Lab 23: Registry authentication failure

Objective

Reproduce a registry auth failure and fix it.

Tasks

Task 1: Attempt to pull from a private registry without auth

docker pull registry.example.com/myorg/app:1.0.0
# Error response from daemon: Head ... no basic auth credentials

Task 2: Log in

docker login registry.example.com
# Username: myorg
# Password: ********
docker pull registry.example.com/myorg/app:1.0.0

Task 3: Verify credentials are stored

cat ~/.docker/config.json | jq '.auths'
# The registry is listed with an encrypted credential.

Task 4: Diagnose an expired token

Rotate the password in the registry, then attempt to pull again:

docker pull registry.example.com/myorg/app:1.0.0
# unauthorized: authentication required

docker login registry.example.com fixes it.

Task 5: Use a credential helper

For CI / automation, avoid interactive login:

# Create a credential helper
docker-credential-secretservice list
# or
echo 'registry.example.com' | docker-credential-ecr-login get

Configure in ~/.docker/config.json:

{
  "credHelpers": {
    "registry.example.com": "ecr-login"
  }
}