I'm using centos:6 and need to build an image -using Dockerfile- which has a number of rpms installed (Oracle client, in fact). I don't want to copy/add the rpms inside the image, as it will make the image bulky (and I have to remove the rpms after install, anyway).
Is there a way to mount a folder on the host (CentOS, itself) which contains the rpms, on the image, via Dockerfile and/or using any option of "docker build" command, during the BUILD phase?
There's no way, according to the docs for build and run as well as from my experience.
Mounting things is done when you're running a container, rather than when building an image.
Related
I have just received the files for a website I have accepted to host in a docker image. I have not used docker before and the hosting site i am currently with does not allow for an image to be run on it. I would like to unpack the image files so i could upload to the host normally. I have been learning for a few days but have not found an easy route to unpack the image without having to manually move the files and change the routes linking some of them. What commands would be required to do this?
I think you have two options:
Read the dockerfile and check where the files come from.
(dockerfile is the recipe to build docker images)
If you don't have the dockerfile, you can run the container in your personal machine and copy them. (from the container to your machine)
docker cp <container_id>:/foo.txt foo.txt
I wonder if it is possible to make Docker automatically mount volumes during build or run container phase. With podman it is easy, using /usr/share/containers/mounts.conf, but I need to use Docker CE.
If it is not, may I somehow use host RHEL subscription during Docker build phase? I need to use RHEL UBI image and I have to use companys Satellite
A container image build in docker is designed to be self contained and portable. It shouldn't matter whether you run the build on your host or a CI server in the cloud. To do that, they rely on the build context and args to the build command, rather than other settings on the host, where possible.
buildah seems to have taken a different approach with their tooling, allowing you to use components from the host in your build, giving you more flexibility, but also fragility.
That's a long way of saying the "feature" doesn't exist in docker, and if it gets created, I doubt it would look like what you're describing. Instead, with buildkit, they allow you to inject secrets from the build command line, which are mounted into the steps where they are required. An example of this is available in the buildkit docs:
# syntax = docker/dockerfile:1.3
FROM python:3
RUN pip install awscli
RUN --mount=type=secret,id=aws,target=/root/.aws/credentials aws s3 cp s3://... ...
And to build that Dockerfile, you would pass the secret as a CLI arg:
$ docker build --secret id=aws,src=$HOME/.aws/credentials .
This is basically a follow-up question to How to include files outside of Docker's build context?: I'm using large files in all of my projects (several GBs) which I keep on an external drive, only used for development.
I want to COPY or ADD these files to my docker container when building it. The answer linked above allows one to specify a different path to a Dockerfile, potentially extending the build context. I find this unpractical, since this would require setting the build context to system root (?), to be able to include a single file.
Long story short: Is there any way or workaround to include a file that is far removed from the docker build context?
Three suggestions on things you could try:
include a file that is far removed from the docker build context?
You could construct your own build context by cp (or tar) files on the host into a dedicated directory tree. You don't have to use the actual source tree or your build tree.
rm -rf docker-build
mkdir docker-build
cp -a Dockerfile build/the-binary docker-build
cp -a /mnt/external/support docker-build
docker build ./docker-build
# reads docker-build/Dockerfile, and the files in the
# docker-build directory, but nothing else; only sends
# the docker-build directory to Docker as the build context
large files [...] (several GBs)
Docker doesn't deal well with build contexts this large. In the past I've at least seen docker build take a long time just on the step of sending the build context to itself, and docker push and docker pull have network issues when trying to send the gigabyte+ layer around.
It's a little hacky and breaks the "self-contained image" model a little bit, but you can provide these files as a Docker bind-mount instead of including them in the image. Your application needs to know what to do if the data isn't there. When you go to deploy the application, you also need to separately distribute the files alongside the Docker image and other deployment artifacts.
docker run \
-v /mnt/external/support:/app/support
...
the-image-without-the-support-files
only used for development
Potentially you can get away with not using Docker at all during this phase of development. Use a local source tree and local development tools; run your unit tests against these large test fixtures as needed. Build a Docker image only when you're about to run pre-commit integration tests; that may be late enough in the development cycle that you don't need these files.
I think the main thing you are worried about is that you do not want to send all files of a directory to docker daemon while it builds the image.
When directory was so big (in GBss) it takes lot of time to build an image.
If the requirement is to just use those files while you build anything inside docker, you can mount those to the container.
A tricky way
Run a container with base image and mount the direcotries inside it. docker run -d -v local-path:container-path
Get inside the container docker exec -it CONTAINER_ID bash
Run build step ./build-something.sh
Create image from the running container docker commit CONTAINER_ID
Tag the image docker tag IMAGE_ID tag:v1. You can get Image ID from previous command
From long term perspective this method may seem to be very tedious, but if you want to build image for 1 or 2 times , you can try this method.
I tried this for one of my docker image, as I want to avoid large amount of files sent to docker daemon during image build
The copy command gets source and destination values,
just specify full absolute path to your hard drive mount point as the src directory
COPY /absolute_path/to/harddrive /container/path
I have searched high and low for an answer to this question. Perhaps it's not possible!
I have some Dockerfiles in directories such as dev/Dockerfile and live/Dockerfile. I cannot find a way to provide these custom Dockerfiles to docker run. docker build has the -f option, but I cannot find a corresponding option for docker run in the root of the app. At the moment I think I will write my npm/gulp script to simply change into those directories, but this is clearly not ideal.
Any ideas?
You can't - that's not how Docker works:
The Dockerfile is used with docker build to build an image
The resulting image is used with docker run to run a container
If you need to make changes at run-time, then you need to modify your base image so that it can take, e.g. a command-line option to docker run, or a configuration file as a mount.
How do I copy files from a docker container to the host machine during docker build command?
As a part of building my docker image for my app, I'm running some tests inside it, and I would like to copy the output of the test run into the host (which is a continuous integration server) to do some reporting.
I wouldn't run the tests during build, this will only increase the size of your image. I would recommend you to build the image and then run it mounting a host volume into the container and changing the working directory to the mount point.
docker run -v `pwd`/results:/results -w /results -t IMAGE test_script
There is no easy way to do this. Volumes are only created at run time. You can grab it out of the docker filesystem, (e.g. mine is /var/lib/docker/devicemapper/mnt/CONTAINER_ID/rootfs/PATH_TO_FILE) though there is no good way to figure out when your test process is complete. You could create a file when it's finished and do an inotify, but this is ugly.