When comparing duplicity vs Déjà Dup, the Slant community recommends duplicity for most people. In the question“What are the best backup programs for Linux?” duplicity is ranked 2nd while Déjà Dup is ranked 4th. The most important reason people chose duplicity is:
Data is encrypted locally before being sent, and kept encrypted by a key that is never stored on the remote machine. So you might even store your data on a public space, people would still need your key or brute force it.
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Pros
Pro Encrypted locally before sending (using GnuPG)
Data is encrypted locally before being sent, and kept encrypted by a key that is never stored on the remote machine. So you might even store your data on a public space, people would still need your key or brute force it.
Pro Bandwidth and space efficient
Duplicity uses the rsync algorithm so only the changed parts of files are sent to the archive when doing an incremental backup. For instance, if a long log file increases by just a few lines of text, a small diff will be sent to and saved in the archive. Other backup programs may save a complete copy of the file.
Pro Versioning and incremental backup
You can retrieve older versions or files you recently deleted locally even after having updated your backup.
Pro Free and open-source
Licensed under GNU GPL v2.
Pro Works with scp/ssh, ftp, rsync, Amazon S3...
Duplicity does not make many demands on its archive server. As long as files can be saved to, read from, listed, and deleted from a location, that location can be used as a duplicity backend. Besides increasing choice for the user, it can make a server more secure, as clients only require minimal access.
Pro Has a Dockerized image
Docker allows to run programs on any Linux without having to really install them, and allows to manage versions so it runs exactly the same on different machines.
Pro Straightforward interface
The program's interface has 4 tabs - overview, storage, folders and schedule. You select where to back up in "storage", what folders to back up and ignore in "folders" and how often to back up in "schedule." Overview displays all these settings and offers a choice of backing up and restoring.
Pro Can back up to any server that Nautilus can connect to
You can connect to both physically connected devices as well as devices that are available over FTP, SSH, as long as Nautilus can connect to them.
Pro Available on Ubuntu by default
For people using Ubuntu, this is already installed.
Cons
Con You have to invest a few minutes in setup time
Con Backend provider choices recently removed
As of version 42, support for backup to Amazon S3, Google Cloud Storage, Openstack Swift, Rackspace, etc has been removed entirely. Google Drive is the default and seemingly only option.
Con No way to set limitations on how much disk space the application should use
The program will use up all available disk space for backups. There's not way to set limitations.
Con No way to set a specific backup time for automatic backups
You can only set the backups to be daily, weekly or monthly without the ability to tell what time the backups should happen.