Duplicity (software)

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Duplicity
Basic data

Maintainer Kenneth Loafman
Current  version 0.8.09
( January 7, 2020 )
operating system Linux
programming language python
category data backup
License GPL
duplicity.nongnu.org

Duplicity is a data backup software developed for Linux that can be used to create so-called incremental backups .

support

The program supports a wide variety of destinations and transmission protocols, including:

Duplicity works best on Unix systems (e.g. Linux, BSD, and Mac OS X), but it can be used on Windows with Cygwin . There, however, it does not record the Windows file system-specific properties. The application currently supports deleted files, Unix file rights , directories, symbolic links, FIFOs and drive files, but not hard links . Since Duplicity encrypts the backups by default using GnuPG , this software is ideally suited for backing up data on external storage locations - the so-called cloud .

The program is published under the GNU General Public License and is therefore free software .

Working method

The program is operated on the command line. A simple example is:

duplicity full --no-encryption Quellverzeichnis file://Zielverzeichnis

The storage location of the backup files must be a URL , so this is the file://case when specifying the directory. "full" specifies that all data will be backed up (this is mandatory for the first backup, optional for each subsequent backup - "full" is then omitted). However, it is advisable to back up all data every now and then and to specify "full". "--no-encryption" creates an unencrypted backup.

Duplicity uses incremental backups . The changes are recorded using the rsync algorithm. The backup data is finally saved in individual tar files that are compressed with gzip to save storage space .

The last saved data is restored with:

duplicity restore file://Zielverzeichnis Quellverzeichnis

With each backup process, three types of files are stored in the target directory:

  • A "manifest" which records which files have been backed up and in which "Difftar" files they can be found.
  • The "Difftar" files, which contain the actual data. They are numbered from "vol1" to "vol ...".
  • The "Sigtar", which contains the SHA-1 checksums of the data. These checksums ensure that a file that has changed is also covered by the next incremental backup.

The Déjà Dup program is a graphical user interface (GUI) for duplicity.

Advantages and disadvantages

Advantages are for example:

  • The standard encryption allows the backups to be made on storage locations with dubious data security and theft security.
  • Modified files are definitely recognized using SHA-1 checksums.
  • The result is a relatively manageable number of backup files with uniform file names, all of which are stored in a single directory (cf. the directory "rdiff-backup-data" in rdiff-backup).
  • At least the incremental backups can easily be interrupted and continued. Existing difftar files are taken into account.
  • At least the full lock can be opened relatively easily by hand if duplicity does not work for any reason.

Disadvantage:

  • Incremental backups are done as "forward deltas". A full backup ("duplicity full ...") can be followed by any number of incremental backups ("duplicity ..."). The changes compared to the previous database are transferred and saved, but the current original data is not mirrored. In the case of data restoration, the original database must first be reconstructed from the incremental backups - in contrast to rdiff-backup, for example, which saves "reverse deltas" and in which the last backup status is easily restored by means of a simple copy process ( cp ) can be.

See also

Web links

Individual evidence

  1. ↑ duplicity.nongnu.org .
  2. ^ The duplicity Open Source Project on Open Hub: Languages ​​Page . In: Open Hub . (accessed on September 26, 2018).
  3. ↑ a b c Behind lock and seal. October 17, 2006, accessed May 12, 2019 .
  4. ↑ Encrypted backup with duplicity. Retrieved May 12, 2019 .
  5. ↑ https://askubuntu.com/questions/473124/extract-duplicity-files-manually (accessed October 8, 2014).