Working with Archives

A lot of software packages will typically come in an archive file.

Archives are either compressed files (single file compression), archive containers (e.g., .tar files), or both (.tar.gz, .tar.bz2, etc.).

More often than not, you'll see a compressed archive container (.tar.gz).

Creating Archives and Unarchiving

tl;dr

# Create archives
tar -czf foo.tar.gz dir/          # gzip
tar -cjf foo.tar.bz2 dir/         # bzip2
tar -cJf foo.tar.xz dir/          # xz
tar --zstd -cf foo.tar.zst dir/   # zstd
zip -r foo.zip dir/               # zip
7z a foo.7z dir/                  # 7zip

# Extract
tar -xzf foo.tar.gz
tar -xjf foo.tar.bz2
tar -xJf foo.tar.xz
tar --zstd -xf foo.tar.zst
unzip foo.zip
7z x foo.7z

Unextracting with tar on modern Linux systems:

# This works for files compressed with gzip and bzip
tar --extract --file filename

# Same as above
tar -xf filename

# Same as above. The leading dash is optional
tar xf filename

# explicitly decompress gzip2-compressed file then
# pass uncompressed result directly into tar
gzip -cd filename.tgz | tar xf -

# same as above, but for bzip2-compressed files
bunzip2 -cd filename.tar.bz2 | tar xf -

The uncompression commands usually have options in tar. But you can decompress and pipe to tar if you don't want to remember all the options.

Overview of Formats

There are a few different formats you'll see when working with archives on Linux/Unix.

• .gz: Gzip file.
  • gzip is a compression utility, not an archiving utility.
  • Compression is often used in conjunction with archives to make the file smaller.
• .tar: Tar archive file.
• .tar.gz: Tar archive file compressed with gzip.
  • Sometimes represented as .tgz

Compression Formats

.gz (gzip)

Gzip is a fast compression utility, but it doesn't have a great compression ratio.
It's usually good for most things and is widely used.

Using gzip

• Compress a file with gzip by simply passing it as an argument.
  

  gzip filename
  

  This creates a filename.gz file, a compressed version of filename.

• Decompress a file with gzip either with gzip -d or gunzip

  gzip -d filename.gz
  gunzip filename.gz
  

• View gzip compressed files as a stream with zcat and zless.
  

  zcat filename.gz
  zless filename.gz
  

  These act the same way as cat and less.

.bz2 (bzip2)

Bzip2 is a compression utility. It's slower than gzip but has a better compression ratio.

Using bzip2

• Compress a file with bzip2 by passing it as an argument.
  

  bzip2 filename
  

  This creates a filename.bz2 file.

• Decompress a .bz2 file with either bzip2 -d or bunzip2.
  

  bzip2 -d filename.bz2
  bunzip2 filename.bz2
  

.xz (xz)

XZ is a compression utility that has a high compression ratio, but it's even slower than bzip2.

Using xz

• Compress in the same way as the other tools.
  

  xz filename
  

  Creates a filename.xz file.

• Decompress with either xz -d or unxz.
  

  xz -d filename.xz
  unxz filename.xz
  

.zst (Zstandard/zstd)

Zstandard (zstd) is a compression utility that is both fast and has a good compression ratio.

Drawback: It's backed by Facebook.

Using zstd

• Compress a file with zstd:
  

  zstd filename
  

  This create a filename.zst file.

• Decompress a file with zstd -d or unzstd.
  

  zstd -d filename.zst
  unzstd filename.zst
  

.lzma and .lz

These are legacy formats that were replaced by .xz.

But, if you have to work with them:

lzma filename        # Compress
unlzma filename.lzma # Decompress

Archive Container Formats

.tar (Tape Archive)

The tar command creates archive files, which bundles multiple files into a single file. There is no compression used by default.

Using tar

• Create a .tar archive with tar -c and specify an output file with -f.
  

  tar -cf archive.tar file1 file2 dir1/
  

  This bundles file1, file2, and dir/ (and all its contents) into the archive.tar archive.
  • By default, archives are not compressed.
  • You can use the -z option to automatically use gzip to compress your archive.
  • You can use the -J option to automatically use xz to compress your archive.

• Extract an archive with tar -x and specify an input file with -f.
  

  tar -xf archive.tar
  

tar -czf archive.tar.gz folder/
# -c: create archive
# -z: use gzip
# -f: filename to create (archive.tar.gz)

tar -xJf archive.tar.xz
# -x: extract
# -J: use xz
# -f: archive file name

.zip

The .zip format is a cross-platform archive format.
Supports compression and multi-file archiving.

• Create an archive with zip:

  zip archive.zip file1 file2 dir/
  

  This bundles file1, file2, and dir/ into archive.zip.

• Extract an archive with unzip.
  

  unzip archive.zip
  

.rar

This is a proprietary archive format.

• You can not create a .rar file without rar, which is not free.

• Extracting a .rar requires the unrar package.
  

  unrar x archive.rar
  

.7z (7zip)

The .7z format has a high compression ratio and requires the p7zip or 7zip package to use.

• Create a .7z archive with 7z a.

  7z a archive.7z file1 dir/
  

  This creates archive.7z with the files given.

• Extract a 7zip archive with 7z x.
  

  7z x archive.7z
  

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