Docker Pull to Running Container — The Full Sequence
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The sequence from pulling an image to running a container has three steps, but in practice you usually do it with one command.
First is docker pull, which downloads the image from a registry like Docker Hub to your local machine. Docker fetches all the layers that make up that image and stores them in your local Docker storage. This is optional because docker run does it automatically if the image isn't already local.
Second is docker create, which takes that local image and sets up a container instance. Docker allocates a unique container ID, stacks the read-only image layers with a new writable layer on top, configures network interfaces, and mounts any volumes you specified. At this point the container exists but it's not running yet — nothing is actually executing.
Third is docker start, which launches the container's main process. For a Spring Boot app, this is where your application's main method gets called and the server starts listening on its port. Now here's the thing: you almost never run these commands separately.
The docker run command does all three steps automatically — it pulls the image if it's missing, creates the container, and starts it in one shot. You can add -d to run it in detached mode so it goes to the background, which is what you want in production. The reason it's useful to know about the three-step split is for debugging.
If a container keeps failing to start, you can use docker create to set it up without starting it, inspect the configuration, maybe attach extra volumes or change the command, then manually docker start it. But for normal deployments, docker run does everything you need.
Docker Pull to Running Container — The Full Sequence
Direct Answer
First, docker pull downloads an image from a registry like Docker Hub to your local machine — this step is optional because docker run does it automatically if the image isn't found locally. Then docker run creates a new container from that image, sets up networking and volumes, and starts the container process. The full workflow is: pull image from registry, create container instance, start container process.
Code Example
// Manual approach: explicit pull, create, start
// Step 1: Pull image from Docker Hub
// docker pull nginx:1.25
// Step 2: Create container without starting it
// docker create --name my-nginx -p 8080:80 nginx:1.25
// Output: container ID like 3f4e5a6b7c8d
// Step 3: Start the created container
// docker start my-nginx
// Output: my-nginx (container is now running)
// Automatic approach: docker run does all three steps
// docker run -d --name auto-nginx -p 8080:80 nginx:1.25
// Pulls image if not local, creates container, starts it immediately
// Verify both approaches result in same running state
// docker ps
// Shows both my-nginx and auto-nginx with STATUS "Up"
// In practice for Spring Boot
// docker run -d --name order-service -p 8080:8080 \
// -e SPRING_PROFILES_ACTIVE=prod \
// mycompany/order-service:1.2.3
// Automatically pulls mycompany/order-service:1.2.3 if missing
// Creates container with environment variable
// Starts Spring Boot app listening on port 8080
Common Mistakes & Pitfalls
- Assuming docker pull is mandatory: Freshers write deployment scripts with docker pull followed by docker run, not realizing docker run already pulls missing images automatically. The extra pull command wastes time when the image is already local and adds unnecessary complexity to scripts.
- Not understanding the create-start split: Running docker run, seeing the container ID printed, then running docker run again with the same --name, which fails with a name conflict error because the first run already created a container with that name. The container exists but might have exited immediately due to an error — use docker ps -a to see it and docker start to restart it instead of creating a duplicate.
- Forgetting -d flag in production: Using
docker runas an ad-hoc production supervisor: detached mode changes client attachment, but a production platform still needs restart, health, logging, and lifecycle policy. - Ignoring pull failures: Relying on a movable
latesttag and implicit pull policy makes the deployed digest unclear. Set an explicit pull policy and deploy a controlled tag or digest.
Check your understanding
Answer these without looking back at the article.
- What is the difference between docker stop and docker kill?
- How do you run a container in detached mode?
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