Nixos unable to modify or chmod nix config - '/etc/nix/nix.conf'

Question

[root@nixos:/etc/nix]# sudo chmod 777 /etc/nix/nix.conf
chmod: changing permissions of '/etc/nix/nix.conf': Read-only file system

I remember this is some filesystem / Linux kernel utility to change this, I'm not sure what it's called though?

Answer 1

This file is managed by Nix - hence it's in the store path - and read only:

readlink -f /etc/nix/nix.conf 
/nix/store/9cidrvc5n3fjf9zplxrwiyh0g9nq07bb-nix.conf

One needs to set the nix.extraOptions in configuration.nix to modify this file.

https://github.com/NixOS/nix/pull/3111