Pushing images from CI in Docker - Step-by-Step Execution

Process Flow - Pushing images from CI

Start CI Pipeline

↓

Build Docker Image

↓

Login to Docker Registry

↓

Push Image to Registry

↓

Confirm Push Success

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End CI Pipeline

This flow shows how a CI pipeline builds a Docker image, logs into a registry, pushes the image, and confirms success.

Execution Sample

Docker

docker build -t myapp:latest .
docker login -u $DOCKER_USER -p $DOCKER_PASS

docker push myapp:latest

Builds a Docker image, logs into the registry using credentials, then pushes the image.

Process Table

Step	Action	Command	Result	Notes
1	Build Image	docker build -t myapp:latest .	Image 'myapp:latest' built successfully	Dockerfile used in current directory
2	Login to Registry	docker login -u $DOCKER_USER -p $DOCKER_PASS	Login successful	Credentials from CI environment variables
3	Push Image	docker push myapp:latest	Image pushed to registry	Image available in remote registry
4	Verify Push	docker pull myapp:latest	Image pulled successfully	Confirms image is stored remotely
5	End	-	CI pipeline completes	All steps succeeded

💡 Pipeline ends after successful image push and verification

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
Image Tag	none	myapp:latest	myapp:latest	myapp:latest	myapp:latest	myapp:latest
Login Status	not logged in	not logged in	logged in	logged in	logged in	logged in
Push Status	not pushed	not pushed	not pushed	pushed	pushed	pushed
Pull Status	not pulled	not pulled	not pulled	not pulled	pulled	pulled

Key Moments - 3 Insights

Why do we need to login before pushing the image?

Because the registry requires authentication to allow image uploads. Step 2 in the execution_table shows login success before pushing.

What happens if the image build fails?

The pipeline stops early. Step 1 must succeed to proceed. If build fails, no login or push happens.

Why verify the image by pulling after push?

To confirm the image is correctly stored in the remote registry. Step 4 shows pulling the image to verify.

Visual Quiz - 3 Questions

Look at the execution table, what is the login status after Step 2?

A logged in

B not logged in

C login failed

D unknown

💡 Hint

Check the 'Login Status' variable after Step 2 in variable_tracker

At which step does the image get pushed to the registry?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Push Image' action in the execution_table

If the login fails, what will happen to the push step?

A Push will succeed anyway

B Push will be skipped or fail

C Push will retry automatically

D Push will push to a different registry

💡 Hint

Refer to key_moments about login necessity before push

Concept Snapshot

Pushing images from CI:
1. Build image with 'docker build -t name:tag .'
2. Login to registry using 'docker login' with credentials
3. Push image using 'docker push name:tag'
4. Verify push by pulling image
Ensure credentials are set in CI environment variables.

Full Transcript

In a CI pipeline, first the Docker image is built using the docker build command. Then the pipeline logs into the Docker registry using credentials stored securely in environment variables. After successful login, the image is pushed to the remote registry. Finally, the pipeline verifies the push by pulling the image back. If any step fails, the pipeline stops to prevent errors. This process automates image delivery from code changes to deployment-ready images stored remotely.