#!/usr/bin/env sh

# Determine extroot partition
UUID=$(uci show fstab.extroot.uuid | sed -e 's/fstab\.extroot\.uuid\=//g' -e "s/\'//g")

# Check if currently mounted `/overlay` is, indeed, the extroot partition
if ! block info | grep -qE "$UUID.*/overlay"; then
   exit 127
fi

# Now that we know it is, take the backup and output it at `/overlay/sysupgrade-backup.tar.gz`
sysupgrade -b /overlay/sysupgrade-backup.tar.gz

# Exit gracefully
exit 0