borg/docs/man/borg-init.1

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.TH BORG-INIT 1 "2022-04-14" "" "borg backup tool"
.SH NAME
borg-init \- Initialize an empty repository
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.SH SYNOPSIS
.sp
borg [common options] init [options] [REPOSITORY]
.SH DESCRIPTION
.sp
This command initializes an empty repository. A repository is a filesystem
directory containing the deduplicated data from zero or more archives.
.SS Encryption mode TLDR
.sp
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):
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.sp
.nf
.ft C
borg init \-\-encryption repokey /path/to/repo
.ft P
.fi
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.sp
Borg will:
.INDENT 0.0
.IP 1. 3
Ask you to come up with a passphrase.
.IP 2. 3
Create a borg key (which contains some random secrets. See \fIkey_files\fP).
.IP 3. 3
Derive a "key encryption key" from your passphrase
.IP 4. 3
Encrypt and sign the key with the key encryption key
.IP 5. 3
Store the encrypted borg key inside the repository directory (in the repo config).
This is why it is essential to use a secure passphrase.
.IP 6. 3
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 \fBoutside\fP the repository \- do not lock yourself out by
"leaving your keys inside your car" (see \fIborg_key_export\fP).
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.
.IP 7. 3
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.
.UNINDENT
.SS Picking a passphrase
.sp
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\(aqt unlock and use it without knowing the
passphrase.
.sp
Be careful with special or non\-ascii characters in your passphrase:
.INDENT 0.0
.IP \(bu 2
Borg processes the passphrase as unicode (and encodes it as utf\-8),
so it does not have problems dealing with even the strangest characters.
.IP \(bu 2
BUT: that does not necessarily apply to your OS / VM / keyboard configuration.
.UNINDENT
.sp
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.
.sp
You can change your passphrase for existing repos at any time, it won\(aqt affect
the encryption/decryption key or other secrets.
.SS Choosing an encryption mode
.sp
Depending on your hardware, hashing and crypto performance may vary widely.
The easiest way to find out about what\(aqs fastest is to run \fBborg benchmark cpu\fP\&.
.sp
\fIrepokey\fP modes: if you want ease\-of\-use and "passphrase" security is good enough \-
the key will be stored in the repository (in \fBrepo_dir/config\fP).
.sp
\fIkeyfile\fP modes: if you rather want "passphrase and having\-the\-key" security \-
the key will be stored in your home directory (in \fB~/.config/borg/keys\fP).
.sp
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:
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.TS
center;
|l|l|l|l|l|.
_
T{
\fBmode (* = keyfile or repokey)\fP
T}	T{
\fBID\-Hash\fP
T}	T{
\fBEncryption\fP
T}	T{
\fBAuthentication\fP
T}	T{
\fBV>=\fP
T}
_
T{
\fB*\-blake2\-chacha20\-poly1305\fP
T}	T{
BLAKE2b
T}	T{
CHACHA20
T}	T{
POLY1305
T}	T{
1.3
T}
_
T{
\fB*\-chacha20\-poly1305\fP
T}	T{
HMAC\-SHA\-256
T}	T{
CHACHA20
T}	T{
POLY1305
T}	T{
1.3
T}
_
T{
\fB*\-blake2\-aes\-ocb\fP
T}	T{
BLAKE2b
T}	T{
AES256\-OCB
T}	T{
AES256\-OCB
T}	T{
1.3
T}
_
T{
\fB*\-aes\-ocb\fP
T}	T{
HMAC\-SHA\-256
T}	T{
AES256\-OCB
T}	T{
AES256\-OCB
T}	T{
1.3
T}
_
T{
\fB*\-blake2\fP
T}	T{
BLAKE2b
T}	T{
AES256\-CTR
T}	T{
BLAKE2b
T}	T{
1.1
T}
_
T{
\fB*\fP
T}	T{
HMAC\-SHA\-256
T}	T{
AES256\-CTR
T}	T{
HMAC\-SHA256
T}	T{
any
T}
_
T{
authenticated\-blake2
T}	T{
BLAKE2b
T}	T{
none
T}	T{
BLAKE2b
T}	T{
1.1
T}
_
T{
authenticated
T}	T{
HMAC\-SHA\-256
T}	T{
none
T}	T{
HMAC\-SHA256
T}	T{
1.1
T}
_
T{
none
T}	T{
SHA\-256
T}	T{
none
T}	T{
none
T}	T{
any
T}
_
.TE
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.sp
\fInone\fP mode uses no encryption and no authentication. You\(aqre advised to NOT use this mode
as it would expose you to all sorts of issues (DoS, confidentiality, tampering, ...) in
case of malicious activity in the repository.
.sp
If you do \fBnot\fP want to encrypt the contents of your backups, but still want to detect
malicious tampering use an \fIauthenticated\fP mode. It\(aqs like \fIrepokey\fP minus encryption.
.SS Key derivation functions
.INDENT 0.0
.IP \(bu 2
\fB\-\-key\-algorithm argon2\fP is the default and is recommended.
The key encryption key is derived from your passphrase via argon2\-id.
Argon2 is considered more modern and secure than pbkdf2.
.IP \(bu 2
You can use \fB\-\-key\-algorithm pbkdf2\fP if you want to access your repo via old versions of borg.
.UNINDENT
.sp
Our implementation of argon2\-based key algorithm follows the cryptographic best practices:
.INDENT 0.0
.IP \(bu 2
It derives two separate keys from your passphrase: one to encrypt your key and another one
to sign it. \fB\-\-key\-algorithm pbkdf2\fP uses the same key for both.
.IP \(bu 2
It uses encrypt\-then\-mac instead of encrypt\-and\-mac used by \fB\-\-key\-algorithm pbkdf2\fP
.UNINDENT
.sp
Neither is inherently linked to the key derivation function, but since we were going
to break backwards compatibility anyway we took the opportunity to fix all 3 issues at once.
.SH OPTIONS
.sp
See \fIborg\-common(1)\fP for common options of Borg commands.
.SS arguments
.INDENT 0.0
.TP
.B REPOSITORY
repository to create
.UNINDENT
.SS optional arguments
.INDENT 0.0
.TP
.BI \-e \ MODE\fR,\fB \ \-\-encryption \ MODE
select encryption key mode \fB(required)\fP
.TP
.B \-\-append\-only
create an append\-only mode repository. Note that this only affects the low level structure of the repository, and running \fIdelete\fP or \fIprune\fP will still be allowed. See \fIappend_only_mode\fP in Additional Notes for more details.
.TP
.BI \-\-storage\-quota \ QUOTA
Set storage quota of the new repository (e.g. 5G, 1.5T). Default: no quota.
.TP
.B \-\-make\-parent\-dirs
create the parent directories of the repository directory, if they are missing.
.TP
.B \-\-key\-algorithm
the algorithm we use to derive a key encryption key from your passphrase. Default: argon2
.UNINDENT
.SH EXAMPLES
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.ft C
# Local repository, recommended repokey AEAD crypto modes
$ borg init \-\-encryption=repokey\-aes\-ocb /path/to/repo
$ borg init \-\-encryption=repokey\-chacha20\-poly1305 /path/to/repo
$ borg init \-\-encryption=repokey\-blake2\-aes\-ocb /path/to/repo
$ borg init \-\-encryption=repokey\-blake2\-chacha20\-poly1305 /path/to/repo

# Local repository (no encryption), not recommended
$ 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\-aes\-ocb user@hostname:backup

# Remote repository (accesses a remote borg via ssh)
# keyfile: stores the (encrypted) key into ~/.config/borg/keys/
$ borg init \-\-encryption=keyfile\-aes\-ocb user@hostname:backup
.ft P
.fi
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.SH SEE ALSO
.sp
\fIborg\-common(1)\fP, \fIborg\-create(1)\fP, \fIborg\-delete(1)\fP, \fIborg\-check(1)\fP, \fIborg\-list(1)\fP, \fIborg\-key\-import(1)\fP, \fIborg\-key\-export(1)\fP, \fIborg\-key\-change\-passphrase(1)\fP
.SH AUTHOR
The Borg Collective
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