Nixos-rebuild --target-host woes

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1

I’m investigating ways to setup and update remote server.

currently everything is tested in a VM.

for initial setup i’m using nixos-anywhere, but as far as I understand, i cannot use it the same way for updating the system like nixos-rebuild

So then to update a remote system i’m trying nixos-rebuild

specifically: nixos-rebuild switch --target-host root@127.0.0.1:6622 --flake .#server1

(also I’m not sure if I specify alternative ssh port correctly)

What I get is

copying 0 paths...
ssh: Could not resolve hostname 127.0.0.1:6622: Name or service not known
error: your NixOS configuration path seems to be missing essential files.
To avoid corrupting your current NixOS installation, the activation will abort.

This could be caused by Nix bug: https://github.com/NixOS/nix/issues/13367.
This is the evaluated NixOS configuration path: /nix/store/06gpbgc2sjlqik8y7qjan0mvkzg7d0k8-nixos-system-server1-25.11.20251226.f560cce.
Change the directory to somewhere else (e.g., `cd $HOME`) before trying again.

If you think this is a mistake, you can set the environment variable
NIXOS_REBUILD_I_UNDERSTAND_THE_CONSEQUENCES_PLEASE_BREAK_MY_SYSTEM to 1
and re-run the command to continue.
Please open an issue if this is the case.

Even though you can see ssh: Could not resolve hostname 127.0.0.1:6622: Name or service not known line in log - I do see a successful ssh connection in the VM

I have no idea how to debug what’s going on from here.

2

Very likely related to.

Which from my understanding should have landed in nix 2.31

3

hm, i’m on 25.11, and nix -–version returns 2.31.2

i guess it was fixed for nix copy, but not for nixos-rebuild ?

but the workaround from the linked issue seem to have solved my problem:

NIX_SSHOPTS=“-p 6622” nixos-rebuild switch --target-host ``root@127.0.0.1`` --flake .#server1 seem to have worked properly

4

nixos-rebuild uses nix copy under the hood AFAIU.

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