Remote build doesn't work from all-in-one terraform module on MacOS

[onnimonni]

Prerequisites

• I have updated to the latest version using nix run --refresh github:nix-community/nixos-anywhere
• I have reproduced the issue with the --debug flag
• I have searched existing issues to make sure this isn't a duplicate

Bug Description

Hey,

Initial deployment worked just fine but on the rebuilds opentofu is giving me following errors:

│ error: Cannot build '/nix/store/1qi155ilplcyz960l3nsz3x9gmp8pdsq-shutdown-ramfs-contents.json.drv'.
│        Reason: required system or feature not available
│        Required system: 'aarch64-linux' with features {}
│        Current system: 'aarch64-darwin' with features {apple-virt, benchmark, big-parallel, nixos-test}

Even if I'm using the build_on_remote = true for the module.

When running the nixos-rebuild from my Mac with aarch64 targets I need to use the --fast and --build-host flags:

nixos-rebuild switch --flake .#my-flake-here --fast --build-host $HOST_IP --target-host $HOST_IP

I guess these flags 2 are is missing from the nixos-anywhere all-in-one terraform module?

Steps to Reproduce

1. Deploy a VPS in Hetzner using MacOS. First nixos-anywhere run works perfectly.
2. Try to run the opentofu apply again after some changes in the flake
3. You should see the issue on the next build

Debug Logs

$ tofu apply -auto-approve
...
module.deploy.module.partitioner-build.data.external.nix-build: Read complete after 3s [id=-]

Planning failed. OpenTofu encountered an error while generating this plan.

╷
│ Error: External Program Execution Failed
│
│   with module.deploy.module.system-build.data.external.nix-build,
│   on .terraform/modules/deploy/terraform/nix-build/main.tf line 7, in data "external" "nix-build":
│    7:   program = ["${path.module}/nix-build.sh"]
│
│ The data source received an unexpected error while attempting to execute the program.
│
│ Program: .terraform/modules/deploy/terraform/nix-build/nix-build.sh
│ Error Message: + '[' '{"options":{}}' '!=' '{"options":{}}' ']'
│ + options=
│ + [[ {"terraformArgs":{"ipv6_block":"XXXX:YYY:ZZZ:WWW::1/64"}} == {} ]]
│ + [[ null != null ]]
│ ++ echo .#nixosConfigurations.my-server.config.system.build.toplevel
│ ++ cut -d '#' -f 2
│ + rest=nixosConfigurations.my-server.config.system.build.toplevel
│ + config_path=nixosConfigurations.my-server
│ + config_attribute=config.system.build.toplevel
│ ++ echo .#nixosConfigurations.my-server.config.system.build.toplevel
│ ++ cut -d '#' -f 1
│ + flake_rel=.
│ ++ nix flake prefetch . --json
│ path '/Users/onnimonni/Projects/my-project/infra' does not contain a 'flake.nix', searching up
│ warning: Git tree '/Users/onnimonni/Projects/my-project' has uncommitted changes
│ +
│ prefetch_result='{"hash":"sha256-45osbpHc8mTM6cxRTnzD7PCDhOZ6u8OD3gWKb5hnoq0=","locked":{"dirtyRev":"9ce2f6cae4c296557f640d46a3aad2be53a647fc-dirty","dirtyShortRev":"9ce2f6c-dirty","lastModified":1758196165,"type":"git","url":"file:///Users/onnimonni/Projects/my-project"},"original":{"type":"git","url":"file:///Users/onnimonni/Projects/my-project"},"storePath":"/nix/store/pvir4zqw1bxm2ivskh3p4iyfgf92g7gw-source"}'
│ ++ echo
│ '{"hash":"sha256-45osbpHc8mTM6cxRTnzD7PCDhOZ6u8OD3gWKb5hnoq0=","locked":{"dirtyRev":"9ce2f6cae4c296557f640d46a3aad2be53a647fc-dirty","dirtyShortRev":"9ce2f6c-dirty","lastModified":1758196165,"type":"git","url":"file:///Users/onnimonni/Projects/my-project"},"original":{"type":"git","url":"file:///Users/onnimonni/Projects/my-project"},"storePath":"/nix/store/pvir4zqw1bxm2ivskh3p4iyfgf92g7gw-source"}'
│ ++ jq -r .storePath
│ + store_path=/nix/store/pvir4zqw1bxm2ivskh3p4iyfgf92g7gw-source
│ ++ echo
│ '{"hash":"sha256-45osbpHc8mTM6cxRTnzD7PCDhOZ6u8OD3gWKb5hnoq0=","locked":{"dirtyRev":"9ce2f6cae4c296557f640d46a3aad2be53a647fc-dirty","dirtyShortRev":"9ce2f6c-dirty","lastModified":1758196165,"type":"git","url":"file:///Users/onnimonni/Projects/my-project"},"original":{"type":"git","url":"file:///Users/onnimonni/Projects/my-project"},"storePath":"/nix/store/pvir4zqw1bxm2ivskh3p4iyfgf92g7gw-source"}'
│ ++ jq -r .hash
│ + nar_hash=sha256-45osbpHc8mTM6cxRTnzD7PCDhOZ6u8OD3gWKb5hnoq0=
│ + flake_url='path:/nix/store/pvir4zqw1bxm2ivskh3p4iyfgf92g7gw-source?narHash=sha256-45osbpHc8mTM6cxRTnzD7PCDhOZ6u8OD3gWKb5hnoq0='
│ + nix_expr='(builtins.getFlake '\'''\''path:/nix/store/pvir4zqw1bxm2ivskh3p4iyfgf92g7gw-source?narHash=sha256-45osbpHc8mTM6cxRTnzD7PCDhOZ6u8OD3gWKb5hnoq0='\'''\'').nixosConfigurations.my-server.extendModules {
│ specialArgs = builtins.fromJSON '\'''\''{"terraformArgs":{"ipv6_block":"XXXX:YYY:ZZZ:WWW::1/64"}}'\'''\''; }'
│ ++ nix build --no-link --json --expr '(builtins.getFlake
│ '\'''\''path:/nix/store/pvir4zqw1bxm2ivskh3p4iyfgf92g7gw-source?narHash=sha256-45osbpHc8mTM6cxRTnzD7PCDhOZ6u8OD3gWKb5hnoq0='\'''\'').nixosConfigurations.my-server.extendModules { specialArgs =
│ builtins.fromJSON '\'''\''{"terraformArgs":{"ipv6_block":"XXXX:YYY:ZZZ:WWW::1/64"}}'\'''\''; }' config.system.build.toplevel
│ these 5 derivations will be built:
│   /nix/store/1qi155ilplcyz960l3nsz3x9gmp8pdsq-shutdown-ramfs-contents.json.drv
│   /nix/store/hk4svijzzhsva5b0z0ni5alf9ikxwjf2-unit-generate-shutdown-ramfs.service.drv
│   /nix/store/9kmwx5b7prsx2dc4f9myjlljk12jr3l5-system-units.drv
│   /nix/store/vbvkzjpf8w4vjb74isnmqg7jqnbaz3r2-etc.drv
│   /nix/store/b1w6kxv2yhp4kc9b74934ymhq2wwsp5l-nixos-system-my-server-25.11.20250914.a870b74.drv
│ error: Cannot build '/nix/store/1qi155ilplcyz960l3nsz3x9gmp8pdsq-shutdown-ramfs-contents.json.drv'.
│        Reason: required system or feature not available
│        Required system: 'aarch64-linux' with features {}
│        Current system: 'aarch64-darwin' with features {apple-virt, benchmark, big-parallel, nixos-test}
│ error: Cannot build '/nix/store/hk4svijzzhsva5b0z0ni5alf9ikxwjf2-unit-generate-shutdown-ramfs.service.drv'.
│        Reason: 1 dependency failed.
│        Output paths:
│          /nix/store/9ip08kmd4wva6hz29az9sb9cm2lk4zv2-unit-generate-shutdown-ramfs.service
│ error: Cannot build '/nix/store/9kmwx5b7prsx2dc4f9myjlljk12jr3l5-system-units.drv'.
│        Reason: 1 dependency failed.
│        Output paths:
│          /nix/store/0v3bz0ycb9g9mwpb20l7jkipwc1absd7-system-units
│ error: Cannot build '/nix/store/vbvkzjpf8w4vjb74isnmqg7jqnbaz3r2-etc.drv'.
│        Reason: 1 dependency failed.
│        Output paths:
│          /nix/store/34fi3i0i0cblz2hhmfihmnxlakziy47y-etc
│ error: Cannot build '/nix/store/b1w6kxv2yhp4kc9b74934ymhq2wwsp5l-nixos-system-my-server-25.11.20250914.a870b74.drv'.
│        Reason: 1 dependency failed.
│        Output paths:
│          /nix/store/j4w2wv2b5n0v45fpl6nqw75pslc1cawh-nixos-system-my-server-25.11.20250914.a870b74
│ + out=
│
│ State: exit status 1

Command Used

tofu apply -auto-approve

Target System

Cloud server (AWS, DigitalOcean, etc.)

NixOS Version

unstable

Environment Information

• Host OS:
• Nix version:
• Target architecture:

Configuration Files

Additional Context

No response

[Mic92]

Yeah, because we currently need nix_build, this needs a remote builder: https://nixos.org/manual/nixpkgs/stable/#sec-darwin-builder