Hacker News Reader

Comment by chung1905 | Hacker News Reader

chung1905

While developing an image, I use layers as much as possible. But usually, when the image is finished, I prefer to minimize the number of layers, it saves some (or little) storage (I think it will not > 10%).

View on HN

Fewer layers also performs better in the final image. Things like listing a directory get very slow with thousands of layers.

I suggest reading about multi-stage builds. They basically squash layers at the end so it's a "have cake and eat it too" scenario.

This pattern of concatenating commands to have a minimal image is a workaround from times when multi-stage builds were not available.

Multistage builds do not squash at the end.

You can do this with experimental flags [0] and --squash [1] [2]

[0] https://github.com/moby/buildkit/blob/master/frontend/docker...

[1] https://geraldonit.com/2017/11/13/how-to-create-small-docker...

[2] https://docs.docker.com/engine/reference/commandline/image_b...

@Leace

> I suggest reading about multi-stage builds. They basically squash layers at the end so it's a "have cake and eat it too" scenario.

That's completely different thing. Multi-stage builds are great for separating build environment from production environment, but if you need several layers for production environment, they won't be squashed. See here: https://github.com/docker/compose/issues/4235#issuecomment-3...

Yeah, I suspect that while the author could use a development image to do all of the compiling, given that all of the nginx files are not in a single directory it's my understanding that you'd need multiple COPY commands, and you'd still want to do all of the package manager operations in the prod build. It's really a tradeoff of development ease vs minimal packaged output.

> given that all of the nginx files are not in a single directory it's my understanding that you'd need multiple COPY commands

Workaround would be to move these files to one directory on host, COPY it in one command to /tmp (or even better, /dev/shm or other ramdisk) and then use script to distribute files where needed.

You can make the multi-stage builds actual images themselves, and setup your CI to auto push them to a registry. Then you can have shared multistage builds, which is pretty useful for things like compiling static libraries in their own images, and COPYing them into images that statically link to them.

Reply on news.ycombinator.com