How to use nix with catalina

You can use synthetic.conf(5) to create a virtual empty directory at / instead of a symlink. That can be your mount point. To do this, you just need to add the following entry:

sudo vim /etc/synthetic.conf

add a new file with the following content:

echo -e 'nix\t/System/Volumes/Data/nix’ | sudo tee -a /etc/synthetic.conf

NOTE: Use \t (tab) to make /etc/synthetic.conf work on osx. Note 2: /System/Volumes/Data/nix must be a case sensitive filesystem

This will tell osx to mount /nix with the external disk directory nix. In our case, we used an external disk, but the directory could be at your home.

reboot

sudo chown -R <username> /Volumes/<username> /nix/
export NIX_IGNORE_SYMLINK_STORE=1
curl https://nixos.org/nix/install | sh