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設定用ConfigMapとSecret

Kubernetes内でConfigMapとSecretを使い、アプリケーション設定と機密データを安全に管理します。

「設定用ConfigMapとSecret」はCoddyKit上の無料Docker & Kubernetes for Developersレッスンです。 これはレッスン3/4です。 下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。 これはDocker & Kubernetes for Developers学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Docker & Kubernetes for Developersコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Configuration Challenges

Managing application configuration and sensitive data can be tricky, especially in dynamic environments like Kubernetes.

Hardcoding values into images makes them less reusable. Storing secrets directly in Git is a security risk.

Kubernetes offers two powerful resources to solve these challenges: ConfigMaps and Secrets.

Meet ConfigMaps

A ConfigMap is an API object used to store non-sensitive configuration data in key-value pairs.

Think of it as a central place for settings like database hostnames, logging levels, or API endpoints.

  • Separates configuration from application code.
  • Allows easy updates without rebuilding images.
  • Can be consumed as environment variables or mounted files.

ConfigMap: Literal Values

You can create a ConfigMap directly from literal key-value pairs using YAML. This is great for simple, direct settings.

Here's an example for an application's settings:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-settings
data:
  log_level: INFO
  feature_flag_a: "true"
  api_url: http://backend-service/api

ConfigMap: From Files

For more complex configurations, you can create a ConfigMap from an entire file.

If you have a config.properties file, its content can be directly embedded into the ConfigMap. The resulting ConfigMap would look like this:

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config-from-file
data:
  config.properties: |
    database.host=db-service
    database.port=5432
    application.name=MyWebApp

ConfigMap as Env Vars

The most common way to use a ConfigMap is by injecting its data as environment variables into your Pods.

This allows your application to read configuration values directly.

apiVersion: v1
kind: Pod
metadata:
  name: my-app-pod
spec:
  containers:
  - name: my-container
    image: nginx
    env:
    - name: LOG_LEVEL
      valueFrom:
        configMapKeyRef:
          name: app-settings
          key: log_level
    - name: API_URL
      valueFrom:
        configMapKeyRef:
          name: app-settings
          key: api_url

ConfigMap as Volume Mounts

ConfigMap data can also be mounted as files into a Pod's filesystem. This is ideal for applications that read configuration from files.

Each key in the ConfigMap becomes a file in the specified mountPath. For example, log_level would be at /etc/config/log_level.

apiVersion: v1
kind: Pod
metadata:
  name: my-app-pod-volume
spec:
  containers:
  - name: my-container
    image: nginx
    volumeMounts:
    - name: config-volume
      mountPath: "/etc/config"
  volumes:
  - name: config-volume
    configMap:
      name: app-settings

Introducing Secrets

A Secret is similar to a ConfigMap but is designed for sensitive data like passwords, API keys, or TLS certificates.

Secrets are stored in Kubernetes in base64 encoded format, but this is NOT encryption. It's just encoding for safe transport.

  • Provides a mechanism to distribute sensitive data.
  • Accessed like ConfigMaps (env vars or volume mounts).
  • Should always be managed with care and access controls.

Secret: Literal Values

Secrets are created similarly to ConfigMaps, but their data values are base64 encoded. This encoding is for safe transport, not encryption.

For example, if your password is "my-secure-password", its base64 encoding is "bXktc2VjdXJlLXBhc3N3b3Jk".

apiVersion: v1
kind: Secret
metadata:
  name: db-credentials
type: Opaque
data:
  username: dXNlcg== # 'user' base64 encoded
  password: bXktc2VjdXJlLXBhc3N3b3Jk # 'my-secure-password' base64 encoded

Secret as Env Vars

Secrets can be consumed as environment variables, just like ConfigMaps. Kubernetes automatically decodes the base64 value for the container.

This makes sensitive data available to your application without hardcoding it directly in the image.

apiVersion: v1
kind: Pod
metadata:
  name: my-db-app
spec:
  containers:
  - name: my-container
    image: my-app:1.0
    env:
    - name: DB_USERNAME
      valueFrom:
        secretKeyRef:
          name: db-credentials
          key: username
    - name: DB_PASSWORD
      valueFrom:
        secretKeyRef:
          name: db-credentials
          key: password

Secret as Volume Mounts

Mounting Secrets as files is often preferred for sensitive data, as it limits the exposure of the secret to the application process.

The mounted files will contain the decoded (plain-text) secret values, and you can set them to be read-only.

apiVersion: v1
kind: Pod
metadata:
  name: my-secure-app
spec:
  containers:
  - name: my-container
    image: my-app:1.0
    volumeMounts:
    - name: secret-volume
      mountPath: "/etc/secrets"
      readOnly: true
  volumes:
  - name: secret-volume
    secret:
      secretName: db-credentials

ConfigMaps vs. Secrets

You need to store an API key for a third-party service and a configuration setting for your application's logging level. Which Kubernetes resources would you use for each?

Recap: Config & Secrets

We've learned how ConfigMaps and Secrets help manage configuration and sensitive data in Kubernetes.

  • ConfigMaps store non-sensitive key-value pairs.
  • Secrets store sensitive data, base64 encoded (not encrypted).
  • Both can be consumed as environment variables or mounted files in Pods.
  • Using them separates configuration from application logic, improving flexibility and security.

よくある質問

「設定用ConfigMapとSecret」レッスンは無料ですか？

はい。「設定用ConfigMapとSecret」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Docker & Kubernetes for Developersコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Docker & Kubernetes for Developersコースには全4レッスンが含まれています。

「設定用ConfigMapとSecret」で何を学びますか？

Kubernetes内でConfigMapとSecretを使い、アプリケーション設定と機密データを安全に管理します。 ブラウザで直接実行するハンズオンコードでDocker & Kubernetes for Developersを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Docker & Kubernetes for Developersを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのDocker & Kubernetes for Developersは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。 これはレッスン3/4です。

「設定用ConfigMapとSecret」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このDocker & Kubernetes for Developersレッスンでコードを書いて実行できますか？

はい。すべてのDocker & Kubernetes for Developersレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

  1. Persistent VolumeとPersistent Volume Claim
  2. StatefulSetによるステートフルアプリケーション管理
  3. 設定用ConfigMapとSecret
  4. ストレージクラスと動的プロビジョニング
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