The EC2 Container Registry requires an image Repository to be setup for each image "name" or "namespace/name" you want to publish to the registry.

You can publish any :tags you want in each Repository though (The default limit is 100 tags).

I haven't seen anywhere in the AWS documentation that specifically states the repository -> image name mapping but it's implied by Creating a Repository - Section 6d in the ECR User Guide

The Docker Image spec includes it's definition of a Repository

Repository

A collection of tags grouped under a common prefix (the name component before :). For example, in an image tagged with the name my-app:3.1.4, my-app is the Repository component of the name. A repository name is made up of slash-separated name components, optionally prefixed by a DNS hostname. The hostname must comply with standard DNS rules, but may not contain _ characters. If a hostname is present, it may optionally be followed by a port number in the format :8080. Name components may contain lowercase characters, digits, and separators. A separator is defined as a period, one or two underscores, or one or more dashes. A name component may not start or end with a separator.

Create a repo per application:

aws ecr create-repository --repository-name worker --region us-east-1
aws ecr create-repository --repository-name gateway --region us-east-1

Login to registry

The AWS usr name is fixed for all registry logins

aws ecr get-login-password \
--region us-east-1 \
| docker login \
--username AWS \
--password-stdin <aws_12_digit_account_number>.dkr.ecr.us-east-1.amazonaws.com

Push image

docker build -f Dockerfile -t <123456789012>.dkr.ecr.us-east-1.amazonaws.com/worker:v1.0.0
docker push <123456789012>.dkr.ecr.us-east-1.amazonaws.com/worker:v1.0.0

You need to create a repository for each image name, but the image name can be of the form "mycompanyname/helloworld". So you create mycompanyname/app1, mycompanyname/app2, etc

aws ecr create-repository --repository-name mycompanyname/helloworld
aws ecr create-repository --repository-name mycompanyname/app1
aws ecr create-repository --repository-name mycompanyname/app2
docker tag helloworld:latest xxxxxxxx.dkr.ecr.us-west-2.amazonaws.com/mycompanyname/helloworld:latest
docker push xxxxxxxx.dkr.ecr.us-west-2.amazonaws.com/mycompanyname/helloworld:latest
docker tag app1:latest xxxxxxxx.dkr.ecr.us-west-2.amazonaws.com/mycompanyname/app1:latest
docker push xxxxxxxx.dkr.ecr.us-west-2.amazonaws.com/mycompanyname/app1:latest

Addition to the above answer, I came across here today, as the login command change with aws-cli v2, posting as an answer might help others. as aws-cli v1 login command no longer work.

V1
$(aws ecr get-login --no-include-email)

To push image to ECR using aws-cli v2 you need

aws ecr get-login-password --region us-west-2 | docker login --username AWS --password-stdin 123456789.dkr.ecr.us-west-2.amazonaws.com

Then you are okay to build and push

docker build -t myrepo .
docker tag myrepo:latest 123456789.dkr.ecr.us-west-2.amazonaws.com/myrepo
docker push 123456789.dkr.ecr.us-west-2.amazonaws.com/myrepot

Typically One image per registry is a clean approach, that why AWS increase image per repository and repository per region from 1000 to 10,000.

I tried the following steps and confirmed working for me:

1. aws ecr get-login-password --region us-west-2 | docker login --username AWS --password-stdin xxxxxxxx.dkr.ecr.us-west-2.amazonaws.com

2. aws ecr create-repository --repository-name test

3. docker build -t test .

4. docker tag test:latest xxxxxxxx.dkr.ecr.us-west-2.amazonaws.com/test:latest

5. docker push xxxxxxxx.dkr.ecr.us-west-2.amazonaws.com/test:latest

For this i automated the script that can read your public images from csv file and pull them. After that it will try to create repository in ECR and push to registry.

1. Prepare CSV file ecr-images.csv

docker.io/amazon/aws-for-fluent-bit,2.13.0
docker.io/couchdb,3.1
docker.io/bitnami/elasticsearch,7.13.1-debian-10-r0
k8s.gcr.io/kube-state-metrics/kube-state-metrics,v2.0.0
k8s.gcr.io/metrics-server-amd64,v0.3.6
--------------------KEEP THIS LINE AT END-------------------------

3. Automated script ecr.sh that will copy images to ecr

#!/bin/bash


set -e


SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"


assert_value() {
if [ -z "$1" ]; then
echo "No args: $2"
exit 1
fi
}


repository_uri=$1
assert_value "$repository_uri" "repository_uri"


create_repo() {
## try to create & failure will ignored by <|| true>
aws ecr create-repository --repository-name "$1" --output text || true
}


## Copy Docker Images to ECR
COUNTER=0
while IFS=, read -r dockerImage tag; do
outputImage=$(echo "$dockerImage" | sed -E 's/(\w+?\.)+\w+?\///')
outputImageUri="$repository_uri/$outputImage"
# shellcheck disable=SC2219
let COUNTER=COUNTER+1
echo "--------------------------------------------------------------------------"
echo "$COUNTER => $dockerImage:$tag pushing to $outputImageUri:$tag"
echo "--------------------------------------------------------------------------"
docker pull "$dockerImage:$tag"
docker tag "$dockerImage:$tag" "$outputImageUri:$tag"
create_repo "$outputImage"
docker push "$outputImageUri:$tag"
done <"$SCRIPT_DIR/ecr-images.csv"

3. Run

repository_uri=<ecr_account_id>.dkr.ecr.<ecr_region>.amazonaws.com


aws ecr get-login-password --region us-east-1 | \
docker login --username AWS --password-stdin $repository_uri


./ecr.sh $repository_uri

# Build an image from azure devops pipeline to aws eks


parameters:
- name: succeed
displayName: Succeed or fail
type: boolean
default: false




trigger:
- main
- releases/*


pool:
vmImage: "windows-latest"






stages:
- stage: init
jobs:
- job: init
continueOnError: false
steps:
- task: Docker@2
inputs:
containerRegistry: 'docker'
repository: 'ecr-name'
command: 'build'
Dockerfile: '**/Dockerfile'
tags: 'latest'
          

- task: ECRPushImage@1
inputs:
awsCredentials: 'aws credentilas'
regionName: 'us-east-1'
imageSource: 'any-name'
sourceImageName: 'ecr-name'
sourceImageTag: 'latest'
repositoryName: 'ecr-name'
pushTag: 'latest'