BORG-INIT(1) borg backup tool BORG-INIT(1)
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 reposi-
tory - 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 mali-
ciously 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 charac-
ters.
• BUT: that does not necessarily apply to your OS / VM / keyboard con-
figuration.
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 ~/.con-
fig/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 key-
file-blake2. Note: for remote backups the hashing is done on your local
machine.
┌─────────┬──────────────────┬──────────────────┬──────────────────┐
│Hash/MAC │ Not encrypted no │ Not encrypted, │ Encrypted (AEAD │
│ │ auth │ but authenti- │ w/ AES) and au- │
│ │ │ cated │ thenticated │
├─────────┼──────────────────┼──────────────────┼──────────────────┤
│SHA-256 │ none │ authenticated │ repokey keyfile │
├─────────┼──────────────────┼──────────────────┼──────────────────┤
│BLAKE2b │ n/a │ authenti- │ repokey-blake2 │
│ │ │ cated-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 hard-
ware-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 mak-
ing 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 re-
pokey. 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
options
-e MODE, --encryption MODE
select encryption key mode (required)
--append-only
create an append-only mode repository. Note that this only af-
fects 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). De-
fault: 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
SEE ALSO
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)
AUTHOR
The Borg Collective
2023-03-22 BORG-INIT(1)
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