Depends very much on the specifics of what the RUN steps are doing and the order of them. One issue is that just changing files will often create a layer with a

Depends very much on the specifics of what the RUN steps are doing and the order of them. One issue is that just changing files will often create a layer with another copy of those files with the different attributes (e.g. chmod) or possibly a layer with an empty directory for files that are deleted. That means you have very similar content in two separate layers which creates bloat. The COPY command now supports performing a chmod at the same time to help with this issue. Another common trick is to have a layer that performs an "apt update" followed by installing software and then deleting the contents of /var/lib/apt/lists/ so that the layer doesn't have unnecessary apt files. When developing scripts for running inside Docker, I'll often try to have the copying of the script as late as possible in the Dockerfile so that the preceding layers can be reused and just a small extra layer is needed for the script changes.