borg repo-create

borg [common options] repo-create [options]

options
	--other-repo SRC_REPOSITORY	reuse the key material from the other repository
	--from-borg1	other repository is Borg 1.x
	-e ENCRYPTION, --encryption ENCRYPTION	select the mode: ‘aes256-ocb’, ‘chacha20-poly1305’, ‘authenticated-sha256’ or ‘authenticated-blake3’ (required)
	-i HASH, --id-hash HASH	select the id hash function of the encrypted modes: ‘sha256’ or ‘blake3’. The ‘authenticated-sha256’ and ‘authenticated-blake3’ modes name their hash themselves.
	--key-location LOCATION	where to store the key: ‘repokey’ (in the repository, default) or ‘keyfile’ (in the local keys directory).
	-C COMPRESSION, --compression COMPRESSION	set the default compression of the repository, see the output of the “borg help compression” command for details. Default: no repository default (lz4 is used).
	--chunker-params PARAMS	set the default chunker parameters of the repository (same format as for borg create). Default: no repository default (fastcdc,19,23,21,2 is used).
	--copy-crypt-key	copy the crypt_key (used for authenticated encryption) from the key of the other repository (default: new random key).
Common options

Description

This command creates a new, empty repository. A repository is a borgstore store containing the deduplicated data from zero or more archives.

Repository creation can be quite slow for some kinds of stores (e.g. for sftp:) - this is due to borgstore pre-creating all directories needed, making usage of the store faster.

Encryption mode TL;DR

The encryption mode can only be configured when creating a new repository - you can neither configure it on a per-archive basis nor change the mode of an existing repository. This example will likely NOT give optimum performance on your machine (performance tips will come below):

borg repo-create --encryption aes256-ocb --key-location repokey

Borg will:

1. Ask you to come up with a passphrase.

2. Create a borg key (which contains some random secrets. See Key files).

3. Derive a “key encryption key” from your passphrase

4. Encrypt and sign the key with the key encryption key

5. Store the encrypted borg key in the repository (as an object in the keys/ namespace of the store). This is why it is essential to use a secure passphrase.

6. Encrypt and sign your backups to prevent anyone from reading or forging them unless they have the key and know the passphrase. Make sure to keep a backup of your key outside the repository - do not lock yourself out by “leaving your keys inside your car” (see borg key export). The encryption is done locally - if you use a remote repository, the remote machine never sees your passphrase, your unencrypted key or your unencrypted files. Chunking and ID generation are also based on your key to improve your privacy.

7. Use the key when extracting files to decrypt them and to verify that the contents of the backups have not been accidentally or maliciously altered.

Picking a passphrase

Make sure you use a good passphrase. Not too short, not too simple. The real encryption / decryption key is encrypted with / locked by your passphrase. If an attacker gets your key, they cannot unlock and use it without knowing the passphrase.

Be careful with special or non-ASCII characters in your passphrase:

• Borg processes the passphrase as Unicode (and encodes it as UTF-8), so it does not have problems dealing with even the strangest characters.

• BUT: that does not necessarily apply to your OS/VM/keyboard configuration.

So better use a long passphrase made from simple ASCII characters than one that includes non-ASCII stuff or characters that are hard or impossible to enter on a different keyboard layout.

You can change your passphrase for existing repositories at any time; it will not affect the encryption/decryption key or other secrets.

Borg also accepts an empty passphrase. The repository is still encrypted with a random key then, but that key is not protected: with repokey storage, anybody who can read the repository can also unlock the key, which is as good as no encryption at all (with keyfile storage, the key is only on your client, so an empty passphrase may be acceptable if e.g. the client’s disk is encrypted). You can add a passphrase later with borg key change-passphrase. borg repo-info shows whether the key has an empty passphrase.

Choosing a crypto suite

Depending on your hardware, hashing and crypto performance may vary widely. The easiest way to find out what is fastest is to run borg benchmark cpu.

--encryption (required) selects the mode:

• aes256-ocb: AES256 in OCB mode (encryption + authentication).

• chacha20-poly1305: ChaCha20 + Poly1305 (encryption + authentication).

• authenticated-sha256 / authenticated-blake3: no encryption, but authentication (tamper detection) using HMAC-SHA-256 resp. keyed BLAKE3.

--id-hash selects the id hash function of the encrypted modes:

• sha256 (default): HMAC-SHA-256.

• blake3: BLAKE3. Often faster on CPUs without SHA hardware acceleration.

For the modes that do not encrypt, the hash is not just used for the chunk ids, it also is what protects your data - therefore it is part of the mode name there and --id-hash does not apply to them.

--key-location selects where the key is stored (orthogonal to the crypto suite):

• repokey (default): the key is stored in the repository (under keys/). Pick this if you want ease-of-use and “passphrase” security is good enough.

• keyfile: the key is stored in your home directory (in ~/.config/borg/keys). Pick this if you want “passphrase and having-the-key” security.

You can move the key between these locations later with borg key change-location. This also applies to the authenticated-* modes: they do not encrypt your data, but they still have a key (used for the id hash and the authentication), so --key-location selects where that key is stored, just like for the encrypted modes.

If you do not want to encrypt the contents of your backups, but still want to detect malicious tampering, use --encryption authenticated-sha256 (or -blake3). These modes are like an encrypted mode minus the data encryption. To normally work with authenticated-* repositories, you will need the passphrase, but there is an emergency workaround; see BORG_WORKAROUNDS=authenticated_no_key docs.

Repository defaults

--compression sets the repository’s default compression: the commands that compress data (borg create, borg recreate, borg import-tar, borg transfer, borg repo-compress) use it if no compression was given via --compression, the environment or the default config file (default.yaml). Without a repository default, they use lz4. See borg help compression for the compression specs.

--chunker-params sets the repository’s default chunker parameters: borg create and borg import-tar use them if no chunker parameters were given (in the same ways as above). borg recreate and borg transfer only rechunk if --chunker-params is given, with --chunker-params default, they rechunk to the repository’s default chunker parameters. Without a repository default, the built-in default chunker parameters are used.

This is useful if several clients back up into the same repository or if some commands are run manually: they all compress and chunk the same way without having to give these options. Using the same chunker parameters is important for deduplication. borg repo-info shows the defaults.

The defaults are stored in the repository and protected by the repository key: changing them (e.g. removing an obfuscate compression) needs the key. The defaults object is always written, also when no default was given, so removing it is noticed, too: the commands refuse to run if it is missing or fails the authentication. borg check reports such an object, borg check --repair replaces it by empty defaults (the built-in defaults are used then).

Creating a related repository

You can use borg repo-create --other-repo ORIG_REPO ... to create a related repository that uses the same secret key material as the given other/original repository.

By default, only the ID key and chunker secret will be the same (these are important for deduplication) and the AE crypto keys will be newly generated random keys.

Optionally, if you use --copy-crypt-key you can also keep the same crypt_key (used for authenticated encryption). This might be desired, for example, if you want to have fewer keys to manage.

Creating related repositories is useful, for example, if you want to use borg transfer later.

Creating a related repository for data migration from Borg 1.2 or 1.4

You can use borg repo-create --other-repo ORIG_REPO --from-borg1 ... to create a related repository that uses the same secret key material as the given other/original repository.

Then use borg transfer --other-repo ORIG_REPO --from-borg1 ... to transfer the archives.

Examples

# Local repository
$ export BORG_REPO=/path/to/repo
# Recommended AEAD cryptographic modes (key stored in the repository by default)
$ borg repo-create --encryption=aes256-ocb
$ borg repo-create --encryption=chacha20-poly1305
# No encryption, only authentication (not recommended)
$ borg repo-create --encryption=authenticated-sha256

# For the encrypted modes, --encryption (the cipher / AE algorithm) and --id-hash
# (the id hash function) are chosen independently. --id-hash defaults to sha256;
# use blake3 if it is faster on your hardware (run 'borg benchmark cpu' to find out).
$ borg repo-create --encryption=aes256-ocb --id-hash=blake3
$ borg repo-create --encryption=chacha20-poly1305 --id-hash=blake3

# The 'authenticated-*' modes name their id hash themselves, so they
# do not take a separate --id-hash.
$ borg repo-create --encryption=authenticated-blake3

# Where the key is stored (--key-location) is also chosen independently.
# --key-location defaults to repokey.
# repokey: stores the encrypted key inside the repository
$ borg repo-create --encryption=aes256-ocb --key-location=repokey
# keyfile: stores the encrypted key in the config dir's keys/ subdir
# (e.g. ~/.config/borg/keys/ on Linux, ~/Library/Application Support/borg/keys/ on macOS)
$ borg repo-create --encryption=aes256-ocb --key-location=keyfile