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I gzip directories very often at work. What I normally do is

tar -zcvf file.tar.gz /path/to/directory

Is there a way to specify the compression level here? I want to use the best compression possible even if it takes more time to compress.

6 Answers 6

196
GZIP=-9 tar cvzf file.tar.gz /path/to/directory

assuming you're using bash. Generally, set GZIP environment variable to "-9", and run tar normally.

Also - if you really want best compression, don't use gzip. Use lzma or 7z.

And when using gzip (which is good idea for various of reasons anyway) consider using pigz program and not the gzip.

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  • 22
    pigz is "parallel gzip" which uses all your cores for gzip compression. You can watch top and see it using anywhere between 200%-400$ CPU. Dec 9, 2013 at 2:01
  • 6
    FYI, for .bz2 format, use: BZIP2=-9 tar cvjf file.tar.bz2 /path/to/directory
    – Tomofumi
    Mar 2, 2017 at 2:59
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    The environment variable seems to now be GZIP_OPT, the usage should be the same.
    – Seer
    Dec 5, 2017 at 11:59
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    From the man page on Ubuntu 16.04 for gzip: "On Vax/VMS, the name of the environment variable is GZIP_OPT, to avoid a conflict with the symbol set for invocation of the program." For sh, csh, and MSDOS it should still just be GZIP
    – Ponyboy47
    Jun 2, 2018 at 16:13
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    This is what I get when I try to set GZIP environment variable to -9: gzip: warning: GZIP environment variable is deprecated; use an alias or script Oct 31, 2019 at 10:43
89

Instead of using the gzip flag for tar, gzip the files manually after the tar process, then you can specify the compression level for the gzip program:

tar -cvf files.tar /path/to/file0 /path/to/file1 ; gzip -9 files.tar

Or you could use:

tar cvf - /path/to/file0 /path/to/file1 | gzip -9 - > files.tar.gz

The -9 in the gzip command line tells gzip to use the maximum possible compression level (default is -6).

Edit: Fixed pipe command line based on @depesz comment.

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    Using pipes should be done with: tar cvf - /path/to/directory | gzip -9 - > file.tar.gz
    – user7385
    Jul 1, 2011 at 18:40
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    1st example should end with file.tar, since gzip adds the ".gz" extension. Feb 4, 2013 at 18:20
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    why don't you skip f -? if there is no file, then it is stdin/out Sep 19, 2013 at 18:52
  • addition to the previos comment. From "man tar" section Environtment: TAPE Device or file to use for the archive if --file is not specified. If this environment variable is unset, use stdin or stdout instead.
    – Mikl
    Sep 24, 2013 at 17:08
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    and we can reduce "gzip -9 -" -> "gzip -9". From "man gzip" section Description: If no files are specified, or if a file name is "-", the standard input is compressed to the standard output.
    – Mikl
    Sep 24, 2013 at 17:18
80

Modern versions of tar support the xz archive format (GNU tar, since 1.22 in 2009, Busybox since 1.17.0 in 2010).

It's based on lzma2, kind of like a 7-Zip version of gz. This gives better compression if you are ok with the requirement of needing xz support.

tar -Jcvf file.tar.xz /path/to/directory

I just found out here (basically a dupe of this question, but in the Unix stackexchange) that there is also a XZ_OPT=-9 environment variable to control the XZ compression level similar to the GZIP one in the other post.

XZ_OPT=-9 tar -Jcvf file.tar.xz /path/to/directory
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    +1 xz is far better than both bzip2 and gzip. Here's a comparison: tukaani.org/lzma/benchmarks.html
    – User1
    Dec 25, 2012 at 15:44
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    The trade-off is speed. XZ is significantly slower.
    – Bell
    Apr 6, 2017 at 23:02
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    no. xz -1 significantly beats bz2 -1~9 in terms of both compression ratio, compression/decompression speed. bz2 is the most awful format among popular formats. In short, if you ever use bz2, try xz -1, that's done.
    – YumeYao
    Oct 14, 2020 at 1:54
  • @YumeYao FYI this is not always true, I just tried to compress some data with both bzip2 and xz at -9 compression level, xz gives me a 38M compressed size whereas bzip2 gives me 36M.
    – Erwan
    May 6, 2021 at 16:44
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    all boils down to type of data that you need to compress I thing - not reversed :) Dec 10, 2021 at 17:34
43
tar cv /path/to/directory | gzip --best > file.tar.gz

This is Matrix Mole's second solution, but slightly shortened:

When calling tar, option f states that the output is a file. Setting it to - (stdout) makes tar write its output to stdout which is the default behavior without both f and -.

And as stated by the gzip man page, if no files are specified gzip will compress from standard input. There is no need for - in the gzip call.

Option --best (equivalent to -9) sets the highest compression level.

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    This works beautifully. Also if you run as root, permissions & owners are preserved too. Otherwise you must specify. Also if it wasn't obvious "-9" is best compression and "-1" is fastest compression. "-1" still takes a looong time if you have lots of files ;-)
    – PJ Brunet
    Dec 12, 2013 at 4:04
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    This works with xz and pixz too. It is a great way to control the number of threads used for parallel compressing without having to create an intermediate .tar file. Like so tar -cv /path/to/dir | pixz -p4 > output.tpxz Feb 12, 2015 at 21:52
21

There is also the option to specify the compression program using -I. This can include the compression level option.

tar -I 'gzip -9' -cvf file.tar.gz /path/to/directory

Note that the -I option is shorthand for --use-compress-program=COMMAND. This is important if you're not using GNU tar but BSD tar. The latter uses the -I option as shorthand for the --files-from filename option.

So to be make your command "cross-platform" you could write:

tar --use-compress-program='gzip -9' -cvf file.tar.gz /path/to/directory
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    Older versions of tar such as that provided in CentOS 6 & 7 do not support providing arguments in the -I arg, they will try to treat the whole thing as a program name to exec, and thus fail. At least as of tar 1.29 in Debian Stretch, this does work.
    – Cheetah
    Dec 7, 2017 at 0:30
  • @Cheetah which version of tar?
    – OrigamiEye
    Apr 1, 2020 at 14:11
  • @Cheetah I can confirm that it doesn't work for tar v1.26 in CentOS 7.x, returns this error : tar (child): gzip -9: Cannot exec: No such file or directory Oct 16, 2020 at 4:16
  • @SaurabhPBhandari "Cannot exec: No such file or directory" that probably means you need to specify the full gzip file name tar -I '/bin/gzip -9' -cvf file.tar.gz /path/to/directory.
    – RonJohn
    Mar 14, 2021 at 4:17
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    @RonJohn no, sadly it's due to the old version of tar. 'gzip' works, '/bin/gzip' works, '/bin/gzip -9' doesn't.
    – mwfearnley
    Jun 6, 2021 at 15:24
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And of course macOS bsd-derived tar has to be different:

tar -czf file.tar.gz --options gzip:compression-level=9 /path/to/directory
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    however --use-compress-program works there too, so I'd use that for portability Jul 6, 2022 at 23:46

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