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borg-import-tar(1) borg backup tool borg-import-tar(1)

Name

borg-import-tar - Create a backup archive from a tarball

SYNOPSIS

borg [common options] import-tar [options] NAME TARFILE

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, .tar.zst or .tzst: zstd (in-process)
  • .tar.lz4: lz4 -d

For zstd, Borg decompresses in-process using libzstd instead of piping through an external program. The other formats are piped through the respective external filter program.

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 needed: sparse members in input tarballs (old GNU and PAX sparse formats) are read correctly and their holes are stored as deduplicated all-zero chunks.

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

To import multiple tarballs into a single archive, they can be simply concatenated (e.g. using "cat") into a single file, and imported with an --ignore-zeros option to skip through the stop markers between them.

OPTIONS

See borg-common(1) for common options of Borg commands.

arguments

specify the archive name
input tar file. "-" to read from stdin instead.

options

filter program to pipe data through
print statistics for the created archive
output verbose list of items (files, dirs, ...)
only display items with the given status characters
output stats as JSON (implies --stats)
ignore zero-filled blocks in the input tarball

Archive options

add a comment text to the archive
manually specify the archive creation date/time (yyyy-mm-ddThh:mm:ss[(+|-)HH:MM] format, (+|-)HH:MM is the UTC offset, default: local time zone). Alternatively, give a reference file/directory.
specify the chunker parameters: buzhash,CHUNK_MIN_EXP,CHUNK_MAX_EXP,HASH_MASK_BITS,WINDOW_SIZE or buzhash64,CHUNK_MIN_EXP,CHUNK_MAX_EXP,HASH_MASK_BITS,WINDOW_SIZE,NC_LEVEL or fastcdc,CHUNK_MIN_EXP,CHUNK_MAX_EXP,HASH_MASK_BITS,NC_LEVEL. default: fastcdc,19,23,21,2
select compression algorithm, see the output of the "borg help compression" command for details.
compute these hash digests over the full content of each file and store them into the archive items. Comma-separated list of hash algorithm names, e.g. "blake3", or "none". default: none

EXAMPLES

# Export as an uncompressed tar archive
$ borg export-tar Monday Monday.tar
# Import an uncompressed tar archive
$ borg import-tar Monday Monday.tar
# Exclude some file types and compress using gzip
$ borg export-tar Monday Monday.tar.gz --exclude '*.so'
# Use a higher compression level with gzip
$ borg export-tar --tar-filter="gzip -9" Monday Monday.tar.gz
# Copy an archive from repoA to repoB
$ borg -r repoA export-tar --tar-format=BORG archive - | borg -r repoB import-tar archive -
# Export a tar, but instead of storing it on disk, upload it to a remote site using curl
$ borg export-tar Monday - | curl --data-binary @- https://somewhere/to/POST
# Remote extraction via 'tarpipe'
$ borg export-tar Monday - | ssh somewhere "cd extracted; tar x"
# Export sparse files (e.g. disk images) as sparse tar members (GNU sparse format 1.0)
$ borg export-tar --sparse disk-images disk-images.tar


Archives transfer script

Outputs a script that copies all archives from repo1 to repo2 (bash, because it uses process substitution). Remove the echo to actually run the commands instead of just printing them:

while read -r N I T
do


  echo "borg -r repo1 export-tar --tar-format=BORG aid:$I - | borg -r repo2 import-tar --timestamp=$T $N -"
done < <(borg -r repo1 repo-list --format='{name} {id} {time:%Y-%m-%dT%H:%M:%S}{NL}')


Kept:

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

Lost:

•
some archive metadata (like the original command line, 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
  • maybe add --sparse to the export-tar command, so runs of all-zero chunks travel as a compact sparse map instead of literal zeros

SEE ALSO

borg-common(1)

Author

The Borg Collective

2026-09-26