How to fix Error response from daemon: container already started in Docker

First, verify whether the container is actually running:

List all containers (including stopped ones):

docker ps -a

Check a specific container:

docker inspect --format='{{.State.Status}}' <container_name_or_id>

If the status shows "running", the container is already active and you can use it directly. Common states include:
- running - Container is active
- exited - Container has stopped
- created - Container exists but never started
- paused - Container is paused

If the container is already running, you don't need to start it again. Simply use it:

Execute commands in the running container:

docker exec -it <container_name> /bin/bash
# Or for Alpine/minimal images:
docker exec -it <container_name> /bin/sh

View container logs:

docker logs <container_name>
# Follow logs in real-time:
docker logs -f <container_name>

Check container resource usage:

docker stats <container_name>

The container is already available for your workload.

If you need to restart the container (e.g., to pick up configuration changes), use the restart command instead of start:

docker restart <container_name>

This command stops and then starts the container in one operation. It's safe to run on both running and stopped containers.

With a timeout (default is 10 seconds):

docker restart -t 30 <container_name>

This gives the container 30 seconds to gracefully shut down before being forcefully stopped.

If you want to stop the running container before making changes:

Stop gracefully:

docker stop <container_name>

Force stop immediately:

docker kill <container_name>

After stopping, you can start it again:

docker start <container_name>

Or remove it entirely and create a new one:

docker rm <container_name>
docker run --name <container_name> <image>

To make scripts idempotent and avoid this error, check container state before starting:

Bash one-liner to start only if not running:

docker start <container_name> 2>/dev/null || true

More robust script pattern:

#!/bin/bash
CONTAINER_NAME="mycontainer"

# Check if container exists and is running
if [ "$(docker inspect -f '{{.State.Running}}' $CONTAINER_NAME 2>/dev/null)" = "true" ]; then
    echo "Container is already running"
else
    # Start existing container or create new one
    docker start $CONTAINER_NAME 2>/dev/null || \
    docker run -d --name $CONTAINER_NAME myimage:latest
fi

Alternative using docker ps:

if ! docker ps --format '{{.Names}}' | grep -q "^${CONTAINER_NAME}$"; then
    docker start $CONTAINER_NAME
fi