Ubuntu Manpage: borg-init - Initialize an empty repository

NAME

       borg-init - Initialize an empty repository

SYNOPSIS

       borg [common options] init [options] [REPOSITORY]

DESCRIPTION

This command initializes an 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 encryption mode of an existing
repository.

Use repokey:

borg init --encryption repokey /path/to/repo

Or repokey-blake2 depending on which is faster on your client machines (see below):

borg init --encryption repokey-blake2 /path/to/repo

Borg will:

1. Ask you to come up with a passphrase.

2. Create a borg key (which contains 3 random secrets. See key_files).

3. Encrypt the key with your passphrase.

4. Store the encrypted borg key inside the repository directory (in the repo config).
This is why it is essential to use a secure passphrase.

5. 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). For remote backups the encryption is done locally - 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.

6. 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.

More encryption modes
Only use --encryption none if you are OK with anyone who has access to your repository
being able to read your backups and tamper with their contents without you noticing.

If you want "passphrase and having-the-key" security, use --encryption keyfile. The key
will be stored in your home directory (in ~/.config/borg/keys).

If you do not want to encrypt the contents of your backups, but still want to detect
malicious tampering use --encryption authenticated.

If BLAKE2b is faster than SHA-256 on your hardware, use --encryption authenticated-blake2,
--encryption repokey-blake2 or --encryption keyfile-blake2. Note: for remote backups the
hashing is done on your local machine.

┌─────────┬─────────────────────┬──────────────────────┬─────────────────────┐
│Hash/MAC │ Not encrypted no │ Not encrypted, but │ Encrypted (AEAD w/ │
│ │ auth │ authenticated │ 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.

OPTIONS

       See borg-common(1) for common options of Borg commands.

   arguments
       REPOSITORY
              repository to create

   optional arguments
       -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 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.

EXAMPLES

          # 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

AUTHOR