I need to know about offline usage of a registry for docker images.
When a docker image is pulled from the official microsoft site, adjusted, and then pushed to a registry, is it the complete image or are layers missing?
When other hosts pull the image from the registry, which might be used offline, will the client host need an internet connection nonetheless to pull missing/secret layers from the microsoft server? (or is it a full image that was pulled from microsoft and later pushed to the registry?)
What about signatures? Will those get updated automatically for each layer, when the image gets adjusted, applications stored within, etc., so that there are no verification errors when other clients pull the adjusted image from the local registry?
When you build an image from another image docker download the base image locally to your computer you can even save it as a file.
When you push an image to local registry it pushed the complete image including the base image it was built from.
When someone will try to pull the new image from your local registry they won't be needing internet access.
Related
I know Watchtower (https://github.com/v2tec/watchtower), but would like to understand if there is a way that I check for docker image updates without pull (downloading it)
I seems that if I ie. use docker pull pihole:latest it download the image, no matter if it the newest or already on my device.
I would like to get the digest or image id from the docker hub, so I can compare it with my local image id
I'm trying to migrate from docker-maven-plugin to kubernetes-maven-plugin for an test-setup for local development and jenkins-builds. The point of the setup is to eliminate differences between the local development and the jenkins-server. Since docker built the image, the image is stored in the local repository and doesn't have to be uploaded to a central server where the base-images are located. So we can basically verify our build without uploading anything to the server and the images is discarded after the task is done (running integrationstests).
Is there a similar way to trick kubernetes to store the image into the local repository without having to take the roundtrip to a central repository? Eg, behave as if the image is already downloaded? Note that I still need to fetch the base-image from the central repository.
If you don't want to use any docker repo (public or private), you can use what is called Pre-pulled-images.
This is a bit annoying as you need to make sure all the kubernetes nodes have the images there and also set the ImagePullPolicy to Never in every kubernetes manifest.
In your case, if what you call local repository is some private docker registry, you just need to store the credentials to the private registry in a kubernetes secret and either patch you default service account with ImagePullSecrets or your actual deployment/pod manifest. More details about that https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/
We're setting up a server to host Windows containers.
This server gets the images from an internal Docker registry we have setup.
The issue is that the server is unable to pull down images because it's trying to get a base image from the internet, and the server has no internet connection.
I found a troubleshooting script from Microsoft and notice one passage:
At least one of 'microsoft/windowsservercore' or
'microsoft/nanoserver' should be installed
Try docker pull microsoft/nanoserver or docker pull
microsoft/windowsservercore to pull a Windows container image
Since my PC has internet connection, I downloaded these images, pushed them to the registry, but pulling the images on the new server fails:
The description for Event ID '1' in Source 'docker' cannot be found. The local computer may not have the necessary registry information or message DLL files to display the message, or you may not have permission to access them. The following information is part of the event:'Error initiating layer download: Get https://go.microsoft.com/fwlink/?linkid=860052: dial tcp 23.207.173.222:443: connectex: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.'
That link it's trying to get is a base image on the internet, but I thought the registry was storing the complete image, so what gives? Is it really not possible to store the base images in a registry?
Doing some reading I found this: https://docs.docker.com/registry/deploying/#considerations-for-air-gapped-registries
Certain images, such as the official Microsoft Windows base images,
are not distributable. This means that when you push an image based on
one of these images to your private registry, the non-distributable
layers are not pushed, but are always fetched from their authorized
location. This is fine for internet-connected hosts, but will not work
in an air-gapped set-up.
The doc then details how to setup the registry to store non-distributable layers, but they also say to be mindful of the terms of use for non-distributable layers.
So two possible solutions are:
Make sure you can store the non-distributable layers, then reconfigure the registry to store the non-distributable layers
Connect the server to the internet, download the base images, then use those images
We have been using locked version of the Minio image (RELEASE.2016-10-07T01-16-39Z), but now it seems to have been removed.
I'm getting this from Docker:
Pulling minio (minio/minio:RELEASE.2016-10-07T01-16-39Z)...
Pulling repository docker.io/minio/minio
ERROR: Tag RELEASE.2016-10-07T01-16-39Z not found in repository docker.io/minio/minio
I'm finding Docker hub hard to navigate. Where can I find a list of available versioned images, or a mirror to my exact image?
You can find the available tags for minio/minio on that repository's tag page.
If you have the image you want already downloaded on any of your systems, you can push it to Docker Hub yourself, then pull it onto your other systems. This has the benefit that you can control whether you delete that image (it's your account, not someone else's).
You can also use a private registry, if you want, which would prevent Docker from deleting the image from Docker Hub against your will for some reason. But that is extra work you may not wish to do (you would have to host the registry yourself, set it up, maintain it...)
We removed the docker version due to incompatibilities, from the recent releases it won't happen.
Is there any way to prevent images being uploaded to docker hub with the same tags as existing images? Our use case is as follows.
We deploy to production with a docker-compose file with the tags of images as version numbers. In order to support roll-back to previous environments and idempotent deployment it is necessary that a certain tagged docker image always refer to the same image.
However, docker hub allows images to be uploaded with the same tags as existing images (they override the old image). This completely breaks the idea of versioning your images.
We currently have work-arounds which involve our build scripts pulling all versions of an image and looking through the tags to check that an overwrite will not happen etc. but it feels like there has to be a better way.
If docker hub does not support this, is there a way to do docker deployment without docker hub?
The tag system has no way of preventing images been overwritten; you have to come up with your own processes to handle this (and h3nrik's answer is an example of this).
However, you could use the digest instead. In the new v2 of the registry, all images are given a checksum, known as a digest. If an image or any of its base layers change, the digest will change. So if you pull by digest, you can be absolutely certain that the contents of that image haven't changed over time and that the image hasn't been tampered with.
Pulling by digest looks like:
docker pull debian#sha256:f43366bc755696485050ce14e1429c481b6f0ca04505c4a3093dfdb4fafb899e
You should get the digest when you do a docker push.
Now, I agree that pulling by digest is a bit unwieldy, so you may want to set up a system that simply tracks digest and tag and can verify that the image hasn't changed.
In the future, this situation is likely to improve, with tools like Notary for signing images. Also, you may want to look at using labels to store metadata such as git hash or build number.
Assuming you have a local build system to build your Docker images: you could include the build number from your local build job in your tag. With that you assure your requirement:
... it is necessary that a certain tagged docker image always refer to the same image.
When your local build automatically pushes to docker hub it is assured that each push pushes an image with a unique tag.