We’ve spent sometime in gaining a reasonable understanding of running a docker container. Sometimes, we have to go bit further to customise docker images by adding missing software tools or any package dependencies you need for your analysis. And the we want to re-use the customised image later or share it with other collaborators. This brings us to the point of sharing your image with others!
Upon completion of this session, you will learn:
Sharing a docker image involves making your local image available for other people to use it. Docker has docker save command option where you can save your image into a tar file. Let’s look at our fastqc container into which you have installed e.g., vim editor and you wish to share the new image now with your friend.
Find container id corresponding to fastqc container (tip: use docker ps -acommand) and use it with the following docker commit command:
docker commit <container id> fastqc-vim:test
note: It is a good idea to stop the container if running before performing docker commit
and then save the resulting image using docker save command as below:
docker save <image id> -o fastqc-vim.test.tar # better yet would be to use `reponame:tag` instead of <image id> (e.g., docker save fastqc-vim:test -o fastqc-vim-name.test.tar)
You can check the existance of tar file in your directory after docker save command has been executed successfully. You can send this tar file to your colllaborator/friend.
Finally, your friend can load the image from tar file uisng *docker load * command.
docker load < fastqc-vim.test.tar
Once image is loaded, you can now use it as if it is downloaded from DockerHub. The newly loaded image can be viewed using docker images command on host machine
Sharing an image via docker registry such as DockerHub (the most popular image registry, hosting hundreds of thousands of images) is an efficient way of sharing and managing your images. Once image is in a docker (public) registry, anyone can pull it from there.
However, this involves setting up an account in Docker registry. Here are few steps you can do to set-up your account:
You can now come back to your virtual machine and login to dockerhub by running docker login command.
docker login --username=your-dockerhub-user-name # this will prompt for your dockerhub password
Before pushing your docker image to DockerHub, you just need to rename docker image to your namespace/account first using docker tag command as below:
docker tag <image id> your-dockerhub-user-name/repo-name[:tag] # find <image id> corresponding to repository, fastqc-vim by typing `docker images` command on host machine
All images should be tagged with an appropriate prefix to repository name before pushing an image.
Let’s push your image finally as below:
docker push your-dockerhub-user-name/repo-name[:tag]
Once the push to repository is successful, your image is now available for everyone to use. Go to your profile page on the DockerHub to view your new docker image on DockerHub. Anybody can pull your image from Dockerhub now.
Summary: In this section, we have explored two ways of sharing a docker image with other in the following two ways: 1) tarball approach and 2)dockerhub approach. Dockerhub approach is the preferred approach and usually involves providing good documentation including dockerfile.