darwin case hack is busted #332

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opened 2024-05-19 18:15:07 +00:00 by pennae · 5 comments

pennae commented

2024-05-19 18:15:07 +00:00

Owner

the way nix extracts nars on darwin (since 276a40b31f) may append ~nix~case~hack~.* strings to paths during extraction, silently fucking up the extracted store path. even worse, during dumping of store paths such suffixes are removed even when they weren't added for disambiguation, which lets us produce invalid nars:

(import <nixpkgs> { system = "aarch64-darwin"; }).runCommand "foo" {} ''
  mkdir $out $out/~nix~case~hack~this-should-be-a-number
  touch $out $out/~nix~case~hack~this-should-be-a-number/1
''

gives

❯ nix-build foo.nix                                   
this derivation will be built:
  /nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv
building '/nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv' on 'ssh-ng://m1@build01.aarch64-darwin.lix.systems'...
copying 0 paths...
building '/nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv'...
copying 1 paths...
copying path '/nix/store/qs1z1sz8lbkazj5xi7x6bkhkisdd58rd-foo' from 'ssh-ng://m1@build01.aarch64-darwin.lix.systems'...
error: NAR contains invalid file name ''
error: builder for '/nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv' failed with exit code 1

we should remove the case hack nonsense, print a loud diagnostic when extracting nars that would require it asking the user to make their nix store cases-sensitive, and maybe even apply case-sensitive settings from the installer.

the way nix extracts nars on darwin (since 276a40b31f631c188d6dcbdf603a738e1380ff74) may append `~nix~case~hack~.*` strings to paths during extraction, silently fucking up the extracted store path. even worse, during *dumping* of store paths such suffixes are removed *even when they weren't added for disambiguation*, which lets us produce invalid nars: ``` (import <nixpkgs> { system = "aarch64-darwin"; }).runCommand "foo" {} '' mkdir $out $out/~nix~case~hack~this-should-be-a-number touch $out $out/~nix~case~hack~this-should-be-a-number/1 '' ``` gives ``` ❯ nix-build foo.nix this derivation will be built: /nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv building '/nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv' on 'ssh-ng://m1@build01.aarch64-darwin.lix.systems'... copying 0 paths... building '/nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv'... copying 1 paths... copying path '/nix/store/qs1z1sz8lbkazj5xi7x6bkhkisdd58rd-foo' from 'ssh-ng://m1@build01.aarch64-darwin.lix.systems'... error: NAR contains invalid file name '' error: builder for '/nix/store/xx9f6533jr88v6i2pq9v8cqxaa9kzqy4-foo.drv' failed with exit code 1 ``` we should remove the case hack nonsense, print a loud diagnostic when extracting nars that would require it asking the user to make their nix store cases-sensitive, and maybe even apply case-sensitive settings from the installer.

pennae added the

bug

label 2024-05-19 18:15:07 +00:00

jade commented

2024-05-19 19:09:26 +00:00

Owner

Arguably the original reason this was added was because /nix used to be on the root partition which is of course hard to make case sensitive. But we could make the store case sensitive in the installer now that it's a separate APFS container, and then just refuse to do these. We just have to figure out if you can retroactively make a container case sensitive.

jade commented

2024-05-19 20:25:25 +00:00

Owner

Thinking harder about this: we cannot fix existing containers either online or offline. Though it's true that case sensitivity is an attribute in the superblock, there's hash maps in the fs that would be probably invalidated by tampering it.

I think the solution here is to make a nix doctor apfs --fix that copies to a new container.

lix-bot commented

2024-06-23 03:06:15 +00:00

Member

This issue was mentioned on Gerrit on the following CLs:

commit message in cl/1503 ("macOS: default to case sensitive")

This issue was mentioned on Gerrit on the following CLs: * commit message in [cl/1503](https://gerrit.lix.systems/c/lix-installer/+/1503) ("macOS: default to case sensitive")