Creating ConfigMaps Imperatively¶

Kubernetes provides multiple ways to create ConfigMaps using the kubectl create configmap command.

1️⃣ Creating a ConfigMap from a Directory¶

kubectl create configmap my-config --from-file=path/to/bar

Effect:¶

• If path/to/bar is a directory, all files inside that directory are added as keys in the ConfigMap.
• Each file name becomes a key, and the file content becomes the value.

Example:¶

If bar/ contains:

bar/
├── file1.txt (contains "hello")
├── file2.txt (contains "world")

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-config
data:
  file1.txt: "hello"
  file2.txt: "world"

Use Case:¶

Use this method when you have multiple configuration files that you want to bundle into a single ConfigMap.

2️⃣ Creating a ConfigMap from a Single File¶

kubectl create configmap my-config --from-file=path/to/bar

Effect:¶

• If path/to/bar is a single file, Kubernetes creates a ConfigMap with a key equal to the file name (bar) and a value containing the file’s contents.

Example:¶

If bar is a file with contents:

hello world

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-config
data:
  bar: "hello world"

Use Case:¶

Use this method when you want to store a single configuration file inside a ConfigMap.

3️⃣ Creating a ConfigMap with Custom Keys from Files¶

kubectl create configmap my-config --from-file=key1=/path/to/file1.txt --from-file=key2=/path/to/file2.txt

Effect:¶

• Allows custom key names instead of using file names.
• Each specified key gets assigned the content of the corresponding file.

Example:¶

If file1.txt contains hello and file2.txt contains world, the ConfigMap will be:

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-config
data:
  key1: "hello"
  key2: "world"

Use Case:¶

Use this method when you want to rename keys while creating the ConfigMap.

4️⃣ Creating a ConfigMap with Key-Value Pairs (Literals)¶

kubectl create configmap my-config --from-literal=key1=config1 --from-literal=key2=config2

Effect:¶

• Directly specifies key-value pairs inside the ConfigMap without using any files.

Example:¶

The resulting ConfigMap will be:

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-config
data:
  key1: "config1"
  key2: "config2"

Use Case:¶

Use this method when you need to quickly create a small set of key-value pairs without using files.

5️⃣ Creating a ConfigMap from an Environment File¶

kubectl create configmap my-config --from-env-file=path/to/foo.env --from-env-file=path/to/bar.env

Effect:¶

• Reads environment variables from an .env file and converts them into a ConfigMap.

Example:¶

If foo.env contains:

DB_USER=root                # Not yaml style    # DB_USER: root
DB_PASS=secret

apiVersion: v1
kind: ConfigMap
metadata:
  name: my-config
data:
  DB_USER: "root"
  DB_PASS: "secret"

Use Case:¶

Use this method when you want to load multiple environment variables at once from a .env file.

Important Key Point¶

When you use multiple --from-env-file flags, Kubernetes processes them in order.

👉 Example:

kubectl create configmap my-config \
  --from-env-file=foo.env \
  --from-env-file=bar.env

• foo.env

APP=foo
PORT=8080

APP=bar

Resulting ConfigMap:

data:
  APP: bar       # from bar.env (overrides foo.env)
  PORT: "8080"   # from foo.env

✅ Rule: If the same key is defined in multiple env files, the value from the last file specified takes precedence.

Summary¶

Understanding these methods allows you to choose the best approach based on your use case and effectively manage configurations in Kubernetes.