Related
By default, if I issue command:
sudo docker pull ruby:2.2.1
it will pull from the docker.io offical site by default.
Pulling repository docker.io/library/ruby
How do I change it to my private registry. That means if I issue
sudo docker pull ruby:2.2.1
it will pull from my own private registry, the output is something like:
Pulling repository my_private.registry:port/library/ruby
UPDATE: Following your comment, it is not currently possible to change the default registry, see this issue for more info.
You should be able to do this, substituting the host and port to your own:
docker pull localhost:5000/registry-demo
If the server is remote/has auth you may need to log into the server with:
docker login https://<YOUR-DOMAIN>:8080
Then running:
docker pull <YOUR-DOMAIN>:8080/test-image
There is the use case of a mirror of Docker Hub (such as Artifactory or a custom one), which I haven't seen mentioned here. This is one of the most valid cases where changing the default registry is needed.
Luckily, Docker (at least version 19.03.3) allows you to set a mirror (tested in Docker CE). I don't know if this will work with additional images pushed to that mirror that aren't on Docker Hub, but I do know it will use the mirror instead. Docker documentation: https://docs.docker.com/registry/recipes/mirror/#configure-the-docker-daemon.
Essentially, you need to add "registry-mirrors": [] to the /etc/docker/daemon.json configuration file. So if you have a mirror hosted at https://my-docker-repo.my.company.com, your /etc/docker/daemon.json should contain:
{
"registry-mirrors": ["https://my-docker-repo-mirror.my.company.com"]
}
Afterwards, restart the Docker daemon. Now if you do a docker pull postgres:12, Docker should fetch the image from the mirror instead of directly from Docker Hub. This is much better than prepending all images with my-docker-repo.my.company.com
It turns out this is actually possible, but not using the genuine Docker CE or EE version.
You can either use Red Hat's fork of docker with the '--add-registry' flag or you can build docker from source yourself with registry/config.go modified to use your own hard-coded default registry namespace/index.
The short answer to this is you don't, or at least you really shouldn't.
Yes, there are some container runtimes that allow you to change the default namespace, specifically those from RedHat. However, RedHat now regrets this functionality and discourages customers from using it. Docker has also refused to support this.
The reason this is so problematic is because is results in an ambiguous namespace of images. The same command run on two different machines could pull different images depending on what registry they are configured to use. Since compose files, helm templates, and other ways of running containers are shared between machines, this actually introduces a security vulnerability.
An attacker could squat on well known image names in registries other than Docker Hub with the hopes that a user may change their default configuration and accidentally run their image instead of the one from Hub. It would be trivial to create a fork of a tool like Jenkins, push the image to other registries, but with some code that sends all the credentials loaded into Jenkins out to an attacker server. We've even seen this causing security vulnerability reports this year for other package managers like PyPI, NPM, and RubyGems.
Instead, the direction of container runtimes like containerd is to make all image names fully qualified, removing the Docker Hub automatic expansion (tooling on top of containerd like Docker still apply the default expansion, so I doubt this is going away any time soon, if ever).
Docker does allow you to define registry mirrors for Docker Hub that it will query first before querying Hub, however this assumes everything is still within the same namespace and the mirror is just a copy of upstream images, not a different namespace of images. The TL;DR on how to set that up is the following in the /etc/docker/daemon.json and then systemctl reload docker:
{
"registry-mirrors": ["https://<my-docker-mirror-host>"]
}
For most, this is a non-issue (this issue to me is the docker engine doesn't have an option to mirror non-Hub registries). The image name is defined in a configuration file, or a script, and so typing it once in that file is easy enough. And with tooling like compose files and Helm templates, the registry can be turned into a variable to allow organizations to explicitly pull images for their deploy from a configurable registry name.
if you are using the fedora distro, you can change the file
/etc/containers/registries.conf
Adding domain docker.io
Docker official position is explained in issue #11815 :
Issue 11815: Allow to specify default registries used in pull command
Resolution:
Like pointed out earlier (#11815), this would fragment the namespace, and hurt the community pretty badly, making dockerfiles no longer portable.
[the Maintainer] will close this for this reason.
Red Hat had a specific implementation that allowed it (see anwser, but it was refused by Docker upstream projet). It relied on --add-registry argument, which was set in /etc/containers/registries.conf on RHEL/CentOS 7.
EDIT:
Actually, Docker supports registry mirrors (also known as "Run a Registry as a pull-through cache").
https://docs.docker.com/registry/recipes/mirror/#configure-the-docker-daemon
It seems it won't be supported due to the fragmentation it would create within the community (i.e. two users would get different images pulling ubuntu:latest). You simply have to add the host in front of the image name. See this github issue to join the discussion.
(Note, this is not intended as an opinionated comment, just a very short summary of the discussion that can be followed in the mentioned github issue.)
I tried to add the following options in the /etc/docker/daemon.json.
(I used CentOS7)
"add-registry": ["192.168.100.100:5001"],
"block-registry": ["docker.io"],
after that, restarted docker daemon.
And it's working without docker.io.
I hope this someone will be helpful.
Earlier this could be achieved using DOCKER_OPTS in the /etc/default/docker config file which worked on Ubuntu 14:04 and had some issues on Ubuntu 15:04. Not sure if this has been fixed.
The below line needs to go into the file /etc/default/docker on the host which runs the docker daemon. The change points to the private registry is installed in your local network. Note: you would require to restart the docker service followed with this change.
DOCKER_OPTS="--insecure-registry <priv registry hostname/ip>:<port>"
I'm adding up to the original answer given by Guy which is still valid today (soon 2020).
Overriding the default docker registry, like you would do with maven, is actually not a good practice.
When using maven, you pull artifacts from Maven Central Repository through your local repository management system that will act as a proxy. These artifacts are plain, raw libs (jars) and it is quite unlikely that you will push jars with the same name.
On the other hand, docker images are fully operational, runnable, environments, and it makes total sens to pull an image from the Docker Hub, modify it and push this image in your local registry management system with the same name, because it is exactly what its name says it is, just in your enterprise context. In this case, the only distinction between the two images would precisely be its path!!
Therefore the need to set the following rule: the prefix of an image indicates its origin; by default if an image does not have a prefix, it is pulled from Docker Hub.
Didn't see the answer for MacOS, so want to add here:
2 Method as below:
Option 1 (Through Docker Desktop GUI):
Preference -> Docker Engine -> Edit file -> Apply and Restart
Option 2:
Directly edit the file ~/.docker/daemon.json
Haven't tried, but maybe hijacking the DNS resolution process by adding a line in /etc/hosts for hub.docker.com or something similar (docker.io?) could work?
By default, if I issue command:
sudo docker pull ruby:2.2.1
it will pull from the docker.io offical site by default.
Pulling repository docker.io/library/ruby
How do I change it to my private registry. That means if I issue
sudo docker pull ruby:2.2.1
it will pull from my own private registry, the output is something like:
Pulling repository my_private.registry:port/library/ruby
UPDATE: Following your comment, it is not currently possible to change the default registry, see this issue for more info.
You should be able to do this, substituting the host and port to your own:
docker pull localhost:5000/registry-demo
If the server is remote/has auth you may need to log into the server with:
docker login https://<YOUR-DOMAIN>:8080
Then running:
docker pull <YOUR-DOMAIN>:8080/test-image
There is the use case of a mirror of Docker Hub (such as Artifactory or a custom one), which I haven't seen mentioned here. This is one of the most valid cases where changing the default registry is needed.
Luckily, Docker (at least version 19.03.3) allows you to set a mirror (tested in Docker CE). I don't know if this will work with additional images pushed to that mirror that aren't on Docker Hub, but I do know it will use the mirror instead. Docker documentation: https://docs.docker.com/registry/recipes/mirror/#configure-the-docker-daemon.
Essentially, you need to add "registry-mirrors": [] to the /etc/docker/daemon.json configuration file. So if you have a mirror hosted at https://my-docker-repo.my.company.com, your /etc/docker/daemon.json should contain:
{
"registry-mirrors": ["https://my-docker-repo-mirror.my.company.com"]
}
Afterwards, restart the Docker daemon. Now if you do a docker pull postgres:12, Docker should fetch the image from the mirror instead of directly from Docker Hub. This is much better than prepending all images with my-docker-repo.my.company.com
It turns out this is actually possible, but not using the genuine Docker CE or EE version.
You can either use Red Hat's fork of docker with the '--add-registry' flag or you can build docker from source yourself with registry/config.go modified to use your own hard-coded default registry namespace/index.
The short answer to this is you don't, or at least you really shouldn't.
Yes, there are some container runtimes that allow you to change the default namespace, specifically those from RedHat. However, RedHat now regrets this functionality and discourages customers from using it. Docker has also refused to support this.
The reason this is so problematic is because is results in an ambiguous namespace of images. The same command run on two different machines could pull different images depending on what registry they are configured to use. Since compose files, helm templates, and other ways of running containers are shared between machines, this actually introduces a security vulnerability.
An attacker could squat on well known image names in registries other than Docker Hub with the hopes that a user may change their default configuration and accidentally run their image instead of the one from Hub. It would be trivial to create a fork of a tool like Jenkins, push the image to other registries, but with some code that sends all the credentials loaded into Jenkins out to an attacker server. We've even seen this causing security vulnerability reports this year for other package managers like PyPI, NPM, and RubyGems.
Instead, the direction of container runtimes like containerd is to make all image names fully qualified, removing the Docker Hub automatic expansion (tooling on top of containerd like Docker still apply the default expansion, so I doubt this is going away any time soon, if ever).
Docker does allow you to define registry mirrors for Docker Hub that it will query first before querying Hub, however this assumes everything is still within the same namespace and the mirror is just a copy of upstream images, not a different namespace of images. The TL;DR on how to set that up is the following in the /etc/docker/daemon.json and then systemctl reload docker:
{
"registry-mirrors": ["https://<my-docker-mirror-host>"]
}
For most, this is a non-issue (this issue to me is the docker engine doesn't have an option to mirror non-Hub registries). The image name is defined in a configuration file, or a script, and so typing it once in that file is easy enough. And with tooling like compose files and Helm templates, the registry can be turned into a variable to allow organizations to explicitly pull images for their deploy from a configurable registry name.
if you are using the fedora distro, you can change the file
/etc/containers/registries.conf
Adding domain docker.io
Docker official position is explained in issue #11815 :
Issue 11815: Allow to specify default registries used in pull command
Resolution:
Like pointed out earlier (#11815), this would fragment the namespace, and hurt the community pretty badly, making dockerfiles no longer portable.
[the Maintainer] will close this for this reason.
Red Hat had a specific implementation that allowed it (see anwser, but it was refused by Docker upstream projet). It relied on --add-registry argument, which was set in /etc/containers/registries.conf on RHEL/CentOS 7.
EDIT:
Actually, Docker supports registry mirrors (also known as "Run a Registry as a pull-through cache").
https://docs.docker.com/registry/recipes/mirror/#configure-the-docker-daemon
It seems it won't be supported due to the fragmentation it would create within the community (i.e. two users would get different images pulling ubuntu:latest). You simply have to add the host in front of the image name. See this github issue to join the discussion.
(Note, this is not intended as an opinionated comment, just a very short summary of the discussion that can be followed in the mentioned github issue.)
I tried to add the following options in the /etc/docker/daemon.json.
(I used CentOS7)
"add-registry": ["192.168.100.100:5001"],
"block-registry": ["docker.io"],
after that, restarted docker daemon.
And it's working without docker.io.
I hope this someone will be helpful.
Earlier this could be achieved using DOCKER_OPTS in the /etc/default/docker config file which worked on Ubuntu 14:04 and had some issues on Ubuntu 15:04. Not sure if this has been fixed.
The below line needs to go into the file /etc/default/docker on the host which runs the docker daemon. The change points to the private registry is installed in your local network. Note: you would require to restart the docker service followed with this change.
DOCKER_OPTS="--insecure-registry <priv registry hostname/ip>:<port>"
I'm adding up to the original answer given by Guy which is still valid today (soon 2020).
Overriding the default docker registry, like you would do with maven, is actually not a good practice.
When using maven, you pull artifacts from Maven Central Repository through your local repository management system that will act as a proxy. These artifacts are plain, raw libs (jars) and it is quite unlikely that you will push jars with the same name.
On the other hand, docker images are fully operational, runnable, environments, and it makes total sens to pull an image from the Docker Hub, modify it and push this image in your local registry management system with the same name, because it is exactly what its name says it is, just in your enterprise context. In this case, the only distinction between the two images would precisely be its path!!
Therefore the need to set the following rule: the prefix of an image indicates its origin; by default if an image does not have a prefix, it is pulled from Docker Hub.
Didn't see the answer for MacOS, so want to add here:
2 Method as below:
Option 1 (Through Docker Desktop GUI):
Preference -> Docker Engine -> Edit file -> Apply and Restart
Option 2:
Directly edit the file ~/.docker/daemon.json
Haven't tried, but maybe hijacking the DNS resolution process by adding a line in /etc/hosts for hub.docker.com or something similar (docker.io?) could work?
We are using Proget as our Docker Repository of choice and we are running into size issues rapidly. There isn't a good mechanism to prune pre-releases or old images that are no longer needed like there is for other artifacts.
I am using Docker.Dotnet nuget library and have a process where I can connect to a Docker API, evaluate the images using their tags and label or purge what has aged out.
The issue I am running into is that I cannot find the Docker API URL:Port anywhere. My current setup is myrepo.com/docker (and is what I have registered locally), but I cannot connect my Docker client to it.
We are planning on migrating away from this repository anyhow, but this would apply for any other docker repository of choice. For example, what is the URL of the docker hub for API interaction?
Did you look at the ProGet Retention Rules? There's a section on Container rules that seems to already purge what you want...
we believe new Websphere Liberty 16.0.0.2 has an important bug related to JAX-RS 2.0 client, which prevents standard REST calls from apps deployed to work. The last version we know to be this bug free is 8.5.5.9, but Dockerfile of the official Docker by IBM has already been updated to 16.0.0.2
Even though we use Dockers, I am no Docker geek. Is it possible to specify in my Dockerfile in first line:
FROM websphere-liberty:webProfile7
That I want the version of the Docker that includes 8.5.5.9 and not the last one? Which one would it be? (other Docker, like Solr, explain the different versions in the doc)
If you look at the 'tags' tab on Docker Hub you will see that there are other historical tags still available including websphere-liberty:8.5.5.9-webProfile7. Note that these images represent a snapshot in time e.g. they are not rebuilt when new versions of the base Ubuntu image are created. The intention is that Liberty provides zero migration and therefore you should always be able to use the latest. You have obviously found the counter-example...
I have two hosts and docker is installed in each.
As we know, each docker stores the images in local /var/lib/docker directory.
So If I want to use some image, such as ubuntu, I must execute the docker pull to download from internet in each host.
I think it's slow.
Can I store the images in a shared disk array? Then have some host pull the image once, allowing every host, with access to the shared disk, to use the image directly.
Is it possible or good practice? Why docker is not designed like this?
It may need to hack the docker's source code to implement this.
Have you looked at this article
Dockerizing an Apt-Cacher-ng Service
http://docs.docker.com/examples/apt-cacher-ng/
extract
This container makes the second download of any package almost instant.
At least one node will be very fast, and I think it should possible to tell the second node to use the cache of the first node.
Edit : you can run your own registry, with a command similar to
sudo docker run -p 5000:5000 registry
see
https://github.com/docker/docker-registry
What you are trying to do is not supposed to work as explained by cpuguy83 at this github/docker issue.
Indeed:
The underlying storage driver would need to synchronize access.
Sharing /var/lib/docker is far not enough and won't work!
According to the doc.docker.com/registry:
You should use the Registry if you want to:
tightly control where your images are being stored
fully own your images distribution pipeline
integrate image storage and distribution tightly into your in-house development workflow
So I guess that this is the (/your) best option to work this out (but I guess that you got that info -- I just add it here to update the details).
Good luck!
Update in 2016.1.25 docker mirror feature is deprecated
Therefore this answer is not applicable now, leave for reference
Old info
What you need is the mirror mode for docker registry, see https://docs.docker.com/v1.6/articles/registry_mirror/
It is supported directly from docker-registry
Surely you can use public mirror service locally.