Ubuntu Manpage: borg - deduplicating and encrypting backup tool

Provided by: borgbackup_1.1.15-1~ubuntu1.20.04.1_amd64

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 backup 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 not fully
       trusted targets.

       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 init --encryption=repokey /path/to/repo

       2. Backup the ~/src and ~/Documents directories into an archive called Monday:

             $ borg create /path/to/repo::Monday ~/src ~/Documents

       3. The next day create a new archive called Tuesday:

             $ borg create --stats /path/to/repo::Tuesday ~/src ~/Documents

          This backup will be a lot quicker and a lot 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 amount of unique data (not shared with other archives):

             ------------------------------------------------------------------------------
             Archive name: Tuesday
             Archive fingerprint: bd31004d58f51ea06ff735d2e5ac49376901b21d58035f8fb05dbf866566e3c2
             Time (start): Tue, 2016-02-16 18:15:11
             Time (end):   Tue, 2016-02-16 18:15:11

             Duration: 0.19 seconds
             Number of files: 127
             ------------------------------------------------------------------------------
                                   Original size      Compressed size    Deduplicated size
             This archive:                4.16 MB              4.17 MB             26.78 kB
             All archives:                8.33 MB              8.34 MB              4.19 MB

                                   Unique chunks         Total chunks
             Chunk index:                     132                  261
             ------------------------------------------------------------------------------

       4. List all archives in the repository:

             $ borg list /path/to/repo
             Monday                               Mon, 2016-02-15 19:14:44
             Tuesday                              Tue, 2016-02-16 19:15:11

       5. List the contents of the Monday archive:

             $ borg list /path/to/repo::Monday
             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 Monday archive by extracting the files relative to the current directory:

             $ borg extract /path/to/repo::Monday

       7. Recover disk space by manually deleting the Monday archive:

             $ borg delete /path/to/repo::Monday

       NOTE:
          Borg is quiet by default (it works on 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) to the left or right
of all positional arguments (repo::archive and path in the example), but not in between
them:

borg create -s --progress repo::archive path # good and preferred
borg create repo::archive path -s --progress # also works
borg create -s repo::archive path --progress # works, but ugly
borg create repo::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 repo directory, absolute path

path/to/repo - filesystem path to repo directory, relative path

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

Note: you may also prepend a file:// to a filesystem path to get URL style.

Remote repositories accessed via ssh user@host:

user@host:/path/to/repo - remote repo, absolute path

ssh://user@host:port/path/to/repo - same, alternative syntax, port can be given

Remote repositories with relative paths can be given using this syntax:

user@host:path/to/repo - path relative to current directory

user@host:~/path/to/repo - path relative to user's home directory

user@host:~other/path/to/repo - path relative to other's home directory

Note: giving user@host:/./path/to/repo or user@host:/~/path/to/repo or
user@host:/~other/path/to/repo is also supported, but not required here.

Remote repositories with relative paths, alternative syntax with port:

ssh://user@host:port/./path/to/repo - path relative to current directory

ssh://user@host:port/~/path/to/repo - path relative to user's home directory

ssh://user@host:port/~other/path/to/repo - path relative to other's home directory

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

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

Then just leave away the repo URL if only a repo URL is needed and you want to use the
default - it will be read from BORG_REPO then.

Use :: syntax to give the repo URL when syntax requires giving a positional argument for
the repo (e.g. borg mount :: /mnt).

Repository / Archive Locations
Many commands want either a repository (just give the repo URL, see above) or an archive
location, which is a repo URL followed by ::archive_name.

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

If you have set BORG_REPO (see above) and an archive location is needed, use
::archive_name - the repo URL part is then read from BORG_REPO.

Logging
Borg writes all log output to stderr by default. But please note that something showing up
on stderr does not indicate an error condition just because it is on stderr. Please check
the log levels of the messages and the return code of borg for determining error, warning
or success conditions.

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

borg create repo::archive myfiles 2>> logfile

Custom logging configurations can be implemented via BORG_LOGGING_CONF.

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,
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 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.

Return codes
Borg can exit with the following return codes (rc):

┌────────────┬──────────────────────────────────┐
│Return code │ Meaning │
├────────────┼──────────────────────────────────┤
│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. 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
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
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 usecase for
this is to fully automate borg 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_HOSTNAME_IS_UNIQUE=no
Borg assumes that it can derive a unique hostname / identity (see borg debug
info). If this is not the case or you do not want Borg to automatically
remove stale locks, set this to no.

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 a all-zero MAC address
or other reasons to better externally control the host id, 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_LOGGING_CONF
When set, use the given filename as INI-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 commandline 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 --remote-path PATH commandline option overrides the
environment variable.

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: 20). The files cache is used to quickly
determine whether a file is unchanged. The FAQ explains this more detailed
in: always_chunking

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_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 behaviour (not
continuously streaming to disk).

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 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 and files:

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 $BORG_BASE_DIR/.cache/borg. If BORG_BASE_DIR is not explicitly
set while XDG env var XDG_CACHE_HOME is set, then $XDG_CACHE_HOME/borg is
being used instead. 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 $BORG_BASE_DIR/.config/borg. If BORG_BASE_DIR is not explicitly
set while XDG env var XDG_CONFIG_HOME is set, then $XDG_CONFIG_HOME/borg is
being used instead. This directory contains all borg configuration
directories, see the FAQ for a security advisory about the data in this
directory: home_config_borg

BORG_SECURITY_DIR
Defaults to $BORG_CONFIG_DIR/security. This directory contains information
borg uses to track its usage of NONCES ("numbers used once" - usually in
encryption context) and other 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 filename as repository key file.

TMPDIR This is where temporary files are stored (might need a lot of temporary
space for some operations), see tempfile for details.

Building:

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

BORG_LIBB2_PREFIX
Adds given prefix directory to the default locations. If a
'include/blake2.h' is found Borg will be linked against the system libb2
instead of a bundled implementation. (setup.py)

BORG_LIBZSTD_PREFIX
Adds given prefix directory to the default locations. If a 'include/zstd.h'
is found Borg will be linked against the system libzstd 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).

File systems
We strongly recommend against using Borg (or any other database-like software) on
non-journaling file systems like FAT, since it is not possible to assume any consistency
in case of power failures (or a sudden disconnect of an external drive or similar
failures).

While Borg uses a data store that is resilient against these failures when used on
journaling file systems, it is not possible to guarantee this with some hardware --
independent of the software used. We don't know a list of affected hardware.

If you are suspicious whether your Borg repository is still consistent and readable after
one of the failures mentioned above occurred, run borg check --verify-data to make sure it
is consistent. Requirements for Borg repository file systems.INDENT 0.0

• Long file names

• At least three directory levels with short names

• Typically, file sizes up to a few hundred MB. Large repositories may require large
files (>2 GB).

• Up to 1000 files per directory (10000 for repositories initialized with Borg 1.0)

• mkdir(2) should be atomic, since it is used for locking

• Hardlinks are needed for borg_upgrade (if --inplace option is not used). Also hardlinks
are used for more safe and secure file updating (e.g. of the repo config file), but the
code tries to work also if hardlinks are not supported.

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.

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

If one uses Borg in a client/server way (with a ssh: repository), the resource usage
occurs in part on the client and in another part on the server.

If one uses Borg as a single process (with a filesystem repo), all the resource usage
occurs in that one process, so just add up client + server to get the approximate resource
usage.

CPU client:

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

• chunks cache sync: quite heavy on CPU, doing lots of hashtable operations.

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

• borg check: similar to extract, but depends on options given.

• borg prune / borg delete archive: low to medium CPU usage

• borg delete repo: done on the server

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. Crypto might be cheap on the CPU (if hardware accelerated) or expensive (if
not).

CPU server:
It usually doesn't need much CPU, it just deals with the key/value store
(repository) and uses the repository index for that.

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

CPU (only for client/server operation):
When using borg in a client/server way with a ssh:-type repo, 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 - esp. if you are pumping big amounts of data.

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

Memory (RAM) server:
The server process will load the repository index into memory. Might need
considerable amounts of memory, but less than on the client (see below).

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

Repository index (server only):
Proportional to the amount of data chunks in your repo. Lots of chunks in your repo
imply a big repository index. It is possible to tweak the chunker params (see
create options) to influence the amount of chunks being created.

Temporary files (client):
Reading data and metadata from a FUSE mounted repository will consume up to the
size of all deduplicated, small chunks in the repository. Big chunks won't be
locally cached.

Temporary files (server):
A non-trivial amount of data will be stored on the remote temp directory for each
client that connects to it. For some remotes, this can fill the default temporary
directory at /tmp. This can be remediated by ensuring the $TMPDIR, $TEMP, or $TMP
environment variable is properly set for the sshd process. For some OSes, this can
be done just by setting the correct value in the .bashrc (or equivalent login
config file for other shells), however in other cases it may be necessary to first
enable PermitUserEnvironment yes in your sshd_config file, then add
environment="TMPDIR=/my/big/tmpdir" at the start of the public key to be used in
the authorized_hosts file.

Cache files (client only):
Contains the chunks index and files index (plus a collection of single- archive
chunk indexes which might need huge amounts of disk space, depending on archive
count and size - see FAQ about how to reduce).

Network (only for client/server operation):
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.

Support for file metadata
Besides regular file and directory structures, Borg can preserve

• symlinks (stored as symlink, the symlink is not followed)

• special files:

• character and block device files (restored via mknod)

• 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.

• hardlinked regular files, devices, FIFOs (considering all items in the same archive)

• timestamps in 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] │
├────────────────────┼──────────┼───────────┼───────────┤
│Mac OS X │ 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 │ No [3] │ No [3] │ n/a │
│derivatives │ │ │ │
├────────────────────┼──────────┼───────────┼───────────┤
│Windows (cygwin) │ No [4] │ No │ No │
└────────────────────┴──────────┴───────────┴───────────┘

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

Note that most of the platform-dependent features also depend on the file system. For
example, ntfs-3g on Linux isn't 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 aren't 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 Mac OS X.

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

AUTHOR