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You run docker service scale web=3 but the service remains at 1 replica. What is the most likely cause?

medium📝 Troubleshoot Q6 of 15
Docker - Swarm
You run docker service scale web=3 but the service remains at 1 replica. What is the most likely cause?
AYou need to restart Docker after scaling
BDocker daemon is not running
CScaling command requires a container ID, not service name
DThe service name 'web' is incorrect or does not exist
Step-by-Step Solution
Solution:

  1. Step 1: Check service name validity

    If the service name is wrong, scaling command has no effect.

  2. Step 2: Evaluate other options

    Docker daemon not running would cause errors, not silent failure. Restart not needed. Command uses service name, not container ID.

  3. Final Answer:

    The service name 'web' is incorrect or does not exist -> Option D

  4. Quick Check:

    Correct service name needed for scaling [OK]
Quick Trick: Verify service name before scaling [OK]
Common Mistakes:
  • Assuming daemon issues without error
  • Restarting Docker unnecessarily
  • Using container ID instead of service name

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