#chown -h -R --from=Plop:Plop reference:reference /
find / /var /home /data /opt -xdev \( -type f -o -type d \) \( -uid $(id -u Plop) -o -gid $(id -g Plop) \) -exec chown $(id -u reference):$(id -g reference) {} \;
usermod -o -u $(id -u reference) -g $(id -g reference) Plop