mirror of
https://github.com/borgbackup/borg.git
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133 lines
4.1 KiB
Groff
133 lines
4.1 KiB
Groff
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..
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.TH "BORG-COMPRESSION" 1 "2022-08-07" "" "borg backup tool"
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.SH NAME
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borg-compression \- Details regarding compression
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.SH DESCRIPTION
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.sp
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It is no problem to mix different compression methods in one repo,
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deduplication is done on the source data chunks (not on the compressed
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or encrypted data).
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.sp
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If some specific chunk was once compressed and stored into the repo, creating
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another backup that also uses this chunk will not change the stored chunk.
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So if you use different compression specs for the backups, whichever stores a
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chunk first determines its compression. See also borg recreate.
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.sp
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Compression is lz4 by default. If you want something else, you have to specify what you want.
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.sp
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Valid compression specifiers are:
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.INDENT 0.0
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.TP
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.B none
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Do not compress.
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.TP
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.B lz4
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Use lz4 compression. Very high speed, very low compression. (default)
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.TP
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.B zstd[,L]
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Use zstd ("zstandard") compression, a modern wide\-range algorithm.
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If you do not explicitly give the compression level L (ranging from 1
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to 22), it will use level 3.
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Archives compressed with zstd are not compatible with borg < 1.1.4.
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.TP
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.B zlib[,L]
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Use zlib ("gz") compression. Medium speed, medium compression.
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If you do not explicitly give the compression level L (ranging from 0
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to 9), it will use level 6.
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Giving level 0 (means "no compression", but still has zlib protocol
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overhead) is usually pointless, you better use "none" compression.
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.TP
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.B lzma[,L]
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Use lzma ("xz") compression. Low speed, high compression.
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If you do not explicitly give the compression level L (ranging from 0
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to 9), it will use level 6.
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Giving levels above 6 is pointless and counterproductive because it does
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not compress better due to the buffer size used by borg \- but it wastes
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lots of CPU cycles and RAM.
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.TP
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.B auto,C[,L]
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Use a built\-in heuristic to decide per chunk whether to compress or not.
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The heuristic tries with lz4 whether the data is compressible.
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For incompressible data, it will not use compression (uses "none").
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For compressible data, it uses the given C[,L] compression \- with C[,L]
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being any valid compression specifier.
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.TP
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.B obfuscate,SPEC,C[,L]
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Use compressed\-size obfuscation to make fingerprinting attacks based on
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the observable stored chunk size more difficult.
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Note:
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\- you must combine this with encryption or it won\(aqt make any sense.
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\- your repo size will be bigger, of course.
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.sp
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The SPEC value will determine how the size obfuscation will work:
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.sp
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Relative random reciprocal size variation:
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Size will increase by a factor, relative to the compressed data size.
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Smaller factors are often used, larger factors rarely.
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1: factor 0.01 .. 100.0
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2: factor 0.1 .. 1000.0
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3: factor 1.0 .. 10000.0
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4: factor 10.0 .. 100000.0
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5: factor 100.0 .. 1000000.0
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6: factor 1000.0 .. 10000000.0
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.sp
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Add a randomly sized padding up to the given size:
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110: 1kiB
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\&...
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120: 1MiB
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\&...
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123: 8MiB (max.)
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.UNINDENT
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.sp
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Examples:
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.INDENT 0.0
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.INDENT 3.5
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.sp
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.nf
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.ft C
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borg create \-\-compression lz4 REPO::ARCHIVE data
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borg create \-\-compression zstd REPO::ARCHIVE data
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borg create \-\-compression zstd,10 REPO::ARCHIVE data
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borg create \-\-compression zlib REPO::ARCHIVE data
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borg create \-\-compression zlib,1 REPO::ARCHIVE data
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borg create \-\-compression auto,lzma,6 REPO::ARCHIVE data
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borg create \-\-compression auto,lzma ...
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borg create \-\-compression obfuscate,3,none ...
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borg create \-\-compression obfuscate,3,auto,zstd,10 ...
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borg create \-\-compression obfuscate,2,zstd,6 ...
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.ft P
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.fi
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.UNINDENT
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.UNINDENT
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.SH AUTHOR
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The Borg Collective
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.\" Generated by docutils manpage writer.
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