trouble setting up setup urxvt & i3

Hi all! So I finally got a linux machine working (I had to switch machines) Now I'm trying to setup urxvt & also i3. I found this blog to guide me: http://johnduhamel.io/posts/2019-01-...-i3-setup.html or https://webcache.googleusercontent.c...&ct=clnk&gl=ca

When I go to post a comment for support I find that it's been removed. My error:<code>

$ sudo nixos-rebuild switch --upgrade

unpacking channels...

building Nix...

building the system configuration...

trace: Default graphical session, 'none', not found.

Valid names for 'services.xserver.displayManager.defaultSession' are:

plasma5+i3

plasma5

none+i3

error: The option value `services.xserver.displayManager.defaultSession' in `/nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/services/x11/display-managers/default.nix' is not of type `session name'.

(use '--show-trace' to show detailed location information)

</code>

Best regards,

Nicholas