Nix: macOS updates often break nix installation (updates replace path-hooks on multi-user install)

[amckinlay]

I have noticed that every once and a while /Users/andrewmckinlay/.nix-profile/bin and /nix/var/nix/profiles/default/bin disappear from my $PATH. The last time this happened, the hook nix installed was missing from /etc/zshrc.

Copying the following hook (copied from /etc/bashrc) to /etc/zshrc and restarting the shell fixed everything again:

# Nix
if [ -e '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh' ]; then
  . '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'
fi
# End Nix

My concern is that macOS updates will periodically overwrite /etc/.zshrc (and /etc/.bashrc), requiring effort on my part to reinstall nix. For example, one macOS update overwrote the entire file to fix this misspelling:

andrewmckinlay@imac ~ % diff /etc/zshrc.backup-before-nix /etc/zshrc
3c3
< # Setup user specific overrides for this in ~/.zhsrc. See zshbuiltins(1)
---
> # Setup user specific overrides for this in ~/.zshrc. See zshbuiltins(1)

Both files are read-only anyway, should they really be written to by the nix installer?

[lilyball]

If they keep updating these files, perhaps we should file an Apple Feedback report asking them to add /etc/bashrc.d/ and /etc/zshrc.d folders whose contents get sourced by the default scripts? This way we can add configuration there that won't get overridden.

Beyond that, the only automatic solution that comes to mind would be to have nix-daemon check these files on launch and re-add the Nix block if it's missing.

[ptitvert]

I have done a few days before the upgrade to Catalina 10.15.6... and today I wanted to install something to discover that my nix installation was gone!
Well after some research, I found that the /nix was still there, but everything else was gone... no nix-env command nothing!
So after cursing a lot... I search until I found this thread...
I would like also that this problem to solved... For the moment, I have put on my 2 users the following lines in the ~/.profile

# Nix
if [ -e '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh' ]; then
  . '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'
fi
# End Nix

So I don't care if the /etc/zshrc is or not overwritten in the future... I agree this is a bad solution, but at least for the time being my workaround...

[lilyball]

I filed feedback for Apple (FB8181728). In the meantime, nix-daemon will need to learn how to modify the files appropriately on launch.

[abathur]

The zsh case seems to have been fixed (but not released yet) in the course of #3456. I haven't observed this same issue with bash shell files.