CODEWITHSUNDEEP
docker
user3180
user3180

Reputation: 1497

Docker dealing with images instead of Dockerfiles

Can someone explain to me why the normal Docker process is to build an image from a Dockerfile and then upload it to a repository, instead of just moving the Dockerfile to and from the repository?

Let's say we have a development laptop and a test server with Docker.

If we build the image, that means uploading and downloading all of the packages inside the Dockerfile. Sometimes this can be very large (e.g. PyTorch > 500MB).

Instead of transporting the large imagefile to and from the server, doesn't it make sense to, perhaps compile the image locally to verify it works, but mostly transport the small Dockerfile and build the image on the server?

Upvotes: 4

Views: 141

Answers (3)

RavinderSingh13
RavinderSingh13

Reputation: 133700

IMHO, one of the reason for building the images concept and putting into repository is sharing with people too. For example we call Python's out of the box image for performing all python related stuff for a python program to run in Dockerfile. Similarly we could create a custom code(let's take example I did for apache installation with some custom steps(like ports changes and additionally doing some steps) I created its image and then finally put it to my company's repository.

I came to know after few days that may other teams are using it too and now when they are sharing it they need NOT to make any changes simply use my image and they should be done.

Upvotes: 0

Max
Max

Reputation: 9889

Instead of transporting the large imagefile to and from the server, doesn't it make sense to, perhaps compile the image locally to verify it works, but mostly transport the small Dockerfile and build the image on the server?

Absolutely! You can, for example, set up an automated build on Docker Hub which will do just that every time you check in an updated version of your Dockerfile to your GitHub repo.

Or you can set up your own build server / CI pipeline accordingly.

Upvotes: 1

MTCoster
MTCoster

Reputation: 6145

This started out as a comment, but it got too long. It is likely to not be a comprehensive answer, but may contain useful information regardless.

Often the Dockerfile will form part of a larger build process, with output files from previous stages being copied into the final image. If you want to host the Dockerfile instead of the final image, you’d also have to host either the (usually temporary) processed files or the entire source repo & build script.

The latter is often done for open source projects, but for convenience pre-built Docker images are also frequently available.

One tidy solution to this problem is to write the entire build process in the Dockerfile using multi-stage builds (introduced in Docker CE 17.05 & EE 17.06). But even with the complete build process described in a platform-independent manner in a single Dockerfile, the complete source repository must still be provided.

TL,DR: Think of a Docker image as a regular binary. It’s convenient to download and install without messing around with source files. You could download the source for a C application and build it using the provided Makefile, but why would you if a binary was made available for your system?

Upvotes: 5

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