document operation with minimal copying from local

[colemickens]

Hi,

I have a situation where it's easy for me to push to a cache, and easy to pull from the cache, but very excruciatingly slow to copy from the local machine.

I'm opening this to collect suggestions on how to minimize the paths that are copied from local.

Potential criteria to close this:

• document how to build all of the paths that nixos-anywhere deploys, and push to cachix
• document an example using --option with a cachix cache
• explore an option that prevents any nix-copy from happening, requiring anything to be pre-cached

Also open to feedback if this is a bad idea, etc.

[phaer]

Would it help to use --build-on-target? This might avoid much of the copying, as nix wouldn't need copy much more than the flake itself, while substituting direct from the cache.

[colemickens]

Aye, indeed, I was doing that. Even copying the source to the destination was excruciatingly slow. My wifi was so bad that I never even managed to get it to work. I had to eventually SSH to another server, and run it from there.

If I could have pre-staged the source derivation, disko script, etc, into a cache, the builder could just download it.

It's probably just a matter of finding the right attr path for the source derivations and pushing those. Then it should just substitute if I pass the right options.

[Mic92]

You can follow our nixos test. You need the disko-script and nixos toplevel in your binary cache:

nixos-anywhere/tests/modules/installer.nix

Line 18 in 024e3d4

"nixos-anywhere/disko".source = system-to-install.config.system.build.diskoScript;

[chreekat]

On this topic, --help makes it sound like nixos-anywhere should be using --substitute-on-destination by default, but I don't observe this happening.

Ha, in fact it looks like the option may have been inverted? I specified --no-substitute-on-destination and now it is substituting on the destination!

[chreekat]

Looks like this happened yesterday. 7637325

[chreekat]

#386