Is there a way to pull docker images from your own registry without providing the registry name
something like
docker pull alpine should pull my image from docker pull docker-myorganisation.com/alpine
This isn't possible, the reason is that it would break the global namespace, which makes sense if you think about it, imagine the following Dockerfile:
FROM debian:latest
...
Would this refer to debian:latest on the official registry, or your own registry?
If you could willingly set your own default registry, the answer would be:
It depends.
This would lead to all kinds of breakage when the author of the file assumes it will be official registry, but your settings say different.
This is currently not supported.
See also: Github
Related
For example, I have an internal docker registry for my kube cluster, hosted on internal-docker-registry.io:5000.
When the pod from the kube cluster pulling image busybox, I don't want to pull from docker hub docker.io. But instead I want it to pull from internal-docker-registry.io:5000.
Note that I cannot change the image name to internal-docker-registry.io:5000/busybox since I don't own the spec and there are too man these kind of third party image in my cluster.
I have posted community wiki answer to summarize the topic:
As David Maze well mentioned in the comment:
there is no "image registry search list"; an image name without a registry always uses docker.io, to avoid surprises where e.g. FROM ubuntu means something different depending on local configuration.
So if you can't change the image name to internal-docker-registry.io:5000/busybox then unfortunately you don't have the option to get the image from your private registry (according to David's comment).
See also similar questions:
How to change the default docker registry from docker.io to my private registry?
How to change default K8s cluster registry?
Here you can find a complete guide on how to accomplish this in the official kubernetes documentation [1]
[1] https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/
There's a well-known approach to have docker images copied from one container registry to another. In case the original registry is dockerhub, the typical workflow would be something like this:
docker pull <image:tag>
docker tag <image:tag> <new-reg-url/uid/image:tag>
docker push <new-reg-url/uid/image:tag>
Now, how do you the above when dealing with images with multi-architecture layers?
As per the information in this link, you can rely on buildx to construct multi-arch images, and while doing that, you can also upload those to whichever repo you wish, but how do i do this without having to first build the images?
Looks like buildx cli has unnecessarily (?) coupled the uploading process with the building one. Any suggestions?
Thanks!
While the docker pull ...; docker tag ...; docker push ... syntax is the easy way to move images between registries, it has a couple drawbacks. First, as you've seen, is that it dereferences a multi-platform image to a single platform. And the second is that it pulls all layers to the docker engine even if the remote registry already has those layers, making it a bad method for ephemeral CI workers that would always need to pull every layer.
To do this, I prefer talking directly to the registry servers rather than the docker engine itself. You don't need the functionality from the engine to run the images, all you need is the registry API. Docker has documented the original registry API and OCI recently went 1.0 on the distribution-spec which should get us some standardization.
There's a variety of tooling based on those specs, from the docker engine itself and containerd, to skopeo, google's crane, and I've also been working on regclient. Doing this with regclient's regctl command looks like:
regctl image copy <source_image:tag> <target_image:tag>
And the result is the various layers, image config, manifests, and multi-platform manifest list will be copied between registries, but only for the layers that don't already exist on the target registry.
2022 (docker builtin) solution
It's posible to perform the copy using the not-well-documented built in command docker buildx imagetools create using --tag
# i.e.
OLD_TAG=registry.example.com/namespaced/repository/example-image:old-tag
NEW_TAG=registry.example.com/namespaced/repository/example-image:new-tag
# we can
docker buildx imagetools create --tag "$NEW_TAG" "$OLD_TAG"
Reference documentation
IMPORTANT NOTE: There is no support at the moment to perform this operation against different repositories. Given tags like
OLD_TAG=registry.example.com/namespaced/repository/example-image:latest
NEW_TAG=registry.example.com/other-repository/example-image:latest
You end with an error like
error: multiple repositories currently not supported
For this situation I'm going to test the actual accepted answer
As #laconbass has written, this can be done with docker buildx imagetools create. The ability to do this over multiple repos was added in this PR
docker buildx imagetools create -t <NEW-TAG> <OLD-TAG>
I have a Git repo with a simple Dockerfile. First row goes like this:
FROM python:3.7
My company has an internal registry with the base images. Because of this, the DevOps guys want me to change the Dockerfile to:
FROM registry.company.com:5000/python:3.7
I don't want this infrastructure detail baked in my code. URLs may change, I may want to build this image in another environment, etc. If possible, I would rather indicate the server in the pipeline, but the documentation regarding docker build has no parameter for this.
Is there a way to avoid editing the Dockerfile in this situation?
You would use a build arg for this:
ARG registry=docker.io/library
FROM ${registry}/python:3.7
Then for the build process:
docker build --build-arg registry=registry.company.com:5000 ...
Use docker.io for the registry name for the default Docker Hub, and library is the repository for official docker images, both of which you normally don't see when using the short format. Note that I usually include the library part in the local mirror so that official docker images and other repos that are mirrored can all use the same registry variable:
ARG registry=docker.io
FROM ${registry}/library/python:3.7
That means your local registry would need to have registry.company.com:5000/library/python:3.7.
To force users to specify the registry as part of the build, then don't provide a default value to the arg (or you could default the value of registry to something internal if that's preferred):
ARG registry
FROM ${registry}/python:3.7
You can work around the situation by manually pulling and re-tagging the image. docker build (and docker run) won't try to pull an image that already appears to be present locally, but that also means there's no verification that it actually matches what Docker Hub has. That means you can pull the image from your mirror, then docker tag it to look like a Docker Hub image:
docker pull registry.company.com:5000/python:3.7
docker tag registry.company.com:5000/python:3.7 python:3.7
My situation is I have two images with the same tag(hash different), one at local and another at the registry. When I build dockerfile, docker always compares the hash of the two images find not equal then will pull the registry one.
I know there has an imagePullPolicy in k8s. My question is docker has any settings like imagePullPolicy?
Thanks a lot.
The Docker tooling by and large either assumes you're going to manually pull images, or provides a --pull option to integrate it with other commands. For example:
docker build has a --pull option to try to retrieve a newer version of FROM images
docker run does not; it will always reuse the image you already have, or pull one if you don't have it
Neither core docker-compose nor docker-compose up has a --pull option, but there is a docker-compose pull command that pulls every image listed in a docker-compose.yml file
docker-compose build does have a --pull option
Core Docker always tries to pull an image if it is not present; there is no equivalent to imagePullPolicy: Never. Conversely, it never tries to communicate with an image registry outside of an explicit "pull" operation; you also cannot make docker run act like imagePullPolicy: Always.
It's good practice in Kubernetes to use a unique tag per build, so you can specify an explicit build and don't have to worry about imagePullPolicy. If you do this, in plain Docker, the implicit "pull if missing" will get you the correct behavior as well.
As a potential addendum to #David Maze's answer, it looks like docker run now also has a --pull option.
I have few docker images composed together in the stack using docker-compose.yml.
Now I want to transfer whole docker compose stack to the other host machine without uploading to the dockerhub,
And deploy it on the docker swarm.
I saw there is a thing called docker compose bundle, would that help?
If you’re deploying on a multi-host swarm (or something similar like Kubernetes or Nomad) you all but need a Docker registry. It doesn’t specifically have to be Docker Hub — quay.io, Amazon’s ECR, Google’s GCR, and self-hosted registries all work fine — but you do need to have pushed the built images somewhere where the orchestrator can retrieve them by name.
I’ve never used docker-compose bundle myself, but its documentation also notes that its operation “requires interaction with a Docker registry”.
The only real alternative is using docker save and docker load to manually move images between machines, but as a manual process it will get tedious very quickly, and you need to make sure an identical set of images are on every machine for consistency. Using a registry will be vastly easier.
The easyest way to do it is to use a Docker registry. The problem with Docker Hub is that you can only have one private registry, the rest must be public or paid.
Thankfully, there are other (free) alternatives:
Deploy your own private registry. Here is a nice tutorial where you can try it in the browser.
Use a free private registry. I personnaly use Codefresh. It can automatically build your image from a private repo (like bitbucket who has free plan too), but you can also just use it like a "simple" docker registry and push and pull your Docker images there.