borg(1)

Name
borg - deduplicating and encrypting backup tool

SYNOPSIS

borg [common options] <command> [options] [arguments]

DESCRIPTION

BorgBackup (short: Borg) is a deduplicating backup program. Optionally, it supports compression and authenticated encryption.

The main goal of Borg is to provide an efficient and secure way to back up data. The data deduplication technique used makes Borg suitable for daily backups since only changes are stored. The authenticated encryption technique makes it suitable for backups to targets not fully trusted.

Borg stores a set of files in an archive. A repository is a collection of archives. The format of repositories is Borg-specific. Borg does not distinguish archives from each other in any way other than their name, it does not matter when or where archives were created (e.g., different hosts).

EXAMPLES

  A step-by-step example

1.  Before a backup can be made, a repository has to be initialized:

        $ borg -r /path/to/repo repo-create --encryption=aes-ocb

2.  Back up the ~/src and ~/Documents directories into an archive called docs:

        $ borg -r /path/to/repo create docs ~/src ~/Documents

3.  The next day, create a new archive using the same archive name:

        $ borg -r /path/to/repo create --stats docs ~/src ~/Documents

    This backup will be much quicker and much smaller, since only new, never-before-seen data is stored. The --stats option causes Borg to output statistics about the newly created archive such as the deduplicated size (the amount of unique data not shared with other archives):

        Repository: /path/to/repo
        Archive name: docs
        Archive fingerprint: bcd1b53f9b4991b7afc2b339f851b7ffe3c6d030688936fe4552eccc1877718d
        Time (start): Sat, 2022-06-25 20:21:43
        Time (end):   Sat, 2022-06-25 20:21:43
        Duration: 0.07 seconds
        Utilization of maximum archive size: 0%
        Number of files: 699
        Original size: 31.14 MB
        Deduplicated size: 502 B

4.  List all archives in the repository:

        $ borg -r /path/to/repo repo-list
        docs                                 Sat, 2022-06-25 20:21:14 [b80e24d2...b179f298]
        docs                                 Sat, 2022-06-25 20:21:43 [bcd1b53f...1877718d]

5.  List the contents of the first archive:

        $ borg -r /path/to/repo list aid:b80e24d2
        drwxr-xr-x user   group          0 Mon, 2016-02-15 18:22:30 home/user/Documents
        -rw-r--r-- user   group       7961 Mon, 2016-02-15 18:22:30 home/user/Documents/Important.doc
        ...

6.  Restore the first archive by extracting the files relative to the current directory:

        $ borg -r /path/to/repo extract aid:b80e24d2

7.  Delete the first archive (please note that this does not free repository disk space):

        $ borg -r /path/to/repo delete aid:b80e24d2

    Be careful if you use an archive NAME (and not an archive ID), as it might match multiple archives. Always use --dry-run and --list first!

8.  Recover disk space by compacting the segment files in the repository:

        $ borg -r /path/to/repo compact -v

    Note: Borg is quiet by default (it defaults to WARNING log level). You can use options like --progress or --list to get specific reports during command execution. You can also add the -v (or --verbose or --info) option to adjust the log level to INFO to get other informational messages.

NOTES

  Positional Arguments and Options: Order matters

Borg only supports taking options (-s and --progress in the example) either to the left or to the right of all positional arguments (repo::archive and path in the example), but not in between them:

    borg create -s --progress archive path  # good and preferred
    borg create archive path -s --progress  # also works
    borg create -s archive path --progress  # works, but ugly
    borg create archive -s --progress path  # BAD

This is due to a problem in the argparse module: <https://bugs.python.org/issue15112>

  Repository URLs

Local filesystem (or locally mounted network filesystem):

/path/to/repo — filesystem path to the repository directory (absolute path)

path/to/repo — filesystem path to the repository directory (relative path)

Also, paths like ~/path/to/repo or ~other/path/to/repo work (this is expanded by your shell).

Note: You may also prepend file:// to a filesystem path to use URL style.

Remote repositories accessed via SSH <user@host> (REST http over stdio):

rest://user@host:port//abs/path/to/repo — absolute path

rest://user@host:port/rel/path/to/repo — path relative to the current directory

Remote repositories accessed via SSH <user@host> (legacy borg RPC protocol):

ssh://user@host:port//abs/path/to/repo — absolute path

ssh://user@host:port/rel/path/to/repo — path relative to the current directory

Remote repositories accessed via SFTP:

sftp://user@host:port//abs/path/to/repo — absolute path

sftp://user@host:port/rel/path/to/repo — path relative to the current directory

For SSH and SFTP URLs, the user@ and :port parts are optional.

Remote repositories accessed via rclone:

rclone:remote:path — see the rclone docs for more details about remote:path.

Remote repositories accessed via S3:

(s3|b2):[(profile|(access_key_id:access_key_secret))@][scheme://hostname[:port]]/bucket/path — see the boto3 docs for more details about credentials.

If you are connecting to AWS S3, [schema://hostname[:port]] is optional, but bucket and path are always required. scheme is usually https here, hostname and optional port refer to your S3/B2 server, if that is not Amazon's.

Note: There is a known issue with some S3-compatible services, e.g., Backblaze B2. If you encounter problems, try using b2: instead of s3: in the URL.

If you frequently need the same repository URL, it is a good idea to set the BORG_REPO environment variable to set a default repository URL:

    export BORG_REPO='ssh://user@host:port/rel/path/to/repo'

Then simply omit the --repo option when you want to use the default — it will be read from BORG_REPO.

  Repository Locations / Archive Names

Many commands need to know the repository location; specify it via -r/--repo or use the BORG_REPO environment variable.

Commands that need one or two archive names usually take them as positional arguments.

Commands that work with an arbitrary number of archives usually accept -a ARCH_GLOB.

Archive names must not contain the / (slash) character. For simplicity, also avoid spaces or other characters that have special meaning to the shell or in a filesystem (borg mount uses the archive name as a directory name).

  Logging

Borg writes all log output to stderr by default. However, output on stderr does not necessarily indicate an error. Check the log levels of the messages and the return code of borg to determine error, warning, or success conditions.

If you want to capture the log output to a file, just redirect it:

    borg create --repo repo archive myfiles 2>> logfile

Custom logging configurations can be implemented via BORG_LOGGING_CONF.

The log level of the built-in logging configuration defaults to WARNING. This is because we want Borg to be mostly silent and only output warnings, errors, and critical messages unless output has been requested by supplying an option that implies output (e.g., --list or --progress).

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

Use --debug to set the DEBUG log level — this prints debug, info, warning, error, and critical messages.

Use --info (or -v or --verbose) to set the INFO log level — this prints info, warning, error, and critical messages.

Use --warning (default) to set the WARNING log level — this prints warning, error, and critical messages.

Use --error to set the ERROR log level — this prints error and critical messages.

Use --critical to set the CRITICAL log level — this prints only critical messages.

While you can set miscellaneous log levels, do not expect every command to produce different output at different log levels — it's merely a possibility.

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

  Return codes

Borg can exit with the following return codes (rc):
Return code | Meaning
0 | success (logged as INFO)
1 | generic warning (operation reached its normal end, but there were warnings — you should check the log; logged as WARNING)
2 | generic error (like a fatal error or a local/remote exception; the operation did not reach its normal end; logged as ERROR)
3..99 | specific error (enabled by BORG_EXIT_CODES=modern)
100..127 | specific warning (enabled by BORG_EXIT_CODES=modern)
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.

The modern exit codes (return codes, "rc") are documented here: see msgid.

  Environment Variables

Borg uses some environment variables for automation:

General:

BORG_REPO
    When set, use the value to give the default repository location. Use this so you do not need to type --repo /path/to/my/repo all the time.

BORG_OTHER_REPO
    Similar to BORG_REPO, but gives the default for --other-repo.

BORG_PASSPHRASE (and BORG_OTHER_PASSPHRASE)
    When set, use the value to answer the passphrase question for encrypted repositories. It is used when a passphrase is needed to access an encrypted repo as well as when a new passphrase should be initially set when initializing an encrypted repo. See also BORG_NEW_PASSPHRASE.

BORG_PASSCOMMAND (and BORG_OTHER_PASSCOMMAND)
    When set, use the standard output of the command (trailing newlines are stripped) to answer the passphrase question for encrypted repositories. It is used when a passphrase is needed to access an encrypted repo as well as when a new passphrase should be initially set when initializing an encrypted repo. Note that the command is executed without a shell. So variables, like $HOME will work, but ~ won't. If BORG_PASSPHRASE is also set, it takes precedence. See also BORG_NEW_PASSPHRASE.

BORG_PASSPHRASE_FD (and BORG_OTHER_PASSPHRASE_FD)
    When set, specifies a file descriptor to read a passphrase from. Programs starting borg may choose to open an anonymous pipe and use it to pass a passphrase. This is safer than passing via BORG_PASSPHRASE, because on some systems (e.g. Linux) environment can be examined by other processes. If BORG_PASSPHRASE or BORG_PASSCOMMAND are also set, they take precedence.

BORG_NEW_PASSPHRASE
    When set, use the value to answer the passphrase question when a new passphrase is asked for. This variable is checked first. If it is not set, BORG_PASSPHRASE and BORG_PASSCOMMAND will also be checked. Main use case for this is to fully automate borg key change-passphrase.

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_DEBUG_PASSPHRASE
    When set to YES, display debugging information that includes passphrases used and passphrase related env vars set.

BORG_EXIT_CODES
    When set to "modern", the borg process will return more specific exit codes (rc). When set to "legacy", the borg process will return rc 2 for all errors, 1 for all warnings, 0 for success. Default is "modern".

BORG_HOST_ID
    Borg usually computes a host id from the FQDN plus the results of uuid.getnode() (which usually returns a unique id based on the MAC address of the network interface. Except if that MAC happens to be all-zero - in that case it returns a random value, which is not what we want (because it kills automatic stale lock removal). So, if you have an all-zero MAC address or other reasons to better control the host id externally, just set this environment variable to a unique value. If all your FQDNs are unique, you can just use the FQDN. If not, use <FQDN@uniqueid>.

BORG_HOSTNAME
    When set, use this value as the hostname (instead of the auto-detected one), e.g. to run borg on one host, but impersonate another host. This affects the hostname stored in newly created archives as well as the {hostname} placeholder.

BORG_USERNAME
    When set, use this value as the username (instead of the auto-detected one), e.g. to run borg as one user, but impersonate another user. This affects the username stored in newly created archives as well as the {user} placeholder.

BORG_LOCK_WAIT
    You can set the default value for the --lock-wait option with this, so you do not need to give it as a command line option.

BORG_LOGGING_CONF
    When set, use the given filename as INI <https://docs.python.org/3/library/logging.config.html#configuration-file-format>-style logging configuration. A basic example conf can be found at docs/misc/logging.conf.

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. Using the --rsh CMD command line option overrides the environment variable.

BORG_REMOTE_PATH
    When set, use the given path as borg executable on the remote (defaults to "borg" if unset). Using the --remote-path PATH command line option overrides the environment variable.

BORG_REPO_PERMISSIONS
    Set repository permissions, see also: borg_serve

BORG_FILES_CACHE_SUFFIX
    When set to a value at least one character long, instructs borg to use a specifically named (based on the suffix) alternative files cache. This can be used to avoid loading and saving cache entries for backup sources other than the current sources.

BORG_FILES_CACHE_TTL
    When set to a numeric value, this determines the maximum "time to live" for the files cache entries (default: 2). The files cache is used to determine quickly whether a file is unchanged.

BORG_SHOW_SYSINFO
    When set to no (default: yes), system information (like OS, Python version, ...) in exceptions is not shown. Please only use for good reasons as it makes issues harder to analyze.

BORG_MSGPACK_VERSION_CHECK
    Controls whether Borg checks the msgpack version. The default is yes (strict check). Set to no to disable the version check and allow any installed msgpack version. Use this at your own risk; malfunctioning or incompatible msgpack versions may cause subtle bugs or repository data corruption.

BORG_FUSE_IMPL
    Choose the low-level FUSE implementation borg shall use for borg mount. This is a comma-separated list of implementation names, they are tried in the given order, e.g.:

•   mfusepy,pyfuse3,llfuse: default, first try to load mfusepy, then pyfuse3, then llfuse.

•   llfuse,pyfuse3: first try to load llfuse, then try to load pyfuse3.

•   mfusepy: only try to load mfusepy

•   pyfuse3: only try to load pyfuse3

•   llfuse: only try to load llfuse

•   none: do not try to load an implementation

BORG_SELFTEST
    This can be used to influence borg's built-in self-tests. The default is to execute the tests at the beginning of each borg command invocation.

    BORG_SELFTEST=disabled can be used to switch off the tests and rather save some time. Disabling is not recommended for normal borg users, but large scale borg storage providers can use this to optimize production servers after at least doing a one-time test borg (with self-tests not disabled) when installing or upgrading machines/OS/Borg.

BORG_WORKAROUNDS
    A list of comma-separated strings that trigger workarounds in borg, e.g. to work around bugs in other software.

    Currently known strings are:

basesyncfile
    Use the more simple BaseSyncFile code to avoid issues with sync_file_range. You might need this to run borg on WSL (Windows Subsystem for Linux) or in systemd.nspawn containers on some architectures (e.g. ARM). Using this does not affect data safety, but might result in a more bursty write-to-disk behavior (not continuously streaming to disk).

retry_erofs
    Retry opening a file without O_NOATIME if opening a file with O_NOATIME caused EROFS. You will need this to make archives from volume shadow copies in WSL1 (Windows Subsystem for Linux 1).

authenticated_no_key
    Work around a lost passphrase or key for an authenticated mode repository (these are only authenticated, but not encrypted). If the key is missing in the repository config, add key = anything there.

    This workaround is only for emergencies and only to extract data from an affected repository (read-only access):

        BORG_WORKAROUNDS=authenticated_no_key borg extract --repo repo archive

    After you have extracted all data you need, you MUST delete the repository:

        BORG_WORKAROUNDS=authenticated_no_key borg delete repo

    Now you can init a fresh repo. Make sure you do not use the workaround any more.

Output formatting:

BORG_CHECK_FORMAT
    Giving the default value for borg check --format=X.

BORG_LIST_FORMAT
    Giving the default value for borg list --format=X.

BORG_REPO_LIST_FORMAT
    Giving the default value for borg repo-list --format=X.

BORG_PRUNE_FORMAT
    Giving the default value for borg prune --format=X.

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 "This is a potentially dangerous function..." (check --repair)

BORG_DELETE_I_KNOW_WHAT_I_AM_DOING=NO (or =YES)
    For "You requested to DELETE the repository completely 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 and files:

    Note: Borg 2 uses the platformdirs <https://pypi.org/project/platformdirs/> library to determine default directory locations. This means that default paths are platform-specific:

•   Linux: Uses XDG Base Directory Specification paths (e.g., ~/.config/borg, ~/.cache/borg, ~/.local/share/borg). XDG env var <https://specifications.freedesktop.org/basedir-spec/0.6/ar01s03.html> variables are honoured.

•   macOS: Uses native macOS directories by default (e.g., ~/Library/Application Support/borg, ~/Library/Caches/borg). XDG env var <https://specifications.freedesktop.org/basedir-spec/0.6/ar01s03.html> variables are honoured if set.

•   Windows: Uses Windows AppData directories (e.g., C:\Users\<user>\AppData\Roaming\borg, C:\Users\<user>\AppData\Local\borg). XDG env var <https://specifications.freedesktop.org/basedir-spec/0.6/ar01s03.html> variables are not honoured.

    On all platforms, you can override each directory individually using the specific environment variables described below. You can also set BORG_BASE_DIR to force borg to use BORG_BASE_DIR/.config/borg, BORG_BASE_DIR/.cache/borg, etc., regardless of the platform.

    Default directory locations by platform (when no BORG_* environment variables are set):
    Directory | Linux | macOS | Windows
    Config | ~/.config/borg | ~/Library/Application Support/borg | %APPDATA%\borg
    Cache | ~/.cache/borg | ~/Library/Caches/borg | %LOCALAPPDATA%\borg\Cache
    Data | ~/.local/share/borg | ~/Library/Application Support/borg | %LOCALAPPDATA%\borg
    Runtime | /run/user/<uid>/borg | ~/Library/Caches/TemporaryItems/borg | %TEMP%\borg
    Keys | <config_dir>/keys | <config_dir>/keys | <config_dir>\keys
    Security | <data_dir>/security | <data_dir>/security | <data_dir>\security

BORG_BASE_DIR
    Defaults to $HOME or ~$USER or ~ (in that order). If you want to move all borg-specific folders to a custom path at once, all you need to do is to modify BORG_BASE_DIR: the other paths for cache, config etc. will adapt accordingly (assuming you didn't set them to a different custom value).

BORG_CACHE_DIR
    Defaults to the platform-specific cache directory (see table above). If BORG_BASE_DIR is set, defaults to $BORG_BASE_DIR/.cache/borg. On Linux and macOS, XDG env var <https://specifications.freedesktop.org/basedir-spec/0.6/ar01s03.html> XDG_CACHE_HOME is also honoured if BORG_BASE_DIR is not set. This directory contains the local cache and might need a lot of space for dealing with big repositories. Make sure you're aware of the associated security aspects of the cache location: cache_security

BORG_CONFIG_DIR
    Defaults to the platform-specific config directory (see table above). If BORG_BASE_DIR is set, defaults to $BORG_BASE_DIR/.config/borg. On Linux and macOS, XDG env var <https://specifications.freedesktop.org/basedir-spec/0.6/ar01s03.html> XDG_CONFIG_HOME is also honoured if BORG_BASE_DIR is not set. This directory contains all borg configuration directories, see the FAQ for a security advisory about the data in this directory: home_config_borg

BORG_DATA_DIR
    Defaults to the platform-specific data directory (see table above). If BORG_BASE_DIR is set, defaults to $BORG_BASE_DIR/.local/share/borg. On Linux and macOS, XDG env var <https://specifications.freedesktop.org/basedir-spec/0.6/ar01s03.html> XDG_DATA_HOME is also honoured if BORG_BASE_DIR is not set. This directory contains all borg data directories, see the FAQ for a security advisory about the data in this directory: home_data_borg

BORG_RUNTIME_DIR
    Defaults to the platform-specific runtime directory (see table above). If BORG_BASE_DIR is set, defaults to $BORG_BASE_DIR/.cache/borg. On Linux and macOS, XDG env var <https://specifications.freedesktop.org/basedir-spec/0.6/ar01s03.html> XDG_RUNTIME_DIR is also honoured if BORG_BASE_DIR is not set. This directory contains borg runtime files, like e.g. the socket file.

BORG_SECURITY_DIR
    Defaults to $BORG_DATA_DIR/security. This directory contains security relevant data.

BORG_KEYS_DIR
    Defaults to $BORG_CONFIG_DIR/keys. This directory contains keys for encrypted repositories.

BORG_KEY_FILE
    When set, use the given path as repository key file. Please note that this is only for rather special applications that externally fully manage the key files:

•   this setting only applies to the keyfile modes (not to the repokey modes).

•   using a full, absolute path to the key file is recommended.

•   all directories in the given path must exist.

•   this setting forces borg to use the key file at the given location.

•   the key file must either exist (for most commands) or will be created (borg repo-create).

•   you need to give a different path for different repositories.

•   you need to point to the correct key file matching the repository the command will operate on.

TMPDIR
    This is where temporary files are stored (might need a lot of temporary space for some operations), see tempfile <https://docs.python.org/3/library/tempfile.html#tempfile.gettempdir> for details.

Building:

BORG_OPENSSL_NAME
    Defines the subdirectory name for OpenSSL (setup.py).

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

BORG_LIBACL_PREFIX
    Adds given prefix directory to the default locations. If an 'include/acl/libacl.h' is found Borg will be linked against the system libacl instead of a bundled implementation. (setup.py)

BORG_LIBLZ4_PREFIX
    Adds given prefix directory to the default locations. If a 'include/lz4.h' is found Borg will be linked against the system liblz4 instead of a bundled implementation. (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).

  Automatically generated Environment Variables (jsonargparse)

Borg uses jsonargparse <https://jsonargparse.readthedocs.io/> with default_env=True, which means that every command-line option can also be set via an environment variable.

The environment variable name is derived from the program name (borg), the subcommand (if any), and the option name, all converted to uppercase with dashes replaced by underscores.

For top-level options (not specific to a subcommand), the pattern is:

    BORG_<OPTION>

For example, --lock-wait can be set via BORG_LOCK_WAIT.

For subcommand options, the subcommand and option are separated by a double underscore:

    BORG_<SUBCOMMAND>__<OPTION>

For example, borg create --comment can be set via BORG_CREATE__COMMENT.

  File systems

We recommend using a reliable, scalable journaling filesystem for the repository, e.g., zfs, btrfs, ext4, apfs.

Borg now uses the borgstore package to implement the key/value store it uses for the repository.

It currently uses the file: store (posixfs backend) either with a local directory or via SSH and a remote borg serve agent using borgstore on the remote side.

This means that it will store each chunk into a separate filesystem file (for more details, see the borgstore project).

This has some pros and cons (compared to legacy Borg 1.x segment files):

Pros:

•   Simplicity and better maintainability of the Borg code.

•   Sometimes faster, less I/O, better scalability: e.g., borg compact can just remove unused chunks by deleting a single file and does not need to read and rewrite segment files to free space.

•   In the future, easier to adapt to other kinds of storage: borgstore's backends are quite simple to implement. sftp: and rclone: backends already exist, others might be easy to add.

•   Parallel repository access with less locking is easier to implement.

    Cons:

•   The repository filesystem will have to deal with a large number of files (there are provisions in borgstore against having too many files in a single directory by using a nested directory structure).

•   Greater filesystem space overhead (depends on the allocation block size — modern filesystems like zfs are rather clever here, using a variable block size).

•   Sometimes slower, due to less sequential and more random access operations.

  Units

To display quantities, Borg takes care of respecting the usual conventions of scale. Disk sizes are displayed in decimal <https://en.wikipedia.org/wiki/Decimal>, using powers of ten (so kB means 1000 bytes). For memory usage, binary prefixes <https://en.wikipedia.org/wiki/Binary_prefix> are used, and are indicated using the IEC binary prefixes <https://en.wikipedia.org/wiki/IEC_80000-13#Prefixes_for_binary_multiples>, using powers of two (so KiB means 1024 bytes).

  Date and Time

We format date and time in accordance with ISO 8601, that is: YYYY-MM-DD and HH:MM:SS (24-hour clock).

For more information, see: <https://xkcd.com/1179/>

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

Some options accept a TIMESPAN or an INTERVAL parameter, which can be given as a number of years (e.g. 2y), months (e.g. 12m), weeks (e.g. 2w), days (e.g. 7d), hours (e.g. 8H), minutes (e.g. 30M), or seconds (e.g. 150S).

The borg prune --keep-* retention options accept either a plain count (e.g. --keep-daily 7, keeping up to 7 daily archives) or a time interval (e.g. --keep-daily 7d, keeping one daily archive per day within a 7-day window). When using interval-based retention, --from may be specified to set the reference timestamp for the interval (defaults to the current time).

Please note that Borg treats months (e.g. 12m) as fixed 31-day periods rather than calendar months. As a result, 12m corresponds to 12 × 31 = 372 days. Similarly, years (e.g. 2y) are treated as fixed 365-day periods and do not take leap years into account.

  Resource Usage

Borg might use significant resources depending on the size of the data set it is dealing with.

If you use Borg in a client/server way (with an SSH repository), the resource usage occurs partly on the client and partly on the server.

If you use Borg as a single process (with a filesystem repository), all resource usage occurs in that one process, so add up client and server to get the approximate resource usage.

CPU client:

•   borg create: chunking, hashing, compression, encryption (high CPU usage)

•   chunks index rebuild: quite heavy on CPU, doing lots of hash table operations

•   borg extract: decryption, decompression (medium to high CPU usage)

•   borg prune/borg delete archive: quick, low CPU usage

•   borg delete repo: done on the server

•   borg compact: medium CPU usage

•   borg check: medium CPU usage, but depends on options given

    It will not use more than 100% of one CPU core as the code is currently single-threaded. Especially higher zlib and lzma compression levels use significant amounts of CPU cycles. Crypto might be cheap on the CPU (if hardware-accelerated) or expensive (if not).

CPU server:
    It usually does not need much CPU; it just deals with the key/value store (repository).

    borg check: the repository check computes the checksums of all chunks (medium CPU usage) borg compact: low to medium CPU usage

CPU (only for client/server operation):
    When using Borg in a client/server way with an ssh-type repository, the SSH processes used for the transport layer will need some CPU on the client and on the server due to the crypto they are doing — especially if you are pumping large amounts of data.

Memory (RAM) client:
    The chunks index and the files index are read into memory for performance reasons. Might need large amounts of memory (see below). Compression, especially with high compression levels, might need substantial amounts of memory.

Memory (RAM) server:
    Usually rather low memory needs, much less than the client.

Chunks index (client only):
    Proportional to the number of data chunks in your repo. Lots of chunks in your repo imply a big chunks index. It is possible to tweak the chunker parameters (see create options).

Files index (client only):
    Proportional to the number of files in your last backups. Can be switched off (see create options), but the next backup might be much slower if you do. The speed benefit of using the files cache is proportional to file size.

Temporary files (client):
    TODO

Temporary files (server):
    TODO

Cache files (client only):
    Contains the files cache, which might become quite large depending on the amount and size of files.

Network (only for client/server operation):
    If your repository is remote, all deduplicated (and optionally compressed/ encrypted) data has to go over the network connection.

  Support for file metadata

Besides regular file and directory structures, Borg can preserve

•   symlinks (stored as a symlink; the symlink is not followed)

•   special files:

•   character and block device files (restored via mknod(2))

•   FIFOs ("named pipes")

•   special file contents can be backed up in --read-special mode. By default, the metadata to create them with mknod(2), mkfifo(2), etc. is stored.

•   hard-linked regular files, devices, symlinks, FIFOs (considering all items in the same archive)

•   timestamps with nanosecond precision: mtime, atime, ctime

•   other timestamps: birthtime (on platforms supporting it)

•   permissions:

•   IDs of owning user and owning group

•   names of owning user and owning group (if the IDs can be resolved)

•   Unix Mode/Permissions (u/g/o permissions, suid, sgid, sticky)

    On some platforms additional features are supported:
    Platform | ACLs [5] | xattr [6] | Flags [7]
    Linux | Yes | Yes | Yes [1]
    macOS | Yes | Yes | Yes (all)
    FreeBSD | Yes | Yes | Yes (all)
    OpenBSD | n/a | n/a | Yes (all)
    NetBSD | n/a | No [2] | Yes (all)
    Solaris and derivatives | No [3] | No [3] | n/a
    Windows (cygwin) | No [4] | No | No

    Other Unix-like operating systems may work as well, but have not been tested yet.

    Note that most platform-dependent features also depend on the filesystem. For example, ntfs-3g on Linux is not able to convey NTFS ACLs.

[1] Only "nodump", "immutable", "compressed" and "append" are supported. Feature request #618 for more flags.

[2] Feature request #1332

[3] Feature request #1337

[4] Cygwin tries to map NTFS ACLs to permissions with varying degrees of success.

[5] The native access control list mechanism of the OS. This normally limits access to non-native ACLs. For example, NTFS ACLs are not completely accessible on Linux with ntfs-3g.

[6] Extended attributes; key-value pairs attached to a file, mainly used by the OS. This includes resource forks on macOS.

[7] Also known as BSD flags. The Linux set of flags [1] is portable across platforms. The BSDs define additional flags.

SEE ALSO

borg-common(1) for common command line options

borg-repo-create(1), borg-repo-delete(1), borg-repo-list(1), borg-repo-info(1), borg-create(1), borg-mount(1), borg-extract(1), borg-list(1), borg-info(1), borg-delete(1), borg-prune(1), borg-compact(1), borg-recreate(1)

borg-compression(1), borg-patterns(1), borg-placeholders(1)

•   Main web site <https://www.borgbackup.org/>

•   Releases <https://github.com/borgbackup/borg/releases>

•   Changelog <https://github.com/borgbackup/borg/blob/master/docs/changes.rst>

•   GitHub <https://github.com/borgbackup/borg>

•   Security contact <https://borgbackup.readthedocs.io/en/latest/support.html#security-contact>

Author
The Borg Collective orphan: