I have a private registry with a set of images. It can be visualized as a store of applications.
My app can take these applications and run them on other machines.
To achieve this, my app first pull the image from the private registry and then copies it to a local registry for later use.
Step as are follow:
docker pull privateregistry:5000/company/app:tag
docker tag privateregistry:5000/company/app:tag localregistry:5000/company/app:tag
docker push localregistry:5000/company/app:tag
Then later on a different machine in my network:
docker pull localregistry:5000/company/app:tag
Is there a way to efficiently copy an image from a repository to another without using a docker client in between ?
you can use docker save to save the images to tar archive and then copy the tar to new host and use docker load to untar it.
read below links for more
https://docs.docker.com/engine/reference/commandline/save/
Is there a way to efficiently copy an image from a repository to another without using a docker client in between?
Yes, there's a variety of tools that implement this today. RedHat has been pushing their skopeo, Google has crane, and I've been working on my own with regclient. Each of these tools talks directly to the registry server without needing a docker engine. And at least with regclient (I haven't tested the others), these will only copy the layers that are not already in the target registry, avoiding the need to pull layers again. Additionally, you can move a multi-platform image, retaining all of the available platforms, which you would lose with a docker pull since that dereferences the image to a single platform.
Related
I just started working with docker this week and came across a 'dockerfile'. I was reading up on what this file does, and the official documentation basically mentions that the FROM keyword is needed to build a "base image". These base images are pulled from Docker hub, or downloaded from there.
Silly question - Are base images always pulled from docker hub?
If so and if I understand correctly I am assuming that running the dockerfile to create an image is not done very often (only when needing to create an image) and once the image is created then the image is whats run all the time?
So the dockerfile then can be migrated to which ever enviroment and things can be set up all over again quickly?
Pardon the silly question I am just trying to understand the over all flow and how dockerfile fits into things.
If the local (on your host) Docker daemon (already) has a copy of the container image (i.e. it's been docker pull'd) specified by FROM in a Dockerfile then it's cached and won't be repulled.
Container images include a tag (be wary of ever using latest) and the image name e.g. foo combined with the tag (which defaults to latest if not specified) is the full name of the image that's checked i.e. if you have foo:v0.0.1 locally and FROM:v0.0.1 then the local copy is used but FROM foo:v0.0.2 will pull foo:v0.0.2.
There's an implicit docker.io prefix i.e. docker.io/foo:v0.0.1 that references the Docker registry that's being used.
You could repeatedly docker build container images on the machines where the container is run but this is inefficient and the more common mechanism is that, once a container image is built, it is pushed to a registry (e.g. DockerHub) and then pulled from there by whatever machines need it.
There are many container registries: DockerHub, Google Artifact Registry, Quay etc.
There are tools other than docker that can be used to interact with containers e.g. (Red Hat's) Podman.
I have 2 machines(separate hosts) running docker and I am using the same image on both the machines. How do I keep both the images in sync. For eg. suppose I make changes to the image in one of the hosts and want the changes to reflect in the other host as well. I can commit the image and copy the image over to the other host. Is there any other efficient way of doing this??
Some ways I can think of:
1. with a Docker registry
the workflow here is:
HOST A: docker commit, docker push
HOST B: docker pull
2. by saving the image to a .tar file
the workflow here is:
HOST A: docker save
HOST B: docker load
3. with a Dockerfile and by building the image again
the workflow here is:
provide a Dockerfile together with your code / files required
everytime your code has changed and you want to make a release, use docker build to create a new image.
from the hosts that you want to take the update, you will have to get the updated source code (maybe by using a version control software like Git), and then docker build the image
4. CI/CD pipeline
you can see a video here: docker.com/use-cases/cicd
Keep in mind that containers are considered to be ephemeral. This means that updating an image inside another host will then require:
to stop and remove any old container (running with the outdated image)
to run a new one (with the updated image)
I quote from: Best practices for writing Dockerfiles
General guidelines and recommendations
Containers should be ephemeral
The container produced by the image your Dockerfile defines should be as ephemeral as possible. By “ephemeral,” we mean that it can be stopped and destroyed and a new one built and put in place with an absolute minimum of set-up and configuration.
You can perform docker push to upload you image to docker registry and perform a docker pull to get the latest image from another host.
For more information please look at this
I want to deploy my project avoiding usage of docker-hub. Is it a good idea to sent an image in tar file or just a Dockerfile combined with all local dependencies would be preferable (in this case user will need to build the image on his own)? Is there a way to deploy container itself?
If you cannot run a local Docker Registry, then sending the image itself is preferable, as it won't force the user to access any dependencies.
Sending the Dockerfile as a complement (to document the image) is good as well.
But the main alternative is to use a docker registry. If however you don't want to depend on local registry storage, you can use a remote storage like S3 with minio.
I was wondering if there was a way to clone images from a local server.
The servers running containers will be hosted behind a bandwidth constrained connection. It would be great if there was a way to pull given containers for one server and then pull from that initial local server to update the containers on the remaining servers.
You could pull those images you want, give hem a new tag, and put them in your own registry.
For instance, let's say you pulled down the official registry image and stood it up at myregistry.internal.mycompany.com. Now, if you wanted to have a CentOS image available for all of your servers but didn't want to pull them all from the official repo (incurring the bandwitch charges) then you could pull a CentOS image (let's say centos:latest - docker pull centos) and then give that image a new tag, like this:
docker tag centos:latest myregistry.internal.mycompany.com/centos:latest
Now from your other servers you just pull 'myregistry.internal.mycompany.com/centos:latest'
Setting up your own repo is really easy as a docker container itself. You can pull the image and learn more at https://registry.hub.docker.com/_/registry/
I think you have a few options. If what you actually want to manage is images rather than containers:
You could set up a private Docker registry, and then push to/pull from that local repository. This may ultimately be the easiest if that is something that you want to do fairly often, because you're just using standard docker push/docker pull commands.
You could use docker save to save images on one server and docker load to load the images on another server.
If you are actually trying to move containers around:
You could use docker export on one server and docker import on another server.
I'm wondering where Docker's images are exactly stored to in my local host machine.
Can I share my Docker-Image without using the Docker-Hub or a Dockerfile but the 'real' Docker-Image? And what is exactly happening when I 'push' my Docker-Image to Docker-Hub?
Docker images are stored as filesystem layers. Every command in the Dockerfile creates a layer. You can also create layers by using docker commit from the command line after making some changes (via docker run probably).
These layers are stored by default under /var/lib/docker. While you could (theoretically) cherry pick files from there and install it in a different docker server, is probably a bad idea to play with the internal representation used by Docker.
When you push your image, these layers are sent to the registry (the docker hub registry, by default… unless you tag your image with another registry prefix) and stored there. When pulling, the layer id is used to check if you already have the layer locally or it needs to be downloaded. You can use docker history to peek at which layers (other images) are used (and, to some extent, which command created the layer).
As for options to share an image without pushing to the docker hub registry, your best options are:
docker save an image or docker export a container. This will output a tar file to standard output, so you will like to do something like docker save 'dockerizeit/agent' > dk.agent.latest.tar. Then you can use docker load or docker import in a different host.
Host your own private registry. - Outdated, see comments See the docker registry image. We have built an s3 backed registry which you can start and stop as needed (all state is kept on the s3 bucket of your choice) which is trivial to setup. This is also an interesting way of watching what happens when pushing to a registry
Use another registry like quay.io (I haven't personally tried it), although whatever concerns you have with the docker hub will probably apply here too.
Based on this blog, one could share a docker image without a docker registry by executing:
docker save --output latestversion-1.0.0.tar dockerregistry/latestversion:1.0.0
Once this command has been completed, one could copy the image to a server and import it as follows:
docker load --input latestversion-1.0.0.tar
Sending a docker image to a remote server can be done in 3 simple steps:
Locally, save docker image as a .tar:
docker save -o <path for created tar file> <image name>
Locally, use scp to transfer .tar to remote
On remote server, load image into docker:
docker load -i <path to docker image tar file>
[Update]
More recently, there is Amazon AWS ECR (Elastic Container Registry), which provides a Docker image registry to which you can control access by means of the AWS IAM access management service. ECR can also run a CVE (vulnerabilities) check on your image when you push it.
Once you create your ECR, and obtain the "URL" you can push and pull as required, subject to the permissions you create: hence making it private or public as you wish.
Pricing is by amount of data stored, and data transfer costs.
https://aws.amazon.com/ecr/
[Original answer]
If you do not want to use the Docker Hub itself, you can host your own Docker repository under Artifactory by JFrog:
https://www.jfrog.com/confluence/display/RTF/Docker+Repositories
which will then run on your own server(s).
Other hosting suppliers are available, eg CoreOS:
http://www.theregister.co.uk/2014/10/30/coreos_enterprise_registry/
which bought quay.io