borg/docs/man/borg-init.1

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.TH BORG-INIT 1 "2021-05-11" "" "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.
.sp
Encryption can be enabled at repository init time. It cannot be changed later.
.sp
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.
.sp
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.
.sp
You need to be careful with the key / the passphrase:
.sp
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).
.sp
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\(aqt
have the key (and also not the passphrase).
.sp
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\(aqt help you with that, of course.
.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 Encryption modes
.sp
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.
.sp
Example: \fIborg init \-\-encryption repokey ...\fP
.\" nanorst: inline-fill
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.TS
center;
|l|l|l|l|.
_
T{
Hash/MAC
T}	T{
Not encrypted
no auth
T}	T{
Not encrypted,
but authenticated
T}	T{
Encrypted (AEAD w/ AES)
and authenticated
T}
_
T{
SHA\-256
T}	T{
none
T}	T{
\fIauthenticated\fP
T}	T{
repokey
keyfile
T}
_
T{
BLAKE2b
T}	T{
n/a
T}	T{
\fIauthenticated\-blake2\fP
T}	T{
\fIrepokey\-blake2\fP
\fIkeyfile\-blake2\fP
T}
_
.TE
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.sp
Modes \fImarked like this\fP in the above table are new in Borg 1.1 and are not
backwards\-compatible with Borg 1.0.x.
.sp
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 \fIauthenticated\-blake2\fP faster than \fInone\fP and \fIauthenticated\fP\&.
.sp
On modern ARM CPUs, NEON provides hardware acceleration for SHA256 making it faster
than BLAKE2b\-256 there. NEON accelerates AES as well.
.sp
Hardware acceleration is always used automatically when available.
.sp
\fIrepokey\fP and \fIkeyfile\fP 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.
.sp
\fIrepokey\-blake2\fP and \fIkeyfile\-blake2\fP 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 \fInot\fP compatible with Borg 1.0.x.
.sp
\fIauthenticated\fP mode uses no encryption, but authenticates repository contents
through the same HMAC\-SHA256 hash as the \fIrepokey\fP and \fIkeyfile\fP modes (it uses it
as the chunk ID hash). The key is stored like \fIrepokey\fP\&.
This mode is new and \fInot\fP compatible with Borg 1.0.x.
.sp
\fIauthenticated\-blake2\fP is like \fIauthenticated\fP, but uses the keyed BLAKE2b\-256 hash
from the other blake2 modes.
This mode is new and \fInot\fP compatible with Borg 1.0.x.
.sp
\fInone\fP 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 \fBborg create\fP on contents controlled by an attacker.
Use it only for new repositories where no encryption is wanted \fBand\fP when compatibility
with 1.0.x is important. If compatibility with 1.0.x is not important, use
\fIauthenticated\-blake2\fP or \fIauthenticated\fP instead.
This mode is compatible with Borg 1.0.x.
.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.
.UNINDENT
.SH EXAMPLES
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
# 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
.ft P
.fi
.UNINDENT
.UNINDENT
.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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