darwin-rebuild segfault

[zmre]

I just did a nix flake update and a darwin-rebuild switch --flake ~/.config/nixpkgs/.#$(hostname -s) --show-trace today -- something I generally do at least once a week, but I'm getting an error:

warning: Git tree '/Users/x/.config/nixpkgs' is dirty
building the system configuration...
warning: Git tree '/Users/x/.config/nixpkgs' is dirty
[25 built, 70 copied (661.4 MiB), 98.0 MiB DL]
/run/current-system/sw/bin/darwin-rebuild: line 159: 96473 Segmentation fault: 11  nix "${flakeFlags[@]}" build "$flake#$flakeAttr.system" "${extraBuildFlags[@]}" "${extraLockFlags[@]}"

I have tracing on, but I don't get any other details on what the error is. Is this a known problem? Any suggestions on how I should troubleshoot? Is it even a darwin-rebuild issue? This is on an M1, but again, things have been working fine for months and nothing has changed since my last successful update except the flake.lock file.

I can experiment with rolling that back and with rebooting, but hoping someone has better suggestions.

[montchr]

I've run into segfaults unexpectedly before, though I haven't seen that particular error. A couple things I would try:

Try setting nix.useSandbox = false; -- while unfortunate, sandbox mode can be troublesome on darwin. Most recently the segfaults I've run into were fixed by disabling the sandbox. But those were different error messages.

darwin-rebuild switch --flake ~/.config/nixpkgs/.#$(hostname -s) --show-trace

You've indicated that you've run this command before, but I would try simplifying it a little to see if you can rule out any issues with the command itself. The error message alludes to a nix command.

As long as your hostname matches one of the outputs in darwinConfigurations, you probably don't even need the whole #$(hostname -s) part.

Does the following work:

darwin-rebuild switch --flake ~/.config/nixpkgs

If not, what happens if you replace the $(hostname -s) part in your original command with the literal hostname?

[zmre]

Thanks for the suggestions. I rebooted, set useSandbox = false, and ran with the simplified command you suggested. Seems it redownloaded and built for awhile and then gave me an almost identical error:

/run/current-system/sw/bin/darwin-rebuild: line 159: 20868 Segmentation fault: 11  nix "${flakeFlags[@]}" build "$flake#$flakeAttr.system" "${extraBuildFlags[@]}" "${extraLockFlags[@]}"

The number after the line number (is that a PID, maybe?) is the only thing that has changed.

I didn't realize that darwin-rebuild was a bash script. Looking at that, line 159 is the end of an if block that looks familiar:

 151 if [ "$action" = switch ] || [ "$action" = build ] || [ "$action" = check ]; then
 152   echo "building the system configuration..." >&2
 153   if [ -z "$flake" ]; then
 154     systemConfig="$(nix-build '<darwin>' "${extraBuildFlags[@]}" -A system)"
 155   else
 156     nix "${flakeFlags[@]}" build "$flake#$flakeAttr.system" "${extraBuildFlags[@]}" "${extraLockFlags[@]}"
 157     systemConfig=$(readlink -f result)
 158   fi
 159 fi

So I'm guessing this is a nix problem and not a darwin-rebuild problem, maybe?

❯ nix --version
nix (Nix) 2.8.1

I'll see if I can figure out the parameters going to Nix to reproduce it more directly. Open to other ideas, too.

[zmre]

I attempted to rollback (that worked fine, but upgrading from there still gave me a segfault), to reboot, and I tried directly calling nix in various ways to try to get more info. Eventually I started for nix troubleshooting commands and options and I found this:

nix-store --verify --check-contents --repair

I ran that, also updated my flake.lock again with nix flake update and my next try succeeded. Closing this. Hope it helps the next person.

[LnL7]

Oh, thought this was the same issue as the git problem #693