borg export-tar

borg [common options] export-tar [options] ARCHIVE FILE [PATH...]
positional arguments
  ARCHIVE archive to export
  FILE output tar file. “-” to write to stdout instead.
  PATH paths to extract; patterns are supported
optional arguments
  --tar-filter filter program to pipe data through
  --list output verbose list of items (files, dirs, …)
  --tar-format FMT select tar format: BORG, PAX or GNU

Common options

Exclusion options
  -e PATTERN, --exclude PATTERN exclude paths matching PATTERN
  --exclude-from EXCLUDEFILE read exclude patterns from EXCLUDEFILE, one per line
  --pattern PATTERN include/exclude paths matching PATTERN
  --patterns-from PATTERNFILE read include/exclude patterns from PATTERNFILE, one per line
  --strip-components NUMBER Remove the specified number of leading path elements. Paths with fewer elements will be silently skipped.

Description

This command creates a tarball from an archive.

When giving ‘-’ as the output FILE, Borg will write a tar stream to standard output.

By default (--tar-filter=auto) Borg will detect whether the FILE should be compressed based on its file extension and pipe the tarball through an appropriate filter before writing it to FILE:

  • .tar.gz or .tgz: gzip
  • .tar.bz2 or .tbz: bzip2
  • .tar.xz or .txz: xz
  • .tar.zstd: zstd
  • .tar.lz4: lz4

Alternatively, a --tar-filter program may be explicitly specified. It should read the uncompressed tar stream from stdin and write a compressed/filtered tar stream to stdout.

Depending on the -tar-format option, these formats are created:

--tar-format Specification Metadata
BORG BORG specific, like PAX all as supported by borg
PAX POSIX.1-2001 (pax) format GNU + atime/ctime/mtime ns
GNU GNU tar format mtime s, no atime/ctime, no ACLs/xattrs/bsdflags

A --sparse option (as found in borg extract) is not supported.

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.

For more help on include/exclude patterns, see the borg help patterns command output.

--progress can be slower than no progress display, since it makes one additional pass over the archive metadata.

borg import-tar

borg [common options] import-tar [options] ARCHIVE TARFILE
positional arguments
  ARCHIVE name of archive to create (must be also a valid directory name)
  TARFILE input tar file. “-” to read from stdin instead.
optional arguments
  --tar-filter filter program to pipe data through
  -s, --stats print statistics for the created archive
  --list output verbose list of items (files, dirs, …)
  --filter STATUSCHARS only display items with the given status characters
  --json output stats as JSON (implies --stats)

Common options

Archive options
  --comment COMMENT add a comment text to the archive
  --timestamp TIMESTAMP manually specify the archive creation date/time (UTC, yyyy-mm-ddThh:mm:ss format). alternatively, give a reference file/directory.
  -c SECONDS, --checkpoint-interval SECONDS write checkpoint every SECONDS seconds (Default: 1800)
  --chunker-params PARAMS specify the chunker parameters (ALGO, CHUNK_MIN_EXP, CHUNK_MAX_EXP, HASH_MASK_BITS, HASH_WINDOW_SIZE). default: buzhash,19,23,21,4095
  -C COMPRESSION, --compression COMPRESSION select compression algorithm, see the output of the “borg help compression” command for details.

Description

This command creates a backup archive from a tarball.

When giving ‘-’ as path, Borg will read a tar stream from standard input.

By default (--tar-filter=auto) Borg will detect whether the file is compressed based on its file extension and pipe the file through an appropriate filter:

  • .tar.gz or .tgz: gzip -d
  • .tar.bz2 or .tbz: bzip2 -d
  • .tar.xz or .txz: xz -d
  • .tar.zstd: zstd -d
  • .tar.lz4: lz4 -d

Alternatively, a --tar-filter program may be explicitly specified. It should read compressed data from stdin and output an uncompressed tar stream on stdout.

Most documentation of borg create applies. Note that this command does not support excluding files.

A --sparse option (as found in borg create) is not supported.

About tar formats and metadata conservation or loss, please see borg export-tar.

import-tar reads these tar formats:

  • BORG: borg specific (PAX-based)
  • PAX: POSIX.1-2001
  • GNU: GNU tar
  • POSIX.1-1988 (ustar)
  • UNIX V7 tar
  • SunOS tar with extended attributes

Examples

# export as uncompressed tar
$ borg export-tar /path/to/repo::Monday Monday.tar

# import an uncompressed tar
$ borg import-tar /path/to/repo::Monday Monday.tar

# exclude some file types, compress using gzip
$ borg export-tar /path/to/repo::Monday Monday.tar.gz --exclude '*.so'

# use higher compression level with gzip
$ borg export-tar --tar-filter="gzip -9" repo::Monday Monday.tar.gz

# copy an archive from repoA to repoB
$ borg export-tar --tar-format=BORG repoA::archive - | borg import-tar repoB::archive -

# export a tar, but instead of storing it on disk, upload it to remote site using curl
$ borg export-tar /path/to/repo::Monday - | curl --data-binary @- https://somewhere/to/POST

# remote extraction via "tarpipe"
$ borg export-tar /path/to/repo::Monday - | ssh somewhere "cd extracted; tar x"

Archives transfer script

Outputs a script that copies all archives from repo1 to repo2:

for A T in `borg list --format='{archive} {time:%Y-%m-%dT%H:%M:%S}{LF}' repo1`
do
  echo "borg export-tar --tar-format=BORG repo1::$A - | borg import-tar --timestamp=$T repo2::$A -"
done

Kept:

  • archive name, archive timestamp
  • archive contents (all items with metadata and data)

Lost:

  • some archive metadata (like the original commandline, execution time, etc.)

Please note:

  • all data goes over that pipe, again and again for every archive
  • the pipe is dumb, there is no data or transfer time reduction there due to deduplication
  • maybe add compression
  • pipe over ssh for remote transfer
  • no special sparse file support