glossary_tooltip text="operators" term_id="operator-pattern" >}} that
adjust their behavior based on a ConfigMap.
{{< /note >}}


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* Read about [Secrets](/docs/concepts/configuration/secret/).
* Read [Configure a Pod to Use a ConfigMap](/docs/tasks/configure-pod-container/configure-pod-configmap/).
* Read [The Twelve-Factor App](https://12factor.net/) to understand the motivation for
  separating code from configuration.

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