Ubuntu Manpage: borg-init - Initialize an empty repository

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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. To normally work with authenticated repos, you will need the passphrase,
but there is an emergency workaround, see BORG_WORKAROUNDS=authenticated_no_key docs.

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 auth │ Not encrypted, but │ Encrypted (AEAD w/ │
│ │ │ 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

       The Borg Collective

                                                   2024-07-02                                       BORG-INIT(1)