Sometimes it may be necessary to 'copy' docker images from one registry to another one - which is a very easy thing to do

At my employer we don’t have direct internet access, so if one needs to download docker image, she/he needs to use the internal registry (JFrog Artifactory), rather the official docker registry. Artifactory itself runs on kubernetes as well, thus relying on docker images - images hosted by itself. This can cause troubles when you want to upgrade Artifactory and requires to download new docker images. This we have setup a fallback registry using docker-registry. In order to have the fallback images stored in this registry we have to “copy” them there.

All you have to do are these simple steps:

1. Download the image you need

   [papanito@archlinux ~]$ docker pull docker.prd.intra/bitnami/postgresql:9.6.18-debian-10-r7
   9.6.18-debian-10-r7: Pulling from bitnami/postgresql
   8639931041da: Pull complete
   4d3c20145e72: Pull complete
   31d2e2fd56b9: Pull complete
   2df5129bdc5b: Pull complete
   4d1738d978de: Pull complete
   64b240571161: Pull complete
   262647e176df: Pull complete
   df100498f366: Pull complete
   2c124d31d59a: Pull complete
   c491889bfe7f: Pull complete
   78eafaf7caa5: Pull complete
   Digest: sha256:a63224f91d0bd2dc9489337862ce37188a2e3378dfb4bef7133cbecea2a64cc0
   Status: Downloaded newer image for docker.prd.intra/bitnami/postgresql:9.6.18-debian-10-r7
   docker.prd.intra/bitnami/postgresql:9.6.18-debian-10-r7
   
   [papanito@archlinux ~]$ docker images
   REPOSITORY TAG IMAGE ID CREATED SIZE
   docker.prd.intra/bitnami/postgresql 9.6.18-debian-10-r7 eb0a50f73ced 10 months ago 338MB

2. Tag the image, using the url from the fallback-registry (docker-fallback.prd.intra):

   [papanito@archlinux ~]$ docker tag docker.prd.intra/bitnami/postgresql:9.6.18-debian-10-r7 docker-fallback.prd.intra/bitnami/postgresql/9.6.18-debian-10-r7
   [papanito@archlinux ~]$ docker images
   REPOSITORY TAG IMAGE ID CREATED SIZE
   docker-fallback.prd.intra/bitnami/postgresql/9.6.18-debian-10-r7 latest eb0a50f73ced 10 months ago 338MB
   docker.prd.intra/bitnami/postgresql 9.6.18-debian-10-r7 eb0a50f73ced 10 months ago 338MB

3. Now that we have tagged the image, we can push it to the fallback-registry

   [papanito@archlinux ~]$ docker login docker-fallback.prd.intra -u fallback
   Password:
   Login Succeeded
   [papanito@archlinux ~]$ docker push docker-fallback.intra/bitnami/postgresql:9.6.18-debian-10-r7
   The push refers to repository [docker-fallback.prd.intra/bitnami/postgresql]
   4af4a3a6d7f5: Layer already exists
   49e1d446487d: Layer already exists
   3cf57cb27d57: Layer already exists
   e4d0e4ffe969: Layer already exists
   58eb215ff1bf: Layer already exists
   24a67c88dc5c: Layer already exists
   e2b9ee1ce16d: Layer already exists
   b2ff695f59b5: Layer already exists
   e47dc03a6e0c: Layer already exists
   b8d0de821c92: Layer already exists
   915e1ffcd29c: Layer already exists
   9.6.18-debian-10-r7: digest: sha256:a63224f91d0bd2dc9489337862ce37188a2e3378dfb4bef7133cbecea2a64cc0 size: 2623

That’s it, the image is now available on the fallback-registry.