Is there a way to clone a Dockerfile from GitLab with the docker command?
I want to use the feature that allow pull and commit.
I am not sure if I have understand well but these pull and commit update the Dockerfile from the git repositories ? Or is it only locally in the next images ?
If not, is there a way to get all the change you made from the previous image made by the Dockerfile into another Dockerfile ?
I know you can clone with Git directly, but like for npm, you can also use Git url like git+https:// or git+ssh://
The pull/commit commands affect the related image and operate directly against your configured registry, which is the official Docker Hub Registry unless configured otherwise. Perhaps some confusion may arise from the registry's support for Automated Builds, where the registry is directly bound to a repository and rebuilds the image every time the targeted repository branch changes.
If you wish to reuse someone's Docker image, the best approach is to simply reference it via the FROM instruction in your Dockerfile and effectively fork the image. While it's certainly possible to clone the original source repository and continue editing the Dockerfile contained therein, you usually do not want to go down that path.
So if there exists such a foo/bar image you want to continue building upon, the best, most direct approach to do so is to create your own Dockerfile, inherit the image by setting it as a base for your succeeding instructions via FROM foo/bar and possibly pushing your baz/bar image back into the registry if you want it to be publicly available for others to re-base upon.
Related
This is my first time using Docker, so excuse my potentially improper terminology. Our team uses a Docker image that contains the entire development environment, minus the git repo that needs to be cloned manually within a persistent container based on this image. The Docker image hosted on our repository is frequently updated, e.g. to include new 3rd party dependencies and other files, making my local environment - which includes a directory with the git repo where I do my work - out-of-date.
Is there a way to update my local environment with the latest image changes without having to pull the entire image with docker pull image:latest and start from scratch? Assuming there are no conflicts, I would like to preserve my local changes (git repo clone, local filesystem modifications etc.); so I'm looking for something like git pull for Docker, if that makes sense.
I must have missed something, but a search on this issue didn't yield any viable solutions.
I have damaged my working docker image by pushing and overwriting by a faulty docker image on hub.docker.com. How can I revert the last push?
There is no revert option that I'm aware of. If you have a good copy of your image somewhere, you can repush that to the registry. To avoid this issue in the future, follow one or more of these steps:
Avoid using the latest tag and give each build a unique tag.
Use a reproducible build process with a Dockerfile that is saved in version control which uses specific versions for all dependencies. This allows you to checkout a previous state of the Dockerfile to rerun a previous build.
Maintain a private registry of your own for your images and any dependencies you have on other images. Make sure to maintain those dependencies (updating periodically) and backup your registry.
You can use the Advanced Image Management page in docker hub to copy the digest of the good image, pull it to your system, overwrite the tag, then push back. Use these commands:
docker image pull myname/example#sha256:1234
docker tag myname/example#sha256:1234 myname/example:mytag
docker push myname/example:mytag
Assuming myname/example#sha256:1234 is your copied digest of the good image from docker hub, myname/example:mytag is what you want to tag the image as.
I want to keep the images that I used in my docker hub account while maintaining reference to the pulled image. Something like when you fork a project in github.
Currently I have tried jwilder/nginx-proxy image. Now that I am satisfied with it, I committed the working container to username/nginx-proxy image and push it.
The problem with this approach is it is like a fresh image and it doesn't show the layer from jwilder/nginx-proxy. No documentation or even Dockerfile.
If you push the image, there is no reference to the original, that behavior is normal. You can put that reference or link using your "repo info".
The Dockerfile is only shown if you did an automated build linking your github or bitbucket account and the push is automatically done based on the Dockerfile of your project.
Why RUN git checkout -b mybranch switch to the branch but the content remain the one fetched from the master branch?
The whole point of Docker is that it only rebuilds the part of an image that has changed. It has no way of knowing that the content in the repo has changed, all it knows is that is already has a cached image "slice" for this step in the Dockerfile. So it uses the image it previously built.
As Mark notes, you can force a regeneration using --no-cache. Another option is to have a source code container that is always built using --no-cache which you add volumes to and then use that code via those volumes in a different container (look at 'volumes from' for docker-compose). Then you always get the changes in the repo, as it is built every time from scratch. You may want to look into 'docker-compose' for this sort of work.
When you run docker build look carefully at the output. When it has a cached version of a step it will say as much. When it has to build it, it will also note that.
Have you tried running your build with the "--no-cache" option?
I'd also recommend reading the following:
https://ryanfb.github.io/etc/2015/07/29/git_strategies_for_docker.html
Finally, do you really need to run git within your build? Personally I use Jenkins that runs my build within a workspace that is separately checked out from git.
We can create Docker images and all push them to Hub without a Dockerfile. Why is it useful, to have a Dockerfile? What are advantages of it? Dockerfile creation is a process with high consumption of time and can made only by a human.
I would like to know what is the main difference between a base image based, committed image and a Dockerfile based image.
Dockerfile is used for automation of work by specifying all step that we want on docker image.
A Dockerfile is a text document that contains all the commands a user
could call on the command line to assemble an image. Using docker
build users can create an automated build that executes several
command-line instructions in succession.
yes , we can create Docker images but every time when we want to make any change then you have to change manually and test and push it .
or if you use Dockerfile with dockerhub then it will rebuild automatically and make change on every modification and if something wrong then rebuild will fail.
Advantages of Dockerfile
Dockerfile is automated script of Docker images
manual image creation will become complicated when you want to test same setup on different OS flavor then you have to create image for all flavor but by small changing in dockerfile you can create images for different flavor
it have simple syntax for image and do many change automatically that will take more time while doing manually.
Dockerfile have systematic step that can be understand by others easily and easy to know what exact configuration changed in base image.
Advantage of Dockerfile with dockerhub
Docker Hub provide private repository for Dockerfile.
Dockerfile can share among team and organization.
Automatic image builds
Webhooks that are attached to your repositories that allow you to trigger an event when an image or updated image is pushed to the repository
we can put Dockerfile on Github or Bitbucket
Difference between committed image and Dockerfile image
Committed image : it commit a container’s file changes or settings into a new image.
Usage: docker commit [OPTIONS] CONTAINER [REPOSITORY[:TAG]]
Create a new image from a container's changes
-a, --author= Author (e.g., "John Hannibal Smith <hannibal#a-team.com>")
-c, --change=[] Apply Dockerfile instruction to the created image
--help=false Print usage
-m, --message= Commit message
-p, --pause=true Pause container during commit
It is good option to debug container and export changed setting into another image.but docker suggest to use dockerfile see here or we can say commit is versioning of docker or backup of image.
The commit operation will not include any data contained in volumes
mounted inside the container.
By default, the container being committed and its processes will be
paused while the image is committed. This reduces the likelihood of
encountering data corruption during the process of creating the
commit. If this behavior is undesired, set the ‘p’ option to false.
Dockerfile based image:
it always use base image for creating new image. let suppose if you made any change in dockerfile then it will apply all dockerfile steps on fresh image and create new image. but commit use same image.
my point of view we have to use dockerfile that have all step that we want on image but if we create image from commit then we have to document all change that we made that may be needed if we want to create new image and we can say dockerfile is a documentation of image.
The advantage is that, even if you do not have a shared image registry to which you could push your images, you still can exchange said images with a "recipe" (the Dockerfile used by docker build), which is only a couple KB of text, and can be passed around very easily (light and small).
That declarative format ensure that you will be able to re-build an identical image, and allows reproducible result.
Docker commit
Using Docker commit command approach to create new images is error prone, one need to remember and update image for small changes and commit every time.
Dockerfile
Dockerfile provides the ability to automate all the steps with set
of Directives which gets executed during build (refer docker build command) to create final image along with commit of the image.
Dockerfile is use anywhere, everything configured and ready to run approach.
Dockerfile can be shared with others and updated easily by others. It
allows to change the image easily depending on the requirement easily
like security hardening, add or update user details etc.