This leverages an rsync feature to back up files but hardlink any files that rsync thinks have not changed. This is not a block level thing, a file is either copied in its entirety, or hardlinked to the last version. TODO: Document how rsync figure out whether files have changed or not.
This script is configured through environment variables. Additionally a file last_backup_suffix.txt must be present in the same directory as the script that says the name of the last backup to link against. The script will update this as it goes.
SOURCE_FOLDER: the folder whose contents should be backed upSSH_COMMAND: options for how rsync should invoke ssh (paradigmatically used for flags not positional arguments), given to rsync -e flag, e.g.SSH_COMMAND='ssh -p 9001'DEST_FOLDER: the folder on the remote server where backups should be stored, e.g.DEST_FOLDER=/home/blzbrg/backups. Don't put trailing slash.DEST_USER: user on the remote server that you intend to authenticate as, e.g.DEST_USER=blzbrg