How to debug a conflict?

I’m trying to deploy a system, and when I use nixos-18.09, I eventually get the following error:

these paths will be fetched (0.13 MiB download, 0.59 MiB unpacked):
building '/nix/store/2ands2ki7jihs6hmim1sc44c80l7sr5q-wmertens-authorized_keys.drv'...
copying path '/nix/store/bcab7ghpc653v0vg35qghw9dakcvdynn-python3.6-acme-0.24.0' from ''...
building '/nix/store/g8zns8qc00df5l7lsdxrzsnz6f09qngd-system-path.drv'...
collision between `/nix/store/xy8gjkzi60fvyb5r7ky1axhawgdx1xr3-systemd-239/sbin/resolvconf' and `/nix/store/6rnjva0v7diwwn747ccbvmglib1dqgv8-openresolv-3.9.0/sbin/resolvconf'
collision between `/nix/store/xy8gjkzi60fvyb5r7ky1axhawgdx1xr3-systemd-239/bin/resolvconf' and `/nix/store/6rnjva0v7diwwn747ccbvmglib1dqgv8-openresolv-3.9.0/bin/resolvconf'
created 7737 symlinks in user environment

I don’t knowingly add anything related to resolv.conf. The same config works fine with 18.03. How to find what causes this?

It’s not an error, it’s a warning. Surely it’s annoying, but I don’t think that these two particular collisions have any negative impact.

I think our defaults now pull both systemd and openresolv into systemPackages. @fpletz: any idea which one should get preference? IIRC it’s possible to set that somewhere; we’d better get rid of the warning.


Hmmm - the build didn’t actually switch to the new configuration though. That last line of my output is the last line of nixos-rebuild switch

That’s weird. What’s the exit code? Anything interesting in systemd journal?

That will be for some other reason. I’m getting the conflicts all the time. IIRC they were there at 18.09 release time.

warn differently about collisions of identical paths by jerith666 · Pull Request #41144 · NixOS/nixpkgs · GitHub “warn differently about collisions of identical paths” might help here?

These two aren’t identical. One is a script and the other one is ELF.

I was experiencing the same issue in a VM with 512MB RAM. Long story short is nix-build was getting OOM killed so the last lines in the nixos-rebuild were are a bit misleading.

The nix daemon log had messages like

Jan 29 14:13:00 machine nix-daemon[960]: unexpected Nix daemon error: writing to file: Broken pipe

and the kernel log

Jan 29 16:28:49 nixos kernel: Out of memory: Kill process 11779 (nix-build) score 654 or sacrifice child
Jan 29 16:28:49 nixos kernel: Killed process 11779 (nix-build) total-vm:443200kB, anon-rss:336860kB, file-rss:0kB, shmem-rss:0kB

I’ve been experiencing the same issue as well. I believe there could be two configurations trying to state the DNS server. This could be a potential issue for security, but not by much.

I’ve made an issue for these warnings a while back: Collision between system-essential packages · Issue #55886 · NixOS/nixpkgs · GitHub

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