Borg Documentation

This is borg2!

Please note that this is the README for borg2 / master branch.

borg2 is currently in beta testing.

For the stable version’s docs, please see there:

TODO: the screencasts need a remake using borg2, see there:

What is BorgBackup?

BorgBackup (short: Borg) is a deduplicating backup program. Optionally, it supports compression and authenticated encryption.

The main goal of Borg is to provide an efficient and secure way to back up data. The data deduplication technique used makes Borg suitable for daily backups since only changes are stored. The authenticated encryption technique makes it suitable for backups to targets not fully trusted.

See the installation manual or, if you have already downloaded Borg, docs/installation.rst to get started with Borg. There is also an offline documentation available, in multiple formats.

Main features

Space efficient storage

Deduplication based on content-defined chunking is used to reduce the number of bytes stored: each file is split into a number of variable length chunks and only chunks that have never been seen before are added to the repository.

A chunk is considered duplicate if its id_hash value is identical. A cryptographically strong hash or MAC function is used as id_hash, e.g. (hmac-)sha256.

To deduplicate, all the chunks in the same repository are considered, no matter whether they come from different machines, from previous backups, from the same backup or even from the same single file.

Compared to other deduplication approaches, this method does NOT depend on:

  • file/directory names staying the same: So you can move your stuff around without killing the deduplication, even between machines sharing a repo.

  • complete files or time stamps staying the same: If a big file changes a little, only a few new chunks need to be stored - this is great for VMs or raw disks.

  • The absolute position of a data chunk inside a file: Stuff may get shifted and will still be found by the deduplication algorithm.

  • performance-critical code (chunking, compression, encryption) is implemented in C/Cython

  • local caching of files/chunks index data

  • quick detection of unmodified files

Data encryption

All data can be protected client-side using 256-bit authenticated encryption (AES-OCB or chacha20-poly1305), ensuring data confidentiality, integrity and authenticity.


Optionally, borg can actively obfuscate e.g. the size of files / chunks to make fingerprinting attacks more difficult.


All data can be optionally compressed:

  • lz4 (super fast, low compression)

  • zstd (wide range from high speed and low compression to high compression and lower speed)

  • zlib (medium speed and compression)

  • lzma (low speed, high compression)

Off-site backups

Borg can store data on any remote host accessible over SSH. If Borg is installed on the remote host, big performance gains can be achieved compared to using a network filesystem (sshfs, nfs, …).

Backups mountable as filesystems

Backup archives are mountable as userspace filesystems for easy interactive backup examination and restores (e.g. by using a regular file manager).

Easy installation on multiple platforms

We offer single-file binaries that do not require installing anything - you can just run them on these platforms:

  • Linux

  • macOS

  • FreeBSD

  • OpenBSD and NetBSD (no xattrs/ACLs support or binaries yet)

  • Cygwin (experimental, no binaries yet)

  • Linux Subsystem of Windows 10 (experimental)

Free and Open Source Software
  • security and functionality can be audited independently

  • licensed under the BSD (3-clause) license, see License for the complete license

Easy to use

For ease of use, set the BORG_REPO environment variable:

$ export BORG_REPO=/path/to/repo

Create a new backup repository (see borg rcreate --help for encryption options):

$ borg rcreate -e repokey-aes-ocb

Create a new backup archive:

$ borg create Monday1 ~/Documents

Now doing another backup, just to show off the great deduplication:

$ borg create -v --stats Monday2 ~/Documents
Repository: /path/to/repo
Archive name: Monday2
Archive fingerprint: 7714aef97c1a24539cc3dc73f79b060f14af04e2541da33d54c7ee8e81a00089
Time (start): Mon, 2022-10-03 19:57:35 +0200
Time (end):   Mon, 2022-10-03 19:57:35 +0200
Duration: 0.01 seconds
Number of files: 24
Original size: 29.73 MB
Deduplicated size: 520 B

Helping, Donations and Bounties, becoming a Patron

Your help is always welcome!

Spread the word, give feedback, help with documentation, testing or development.

You can also give monetary support to the project, see there for details:

Compatibility notes

EXPECT THAT WE WILL BREAK COMPATIBILITY REPEATEDLY WHEN MAJOR RELEASE NUMBER CHANGES (like when going from 0.x.y to 1.0.0 or from 1.x.y to 2.0.0).



Security issues should be reported to the Security contact (or see docs/support.rst in the source distribution).

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