Pushing images to registry in Docker - Step-by-Step Execution

Process Flow - Pushing images to registry

Build Docker Image

↓

Tag Image with Registry URL

↓

Login to Registry

↓

Push Image to Registry

↓

Verify Image in Registry

↓

Done

This flow shows the steps to build a Docker image, tag it for a registry, login, push it, and verify the push.

Execution Sample

Docker

docker build -t myapp:1.0 .
docker tag myapp:1.0 myregistry.com/myapp:1.0
docker login myregistry.com
docker push myregistry.com/myapp:1.0

Builds an image, tags it with registry URL, logs in, then pushes the image to the registry.

Process Table

Step	Command	Action	Result	Notes
1	docker build -t myapp:1.0 .	Build image from Dockerfile	Image 'myapp:1.0' created locally	Image ready for tagging
2	docker tag myapp:1.0 myregistry.com/myapp:1.0	Tag image with registry URL	Image tagged as 'myregistry.com/myapp:1.0'	Tag links local image to remote name
3	docker login myregistry.com	Authenticate to registry	Login successful	Allows pushing images
4	docker push myregistry.com/myapp:1.0	Push image to registry	Image uploaded to registry	Image now available remotely
5	Verify image in registry	Check registry for image	Image found with tag '1.0'	Push confirmed successful

💡 Image pushed and verified in registry, process complete

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 4	Final
Image Name	none	myapp:1.0	myregistry.com/myapp:1.0	myregistry.com/myapp:1.0	myregistry.com/myapp:1.0
Registry Login Status	not logged in	not logged in	not logged in	logged in	logged in
Image Location	none	local	local	remote and local	remote and local

Key Moments - 3 Insights

Why do we need to tag the image before pushing?

Tagging links the local image to the remote registry name. Without tagging, Docker doesn't know where to push the image. See execution_table step 2.

What happens if we try to push without logging in?

The push will fail because the registry requires authentication. Step 3 shows login is needed before pushing in step 4.

Does pushing remove the local image?

No, pushing uploads a copy to the registry but keeps the local image intact. Variable 'Image Location' shows it remains local and remote after push.

Visual Quiz - 3 Questions

Look at the execution table, what is the image name after tagging (step 2)?

A myregistry.com/myapp:1.0

B myapp:1.0

C myregistry.com:1.0

D myapp

💡 Hint

Check the 'Result' column in step 2 of the execution_table.

At which step does the user authenticate to the registry?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look for the 'Action' column mentioning authentication in the execution_table.

If the login step is skipped, what will happen at the push step?

A Push succeeds without issues

B Push fails due to authentication error

C Image is pushed but not tagged

D Docker automatically logs in

💡 Hint

Refer to key_moments explanation about login necessity before push.

Concept Snapshot

Docker image push steps:
1. Build image locally with 'docker build -t name:tag .'
2. Tag image with registry URL using 'docker tag'
3. Login to registry with 'docker login'
4. Push image using 'docker push'
5. Verify image is in registry
Tagging links local image to remote name; login is required before push.

Full Transcript

To push a Docker image to a registry, first build the image locally using 'docker build'. Then tag the image with the registry URL so Docker knows where to send it. Next, login to the registry to authenticate. After successful login, push the tagged image to the registry. Finally, verify the image is available remotely. Tagging is essential to link the image to the registry path. Login is required to allow pushing. Pushing uploads the image but keeps the local copy intact.