How to fix Error response from daemon: Cannot pause container: Container is not running in Docker

Understanding container states: Docker containers can be in several states, and only the "running" state allows pausing:

| State | Can Pause? | Description |
|-------|------------|-------------|
| created | No | Container created but never started |
| running | Yes | Container is active with processes |
| paused | No | Already paused |
| restarting | No | Container is restarting |
| exited | No | Container stopped (cleanly or with error) |
| dead | No | Container failed to stop properly |

Pause vs Stop decision tree:
- Use pause when you want to temporarily freeze a container and resume it quickly with all state preserved
- Use stop when you want to shut down the container and don't need to preserve in-memory state

Scripting considerations: When writing scripts that need to pause containers, always check the container state first:

# Check if container is running before pausing
if [ "$(docker inspect -f '{{.State.Running}}' my_container 2>/dev/null)" = "true" ]; then
    docker pause my_container
else
    echo "Container is not running, cannot pause"
fi

Docker Compose behavior: The docker compose pause command only affects running services. Services that are not started will be silently skipped - no error is thrown, but they won't be paused either.

Alternative: Use stop instead: If you're trying to pause a container just to free up resources and don't need to preserve state, consider using docker stop instead, which works on running containers and doesn't require the container to be in a specific state beforehand.