When I run docker build . the id that is spit out is of the image, which is what I thought was being committed to the docker repo. But when i run docker commit <id>, it says that it is not a valid container id. I usually get around this by starting the image in a container and then committing that id. But what should I do if the container requires linked containers to run? Running the container can take a long time especially when the build process is in the run script. If this fails, or requires a linked container to succeed, the process will exit, and my container will shut down, which does not allow me to create my new image. Is there a way to build your dockerfile and commit to the repo at the same time? Alternatives?
A Dockerfile is designed to provide a completely host independent way to repeatably build images without depending on any aspect of the host's configuration. This is why linking is not included in individual build steps, as it would render the build dependent on the other containers on the host at the time of build. Because of this Dockerfiles are not the only way to build containers.
When you must have a host dependent build environment, use a Dockerfile for the base part, installing dependencies etc, then use docker run from a script/configuration management system of your choice to setup the other containers and do the actual build. Once the build is complete, you can commit the resulting container, tag it with a name, and then push it to the repo.
To address the question at the top of the post, If you want to give a name to an image produced by a Dockerfile use docker tag image-id name
Committing takes a container and produces an image
tagging takes an image and gives it a name
pushing takes an image an a name and makes it available to pull later.
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I'm trying to deploy a docker image that is an asp.net core (.NET6) WebApi to ssh server.
I know the command for transferring the image file is:
docker save <my_image_namee> | ssh -C user#address docker load
Is it possible to execute this command within the Dockerfile right after building the image?
A Dockerfile can never run commands on the host, push its own image, save its output to a file, or anything else. The only thing it's possible to do in a Dockerfile is specify the commands needed to build the image within its isolated environment.
So, for example, in your Dockerfile you can't specify the image name that will be used (or its tag), or forcibly push something to a registry, or the complex docker save | ssh sequence you show. There's no option in the Dockerfile to do it.
You must run this as two separate commands using pretty much the syntax you show as your second command. If the two systems are on a shared network, a better approach would be to set up a registry server of some sort and docker push the image there; the docker save...docker load sequence isn't usually a preferred option, unless the two systems are on physically isolated networks. Whatever you need to do after you build the image, you could also consider asking your continuous-integration system to do it for you to avoid the manual step.
I need a suggestion about this problem statement.
I am rolling out a k8s job which uses a docker image and it does some computation, later on, I needed some folder which is basically present in a different docker image.
I want to understand how would I tackle this scenario, given I have to use a loop and copy the content from almost 30 docker images.
My thought,
install docker in my docker images which k8s job is using, run the container, copy the content, and kill it after that.
roll out a new job to copy the content and copy it to a mount location, which can be utilized.
I am afraid, if I have limited access to the host on which the k8s job is running, would I be able to run native docker commands.
I am just thinking out loud. Appreciate the suggestions.
I'm writing some automated build scripts which use a docker container as a build environment.
One thing that's been bugging me is finding a way to extract the build artifacts from the container and retaining the user ownership of the calling process.
Usually this is automatic; when a process creates a file, the file is owned by the user running the process. But where a process invokes a docker container, the container runs as a different user (often root). I see no simple way for the container to run as the same user as the calling process. So if I map a local directory when invoking docker (docker run --volume $(pwd)/target:/target) then when the build script in the image writes it's files, they will turn up in the host's build directory owned by root.
The other alternative I can see is to run the container, wait for it to complete, then use docker cp to extract the build artifacts. The trouble with this is I don't see a way to run a container to completion and then get the container ID of the recently created container.
Is there a common way to automatically / programmatically extract build artifacts from a docker container keeping the ownership of the calling process?
I have a use case where I call docker build . on one of our build machines.
During the build, a volume mount from the host machine is used to persist intermediate artifacts.
I don't care about this image at all. I have been tagging it with -t during the build and calling docker rmi after it's been created, but I was wondering if there was a one-liner/flag that could do this.
The docker build steps don't seem to have an appropriate flag for this behavior, but it may be simply because build is the wrong term.
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