Disadvantages of docker --squash

Question

I wanted to know about the disadvantages of docker --squash in a production environment. The reason why I am using this command is: I needed dependencies(gcc,make,autoconf, etc) to build my PHP-react project. Also, I have created my own PHP base image which gives me these packages. Now, the problem is I want to uninstall these dependencies once my project is built. I tried adding a RUN apt-get remove gcc make command at the end of Dockerfile but as this will be a separate layer from where these dependencies were installed, the overall size of the docker image remains the same. I found about the docker --squash which will merge all layers into 1 layer and I have achieved ~33% space reduction. But the problem is I can't use the docker squash command with docker-compose and also I don't understand if there are any performance issues or other disadvantages of using docker --squash in production.

I got to know about multi stage build but this is not same as I don't know which files I should not be copying in order to remove those dependencies. And also there will be lot of directories to be copied if I use multi-stage build

Thanks!

Answer 1

I think they've provided the pros and the cons in its own document clearly.

Pro:

• Squashing layers can be beneficial if your Dockerfile produces multiple layers modifying the same files, for example, files that are created in one step, and removed in another step.

Con:

• The --squash option is an experimental feature, and should not be considered stable.

• Squashing images may actually have a negative impact on performance; when pulling an image consisting of multiple layers, layers can be pulled in parallel, and allows sharing layers between images (saving space).

Alternatively

• For most use cases, multi-stage builds are a better alternative, as they give more fine-grained control over your build, and can take advantage of future optimizations in the builder. Refer to the use multi-stage builds section in the userguide for more information.

See the documentation