What I never understood in incremental backup, via duplicity, is whether amended local files are overwritten in the backup storage, i.e., is it possible with incremental backup to restore an old version of a file that has been amended?
first question "files are overwritten in backup".
As duplicity is using librsync's rolling-checksum algorithm only changed blocks will be backed up. Imagine each backup as a bucket of blocks of files. On each incremental new time stamped buckets are added containing only changed blocks. Older buckets (incrementals/fulls) will never be modified.
second question "restorability of older file versions".
Of course you can go back in time if you have multiple full/incremental backups.
Typically, you have one or more backup chains containing
and multiple incremental files which permit you to fetch a given backup
You have the following
duplicity option which defines when you want to go in your backup:
-ttime, --time time, --restore-time time Specify the time from which to restore or list files.
You can also type
duplicity collection-status file://duplicity_directory to get the list of available backups and their dates.