When comparing duplicity vs BackupPC, the Slant community recommends duplicity for most people. In the question“What are the best backup programs for Linux?” duplicity is ranked 2nd while BackupPC is ranked 7th. 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.
Specs
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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 No need to install anything more on the backed-up PC
Pro Able to handle large amount of servers and data
The disk IO can be a bootleneck but the system itself handles even multi terabyte servers easily.
Pro Supports various platforms
Backup method is highly configurable, using local copy, ssh, rsync, SMB or custom transfer, so able to backup almost any OS supporting these.
Pro Open Source
Pro Efficient disk format
The disk format automatically deduplicates files, and optionally compress files or assist recovery with redundancy information (par2); storage disk usage is very efficient.
Pro Combining full and incremental backups into "filled" view
Backups are always viewed as a whole, regardless of the count or data content of past incrementals.
Pro Rich command line tools
Apart from the Web UI there are command line tools for doing all tasks related to the backup system.
Cons
Con You have to invest a few minutes in setup time
Con Version 3 on-disk format is impossible to "file-copy"
V3 format uses hard-links which is almost impossble to "file-copy" (using filesystem level tools like cp or rsync) on a large system, since the hardlink management eats up vast amounts of memory (the only way to copy a backup server is to copy using a whole-disk copying method). This has been fixed in version 4 format which uses pointer files instead of hardlinks.
Con Web UI timeouts on large amount of data to be displayed
The Web UI needs large amount of time to walk a directory with thousands of entries and it may cause the webserver or client to timeout. Large directories may require the admin to use the command line tools to list or restore files or directories.