Check the machine before installing, and keep old shells' mise working

install.sh now stops early, with a clear message, if this isn't 64-bit
Arch, it's run as root, there's no internet, or sudo doesn't work.
system/preflight.sh then asks before going on with too little disk space
or / not on btrfs, and offers to switch another login screen to GDM and
PulseAudio to PipeWire. Keeping another login screen puts GDM in
services-off, so install and update stop failing to enable it; a
migration does the same on existing machines. It says nothing when all
is well, as refresh runs install.sh again.

Intel GPUs also get intel-media-driver for hardware video decoding, with
a migration for existing machines.

The mise migration links ~/.local/bin/mise to /usr/bin/mise instead of
deleting it, so shells opened before the update don't print an error at
every prompt.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

system/preflight.sh

@@ -0,0 +1,109 @@
+#!/bin/bash
+#
+# Purpose : Check the machine before install.sh sets it up, and offer to fix
+#           what can be fixed: too little disk space, / not on btrfs, a login
+#           screen other than GNOME's GDM, PulseAudio instead of PipeWire.
+#           Exits 1 to stop the install. refresh runs install.sh again, so it
+#           says nothing on a machine where all is well.
+
+COREDESKTOP="$HOME/.local/share/coredesktop"
+source "$COREDESKTOP/utils.sh"
+
+SERVICES_OFF="$HOME/.config/coredesktop/services-off"
+
+# install.sh is usually piped into bash, so ask on the terminal
+TTY="${COREDESKTOP_TTY:-/dev/tty}"
+
+# ask <question> <default y|n> <answer without a terminal y|n>
+ask() {
+  local answer
+  if ! { : < "$TTY"; } 2> /dev/null; then
+    [ "$3" = y ]
+    return
+  fi
+  if [ "$2" = y ]; then
+    read -rp "$1 [Y/n] " answer < "$TTY"
+    [[ "$answer" != [nN]* ]]
+  else
+    read -rp "$1 [y/N] " answer < "$TTY"
+    [[ "$answer" == [yY]* ]]
+  fi
+}
+
+# Set up before: install.sh records migrations as its last step
+already_installed() {
+  [ -d "$HOME/.local/state/coredesktop/migrations" ]
+}
+
+check_disk() {
+  local need=60 free
+  already_installed && need=10
+  free="$(df -k --output=avail / | tail -n 1 | tr -d ' ')"
+  [[ "$free" =~ ^[0-9]+$ ]] || return 0
+  free=$(( free / 1024 / 1024 ))
+  (( free < need )) || return 0
+  echo "Only $free GB is free on /, and this needs about $need GB."
+  ask "Continue anyway?" n n
+}
+
+# Can't be fixed without reinstalling Arch, so only asked about the first time
+check_btrfs() {
+  local fstype
+  already_installed && return 0
+  fstype="$(findmnt -no FSTYPE /)"
+  [ "$fstype" = btrfs ] && return 0
+  echo "/ is on $fstype, not btrfs, so update can't take a snapshot first, and a bad"
+  echo "update can't be rolled back (see Snapshots in the README). Only reinstalling Arch"
+  echo "with btrfs, archinstall's default, changes that."
+  ask "Continue without snapshots?" y y
+}
+
+# CoreDesktop turns on GDM, which fails while another login screen is on
+check_display_manager() {
+  local dm
+  dm="$(readlink /etc/systemd/system/display-manager.service 2> /dev/null)"
+  dm="$(basename "${dm:-none}")"
+  [ "$dm" = none ] || [ "$dm" = gdm.service ] && return 0
+  grep -qsx "system gdm.service" "$SERVICES_OFF" && return 0
+
+  echo "This machine's login screen is ${dm%.service}, not GNOME's (GDM)."
+  if ask "Switch to GNOME's login screen? It takes over when you restart." y n; then
+    # enable_services turns GDM on later in the install
+    sudo systemctl disable "$dm" || return 1
+  else
+    mkdir -p "$(dirname "$SERVICES_OFF")"
+    echo "system gdm.service" >> "$SERVICES_OFF"
+    echo "Keeping ${dm%.service}. Choose GNOME from its session menu when you log in."
+    echo "To switch later: sudo systemctl disable $dm && sudo systemctl enable gdm"
+    echo "then delete the line \"system gdm.service\" from $SERVICES_OFF"
+  fi
+}
+
+# PipeWire replaces PulseAudio; GNOME's screen sharing needs it, and calls in
+# Jitsi and Element work best with it
+check_sound() {
+  local plugins=()
+  is_installed pulseaudio || return 0
+
+  echo "This machine plays sound through PulseAudio. PipeWire replaces it: GNOME's"
+  echo "screen sharing needs it, and calls in Jitsi and Element work best with it."
+  if ! ask "Switch to PipeWire?" y n; then
+    echo "Keeping PulseAudio."
+    return 0
+  fi
+  # Its modules (bluetooth, ...) need it, so they go first; PipeWire does
+  # what they did
+  mapfile -t plugins < <(pacman -Qq | grep '^pulseaudio-')
+  if (( ${#plugins[@]} > 0 )); then
+    sudo pacman -R --noconfirm "${plugins[@]}" || return 1
+  fi
+  # --ask=4 answers yes to removing pulseaudio, which pipewire-pulse replaces
+  sudo pacman -S --needed --noconfirm --ask=4 pipewire pipewire-pulse pipewire-alsa wireplumber || return 1
+  echo "Switched to PipeWire. It takes over when you log out and in again."
+}
+
+check_disk || exit 1
+check_btrfs || exit 1
+check_display_manager || exit 1
+check_sound || exit 1
+exit 0

system/vulkan.sh

@@ -1,7 +1,9 @@
 #!/bin/bash
 #
-# Purpose : Install the Vulkan driver for each Intel or AMD GPU in the machine.
-#           NVIDIA's Vulkan driver comes with nvidia-utils (see nvidia.sh).
+# Purpose : Install the Vulkan driver for each Intel or AMD GPU in the machine,
+#           and Intel's video decoding driver (VA-API), so video and calls
+#           don't decode on the CPU. AMD's comes with mesa, NVIDIA's with its
+#           driver (see nvidia.sh).
 
 set -e
 
@@ -12,7 +14,8 @@ PACKAGES=()
 for device in /sys/bus/pci/devices/*; do
   [[ $(< "$device/class") == 0x03* ]] || continue
   case "$(< "$device/vendor")" in
-    0x8086) PACKAGES+=(vulkan-intel) ;;
+    # intel-media-driver covers Broadwell (2014) and newer
+    0x8086) PACKAGES+=(vulkan-intel intel-media-driver) ;;
     0x1002) PACKAGES+=(vulkan-radeon) ;;
   esac
 done