Following this thread on getting Nix set up on macOS Catalina, there's a few steps involved (assuming you have no /nix folder):
-
Set up nix folder:
echo 'nix' | sudo tee -a /etc/synthetic.conf -
Reboot for it to take effect
-
Create an APFS volume for Nix (might need to use a different
diskXnumber, checkdiskutil listfor more):
sudo diskutil apfs addVolume disk1 APFSX Nix -mountpoint /nix