[Keenetic] Entware migration between partitions

#!/bin/sh
# The last version of this script is available at https://pastebin.com/Wm0yDd6x
# Create two ext partitions with OPT1, OPT2 labels first, fix URL below if necessary
#URL=http://bin.entware.net/mipselsf-k3.4/installer/mipsel-installer.tar.gz
URL=http://bin.entware.net/aarch64-k3.10/installer/aarch64-installer.tar.gz

echo -n  '[1/5] Checking for OPT1 and OPT2 partitions... '
OPT1=$(readlink /tmp/mnt/OPT1) && OPT2=$(readlink /tmp/mnt/OPT2)
if [ $? -ne 0 ] ; then
    echo "I presume I've got two partitions labeled as OPT1 and OPT2."
    echo 'See you next time!'
    exit 1
else
    echo 'done.'
fi

echo -n '[2/5] Detecting current /opt partition... '
OPT_MPOINT=$(mount | grep ' /opt type ' | cut -d' ' -f1)
OPT=$(mount | grep $OPT_MPOINT | grep ' on /tmp/mnt/' | cut -d' ' -f 3 | cut -d'/' -f 4)
if [ -z "$OPT_MPOINT" ] || [ -z "$OPT" ]; then
    echo "Can't detect current /opt mountpoint. I'm too stupid for that, sorry."
    exit 1
fi
if [ "$OPT" = "$OPT1" ]; then
    echo 'done. Migrating from OPT1 to OPT2'
    SRC=$OPT1
    DST=$OPT2
else
    echo 'done. Migrating from OPT2 to OPT1'
    SRC=$OPT2
    DST=$OPT1
fi

echo '[3/5] Cleaning up target partition... '
rm -fr /tmp/mnt/$DST/*
mkdir /tmp/mnt/$DST/root
if [ $? -ne 0 ] ; then
    echo "Can't create destination folder, exiting."
    exit 1
fi

echo '[4/5] Saving installed packages list...'
#tar cf /tmp/mnt/$DST/root/opt.tar /opt
opkg list_installed | cut -d ' ' -f 1 > /tmp/mnt/$DST/root/installed_packages.txt
cp $0 /tmp/mnt/$DST/root

echo '[5/5] Downloading installation archive...'
mkdir /tmp/mnt/$DST/install
wget -qO /tmp/mnt/$DST/install/installer.tgz $URL

echo 'Done! You may switch OPKG partition from WebUI.'