I would like to be able to pull a docker image from dockerhub and edit the dockerfile.. I am wondering if dockerhub actually downloads the dockerfile to the localhost and to where it is stored (I am running it from a MAC).
You dont download the docker image and edit their Dockerfile. The Dockerfile is an instruction set on how to build an image. Once the image is made, theres no going backwards. However if its on Dockerhub there should be a link to the Dockerfile. Look around at the page for links to the Dockerfile. Probably just a link to Github.
Once you have the dockerfile you then build it. For instance if you have a terminal open in the same folder as a Dockerimage file you could run
docker build -t myimage .
where myimage is the tag of your image. You will then have an instance of myimage on your local machine.
Also you can make a docker file that extends theres using FROM. For instance your docker file might start with
FROM java:6b38-jdk
# append to their image.
An image does not include a complete Dockerfile. When pulling an image you get an image manifest along with the required file system layers.
You can see some of the build steps with docker history --no-trunc IMAGE but it's not the complete Dockerfile.
There are utilities that try and generate a Dockerfile from the image history
Related
I want to generate/get a Dockerfile for an image that is pushed to registry, one that I don't have locally, without docker pull that image. I know it's possible to do this with docker CLI if the image already exists locally.
I have to take a Docker image from a vendor site and then push the image into the private repository (Artifactory). This way the CI/CD pipeline can retrieve the image from the private repository and deploy the image.
What is the best way to achieve it, do I need to recreate the image?
steps:
take a pull of the base docker image from vendor.
create new folder for your new docker image.
create a Dockerfile.
write your base docker image.
do the changes inside this folder.
build new docker image using cmd.
push the image into docker hub.
refer this (not exactly according to your need, but this helps): https://www.howtoforge.com/tutorial/how-to-create-docker-images-with-dockerfile/
for cmd and Dockerfile changes, refer docker office doc site
I believe its a tar or zip file that they have given you by docker save and docker export.
You can perform below operations.
1. Perform docker load < file.tar - You will get the image name that's loaded. Note down the name.
1. Download the tar or zip file to your local.
2. Perform cat file.tar | docker import image_name_that_you_noted_above
3. You are good to use the image now. tag it to your repo and push, or directly run using docker run
I've created a docker image of a project (very large project that takes time to compile) and I forgot to add a file in it.
I does not have to do with the build, it's just a test file.
Is it possible to add this file into my image without rebuilding everything ?
Thanks
Here's a full example to pull an image, add a local file to it, retag the image and push it back:
export IMAGE_URL=example.com/your_image:your_tag
docker pull $IMAGE_URL
docker create --name temp_container $IMAGE_URL
docker cp /host/path/to/file temp_container:/container/path/to/file
docker commit temp_container $IMAGE_URL
docker push $IMAGE_URL
Yes its possible, do the steps:
Mount the image and make a container
Do the command:
docker cp textFile.txt docker_container_name:/textFile.txt
Commit the container to build a new image with new tag version or another name;
Add the image using docker commit of a container as described above, or using Dockerfile.
Create a directory say temp and navigate into it
Move file file-to-be-added.extension to be added to the docker image into the newly created temp directory
Create a Dockerfile with below contents
Dockerfile
FROM your-registry/your-image:tag
COPY file-to-be-added.extension /destination/path/of/file-to-be-added.extension
Run below command to build the new image:
docker build -t your-registry/your-image:new-tag .
If required, push the image
docker push your-registry/your-image:new-tag
You should try to use docker commit.
Example: docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]
There's docker cp too, but it only works in running containers.
I hope this helps!
Brhaka
The ADD command is used to copy files/directories into a Docker image. It can copy data in three ways:
1. List item Copy files from the local storage to a destination in the Docker image.
2. Copy a tarball from the local storage and extract it automatically inside a destination in the Docker image.
3. Copy files from a URL to a destination inside the Docker image.
source: https://www.educative.io/edpresso/what-is-the-docker-add-command
I am trying to create a docker image using the below command .
docker build -t mytestapp .
My DockerFile looks like this
# Set the base image
FROM rhel7:latest
USER root
# Dockerfile author / maintainer
MAINTAINER Name <email.id#example.com>
# Update application repository list and install the Redis server.
RUN mkdir /usr/local/myapp/
ADD myapp-0.0.1-jar /usr/local/myapp/
RUN java -Dspring.profiles.active=qa -jar /usr/local/myapp/myapp-0.0.1.jar
# Expose default port
EXPOSE 8080
Questions:
1) Is it fine the way I am adding the JAR file. Will it be available inside /usr/local on the container after I prepared am image from the above build.
2) When I build the image using docker build command , is the build image is pushed to docker repository hub by default.
Since the WAR file contains credentials, I don't want to push the image to Docker Hub but we would like to push to our local Docker registry using Docker distribution and pushing with docker push.
Please clarify.
Answering your questions:
Docker recommends using the COPY instructions for adding single files into an image. It will be available inside the container at /usr/local/myapp/myapp-0.0.1-jar
When you build the image it will be available on your local docker-host. It won't leave the server unless you explicitly tell it so.
Another tip I want to give you is the recommended docker image naming convention, which is [Repository/Author]/[Imagename]:[Version].
So for your image it might be called zama/mytestapp:1.0
If you want to push it into your local registry, you'll have to name your image after the syntax [LocalRegistry:Port]/[Repository/Author]/[Imagename]:[Version].
So your image might now be called registry.example.com:5000/zama/mystestapp:1.0
If you have authentication on your registry, you need to docker login first and then simply push the image with docker push registry.example.com:5000/zama/mystestapp:1.0.
Is there a way to see the Dockerfile that generated an image I downloaded, to use as a template for my own docker images?
Use
docker history --no-trunc IMAGE_NAME_OR_ID
This will show all commands run in the image building process in reverse order. It's not exactly a Dockerfile, but you can find all essential content.