BORG(1)

NAME
borg - BorgBackup is a deduplicating backup program with optional compression and authenticated encryption.

Borg 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 Borg 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

Borg 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

Borg 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

Borg 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, Borg 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.

BORG INIT

usage: borg init [-h] [--critical] [--error] [--warning] [--info] [--debug]
                 [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                 [--remote-path PATH] [-e {none,keyfile,repokey}]
                 [REPOSITORY]
Initialize an empty repository
positional arguments:
  REPOSITORY            repository to create
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  -e {none,keyfile,repokey}, --encryption {none,keyfile,repokey}
                        select encryption key mode (default: "repokey")

  Description

This command initializes an empty repository. A repository is a filesystem directory containing the deduplicated data from zero or more archives. Encryption can be enabled at repository init time.

  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:

•   Borg 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.

BORG CREATE

usage: borg create [-h] [--critical] [--error] [--warning] [--info] [--debug]
                   [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                   [--remote-path PATH] [-s] [-p] [--list]
                   [--filter STATUSCHARS] [-e PATTERN]
                   [--exclude-from EXCLUDEFILE] [--exclude-caches]
                   [--exclude-if-present FILENAME] [--keep-tag-files]
                   [-c SECONDS] [-x] [--numeric-owner]
                   [--timestamp yyyy-mm-ddThh:mm:ss]
                   [--chunker-params CHUNK_MIN_EXP,CHUNK_MAX_EXP,HASH_MASK_BITS,HASH_WINDOW_SIZE]
                   [--ignore-inode] [-C COMPRESSION] [--read-special] [-n]
                   ARCHIVE PATH [PATH ...]
Create new archive
positional arguments:
  ARCHIVE               name of archive to create (must be also a valid
                        directory name)
  PATH                  paths to archive
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  -s, --stats           print statistics for the created archive
  -p, --progress        show progress display while creating the archive,
                        showing Original, Compressed and Deduplicated sizes,
                        followed by the Number of files seen and the path
                        being processed, default: False
  --list                output verbose list of items (files, dirs, ...)
  --filter STATUSCHARS  only display items with the given status characters
  -e PATTERN, --exclude PATTERN
                        exclude paths matching PATTERN
  --exclude-from EXCLUDEFILE
                        read exclude patterns from EXCLUDEFILE, one per line
  --exclude-caches      exclude directories that contain a CACHEDIR.TAG file
                        (http://www.brynosaurus.com/cachedir/spec.html)
  --exclude-if-present FILENAME
                        exclude directories that contain the specified file
  --keep-tag-files      keep tag files of excluded caches/directories
  -c SECONDS, --checkpoint-interval SECONDS
                        write checkpoint every SECONDS seconds (Default: 300)
  -x, --one-file-system
                        stay in same file system, do not cross mount points
  --numeric-owner       only store numeric user and group identifiers
  --timestamp yyyy-mm-ddThh:mm:ss
                        manually specify the archive creation date/time (UTC).
                        alternatively, give a reference file/directory.
  --chunker-params CHUNK_MIN_EXP,CHUNK_MAX_EXP,HASH_MASK_BITS,HASH_WINDOW_SIZE
                        specify the chunker parameters. default: 19,23,21,4095
  --ignore-inode        ignore inode data in the file metadata cache used to
                        detect unchanged files.
  -C COMPRESSION, --compression COMPRESSION
                        select compression algorithm (and level): none == no
                        compression (default), lz4 == lz4, zlib == zlib
                        (default level 6), zlib,0 .. zlib,9 == zlib (with
                        level 0..9), lzma == lzma (default level 6), lzma,0 ..
                        lzma,9 == lzma (with level 0..9).
  --read-special        open and read special files as if they were regular
                        files
  -n, --dry-run         do not create a backup archive

  Description

This command creates a backup archive containing all files found while recursively traversing all paths specified. The archive will consume almost no disk space for files or parts of files that have already been stored in other archives.

To speed up pulling backups over sshfs and similar network file systems which do not provide correct inode information the --ignore-inode flag can be used. This potentially decreases reliability of change detection, while avoiding always reading all files on these file systems.

See the output of the "borg help patterns" command for more help on exclude patterns.

  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 ~
# Format tags available for archive name:
# {now}, {utcnow}, {fqdn}, {hostname}, {user}, {pid}
# add short hostname, backup username and current unixtime (seconds from epoch)
$ borg create  /path/to/repo::{hostname}-{user}-{now:%s} ~

BORG EXTRACT

usage: borg extract [-h] [--critical] [--error] [--warning] [--info] [--debug]
                    [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                    [--remote-path PATH] [--list] [-n] [-e PATTERN]
                    [--exclude-from EXCLUDEFILE] [--numeric-owner]
                    [--strip-components NUMBER] [--stdout] [--sparse]
                    ARCHIVE [PATH [PATH ...]]
Extract archive contents
positional arguments:
  ARCHIVE               archive to extract
  PATH                  paths to extract; patterns are supported
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  --list                output verbose list of items (files, dirs, ...)
  -n, --dry-run         do not actually change any files
  -e PATTERN, --exclude PATTERN
                        exclude paths matching PATTERN
  --exclude-from EXCLUDEFILE
                        read exclude patterns from EXCLUDEFILE, one per line
  --numeric-owner       only obey numeric user and group identifiers
  --strip-components NUMBER
                        Remove the specified number of leading path elements.
                        Pathnames with fewer elements will be silently
                        skipped.
  --stdout              write all extracted data to stdout
  --sparse              create holes in output sparse file from all-zero
                        chunks

  Description

This command extracts the contents of an archive. By default the entire archive is extracted but a subset of files and directories can be selected by passing a list of PATHs as arguments. The file selection can further be restricted by using the --exclude option.

See the output of the "borg help patterns" command for more help on exclude patterns.

  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.

BORG CHECK

usage: borg check [-h] [--critical] [--error] [--warning] [--info] [--debug]
                  [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                  [--remote-path PATH] [--repository-only] [--archives-only]
                  [--repair] [--save-space] [--last N] [-P PREFIX]
                  [REPOSITORY_OR_ARCHIVE]
Check repository consistency
positional arguments:
  REPOSITORY_OR_ARCHIVE
                        repository or archive to check consistency of
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  --repository-only     only perform repository checks
  --archives-only       only perform archives checks
  --repair              attempt to repair any inconsistencies found
  --save-space          work slower, but using less space
  --last N              only check last N archives (Default: all)
  -P PREFIX, --prefix PREFIX
                        only consider archive names starting with this prefix

  Description

The check command verifies the consistency of a repository and the corresponding archives.

First, the underlying repository data files are checked:

•   For all segments the segment magic (header) is checked

•   For all objects stored in the segments, all metadata (e.g. crc and size) and all data is read. The read data is checked by size and CRC. Bit rot and other types of accidental damage can be detected this way.

•   If we are in repair mode and a integrity error is detected for a segment, we try to recover as many objects from the segment as possible.

•   In repair mode, it makes sure that the index is consistent with the data stored in the segments.

•   If you use a remote repo server via ssh:, the repo check is executed on the repo server without causing significant network traffic.

•   The repository check can be skipped using the --archives-only option.

    Second, the consistency and correctness of the archive metadata is verified:

•   Is the repo manifest present? If not, it is rebuilt from archive metadata chunks (this requires reading and decrypting of all metadata and data).

•   Check if archive metadata chunk is present. if not, remove archive from manifest.

•   For all files (items) in the archive, for all chunks referenced by these files, check if chunk is present (if not and we are in repair mode, replace it with a same-size chunk of zeros). This requires reading of archive and file metadata, but not data.

•   If we are in repair mode and we checked all the archives: delete orphaned chunks from the repo.

•   if you use a remote repo server via ssh:, the archive check is executed on the client machine (because if encryption is enabled, the checks will require decryption and this is always done client-side, because key access will be required).

•   The archive checks can be time consuming, they can be skipped using the --repository-only option.

BORG RENAME

usage: borg rename [-h] [--critical] [--error] [--warning] [--info] [--debug]
                   [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                   [--remote-path PATH]
                   ARCHIVE NEWNAME
Rename an existing archive
positional arguments:
  ARCHIVE               archive to rename
  NEWNAME               the new archive name to use
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")

  Description

This command renames an archive in the repository.

  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

BORG LIST

usage: borg list [-h] [--critical] [--error] [--warning] [--info] [--debug]
                 [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                 [--remote-path PATH] [--short] [--list-format LISTFORMAT]
                 [-P PREFIX]
                 [REPOSITORY_OR_ARCHIVE]
List archive or repository contents
positional arguments:
  REPOSITORY_OR_ARCHIVE
                        repository/archive to list contents of
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  --short               only print file/directory names, nothing else
  --list-format LISTFORMAT
                        specify format for archive file listing (default:
                        "{mode} {user:6} {group:6} {size:8d} {isomtime}
                        {path}{extra}{NEWLINE}") Special "{formatkeys}" exists
                        to list available keys
  -P PREFIX, --prefix PREFIX
                        only consider archive names starting with this prefix

  Description

This command lists the contents of a repository or an archive.

  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
...

BORG DELETE

usage: borg delete [-h] [--critical] [--error] [--warning] [--info] [--debug]
                   [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                   [--remote-path PATH] [-p] [-s] [-c] [--save-space]
                   [TARGET]
Delete an existing repository or archive
positional arguments:
  TARGET                archive or repository to delete
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  -p, --progress        show progress display while deleting a single archive
  -s, --stats           print statistics for the deleted archive
  -c, --cache-only      delete only the local cache for the given repository
  --save-space          work slower, but using less space

  Description

This command deletes an archive from the repository or the complete repository. Disk space is reclaimed accordingly. If you delete the complete repository, the local cache for it (if any) is also deleted.

  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

BORG PRUNE

usage: borg prune [-h] [--critical] [--error] [--warning] [--info] [--debug]
                  [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                  [--remote-path PATH] [-n] [-s] [--list]
                  [--keep-within WITHIN] [-H HOURLY] [-d DAILY] [-w WEEKLY]
                  [-m MONTHLY] [-y YEARLY] [-P PREFIX] [--save-space]
                  [REPOSITORY]
Prune repository archives according to specified rules
positional arguments:
  REPOSITORY            repository to prune
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  -n, --dry-run         do not change repository
  -s, --stats           print statistics for the deleted archive
  --list                output verbose list of archives it keeps/prunes
  --keep-within WITHIN  keep all archives within this time interval
  -H HOURLY, --keep-hourly HOURLY
                        number of hourly archives to keep
  -d DAILY, --keep-daily DAILY
                        number of daily archives to keep
  -w WEEKLY, --keep-weekly WEEKLY
                        number of weekly archives to keep
  -m MONTHLY, --keep-monthly MONTHLY
                        number of monthly archives to keep
  -y YEARLY, --keep-yearly YEARLY
                        number of yearly archives to keep
  -P PREFIX, --prefix PREFIX
                        only consider archive names starting with this prefix
  --save-space          work slower, but using less space

  Description

The prune command prunes a repository by deleting archives not matching any of the specified retention options. This command is normally used by automated backup scripts wanting to keep a certain number of historic backups.

As an example, "-d 7" means to keep the latest backup on each day, up to 7 most recent days with backups (days without backups do not count). The rules are applied from hourly to yearly, and backups selected by previous rules do not count towards those of later rules. The time that each backup completes is used for pruning purposes. Dates and times are interpreted in the local timezone, and weeks go from Monday to Sunday. Specifying a negative number of archives to keep means that there is no limit.

The "--keep-within" option takes an argument of the form "<int><char>", where char is "H", "d", "w", "m", "y". For example, "--keep-within 2d" means to keep all archives that were created within the past 48 hours. "1m" is taken to mean "31d". The archives kept with this option do not count towards the totals specified by any other options.

If a prefix is set with -P, then only archives that start with the prefix are considered for deletion and only those archives count towards the totals specified by the rules. Otherwise, all archives in the repository are candidates for deletion!

  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

BORG INFO

usage: borg info [-h] [--critical] [--error] [--warning] [--info] [--debug]
                 [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                 [--remote-path PATH]
                 ARCHIVE
Show archive details such as disk space used
positional arguments:
  ARCHIVE               archive to display information about
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")

  Description

This command displays some detailed information about the specified archive.

  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

BORG MOUNT

usage: borg mount [-h] [--critical] [--error] [--warning] [--info] [--debug]
                  [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                  [--remote-path PATH] [-f] [-o OPTIONS]
                  REPOSITORY_OR_ARCHIVE MOUNTPOINT
Mount archive or an entire repository as a FUSE fileystem
positional arguments:
  REPOSITORY_OR_ARCHIVE
                        repository/archive to mount
  MOUNTPOINT            where to mount filesystem
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  -f, --foreground      stay in foreground, do not daemonize
  -o OPTIONS            Extra mount options

  Description

This command mounts an archive as a FUSE filesystem. This can be useful for browsing an archive or restoring individual files. Unless the --foreground option is given the command will run in the background until the filesystem is umounted.

  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

BORG CHANGE-PASSPHRASE

usage: borg change-passphrase [-h] [--critical] [--error] [--warning] [--info]
                              [--debug] [--lock-wait N] [--show-rc]
                              [--no-files-cache] [--umask M]
                              [--remote-path PATH]
                              [REPOSITORY]
Change repository key file passphrase
positional arguments:
  REPOSITORY
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")

  Description

The key files used for repository encryption are optionally passphrase protected. This command can be used to change this passphrase.

  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

BORG SERVE

usage: borg serve [-h] [--critical] [--error] [--warning] [--info] [--debug]
                  [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                  [--remote-path PATH] [--restrict-to-path PATH]
Start in server mode. This command is usually not used manually.
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  --restrict-to-path PATH
                        restrict repository access to PATH

  Description

This command starts a repository server process. This command is usually not used manually.

  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[...]

BORG UPGRADE

usage: borg upgrade [-h] [--critical] [--error] [--warning] [--info] [--debug]
                    [--lock-wait N] [--show-rc] [--no-files-cache] [--umask M]
                    [--remote-path PATH] [-p] [-n] [-i]
                    [REPOSITORY]
upgrade a repository from a previous version
positional arguments:
  REPOSITORY            path to the repository to be upgraded
optional arguments:
  -h, --help            show this help message and exit
  --critical            work on log level CRITICAL
  --error               work on log level ERROR
  --warning             work on log level WARNING (default)
  --info, -v, --verbose
                        work on log level INFO
  --debug               work on log level DEBUG
  --lock-wait N         wait for the lock, but max. N seconds (default: 1).
  --show-rc             show/log the return code (rc)
  --no-files-cache      do not load/update the file metadata cache used to
                        detect unchanged files
  --umask M             set umask to M (local and remote, default: 0077)
  --remote-path PATH    set remote path to executable (default: "borg")
  -p, --progress        show progress display while upgrading the repository
  -n, --dry-run         do not change repository
  -i, --inplace         rewrite repository in place, with no chance of going
                        back to older versions of the repository.

  Description

Upgrade an existing Borg repository. This currently supports converting an Attic repository to Borg and also helps with converting Borg 0.xx to 1.0.

Currently, only LOCAL repositories can be upgraded (issue #465).

It will change the magic strings in the repository's segments to match the new Borg magic strings. The keyfiles found in $ATTIC_KEYS_DIR or ~/.attic/keys/ will also be converted and copied to $BORG_KEYS_DIR or ~/.config/borg/keys.

The cache files are converted, from $ATTIC_CACHE_DIR or ~/.cache/attic to $BORG_CACHE_DIR or ~/.cache/borg, but the cache layout between Borg and Attic changed, so it is possible the first backup after the conversion takes longer than expected due to the cache resync.

Upgrade should be able to resume if interrupted, although it will still iterate over all segments. If you want to start from scratch, use borg delete over the copied repository to make sure the cache files are also removed: borg delete borg

Unless --inplace is specified, the upgrade process first creates a backup copy of the repository, in REPOSITORY.upgrade-DATETIME, using hardlinks. This takes longer than in place upgrades, but is much safer and gives progress information (as opposed to cp -al). Once you are satisfied with the conversion, you can safely destroy the backup copy.

WARNING: Running the upgrade in place will make the current copy unusable with older version, with no way of going back to previous versions. This can PERMANENTLY DAMAGE YOUR REPOSITORY! Attic CAN NOT READ BORG REPOSITORIES, as the magic strings have changed. You have been warned.

  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

  borg help patterns

Exclusion patterns support four separate styles, fnmatch, shell, regular expressions and path prefixes. If followed by a colon (':') the first two characters of a pattern are used as a style selector. Explicit style selection is necessary when a non-default style is desired or when the desired pattern starts with two alphanumeric characters followed by a colon (i.e. aa:something/*).

Fnmatch, selector fm: These patterns use a variant of shell pattern syntax, with '*' matching any number of characters, '?' matching any single character, '[...]' matching any single character specified, including ranges, and '[!...]' matching any character not specified. For the purpose of these patterns, the path separator ('' for Windows and '/' on other systems) is not treated specially. Wrap meta-characters in brackets for a literal match (i.e. [?] to match the literal character ?). For a path to match a pattern, it must completely match from start to end, or must match from the start to just before a path separator. Except for the root path, paths will never end in the path separator when matching is attempted. Thus, if a given pattern ends in a path separator, a '*' is appended before matching is attempted.

Shell-style patterns, selector sh: Like fnmatch patterns these are similar to shell patterns. The difference is that the pattern may include **/ for matching zero or more directory levels, * for matching zero or more arbitrary characters with the exception of any path separator.

Regular expressions, selector re: Regular expressions similar to those found in Perl are supported. Unlike shell patterns regular expressions are not required to match the complete path and any substring match is sufficient. It is strongly recommended to anchor patterns to the start ('^'), to the end ('$') or both. Path separators ('' for Windows and '/' on other systems) in paths are always normalized to a forward slash ('/') before applying a pattern. The regular expression syntax is described in the Python documentation for the re module.

Prefix path, selector pp: This pattern style is useful to match whole sub-directories. The pattern pp:/data/bar matches /data/bar and everything therein.

Exclusions can be passed via the command line option --exclude. When used from within a shell the patterns should be quoted to protect them from expansion.

The --exclude-from option permits loading exclusion patterns from a text file with one pattern per line. Lines empty or starting with the number sign ('#') after removing whitespace on both ends are ignored. The optional style selector prefix is also supported for patterns loaded from a file. Due to whitespace removal paths with whitespace at the beginning or end can only be excluded using regular expressions.

Examples:

# Exclude '/home/user/file.o' but not '/home/user/file.odt': $ borg create -e '
*
.o' backup /

# Exclude '/home/user/junk' and '/home/user/subdir/junk' but # not '/home/user/importantjunk' or '/etc/junk': $ borg create -e '/home/
*
/junk' backup /

# Exclude the contents of '/home/user/cache' but not the directory itself: $ borg create -e /home/user/cache/ backup /

# The file '/home/user/cache/important' is not backed up: $ borg create -e /home/user/cache/ backup / /home/user/cache/important

# The contents of directories in '/home' are not backed up when their name # ends in '.tmp' $ borg create --exclude 're:^/home/[^/]+.tmp/' backup /

# Load exclusions from file $ cat >exclude.txt <<EOF # Comment line /home//junk *.tmp fm:aa:something/ re:^/home/[^/].tmp/ sh:/home/
*
/.thumbnails EOF $ borg create --exclude-from exclude.txt backup /

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 Borg 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.

AUTHOR
The Borg Collective (see AUTHORS file)

COPYRIGHT
2010-2014 Jonas Borgström, 2015-2016 The Borg Collective (see AUTHORS file)