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Usage

consists of a number of commands. Each command accepts a number of arguments and options. The following sections will describe each command in detail.

General

Type of log output

The log level of the builtin logging configuration defaults to WARNING. This is because we want to be mostly silent and only output warnings, errors and critical messages.

Log levels: DEBUG < INFO < WARNING < ERROR < CRITICAL

Use --debug to set DEBUG log level -to get debug, info, warning, error and critical level output.

Use --info (or -v or --verbose) to set INFO log level -to get info, warning, error and critical level output.

Use --warning (default) to set WARNING log level -to get warning, error and critical level output.

Use --error to set ERROR log level -to get error and critical level output.

Use --critical to set CRITICAL log level -to get critical level output.

While you can set misc. log levels, do not expect that every command will give different output on different log levels - it's just a possibility.

Warning

Options --critical and --error are provided for completeness, their usage is not recommended as you might miss important information.

Warning

While some options (like --stats or --list) will emit more informational messages, you have to use INFO (or lower) log level to make them show up in log output. Use -v or a logging configuration.

Return codes

can exit with the following return codes (rc):

0 = success (logged as INFO)
1 = warning (operation reached its normal end, but there were warnings -
    you should check the log, logged as WARNING)
2 = error (like a fatal error, a local or remote exception, the operation
    did not reach its normal end, logged as ERROR)
128+N = killed by signal N (e.g. 137 == kill -9)

If you use --show-rc, the return code is also logged at the indicated level as the last log entry.

Environment Variables

uses some environment variables for automation:

General:
BORG_REPO

When set, use the value to give the default repository location. If a command needs an archive parameter, you can abbreviate as ::archive. If a command needs a repository parameter, you can either leave it away or abbreviate as ::, if a positional parameter is required.

BORG_PASSPHRASE

When set, use the value to answer the passphrase question for encrypted repositories.

BORG_DISPLAY_PASSPHRASE

When set, use the value to answer the "display the passphrase for verification" question when defining a new passphrase for encrypted repositories.

BORG_LOGGING_CONF

When set, use the given filename as INI-style logging configuration.

BORG_RSH

When set, use this command instead of ssh. This can be used to specify ssh options, such as a custom identity file ssh -i /path/to/private/key. See man ssh for other options.

TMPDIR

where temporary files are stored (might need a lot of temporary space for some operations)

Some automatic "answerers" (if set, they automatically answer confirmation questions):
BORG_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK=no (or =yes)

For "Warning: Attempting to access a previously unknown unencrypted repository"

BORG_RELOCATED_REPO_ACCESS_IS_OK=no (or =yes)

For "Warning: The repository at location ... was previously located at ..."

BORG_CHECK_I_KNOW_WHAT_I_AM_DOING=NO (or =YES)

For "Warning: 'check --repair' is an experimental feature that might result in data loss."

BORG_DELETE_I_KNOW_WHAT_I_AM_DOING=NO (or =YES)

For "You requested to completely DELETE the repository including all archives it contains:"

Note: answers are case sensitive. setting an invalid answer value might either give the default answer or ask you interactively, depending on whether retries are allowed (they by default are allowed). So please test your scripts interactively before making them a non-interactive script.

Directories:
BORG_KEYS_DIR

Default to '~/.config/borg/keys'. This directory contains keys for encrypted repositories.

BORG_CACHE_DIR

Default to '~/.cache/borg'. This directory contains the local cache and might need a lot of space for dealing with big repositories).

Building:
BORG_OPENSSL_PREFIX

Adds given OpenSSL header file directory to the default locations (setup.py).

BORG_LZ4_PREFIX

Adds given LZ4 header file directory to the default locations (setup.py).

Please note:

  • be very careful when using the "yes" sayers, the warnings with prompt exist for your / your data's security/safety
  • also be very careful when putting your passphrase into a script, make sure it has appropriate file permissions (e.g. mode 600, root:root).

Resource Usage

might use a lot of resources depending on the size of the data set it is dealing with.

CPU:

It won't go beyond 100% of 1 core as the code is currently single-threaded. Especially higher zlib and lzma compression levels use significant amounts of CPU cycles.

Memory (RAM):

The chunks index and the files index are read into memory for performance reasons. Compression, esp. lzma compression with high levels might need substantial amounts of memory.

Temporary files:

Reading data and metadata from a FUSE mounted repository will consume about the same space as the deduplicated chunks used to represent them in the repository.

Cache files:

Contains the chunks index and files index (plus a compressed collection of single-archive chunk indexes).

Chunks index:

Proportional to the amount of data chunks in your repo. Lots of chunks in your repo imply a big chunks index. It is possible to tweak the chunker params (see create options).

Files index:

Proportional to the amount of files in your last backup. Can be switched off (see create options), but next backup will be much slower if you do.

Network:

If your repository is remote, all deduplicated (and optionally compressed/ encrypted) data of course has to go over the connection (ssh: repo url). If you use a locally mounted network filesystem, additionally some copy operations used for transaction support also go over the connection. If you backup multiple sources to one target repository, additional traffic happens for cache resynchronization.

In case you are interested in more details, please read the internals documentation.

Units

To display quantities, takes care of respecting the usual conventions of scale. Disk sizes are displayed in decimal, using powers of ten (so kB means 1000 bytes). For memory usage, binary prefixes are used, and are indicated using the IEC binary prefixes, using powers of two (so KiB means 1024 bytes).

Date and Time

We format date and time conforming to ISO-8601, that is: YYYY-MM-DD and HH:MM:SS (24h clock).

For more information about that, see: https://xkcd.com/1179/

Unless otherwise noted, we display local date and time. Internally, we store and process date and time as UTC.

Examples

# Local repository (default is to use encryption in repokey mode)
$ borg init /path/to/repo

# Local repository (no encryption)
$ borg init --encryption=none /path/to/repo

# Remote repository (accesses a remote borg via ssh)
$ borg init user@hostname:backup

# Remote repository (store the key your home dir)
$ borg init --encryption=keyfile user@hostname:backup

Important notes about encryption:

It is not recommended to disable encryption. Repository encryption protects you e.g. against the case that an attacker has access to your backup repository.

But be careful with the key / the passphrase:

If you want "passphrase-only" security, use the repokey mode. 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).

If you want "passphrase and having-the-key" security, use the keyfile mode. 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't have the key (and also not the passphrase).

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't help you with that, of course.

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:

  • 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.

Examples

# Backup ~/Documents into an archive named "my-documents"
$ borg create /path/to/repo::my-documents ~/Documents

# same, but verbosely list all files as we process them
$ borg create -v --list /path/to/repo::my-documents ~/Documents

# Backup ~/Documents and ~/src but exclude pyc files
$ borg create /path/to/repo::my-files \
    ~/Documents                       \
    ~/src                             \
    --exclude '*.pyc'

# Backup home directories excluding image thumbnails (i.e. only
# /home/*/.thumbnails is excluded, not /home/*/*/.thumbnails)
$ borg create /path/to/repo::my-files /home \
    --exclude 're:^/home/[^/]+/\.thumbnails/'

# Do the same using a shell-style pattern
$ borg create /path/to/repo::my-files /home \
    --exclude 'sh:/home/*/.thumbnails'

# Backup the root filesystem into an archive named "root-YYYY-MM-DD"
# use zlib compression (good, but slow) - default is no compression
$ borg create -C zlib,6 /path/to/repo::root-{now:%Y-%m-%d} / --one-file-system

# Make a big effort in fine granular deduplication (big chunk management
# overhead, needs a lot of RAM and disk space, see formula in internals
# docs - same parameters as borg < 1.0 or attic):
$ borg create --chunker-params 10,23,16,4095 /path/to/repo::small /smallstuff

# Backup a raw device (must not be active/in use/mounted at that time)
$ dd if=/dev/sdx bs=10M | borg create /path/to/repo::my-sdx -

# No compression (default)
$ borg create /path/to/repo::arch ~

# Super fast, low compression
$ borg create --compression lz4 /path/to/repo::arch ~

# Less fast, higher compression (N = 0..9)
$ borg create --compression zlib,N /path/to/repo::arch ~

# Even slower, even higher compression (N = 0..9)
$ borg create --compression lzma,N /path/to/repo::arch ~

# Use short hostname, user name and current time in archive name
$ borg create /path/to/repo::{hostname}-{user}-{now} ~
$ borg create /path/to/repo::{hostname}-{user}-{now:%Y-%m-%d_%H:%M:%S} ~

Examples

# Extract entire archive
$ borg extract /path/to/repo::my-files

# Extract entire archive and list files while processing
$ borg extract -v --list /path/to/repo::my-files

# Extract the "src" directory
$ borg extract /path/to/repo::my-files home/USERNAME/src

# Extract the "src" directory but exclude object files
$ borg extract /path/to/repo::my-files home/USERNAME/src --exclude '*.o'

# Restore a raw device (must not be active/in use/mounted at that time)
$ borg extract --stdout /path/to/repo::my-sdx | dd of=/dev/sdx bs=10M
Note: currently, extract always writes into the current working directory ("."),

so make sure you cd to the right place before calling borg extract.

Examples

$ borg create /path/to/repo::archivename ~
$ borg list /path/to/repo
archivename                          Mon, 2016-02-15 19:50:19

$ borg rename /path/to/repo::archivename newname
$ borg list /path/to/repo
newname                              Mon, 2016-02-15 19:50:19

Examples

$ borg list /path/to/repo
Monday                               Mon, 2016-02-15 19:15:11
repo                                 Mon, 2016-02-15 19:26:54
root-2016-02-15                      Mon, 2016-02-15 19:36:29
newname                              Mon, 2016-02-15 19:50:19
...

$ borg list /path/to/repo::root-2016-02-15
drwxr-xr-x root   root          0 Mon, 2016-02-15 17:44:27 .
drwxrwxr-x root   root          0 Mon, 2016-02-15 19:04:49 bin
-rwxr-xr-x root   root    1029624 Thu, 2014-11-13 00:08:51 bin/bash
lrwxrwxrwx root   root          0 Fri, 2015-03-27 20:24:26 bin/bzcmp -> bzdiff
-rwxr-xr-x root   root       2140 Fri, 2015-03-27 20:24:22 bin/bzdiff
...

$ borg list /path/to/repo::archiveA --list-format="{mode} {user:6} {group:6} {size:8d} {isomtime} {path}{extra}{NEWLINE}"
drwxrwxr-x user   user          0 Sun, 2015-02-01 11:00:00 .
drwxrwxr-x user   user          0 Sun, 2015-02-01 11:00:00 code
drwxrwxr-x user   user          0 Sun, 2015-02-01 11:00:00 code/myproject
-rw-rw-r-- user   user    1416192 Sun, 2015-02-01 11:00:00 code/myproject/file.ext
...

# see what is changed between archives, based on file modification time, size and file path
$ borg list /path/to/repo::archiveA --list-format="{mtime:%s}{TAB}{size}{TAB}{path}{LF}" |sort -n > /tmp/list.archiveA
$ borg list /path/to/repo::archiveB --list-format="{mtime:%s}{TAB}{size}{TAB}{path}{LF}" |sort -n > /tmp/list.archiveB
$ diff -y /tmp/list.archiveA /tmp/list.archiveB
1422781200      0       .                                       1422781200      0       .
1422781200      0       code                                    1422781200      0       code
1422781200      0       code/myproject                          1422781200      0       code/myproject
1422781200      1416192 code/myproject/file.ext               | 1454664653      1416192 code/myproject/file.ext
...

Examples

# delete a single backup archive:
$ borg delete /path/to/repo::Monday

# delete the whole repository and the related local cache:
$ borg delete /path/to/repo
You requested to completely DELETE the repository *including* all archives it contains:
repo                                 Mon, 2016-02-15 19:26:54
root-2016-02-15                      Mon, 2016-02-15 19:36:29
newname                              Mon, 2016-02-15 19:50:19
Type 'YES' if you understand this and want to continue: YES

Examples

Be careful, prune is a potentially dangerous command, it will remove backup archives.

The default of prune is to apply to all archives in the repository unless you restrict its operation to a subset of the archives using --prefix. When using --prefix, be careful to choose a good prefix - e.g. do not use a prefix "foo" if you do not also want to match "foobar".

It is strongly recommended to always run prune --dry-run ... first so you will see what it would do without it actually doing anything.

# Keep 7 end of day and 4 additional end of week archives.
# Do a dry-run without actually deleting anything.
$ borg prune --dry-run --keep-daily=7 --keep-weekly=4 /path/to/repo

# Same as above but only apply to archive names starting with "foo":
$ borg prune --keep-daily=7 --keep-weekly=4 --prefix=foo /path/to/repo

# Keep 7 end of day, 4 additional end of week archives,
# and an end of month archive for every month:
$ borg prune --keep-daily=7 --keep-weekly=4 --keep-monthly=-1 /path/to/repo

# Keep all backups in the last 10 days, 4 additional end of week archives,
# and an end of month archive for every month:
$ borg prune --keep-within=10d --keep-weekly=4 --keep-monthly=-1 /path/to/repo

Examples

$ borg info /path/to/repo::root-2016-02-15
Name: root-2016-02-15
Fingerprint: 57c827621f21b000a8d363c1e163cc55983822b3afff3a96df595077a660be50
Hostname: myhostname
Username: root
Time (start): Mon, 2016-02-15 19:36:29
Time (end):   Mon, 2016-02-15 19:39:26
Command line: /usr/local/bin/borg create -v --list -C zlib,6 /path/to/repo::root-2016-02-15 / --one-file-system
Number of files: 38100

                       Original size      Compressed size    Deduplicated size
This archive:                1.33 GB            613.25 MB            571.64 MB
All archives:                1.63 GB            853.66 MB            584.12 MB

                       Unique chunks         Total chunks
Chunk index:                   36858                48844

Examples

$ borg mount /path/to/repo::root-2016-02-15 /tmp/mymountpoint
$ ls /tmp/mymountpoint
bin  boot  etc  home  lib  lib64  lost+found  media  mnt  opt  root  sbin  srv  tmp  usr  var
$ fusermount -u /tmp/mymountpoint

Examples

# Create a key file protected repository
$ borg init --encryption=keyfile -v /path/to/repo
Initializing repository at "/path/to/repo"
Enter new passphrase:
Enter same passphrase again:
Remember your passphrase. Your data will be inaccessible without it.
Key in "/root/.config/borg/keys/mnt_backup" created.
Keep this key safe. Your data will be inaccessible without it.
Synchronizing chunks cache...
Archives: 0, w/ cached Idx: 0, w/ outdated Idx: 0, w/o cached Idx: 0.
Done.

# Change key file passphrase
$ borg change-passphrase -v /path/to/repo
Enter passphrase for key /root/.config/borg/keys/mnt_backup:
Enter new passphrase:
Enter same passphrase again:
Remember your passphrase. Your data will be inaccessible without it.
Key updated

Examples

borg serve has special support for ssh forced commands (see authorized_keys example below): it will detect that you use such a forced command and extract the value of the --restrict-to-path option(s). It will then parse the original command that came from the client, makes sure that it is also borg serve and enforce path restriction(s) as given by the forced command. That way, other options given by the client (like --info or --umask) are preserved (and are not fixed by the forced command).

# Allow an SSH keypair to only run borg, and only have access to /path/to/repo.
# Use key options to disable unneeded and potentially dangerous SSH functionality.
# This will help to secure an automated remote backup system.
$ cat ~/.ssh/authorized_keys
command="borg serve --restrict-to-path /path/to/repo",no-pty,no-agent-forwarding,no-port-forwarding,no-X11-forwarding,no-user-rc ssh-rsa AAAAB3[...]

Examples

# Upgrade the borg repository to the most recent version.
$ borg upgrade -v /path/to/repo
making a hardlink copy in /path/to/repo.upgrade-2016-02-15-20:51:55
opening attic repository with borg and converting
no key file found for repository
converting repo index /path/to/repo/index.0
converting 1 segments...
converting borg 0.xx to borg current
no key file found for repository

Miscellaneous Help

Debug Commands

There are some more commands (all starting with "debug-") which are all not intended for normal use and potentially very dangerous if used incorrectly.

They exist to improve debugging capabilities without direct system access, e.g. in case you ever run into some severe malfunction. Use them only if you know what you are doing or if a trusted developer tells you what to do.

Additional Notes

Here are misc. notes about topics that are maybe not covered in enough detail in the usage section.

Item flags

borg create -v --list outputs a verbose list of all files, directories and other file system items it considered (no matter whether they had content changes or not). For each item, it prefixes a single-letter flag that indicates type and/or status of the item.

If you are interested only in a subset of that output, you can give e.g. --filter=AME and it will only show regular files with A, M or E status (see below).

A uppercase character represents the status of a regular file relative to the "files" cache (not relative to the repo -- this is an issue if the files cache is not used). Metadata is stored in any case and for 'A' and 'M' also new data chunks are stored. For 'U' all data chunks refer to already existing chunks.

  • 'A' = regular file, added (see also a_status_oddity in the FAQ)
  • 'M' = regular file, modified
  • 'U' = regular file, unchanged
  • 'E' = regular file, an error happened while accessing/reading this file

A lowercase character means a file type other than a regular file, borg usually just stores their metadata:

  • 'd' = directory
  • 'b' = block device
  • 'c' = char device
  • 'h' = regular file, hardlink (to already seen inodes)
  • 's' = symlink
  • 'f' = fifo

Other flags used include:

  • 'i' = backup data was read from standard input (stdin)
  • '-' = dry run, item was not backed up
  • '?' = missing status code (if you see this, please file a bug report!)

--chunker-params

The chunker params influence how input files are cut into pieces (chunks) which are then considered for deduplication. They also have a big impact on resource usage (RAM and disk space) as the amount of resources needed is (also) determined by the total amount of chunks in the repository (see Indexes / Caches memory usage for details).

--chunker-params=10,23,16,4095 results in a fine-grained deduplication and creates a big amount of chunks and thus uses a lot of resources to manage them. This is good for relatively small data volumes and if the machine has a good amount of free RAM and disk space.

--chunker-params=19,23,21,4095 (default) results in a coarse-grained deduplication and creates a much smaller amount of chunks and thus uses less resources. This is good for relatively big data volumes and if the machine has a relatively low amount of free RAM and disk space.

If you already have made some archives in a repository and you then change chunker params, this of course impacts deduplication as the chunks will be cut differently.

In the worst case (all files are big and were touched in between backups), this will store all content into the repository again.

Usually, it is not that bad though:

  • usually most files are not touched, so it will just re-use the old chunks it already has in the repo
  • files smaller than the (both old and new) minimum chunksize result in only one chunk anyway, so the resulting chunks are same and deduplication will apply

If you switch chunker params to save resources for an existing repo that already has some backup archives, you will see an increasing effect over time, when more and more files have been touched and stored again using the bigger chunksize and all references to the smaller older chunks have been removed (by deleting / pruning archives).

If you want to see an immediate big effect on resource usage, you better start a new repository when changing chunker params.

For more details, see chunker_details.

--read-special

The option --read-special is not intended for normal, filesystem-level (full or partly-recursive) backups. You only give this option if you want to do something rather ... special -- and if you have hand-picked some files that you want to treat that way.

borg create --read-special will open all files without doing any special treatment according to the file type (the only exception here are directories: they will be recursed into). Just imagine what happens if you do cat filename --- the content you will see there is what borg will backup for that filename.

So, for example, symlinks will be followed, block device content will be read, named pipes / UNIX domain sockets will be read.

You need to be careful with what you give as filename when using --read-special, e.g. if you give /dev/zero, your backup will never terminate.

The given files' metadata is saved as it would be saved without --read-special (e.g. its name, its size [might be 0], its mode, etc.) -- but additionally, also the content read from it will be saved for it.

Restoring such files' content is currently only supported one at a time via --stdout option (and you have to redirect stdout to where ever it shall go, maybe directly into an existing device file of your choice or indirectly via dd).

Example

Imagine you have made some snapshots of logical volumes (LVs) you want to backup.

Note

For some scenarios, this is a good method to get "crash-like" consistency (I call it crash-like because it is the same as you would get if you just hit the reset button or your machine would abrubtly and completely crash). This is better than no consistency at all and a good method for some use cases, but likely not good enough if you have databases running.

Then you create a backup archive of all these snapshots. The backup process will see a "frozen" state of the logical volumes, while the processes working in the original volumes continue changing the data stored there.

You also add the output of lvdisplay to your backup, so you can see the LV sizes in case you ever need to recreate and restore them.

After the backup has completed, you remove the snapshots again. :

$ # create snapshots here
$ lvdisplay > lvdisplay.txt
$ borg create --read-special /path/to/repo::arch lvdisplay.txt /dev/vg0/*-snapshot
$ # remove snapshots here

Now, let's see how to restore some LVs from such a backup. :

$ borg extract /path/to/repo::arch lvdisplay.txt
$ # create empty LVs with correct sizes here (look into lvdisplay.txt).
$ # we assume that you created an empty root and home LV and overwrite it now:
$ borg extract --stdout /path/to/repo::arch dev/vg0/root-snapshot > /dev/vg0/root
$ borg extract --stdout /path/to/repo::arch dev/vg0/home-snapshot > /dev/vg0/home

Append-only mode

A repository can be made "append-only", which means that Borg will never overwrite or delete committed data. This is useful for scenarios where multiple machines back up to a central backup server using borg serve, since a hacked machine cannot delete backups permanently.

To activate append-only mode, edit the repository config file and add a line append_only=1 to the [repository] section (or edit the line if it exists).

In append-only mode Borg will create a transaction log in the transactions file, where each line is a transaction and a UTC timestamp.

Example

Suppose an attacker remotely deleted all backups, but your repository was in append-only mode. A transaction log in this situation might look like this: :

transaction 1, UTC time 2016-03-31T15:53:27.383532
transaction 5, UTC time 2016-03-31T15:53:52.588922
transaction 11, UTC time 2016-03-31T15:54:23.887256
transaction 12, UTC time 2016-03-31T15:55:54.022540
transaction 13, UTC time 2016-03-31T15:55:55.472564

From your security logs you conclude the attacker gained access at 15:54:00 and all the backups where deleted or replaced by compromised backups. From the log you know that transactions 11 and later are compromised. Note that the transaction ID is the name of the last file in the transaction. For example, transaction 11 spans files 6 to 11.

In a real attack you'll likely want to keep the compromised repository intact to analyze what the attacker tried to achieve. It's also a good idea to make this copy just in case something goes wrong during the recovery. Since recovery is done by deleting some files, a hard link copy (cp -al) is sufficient.

The first step to reset the repository to transaction 5, the last uncompromised transaction, is to remove the hints.N and index.N files in the repository (these two files are always expendable). In this example N is 13.

Then remove or move all segment files from the segment directories in data/ starting with file 6:

rm data/**/{6..13}

That's all to it.

Drawbacks

As data is only appended, and nothing deleted, commands like prune or delete won't free disk space, they merely tag data as deleted in a new transaction.

Note that you can go back-and-forth between normal and append-only operation by editing the configuration file, it's not a "one way trip".

Further considerations

Append-only mode is not respected by tools other than Borg. rm still works on the repository. Make sure that backup client machines only get to access the repository via borg serve.

Ensure that no remote access is possible if the repository is temporarily set to normal mode for e.g. regular pruning.

Further protections can be implemented, but are outside of Borgs scope. For example, file system snapshots or wrapping borg serve to set special permissions or ACLs on new data files.