borg/docs/man/borg-init.1

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.TH "BORG-INIT" "1" "2025-04-18" "" "borg backup tool"
.SH NAME
borg-init \- Initialize an empty repository
.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
encryption mode of an existing repository.
.sp
Use \fBrepokey\fP:
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.INDENT 3.5
.sp
.EX
borg init \-\-encryption repokey /path/to/repo
.EE
.UNINDENT
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.sp
Or \fBrepokey\-blake2\fP depending on which is faster on your client machines (see below):
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.INDENT 3.5
.sp
.EX
borg init \-\-encryption repokey\-blake2 /path/to/repo
.EE
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.sp
Borg will:
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.IP 1. 3
Ask you to come up with a passphrase.
.IP 2. 3
Create a borg key (which contains 3 random secrets. See \fIkey_files\fP).
.IP 3. 3
Encrypt the key with your passphrase.
.IP 4. 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 5. 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
\(dqleaving your keys inside your car\(dq (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 6. 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 More encryption modes
.sp
Only use \fB\-\-encryption none\fP 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.
.sp
If you want \(dqpassphrase and having\-the\-key\(dq security, use \fB\-\-encryption keyfile\fP\&.
The key will be stored in your home directory (in \fB~/.config/borg/keys\fP).
.sp
If you do \fBnot\fP want to encrypt the contents of your backups, but still
want to detect malicious tampering use \fB\-\-encryption authenticated\fP\&.
To normally work with \fBauthenticated\fP repos, you will need the passphrase, but
there is an emergency workaround, see \fBBORG_WORKAROUNDS=authenticated_no_key\fP docs.
.sp
If \fBBLAKE2b\fP is faster than \fBSHA\-256\fP on your hardware, use \fB\-\-encryption authenticated\-blake2\fP,
\fB\-\-encryption repokey\-blake2\fP or \fB\-\-encryption keyfile\-blake2\fP\&. Note: for remote backups
the hashing is done on your local machine.
.\" nanorst: inline-fill
.
.TS
box 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
.\" nanorst: inline-replace
.
.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 options
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.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
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.INDENT 3.5
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.EX
# 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
.EE
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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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