Adopt the solution for resizing root from openwrt expand_root guide

Closes: #37

.buildbot/openwrt/build.sh

@@ -118,6 +118,7 @@ chmod 0400 files/etc/dropbear/authorized_keys
 mkdir -p files/etc/docker
 chmod 0750 files/etc/docker
 cp ${pwd}/daemon.json files/etc/docker
+cp ${pwd}/sysupgrade.conf files/etc
 mkdir -p files/etc/uci-defaults
 cp ${pwd}/defaults/* files/etc/uci-defaults
 

defaults/70-rootpt-resize

@@ -0,0 +1,20 @@
+# Copied from https://openwrt.org/docs/guide-user/advanced/expand_root
+
+if [ ! -e /etc/rootpt-resize ] \
+&& type parted > /dev/null \
+&& lock -n /var/lock/root-resize
+then
+ROOT_BLK="$(readlink -f /sys/dev/block/"$(awk -e \
+'$9=="/dev/root"{print $3}' /proc/self/mountinfo)")"
+ROOT_DISK="/dev/$(basename "${ROOT_BLK%/*}")"
+ROOT_PART="${ROOT_BLK##*[^0-9]}"
+parted -l ---pretend-input-tty << EOI
+ok
+fix
+EOI
+parted -s "${ROOT_DISK}" resizepart "${ROOT_PART}" 100%
+mount_root done
+touch /etc/rootpt-resize
+reboot
+fi
+exit 1

defaults/80-rootfs-resize

@@ -0,0 +1,23 @@
+# Copied from https://openwrt.org/docs/guide-user/advanced/expand_root
+# Updated for f2fs using
+# https://github.com/anaelorlinski/OpenWrt-NanoPi-R2S-R4S-Builds/blob/main/docs/resize-f2fs.md
+
+if [ ! -e /etc/rootfs-resize ] \
+&& [ -e /etc/rootpt-resize ] \
+&& type losetup > /dev/null \
+&& type resize.f2fs > /dev/null \
+&& lock -n /var/lock/root-resize
+then
+LOOP="$(losetup -n -O NAME | sort | sed -n -e "1p")"
+ROOT="$(losetup -n -O BACK-FILE ${LOOP} | sed -e "s|^|/dev|")"
+OFFS="$(losetup -n -O OFFSET ${LOOP})"
+LOOP="$(losetup -f)"
+losetup -o ${OFFS} ${LOOP} ${ROOT}
+fsck.f2fs -f ${LOOP}
+mount ${LOOP} /mnt
+touch /mnt/upper/etc/rootfs-resize
+umount ${LOOP}
+resize.f2fs ${LOOP}
+reboot
+fi
+exit 1

sysupgrade.conf

@@ -0,0 +1,5 @@
+## This file contains files and directories that should
+## be preserved during an upgrade.
+
+/etc/uci-defaults/70-rootpt-resize
+/etc/uci-defaults/80-rootfs-resize