umorpha-boxes/modules/umorpha-disk.sh

#!/hint/bash -euE
# Copyright (C) 2023  Umorpha Systems
# SPDX-License-Identifier: AGPL-3.0-or-later

packages+=(
	# Normal runtime
	lvm2

	# Updates
	arch-install-scripts
	pv
)

pre_install+=(20:umorpha-disk:pre_install)
post_install+=(20:umorpha-disk:post_install)

umorpha-disk:pre_install() {
	local arg_mountpoint=$1

	mkdir -p "$arg_mountpoint/etc/pacman.d/hooks"
	ln -sT /dev/null "$arg_mountpoint/etc/pacman.d/hooks/90-mkinitcpio-install.hook"
}

umorpha-disk:post_install() {
	local arg_mountpoint=$1

	rm "$arg_mountpoint/etc/pacman.d/hooks/90-mkinitcpio-install.hook"
	rmdir "$arg_mountpoint/etc/pacman.d/hooks" || true

	########################################################################

	cat >"$arg_mountpoint/etc/mkinitcpio.conf.d/umorpha.conf" <<'EOF'
#!/hint/bash
# Copyright (C) 2023  Umorpha Systems
# SPDX-License-Identifier: AGPL-3.0-or-later

# Insert 'umorpha-overlayfs' and 'lvm2' into HOOKS.
for ((i=0; i<${#HOOKS[@]}; i++)); do
	if [[ ${HOOKS[i]} == filesystems ]]; then
		HOOKS=("${HOOKS[@]:0:i}" umorpha-overlayfs lvm2 "${HOOKS[@]:i}" )
		break
	fi
done
EOF

	cat >"$arg_mountpoint/usr/lib/initcpio/install/umorpha-overlayfs" <<-'EOF'
		#!/hint/bash
		# Copyright (C) 2023  Umorpha Systems
		# SPDX-License-Identifier: AGPL-3.0-or-later

		build() {
		    add_module 'overlay'

		    add_binary umorpha-mount
		    add_runscript
		}

		help() {
		    cat <<HELPEOF
This hook mounts a read-only root filesystem with a persistent
overlayfs on top of it.

Standard mkinitcpio boot parameters: 
  ro / rw         default: 'ro'     whether to mount the 'overlay' device
                                    and (if if there is one) the 'boot'
                                    device read-only or read+write
  root            required          device of the read-only root filesystem
  rootfstype      default: 'auto'   filesystem type of the 'root' device
  rootflags       default: empty    mount options for the 'root' device
Additional boot parameters:
  overlay         required          device of the persistent overlay filesystem
  overlayfstype   default: 'auto'   filesystem type of the 'overlay' device
  overlayflags    default: empty    mount options for the 'overlay' device
  boot            default: none     device of the '/boot' filesystem
  bootfstype      default: 'auto'   filesystem type of the 'boot' device
  bootflags       default: empty    mount options for the 'boot' device
HELPEOF
		}
	EOF

	cat >"$arg_mountpoint/usr/lib/initcpio/hooks/umorpha-overlayfs" <<-'EOF'
		#!/hint/ash
		# Copyright (C) 2023  Umorpha Systems
		# SPDX-License-Identifier: AGPL-3.0-or-later

		# args: errmsg
		umorpha_emergency_shell() {
		    run_hookfunctions 'run_emergencyhook' 'emergency hook' $EMERGENCYHOOKS
		    err "$*"
		    echo "You are now being dropped into an emergency shell."
		    launch_interactive_shell
		    msg "Trying to continue (this will most likely fail) ..."
		}

		# args: /path/to/newroot
		umorpha_mount_handler() {
		    local newroot="$1"

		    msg ":: mounting '$root'+'$overlay' on real root"
		    if ! umorpha-mount \
		        --root="$root:$rootfstype:ro${rootflags:+,$rootflags}" \
		        --overlay="$overlay:$overlayfstype:${rwopt:-ro}${overlayflags:+,$overlayrootflags}" \
		        ${boot:+--boot="$boot:$bootfstype:${rwopt:-ro}${bootflags:+,$bootflags}"} \
		        --basedir=/run/umorpah-root \
		        --final-mountpoint="$newroot"
		    then
		        umorpha_emergency_shell "Failed to mount base filesystem"
		    fi
		}

		run_hook() {
		    export mount_handler='umorpha_mount_handler'
		}
	EOF
}