treewide: migrate nixos modules to networking.hosts

[JohnRTitor]

Split off from #413925 as this doesn't need a discussion on whether extraHosts need to be kept.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Fits CONTRIBUTING.md.

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[JohnRTitor]

Tests built successfully on nix community linux builder..

[johnrtitor@build01:~]$ nix build github:nixos/nixpkgs/refs/pull/414780/merge#nixosTests.kubernetes.dns-multi-node --print-out-paths
/nix/store/3sag9grqi74v8sf4k9f94pvl2xjwyf8f-vm-test-run-kubernetes-dns-multinode

[johnrtitor@build01:~]$ nix build github:nixos/nixpkgs/master#nixosTests.kubernetes.rbac-single-node --print-out-paths
/nix/store/ykhzag3wlfp9xz555zp3val6bb0gsf0l-vm-test-run-kubernetes-rbac-singlenode

[johnrtitor@build01:~]$ nix build github:nixos/nixpkgs/master#nixosTests.kubernetes.rbac-multi-node --print-out-paths
/nix/store/rypj7gqcq7fi2vds5whgdz6shmr44xqq-vm-test-run-kubernetes-rbac-multinode


[johnrtitor@build01:~]$ nix build github:nixos/nixpkgs/master#nixosTests.kubernetes.dns-multi-node --print-out-paths
/nix/store/p6njkf9w9ywb34q1nsk801pvh2vcyi1w-vm-test-run-kubernetes-dns-multinode

[johnrtitor@build01:~]$ nix build github:nixos/nixpkgs/refs/pull/414780/merge#nixosTests.containers-hosts --print-out-paths
evaluation warning: system.stateVersion is not set, defaulting to 25.11. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.
evaluation warning: system.stateVersion is not set, defaulting to 25.11. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.
/nix/store/pqhggz01m4x45yjaslzqbiwysicdprdz-vm-test-run-containers-hosts

[johnrtitor@build01:~]$ nix build github:nixos/nixpkgs/refs/pull/414780/merge#nixosTests.gitlab --print-build-logs --print-out-paths
/nix/store/jq0zihw1cg5hbhq318mj7p4h0jippc5x-vm-test-run-gitlab

[vcunat]

nixosTests.acme.http01-builtin did break:
https://hydra.nixos.org/build/299342505

and so nixos-unstable* channels are blocked by that now.

[JohnRTitor]

Could you give me 2 hrs? I can try preparing a fix, else I'll open a revert PR.

[gravndal]

This broke eval for simple nixos containers like:

  containers.evalfailure.config =
    { ... }:
    {
      environment.systemPackages = [ pkgs.hello ];
    };

       … from call site                                                                                                                                                                     
         at /nix/store/wshl2a8akx0g41wkb8k5i3c8131y0lfx-source/nixos/modules/virtualisation/nixos-containers.nix:1087:28:                                                                   
         1086|         # Generate /etc/hosts entries for the containers.                                                                                                                    
         1087|         networking.hosts = lib.mapAttrs' (name: cfg: {                                                                                                                       
             |                            ^                                                                                                                                                 
         1088|           name = head (splitString "/" cfg.localAddress);                                                                                                                    
                                                                                                                                                                                            
       … while calling 'mapAttrs''                                                                                                                                                          
         at /nix/store/wshl2a8akx0g41wkb8k5i3c8131y0lfx-source/lib/attrsets.nix:1045:18:                                                                                                    
         1044|   */                                                                                                                                                                         
         1045|   mapAttrs' = f: set: listToAttrs (mapAttrsToList f set);                                                                                                                    
             |                  ^                                                                                                                                                           
         1046|                                                                                                                                                                              
                                                                                                                                                                                            
       … while calling the 'listToAttrs' builtin                                                                                                                                            
         at /nix/store/wshl2a8akx0g41wkb8k5i3c8131y0lfx-source/lib/attrsets.nix:1045:23:                                                                                                    
         1044|   */                                                                                                                                                                         
         1045|   mapAttrs' = f: set: listToAttrs (mapAttrsToList f set);                                                                                                                    
             |                       ^                                                                                                                                                      
         1046|                                                                                                                                                                              
                                                                                                                                                                                            
       … while evaluating the `name` attribute of an element of the list passed to builtins.listToAttrs                                                                                     
         at /nix/store/wshl2a8akx0g41wkb8k5i3c8131y0lfx-source/nixos/modules/virtualisation/nixos-containers.nix:1088:11:                                                                   
         1087|         networking.hosts = lib.mapAttrs' (name: cfg: {                                                                                                                       
         1088|           name = head (splitString "/" cfg.localAddress);                                                                                                                    
             |           ^                                                                                                                                                                  
         1089|           value = lib.optionals (cfg.localAddress != null) [ "${name}.containers" ];                                                                                         
                                                                                                                                                                                            
       … while calling the 'head' builtin                                                                                                                                                   
         at /nix/store/wshl2a8akx0g41wkb8k5i3c8131y0lfx-source/nixos/modules/virtualisation/nixos-containers.nix:1088:18:                                                                   
         1087|         networking.hosts = lib.mapAttrs' (name: cfg: {                                                                                                                       
         1088|           name = head (splitString "/" cfg.localAddress);                                                                                                                    
             |                  ^                                                                                                                                                           
         1089|           value = lib.optionals (cfg.localAddress != null) [ "${name}.containers" ];                                                                                         
                                                                                                                                                                                            
       … while calling 'addContextFrom'                                                                                                                                                     
         at /nix/store/wshl2a8akx0g41wkb8k5i3c8131y0lfx-source/lib/strings.nix:1645:25:                                                                                                     
         1644|   */                                                                                                                                                                         
         1645|   addContextFrom = src: target: substring 0 0 src + target;                                                                                                                  
             |                         ^                                                                                                                                                    
         1646|                                                                                                                                                                              
                                                                                                                                                                                            
       … while calling the 'substring' builtin                                                                                                                                              
         at /nix/store/wshl2a8akx0g41wkb8k5i3c8131y0lfx-source/lib/strings.nix:1645:33:                                                                                                     
         1644|   */                                                                                                                                                                         
         1645|   addContextFrom = src: target: substring 0 0 src + target;                                                                                                                  
             |                                 ^                                                                                                                                            
         1646|                                                                                                                                                                              
                                                                                                                                                                                            
       … while evaluating the third argument (the string) passed to builtins.substring                                                                                                      
                                                                                                                                                                                            
       error: cannot coerce null to a string: null

[JohnRTitor]

I absoulutely love how these aren't caught by our nixosTests.containers-hosts.

Revert PR: #415085