Using X without a Display Manager

Note: This page is a WIP, it doesn't describe best-practices with nix and NixOS and should be updated to use a nix derivation generating the necessary files instead of manipulating the contents of the store.

Setting up Xorg without system wide modifications

To run X11 as a regular user, without services.xserver.enable = true; in configuration.nix, do the following:

First, install packages:

• X11 itself:
  • xorg.xorgserver
• X11 input modules
  • xorg.xf86inputevdev
  • xorg.xf86inputsynaptics
  • xorg.xf86inputlibinput
• X11 video modules
  • xorg.xf86videointel
  • xorg.xf86videoati
  • xorg.xf86videonouveau

You probably want to use DRI acceleration for X; enable it and OpenGL in configuration.nix: hardware.opengl.enable = true; and hardware.opengl.driSupport = true;.

Then, it's just necessary to gather X configuration files into one directory and create a config file that also points X at the correct module paths, by running the following script (which should be re-run each time you run nixos-rebuild switch), but you will need to add or remove to the pkgs and fontpkgs arrays according to your preferences:

#!/bin/sh
#generate unprivileged user xorg.conf for nixOS
#before running:
#    install any desired packages by placing them in `/etc/nixos/configuration.nix`
#    update by running `nix-channel --update` and `nixos-rebuild switch`

config_dir=${XDG_CONFIG_HOME:-~/.config}/xorg.conf.d

mkdir -p "$config_dir"
cd "$config_dir"

#failed glob expansions become empty, not literal 'foo/*'
shopt -s nullglob

get_pkg_path() {
	attr=$1
	nix show-derivation -f '<nixpkgs>' "$attr" | jq -r '.[].env.out' 
}

#add to this set according to your driver needs
pkgs="
	xorg.xf86inputevdev
	xorg.xf86videointel
	xorg.xf86inputsynaptics
	xorg.xorgserver
"

#make the intel backlight helper setuid if it isn't already
xf86videointel_path=$(get_pkg_path xorg.xf86videointel)
backlight_helper_path="${xf86_video_intel_path}/libexec/xf86-video-intel-backlight-helper"
if [ -e "$backlight_helper_path" -a ! -u "$backlight_helper_path" ]; then
	sudo chmod +s ${xf86_video_intel_path}/libexec/xf86-video-intel-backlight-helper
fi

echo 'Section "Files"' > 00-nix-module-paths.conf
for pkg in $pkgs; do
	pkg_path=$(get_pkg_path $pkg)
	for conf in "$pkg_path"/share/X11/xorg.conf.d/*; do 
		ln -sf "$conf" ./
	done
	echo '	ModulePath "'"$pkg_path"'/lib/xorg/modules/"' >> 00-nix-module-paths.conf
done

#add to this set according to your font preferences
fontpkgs="
	xorg.fontmiscmisc
	ucsFonts
"

for pkg in $fontpkgs; do
	pkg_path=$(get_pkg_path $pkg)
	path="$pkg_path"'/share/fonts/'
	[ -d "$path" ] && echo '	FontPath "'"$path"'"' >> 00-nix-module-paths.conf
	path="$pkg_path"'/lib/X11/fonts/misc/'
	[ -d "$path" ] && echo '	FontPath "'"$path"'"' >> 00-nix-module-paths.conf
done

echo 'EndSection' >> 00-nix-module-paths.conf

You can now start X11 by running:

startx -- :0 -configdir ~/.config/xorg.conf.d

Setting up Xorg system-wide but without a Display Manager

If you don't mind having services.xserver.enable = true; but you don't want a display manager, and you want only a TTY login prompt, use the following in your configuration.nix:

services.xserver.displayManager.startx.enable = true;

startx is treated as a displayManager and therefore it is used instead of the default (lightdm).

Setting up the user's D-Bus Daemon

Both of the methods above, don't start the user's dbus-daemon properly on startup. Unfortunately, it is unclear exactly why this is missing, but here's a fix for startx users:

Put the following in your ~/.xinitrc:

if test -z "$DBUS_SESSION_BUS_ADDRESS"; then
	eval $(dbus-launch --exit-with-session --sh-syntax)
fi
systemctl --user import-environment DISPLAY XAUTHORITY

if command -v dbus-update-activation-environment >/dev/null 2>&1; then
        dbus-update-activation-environment DISPLAY XAUTHORITY
fi