/etc/nix/machines: No such file or directory when trying to install linuxkit-nix

[siraben]

This is because on macOS Catalina and above, the root partition is no longer writable.

/Users/siraben/.cache/nix-linuxkit-builder/gcroot
Setting up /var/root//.ssh/nix-linuxkit-ssh-config...
Password:
Adding the SSH configuration (/var/root//.ssh/nix-linuxkit-ssh-config) to /var/root//.ssh/config...
Adding the Nix Machines configuration (/etc/nix/machines) to /etc/nix/machines...
tee: /etc/nix/machines: No such file or directory

ssh://nix-linuxkit x86_64-linux /Users/siraben/.cache/nix-linuxkit-builder/keys/client 1 1 kvm,big-parallel

[siraben]

Resolved by sudo mkdir /etc/nix and append the contents of /var/root/.ssh/nix-linuxkit-ssh-config to ~/.ssh/config. This should be documented in the README.