At the moment all the build-deps are installed as binary packages, so I think this wouldn't work? I thought of trying to figure out which packages had shared bu

At the moment all the build-deps are installed as binary packages, so I think this wouldn't work? I thought of trying to figure out which packages had shared build dependencies and building a tree of images that way, but solving the dependency constraints to get an efficient tree sounded unpleasant. I did experiment with just preinstalling the top 300 or so most common build dependencies, but this ended up causing more problems due to conflicts (and not just version conflicts – some packages behave differently at build time depending on what's already installed; an example is any R package which will use my old nemesis xvfb-run if it's present on the system [1]) than it saved in time or space. I do feel a bit guilty about how much I'm hammering the debian repos though, so I will probably set up a local apt mirror and point my sources.list to that instead next time. [1] https://salsa.debian.org/r-pkg-team/dh-r/-/blob/master/dh/R.pm#L165-171 https://salsa.debian.org/r-pkg-team/dh-r/-/blob/master/dh/R....