Option to add root for copy commands.

[kevincox]

Is your feature request related to a problem? Please describe.

Right now if you copy a derivation to another machine such as nix-copy-closure machine.example ./result it is liable to be garbage collected as soon as it is copied.

Describe the solution you'd like

A way to copy a closure to a remote machine and atomically root it. Both system roots and indirect roots would be useful.

[aycanirican]

To tackle this problem we first copy the closure and then install it to the environment:

nix copy --from https://$BINARY_CACHE/nix $DRV
# optionally: nix-env -e package_name
nix-env -i $DRV

[kevincox]

This is similar to what I am doing right now, just using nix-store -r --add-root after the copy. However neither of these options are convenient or atomic. If you get unlucky the garbage collector will run between your two commands and delete the packages you just copied.

[kloenk]

So you would propose something like:

nix copy --to ssh-ng://target?gc-root=/home/$USER/result ./result

[kevincox]

I think the following would work and be slightly more obvious:

nix copy --to ssh-ng://target --add-root=/home/$USER/result ./result

Currently nix-store -r --add-root requires a separate argument for indirect, however I think that can be simplified if the root is outside of /nix/var/nix/gcroots just automatically make it indirect.

[kevincox]

Your option would make more sense if you can specify multiple targets. However right now it appears that additional --to flags overwrite the former ones. (That should probably be fixed too, but that's another issue).

[stale]

I marked this as stale due to inactivity. → More info

[kevincox]

Bad bot

[stale]

I marked this as stale due to inactivity. → More info

[edolstra]

#11657 adds --profile and --out-link options to nix copy that would enable doing this for local stores. If remote stores ever get support for creating roots (#11812), then it would automatically work for remote stores as well.