12 Jul
If you are working as a DevOps Engineer somewhere, it would be your core responsibility to pull and push Docker images to a registry. Earlier, we discussed how to pull a Docker image from a public repository. Also, we learned about tagging Docker images and it’s importance. This is important to note that we’ve been working on public repositories. You can create unlimited public repositories while setting up an account on Docker Hub. In this guide, we’ll learn how to push a Docker image. So, buckle up for the docker push command drill.
Let’s get started!
1. The docker push Command
The docker push command pushes the images to the registries. More simply, it uploads the images to the registries. We have already created a public repository on Docker Hub.
The repository name is softwarespice/devimages
Let’s assume that we have some test images that we want to push to this public repository.
Also, you can see the repo is empty and have no images pushed to it.
We can see the push command on the right-hand side. I will paste the command here.
docker push softwarespice/devimages:tagname
For every push, you have to run this command changing your own repository and the tagname.
2. Login to Docker Hub via SSH
You can not push the images to the public repository until you login to the Docker Hub via SSH on your virtual machine. You will get an “access to the resource is denied” error.
I will quickly login to my Docker Hub account with docker login command. You have to put the following credentials.
- Username [Your Docker ID]
- Password [Your Docker Hub account password]
You can see in the following image, I have logged into successfully. I should not get the denial error again now.
3. Pushing the First Image to Docker Hub
I am so excited to push the image to the public repo. Again, I will remind you here to properly tag the image according to the repository name. If the repository’s name is wrong in the image name, it will not get pushed.
So, to push an image to the Docker Hub, run the following command.
docker push softwarespice/devimages:image1
You should see an output similar to that.
[email protected]:~$ docker push softwarespice/devimages:image1
The push refers to repository [docker.io/softwarespice/devimages]
9d1af766c818: Pushed
d97733c0a3b6: Pushed
c553c6ba5f13: Pushed
48b4a40de359: Pushed
ace9ed9bcfaf: Pushed
764055ebc9a7: Pushed
image1: digest: sha256:1c70a669bbf07f9862f269162d776c35144b116938d1becb4e4676270cff8f75 size: 1570
[email protected]:~$
Booom!
The image has been pushed successfully and it’s available in the public repository.
If we run the command again, it will say the image layers already exist. It means there is nothing new in the image that you are pushing.
[email protected]:~$ docker push softwarespice/devimages:image1
The push refers to repository [docker.io/softwarespice/devimages]
9d1af766c818: Layer already exists
d97733c0a3b6: Layer already exists
c553c6ba5f13: Layer already exists
48b4a40de359: Layer already exists
ace9ed9bcfaf: Layer already exists
764055ebc9a7: Layer already exists
image1: digest: sha256:1c70a669bbf07f9862f269162d776c35144b116938d1becb4e4676270cff8f75 size: 1570
4. Repository Names in Images
It is an important thing to note and that’s why I am repeating it again. You will not be able to push if the images do not have the correct repository names. The docker push command checks the image tags before pushing.
Check out the following two errors.
Error#1:
[email protected]:~$ docker push softwarespice123/devimages:image3
The push refers to repository [docker.io/softwarespice123/devimages]
An image does not exist locally with the tag: softwarespice123/devimages
Error#2:
[email protected]:~$ docker push softwarespice123/devimages:image3
The push refers to repository [docker.io/softwarespice123/devimages]
72e830a4dff5: Preparing
denied: requested access to the resource is denied
In the first error, the Docker Engine is unable to find an image with a tag softwarespice123/devimages.
In the second error, the Docker Engine is unable to find the repository which is softwarespice123/devimages in Docker Hub.
The images will be pushed smoothly if they have the correct names and tags.
Additionally, you can have colons [:] in the image tags but can not have slash[/] in the images.
5. Pushing Images with All Tags
If you want to push all the images with different tags using a single command, we will use the --all-tags option in the docker push command.
Let’s suppose we have the following images locally on our virtual machine. You can see the repository name is the same as on Docker Hub. I’ll run the following command to push all these images to the public repository on Docker Hub.
docker push --all-tags softwarespice/devimages
Wait for the images to be pushed and get back to your public repository on Docker Hub. You can see in the following images, all images have been pushed at the same time with--all-tags option in the docker push command.
6. A Quick Summary
I hope you have a clear picture of the docker push command. I have covered the basics of it. We have used the Docker Hub registry for the images. You can also push your images to a self-hosted repository. The method is the same whether it is Docker Hub, AWS Elastic Container Registry, or Google Container Registry.
One of the most important things that you should remember to login into the registry before pushing images. The AWS ECR and Google Container Registries also need authentication before pushing images. That’s a bit out of the topic scope here.
Finally, we learned about pushing Docker images in this short guide. We pushed two images with different tags in our public repo.
Let me know in the comments how can we fix the above two errors.
That is a tiny assignment for you.
If you want to know more about Docker in the meanwhile, go through the following simple guides:
- What is Docker? An Overview Tutorial on Docker for Beginners
- What is Docker Used For? Why is Docker So Popular?
- Getting Started With Docker, Our Journey to Learn Docker Begins
- How to Install Docker on Ubuntu 18.04 — An Ultimate Guide
Happy Docking!!!
Hi, I am Faisal Rehman.
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