from https://www.reddit.com/r/docker/comments/a72isd/migrating_from_docker_registry_to_amazon_ecr/

account-migration.sh

#!/bin/bash

srcreg="my.privateregistry.com"
tgtreg="awsacctnum.dkr.ecr.awsregion.amazonaws.com"

repos=`curl -s http://$srcreg/v2/_catalog?n=2048 | jq '.repositories[]' | tr -d '"'`

for repo in $repos; do

   echo -e "\n===WORKING ON REPOSITORY" $repo"==="

   #check for existing repo at ECR and create if not exist
   awsrepo=`aws ecr describe-repositories | grep -o \"$repo\" | tr -d '"'`
   if [ "$awsrepo" != "$repo" ]; then aws ecr create-repository --repository-name $repo; fi

   tags=`curl -s http://$srcreg/v2/$repo/tags/list?n=2048 | jq '.tags[]' | tr -d '"'`

      #check for existing tags at ECR and push if not exist
      for tag in $tags; do
         awstag=`aws ecr list-images --repository-name $repo | grep -o \"$tag\" | tr -d '"'`
         echo -e "\n===WORKING ON" $repo:$tag"==="

         if [ "$awstag" != "$tag" ]; then
            echo -e "\n===PULLING==="
            docker pull $srcreg/$repo:$tag

            echo -e "\n===RETAGGING==="
            docker tag $srcreg/$repo:$tag $tgtreg/$repo:$tag
            echo $srcreg/$repo:$tag "retagged to" $tgtreg/$repo:$tag

            echo -e "\n===PUSHING==="
            docker push $tgtreg/$repo:$tag
         fi

      done

   #check local images and cleanup if necessary
   cleanup=`docker images -a | grep "$repo "`
   if [ "$cleanup" != "" ]; then
      echo -e "\n===CLEANING UP==="
      #add -f at end of the command below to force cleanup of matching repository images on local disk.
      #this may result in extra network traffic and longer migration times if you have inter-repo dependencies.
      #especially useful if disk space is a factor - only the working repo is retained on disk.
      docker images -a | grep $repo | awk '{print $3}' | xargs docker rmi
   fi

done

repo-migration.sh

#!/bin/bash

repo=$1
srcreg="my.privateregistry.com"
tgtreg="awsacctnum.dkr.ecr.awsregion.amazonaws.com"

echo -e "\n===WORKING ON REPOSITORY" $repo"==="

#check for existing repo at ECR and create if not exist
awsrepo=`aws ecr describe-repositories | grep -o \"$repo\" | tr -d '"'`
if [ "$awsrepo" != "$repo" ]; then aws ecr create-repository --repository-name $repo; fi

tags=`curl -s http://$srcreg/v2/$repo/tags/list?n=2048 | jq '.tags[]' | tr -d '"'`

    #check for existing tags at ECR and push if not exist
    for tag in $tags; do
        awstag=`aws ecr list-images --repository-name $repo | grep -o \"$tag\" | tr -d '"'`
        echo -e "\n===WORKING ON" $repo:$tag"==="

        if [ "$awstag" != "$tag" ]; then
        echo -e "\n===PULLING==="
        docker pull $srcreg/$repo:$tag

        echo -e "\n===RETAGGING==="
        docker tag $srcreg/$repo:$tag $tgtreg/$repo:$tag
        echo $srcreg/$repo:$tag "retagged to" $tgtreg/$repo:$tag

        echo -e "\n===PUSHING==="
        docker push $tgtreg/$repo:$tag
        fi

    done

#check local images and cleanup if necessary
cleanup=`docker images -a | grep "$repo "`
if [ "$cleanup" != "" ]; then
    echo -e "\n===CLEANING UP==="
    #add -f at end of the command below to force cleanup of matching repository images on local disk.
    #this may result in extra network traffic and longer migration times if you have inter-repo dependencies.
    #especially useful if disk space is a factor - only the working repo is retained on disk.
    docker images -a | grep $repo | awk '{print $3}' | xargs docker rmi
fi