This mounts an arbitrary Nix store on the specified mount point.
Typical usage:
$ /nix/store/d0am5d8gwh2kfdcgyxh4y684mb5b2v54-blender-2.79/bin/blender --version
bash: /nix/store/d0am5d8gwh2kfdcgyxh4y684mb5b2v54-blender-2.79/bin/blender: No such file or directory
$ nix mount-store /tmp/mp --store https://cache.nixos.org?local-nar-cache=/tmp/nars
$ unshare -m -r
$ mount -o bind /tmp/mp /nix/store
$ /nix/store/d0am5d8gwh2kfdcgyxh4y684mb5b2v54-blender-2.79/bin/blender --version
[after a lot of downloading...]
Blender 2.79 (sub 0)
One application is to replace the current remote store file access in
hydra-server implemented via "nix {cat,ls}-store", which doesn't work
all that well (e.g. it doesn't resolve symlinks properly).
Another application would be on-demand fetching of build inputs on
Hydra build slaves (to speed up builds that don't access their entire
closure). However, that will require a lot more machinery.
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