| BORG-INIT(1) | borg backup tool | BORG-INIT(1) |
borg-init - Initialize an empty repository
borg [common options] init [options] [REPOSITORY]
This command initializes an empty repository. A repository is a filesystem directory containing the deduplicated data from zero or more archives.
Encryption can be enabled at repository init time. It cannot be changed later.
It is not recommended to work without encryption. Repository encryption protects you e.g. against the case that an attacker has access to your backup repository.
Borg relies on randomly generated key material and uses that for chunking, id generation, encryption and authentication. The key material is encrypted using the passphrase you give before it is stored on-disk.
You need to be careful with the key / the passphrase:
If you want "passphrase-only" security, use one of the repokey modes. The key will be stored inside the repository (in its "config" file). In above mentioned attack scenario, the attacker will have the key (but not the passphrase).
If you want "passphrase and having-the-key" security, use one of the keyfile modes. The key will be stored in your home directory (in .config/borg/keys). In the attack scenario, the attacker who has just access to your repo won't have the key (and also not the passphrase).
Make a backup copy of the key file (keyfile mode) or repo config file (repokey mode) and keep it at a safe place, so you still have the key in case it gets corrupted or lost. Also keep the passphrase at a safe place. The backup that is encrypted with that key won't help you with that, of course.
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:
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.
You can choose from the encryption modes seen in the table below on a per-repo basis. The mode determines encryption algorithm, hash/MAC algorithm and also the key storage location.
Example: borg init --encryption repokey ...
| Hash/MAC | Not encrypted no auth | Not encrypted, but authenticated | Encrypted (AEAD w/ AES) and authenticated |
| SHA-256 | none | authenticated | repokey keyfile |
| BLAKE2b | n/a | authenticated-blake2 | repokey-blake2 keyfile-blake2 |
Modes marked like this in the above table are new in Borg 1.1 and are not backwards-compatible with Borg 1.0.x.
On modern Intel/AMD CPUs (except very cheap ones), AES is usually hardware-accelerated. BLAKE2b is faster than SHA256 on Intel/AMD 64-bit CPUs (except AMD Ryzen and future CPUs with SHA extensions), which makes authenticated-blake2 faster than none and authenticated.
On modern ARM CPUs, NEON provides hardware acceleration for SHA256 making it faster than BLAKE2b-256 there. NEON accelerates AES as well.
Hardware acceleration is always used automatically when available.
repokey and keyfile use AES-CTR-256 for encryption and HMAC-SHA256 for authentication in an encrypt-then-MAC (EtM) construction. The chunk ID hash is HMAC-SHA256 as well (with a separate key). These modes are compatible with Borg 1.0.x.
repokey-blake2 and keyfile-blake2 are also authenticated encryption modes, but use BLAKE2b-256 instead of HMAC-SHA256 for authentication. The chunk ID hash is a keyed BLAKE2b-256 hash. These modes are new and not compatible with Borg 1.0.x.
authenticated mode uses no encryption, but authenticates repository contents through the same HMAC-SHA256 hash as the repokey and keyfile modes (it uses it as the chunk ID hash). The key is stored like repokey. This mode is new and not compatible with Borg 1.0.x.
authenticated-blake2 is like authenticated, but uses the keyed BLAKE2b-256 hash from the other blake2 modes. This mode is new and not compatible with Borg 1.0.x.
none mode uses no encryption and no authentication. It uses SHA256 as chunk ID hash. This mode is not recommended, you should rather consider using an authenticated or authenticated/encrypted mode. This mode has possible denial-of-service issues when running borg create on contents controlled by an attacker. Use it only for new repositories where no encryption is wanted and when compatibility with 1.0.x is important. If compatibility with 1.0.x is not important, use authenticated-blake2 or authenticated instead. This mode is compatible with Borg 1.0.x.
See borg-common(1) for common options of Borg commands.
# Local repository, repokey encryption, BLAKE2b (often faster, since Borg 1.1) $ borg init --encryption=repokey-blake2 /path/to/repo # Local repository (no encryption) $ borg init --encryption=none /path/to/repo # Remote repository (accesses a remote borg via ssh) # repokey: stores the (encrypted) key into <REPO_DIR>/config $ borg init --encryption=repokey-blake2 user@hostname:backup # Remote repository (accesses a remote borg via ssh) # keyfile: stores the (encrypted) key into ~/.config/borg/keys/ $ borg init --encryption=keyfile user@hostname:backup
borg-common(1), borg-create(1), borg-delete(1), borg-check(1), borg-list(1), borg-key-import(1), borg-key-export(1), borg-key-change-passphrase(1)
The Borg Collective
| 2021-03-22 |