[Unit]
Before=umount.target

[Service]
Type=oneshot
User=root
ExecStartPre=/bin/chown -Rf peter /mnt/ramdisk/
ExecStart=/usr/bin/rsync -ar /mnt/ramdisk_backup/ /mnt/ramdisk/
ExecStop=/usr/bin/rsync -ar /mnt/ramdisk/ /mnt/ramdisk_backup/
ExecStopPost=/bin/chown -Rf peter /mnt/ramdisk_backup
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target