Ludovic Courtès <l...@gnu.org> writes: >> I think it would be great if "guix pack -f docker" could avoid building >> all these identical layers again and again. Perhaps it would be >> possible to have a single derivation for each layer? This way we >> wouldn't have to recreate the same layer archives every time. > > That sounds nice in terms of saving CPU time. It’s less nice in terms > of disk usage: a single ‘guix pack -f docker’ run would populate the > store with roughly twice the size of the closure.
Arguably we don't actually care all that much for the Docker image that ends up in the store. It's really a temporary thing that we want to load into Docker or upload somewhere else. I've often wanted to stream the eventual output of "guix pack" to a pipe, precisely because I don't want to store the same thing twice: once in the store and once in the Docker storage backend. It's actually worse than that: I often end up having dozens of packs in the store whose layers are almost all identical. > I think each solution (single derivation vs. one derivation per layer) > makes a different tradeoff. I don’t have a strong feeling about which > one is better. Can we have both? I realize that adding the option to stream build output to a pipe is not a trivial change, but it would solve the unnecessary storage requirement for packs. "docker load" reads from standard input, but other packs would also benefit from a streaming output; an example is Docker-free deployment to a remote server: just pipe "guix pack" to a remote tar process and you're all set. -- Ricardo
