borg rcreate

borg [common options] rcreate [options]

options
	--other-repo SRC_REPOSITORY	reuse the key material from the other repository
	-e MODE, --encryption MODE	select encryption key mode (required)
	--append-only	create an append-only mode repository. Note that this only affects the low level structure of the repository, and running delete or prune will still be allowed. See Append-only mode (forbid compaction) in Additional Notes for more details.
	--storage-quota QUOTA	Set storage quota of the new repository (e.g. 5G, 1.5T). Default: no quota.
	--make-parent-dirs	create the parent directories of the repository directory, if they are missing.
	--copy-crypt-key	copy the crypt_key (used for authenticated encryption) from the key of the other repo (default: new random key).
Common options

Description

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

Encryption mode TLDR

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 rcreate --encryption repokey-aes-ocb

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 inside the repository directory (in the repo config). 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, he can’t 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 chars than one that includes non-ascii stuff or characters that are hard/impossible to enter on a different keyboard layout.

You can change your passphrase for existing repos at any time, it won’t affect the encryption/decryption key or other secrets.

Choosing an encryption mode

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

repokey modes: if you want ease-of-use and “passphrase” security is good enough - the key will be stored in the repository (in repo_dir/config).

keyfile modes: if you want “passphrase and having-the-key” security - the key will be stored in your home directory (in ~/.config/borg/keys).

The following table is roughly sorted in order of preference, the better ones are in the upper part of the table, in the lower part is the old and/or unsafe(r) stuff:

Mode (K = keyfile or repokey)	ID-Hash	Encryption	Authentication
K-blake2-chacha20-poly1305	BLAKE2b	CHACHA20	POLY1305
K-chacha20-poly1305	HMAC-SHA-256	CHACHA20	POLY1305
K-blake2-aes-ocb	BLAKE2b	AES256-OCB	AES256-OCB
K-aes-ocb	HMAC-SHA-256	AES256-OCB	AES256-OCB
authenticated-blake2	BLAKE2b	none	BLAKE2b
authenticated	HMAC-SHA-256	none	HMAC-SHA256
none	SHA-256	none	none

none mode uses no encryption and no authentication. You’re advised NOT to use this mode as it would expose you to all sorts of issues (DoS, confidentiality, tampering, …) in case of malicious activity in the repository.

If you do not want to encrypt the contents of your backups, but still want to detect malicious tampering use an authenticated mode. It’s like repokey minus encryption. To normally work with authenticated repos, you will need the passphrase, but there is an emergency workaround, see BORG_WORKAROUNDS=authenticated_no_key docs.

Creating a related repository

You can use borg rcreate --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). Might be desired e.g. if you want to have less keys to manage.

Creating related repositories is useful e.g. if you want to use borg transfer later.

Examples

# Local repository
$ export BORG_REPO=/path/to/repo
# recommended repokey AEAD crypto modes
$ borg rcreate --encryption=repokey-aes-ocb
$ borg rcreate --encryption=repokey-chacha20-poly1305
$ borg rcreate --encryption=repokey-blake2-aes-ocb
$ borg rcreate --encryption=repokey-blake2-chacha20-poly1305
# no encryption, not recommended
$ borg rcreate --encryption=authenticated
$ borg rcreate --encryption=authenticated-blake2
$ borg rcreate --encryption=none

# Remote repository (accesses a remote borg via ssh)
$ export BORG_REPO=ssh://user@hostname/~/backup
# repokey: stores the (encrypted) key into <REPO_DIR>/config
$ borg rcreate --encryption=repokey-aes-ocb
# keyfile: stores the (encrypted) key into ~/.config/borg/keys/
$ borg rcreate --encryption=keyfile-aes-ocb