upgrade instructions

README.md

@@ -2,7 +2,7 @@
 
 ## Upgrade
 
-```
+```bash
 # Update System Channels
 sudo nix-channel --add https://nixos.org/channels/nixpkgs-23.05-darwin nixpkgs
 sudo nix-channel --update
@@ -19,7 +19,19 @@ home-manager switch
 
 NOTE: This will remove previous generations
 
-```
-nix-collect-garbage --delete-old
+```bash
 sudo nix-collect-garbage --delete-old
+nix-collect-garbage --delete-old
+```
+
+## OS Update
+
+`/etc/bashrc` may get overridden. To properly load Nix, prepend the following:
+
+```bash
+# Nix
+if [ -e '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh' ]; then
+  . '/nix/var/nix/profiles/default/etc/profile.d/nix-daemon.sh'
+fi
+# End Nix
 ```