Well, it's in the nix-store library code so presumably that nix-copy-closure passes through there. If you want to be sure, just run nix-store --optimise -v and see if it finds anything to update. Also, wow, 15GB saved :)
On Fri Feb 13 2015 at 6:43:05 PM Richard Wallace < rwall...@thewallacepack.net> wrote: > Thank you for pointing this option out! I had no idea it existed before > and it should prove very useful! > > $ du -hs /nix/store/ > 38G /nix/store/ > $ sudo nix-store --optimise -v > <snip> > 12456.46 MiB freed by hard-linking 881561 files > $ du -hs /nix/store/ > 23G /nix/store/ > > Does the auto linking also happen if you use nix-copy-closure? > > Rich > > On Thu, Feb 12, 2015 at 3:47 AM, Wout Mertens <wout.mert...@gmail.com> > wrote: > >> Hi all, >> >> (TL;DR: regain disk space, see at the bottom for instructions) >> >> the Nix store can be optimised by hard-linking files with the same >> contents together, so they are only stored once. This is done by reading >> all the files in your store, calculating their checksums and linking them >> to /nix/store/.links/*[checksum]*. This is especially useful in Nix >> where differing build inputs for a package end up with many of the same >> files. >> >> Nix 1.8 has a few optimizations that make this operation very fast if you >> run it multiple times. Nix also has the auto-optimise-store setting, which >> will link new files added to the store. If your store was optimised, it >> stays optimised. >> >> I feel this optimisation should be turned on by default but there were >> some regressions in the past which is why it wasn't. Therefore I'd like to >> ask you to turn on auto-optimise and run optimisation once. Your disk space >> and memory footprint will thank you. >> >> Advantage: >> - Use less disk space and memory cache >> Disadvantages: >> - Need to checksum all files written to the store >> * this is fast while writing the files because they still are in cache >> - /nix/store/.links can get very large >> * a decent filesystem should handle it >> * E.g. ext3, ext4, btrfs, zfs etc should have no problems >> >> Hopefully this will prove that it's safe to use and Hydra will start >> using it, which should give it tons more headroom for builds. >> >> *How to enable*: >> - Run "du -hs /nix/store" to see how much you're using >> >> - If you use nixpkgs, put >> auto-optimise-store = true >> in /etc/nix/nix.conf and run "nix-store --optimise -v". >> - If you use NixOS, put >> nix.extraOptions = "auto-optimise-store = true"; >> in your configuration.nix and, as root, run >> "nixos-rebuild switch" and "nix-store --optimise -v". >> >> - Run "du -hs /nix/store" to see how much you regained >> >> It is safe to interrupt the optimisation. It is also safe to clear out >> /nix/store/.links but this will result in more work on the next >> optimisation run. >> >> Please report any issues you encounter, and it would be nice if you reply >> to this mail in a while to report that you have encountered no issues. >> >> Cheers, >> >> Wout. >> >> PS: Optimise is the British spelling, nix-store also has --optimize but >> not auto-optimize-store :) >> >> _______________________________________________ >> nix-dev mailing list >> nix-dev@lists.science.uu.nl >> http://lists.science.uu.nl/mailman/listinfo/nix-dev >> >>
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