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_runscript
		}

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

Boot parameters:
 - overlay_root
 - overlay_rootfstype
 - overlay_rootflags
 - boot
 - bootfstype
 - bootflags
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_root' on real root"
		    mkdir -p /run/umorpha-root/root /run/umorpha-root/overlay
		    local mnt_root=/run/umorpha-root/root
		    local mnt_overlay=/run/umorpha-root/overlay
		    if ! mount -t "${rootfstype:-auto}" -o "ro${rootflags:+,$rootflags}" "$root" "$mnt_root"; then
		        umorpha_emergency_shell "Failed to mount root '$root'"
		    fi
		    if ! mount -t "${overlay_rootfstype:-auto}" -o "${rwopt:-ro}${overlay_rootflags:+,$overlayrootflags}" "$overlay_root" "$mnt_overlay"; then
		        umorpha_emergency_shell "Failed to mount overlay root '$overlay_root'"
		    fi
		    mkdir -p -- "$mnt_overlay/upperdir" "$mnt_overlay/workdir"
		    local overlay_opts
		    overlay_opts="lowerdir=${mnt_root}"
		    overlay_opts+=",upperdir=${mnt_overlay}/upperdir"
		    overlay_opts+=",workdir=${mnt_overlay}/workdir"
		    # > Offline changes to the lower tree are only allowed if the
		    # > "metadata only copy up", "inode index", "xino" and
		    # > "redirect_dir" features have not been used.
		    #
		    # -- https://www.kernel.org/doc/html/v6.6/filesystems/overlayfs.html#changes-to-underlying-filesystems
		    overlay_opts+=',metacopy=off'
		    overlay_opts+=',index=off'
		    overlay_opts+=',xino=off'
		    overlay_opts+=',redirect_dir=off'
		    if ! mount -t overlay -o "$overlay_opts" umorpha-rootfs "$newroot"; then
		        umorpha_emergency_shell "Failed to mount overlayfs lowerdir='${mnt_root}' overlaydir='${mnt_overlay}'"
		    fi

		    if [ -n "$boot" ]; then
		        local bootdev
		        if bootdev=$(resolve_device "$boot"); then
		            case "$boot" in
		                'UUID='* | 'LABEL='* | 'PARTUUID='* | 'PARTLABEL='*) : ;;
		                 *) boot="$bootdev" ;;
		            esac
		        fi
		        msg ":: mounting '${boot}' on /boot"
		        if ! mount -t "${bootfstype:-auto}" -o "${rwopt:-ro}${bootflags:+,$bootflags}" "$boot" "$newroot/boot"; then
		            umorpha_emergency_shell "Failed to mount boot '$boot'"
		        fi
		    fi
		}

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