#!/bin/bash
clear
echo
echo "Minimal reproducible example (MRE)"
echo "----------------------------------"
echo
echo "Tested with"
echo "- rsync  version 3.2.7  protocol version 31"
echo "- ext4 file system"
echo
rm -rf MRE
mkdir MRE
cd MRE
mkdir source
touch source/read_only.txt
chmod 444 source/read_only.txt

mkdir snapshot1
# rsync --recursive --times --devices --specials --hard-links --human-readable -s --links --perms --executability --group --owner source/* snapshot1/
rsync --perms --executability --group --owner source/* snapshot1/

mkdir snapshot2
# rsync --recursive --times --devices --specials --hard-links --human-readable -s --links --perms --executability --group --owner --link-dest=../snapshot1 source/* snapshot2/
rsync --perms --executability --group --owner --link-dest=../snapshot1 source/* snapshot2/
# stat snapshot1/read_only.txt 
echo "File stats BEFORE rsync --delete":
echo
stat snapshot2/read_only.txt

mkdir empty
# delete snapshot1 using an empty source directory (shall be the fastest way to delete a subdir)
# --debug=ALL
rsync -a --delete -s empty/ snapshot1/
# rm -f snapshot1/  # works as expected (unlink does neither change 'Changed' time nor file permissions)
# strace -c rm -rf snapshot1
echo
stat snapshot2/read_only.txt

echo
echo "Results (after deleting snapshot1 via rsync --delete):"
echo "1. The 'Change' time of the hardlinked file was updated"
echo "2. The hardlinked file has now different access rights (644 instead of 444 so it is writable again!)"
echo "This does NOT happen if 'rm -f snapshot1/' is used!"
echo

echo "Files in snapshot2:"
ls -l snapshot2