Archiving and Compression – Variety in Options for Unix Machine

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In any part of this world, people would agree that information should be stored in minimum size. Ideally, any information gained can be stored with size as small as possible but can contain data as large as possible. In the past, size would be really matter. A bigger storage device such as floppy disk would only store around 4MB, far smaller than the smallest capacity we can find today. Even though we now have such an abundant resource today, the same problem still arise: how to store information as minimum as possible and also how to collect scattered data into a single named resource. One of solution proposed is using archive files.

A practical problem we would meet in daily life is data transmission. Often we are involved in transfer data activity, whether we send or receive data. Storage is cheaper, but bandwidth is not in the same condition. Bandwidth is limited and speed would be slower than read/write operation on storage. We agree that a smaller size would theoretically transferred faster than bigger size in same link / connection. Also, if we have multiple file we want to send, it is wise to join them as a single file and then send them rather than send them one by one. The case we see here is how archive files take role.

The Archive Files – About Archiving and Compressing

An archive file is a file that is composed of one or more files along with metadata. Archive file is used to collect multiple data files together and pack them as a single file to achieve easier portability and storage. An archive file might also be compressed to reduce the size. Basically, archive file relies to two part: archiving and compressing.

Archiving is an activity of combining a number of files together into one archive file, or series of archive files. This enable easier transportation as well as storage.

Compression is the reduction in size of data. The process usually employ an algorithm which can modify data to create more compact file.

There are many archive files format. Different algorithm might create different result and thus different size. Also note that an archive format might only consist of archiving only process, or compression only process. Aside of that, some format also offer both archiving and also compression at one.

In this article, I will present some known format for archiving data in UNIX and UNIX-like machine.

Archiving Only

File Extension MIME type Official Name Description
 .a .ar  Unix Archiver  Traditional archive format on Unix-like system. Today used mainly for the creation of static library
 .cpio  application/x-cpio  cpio  Obsolete archive format. Used by RPM files for archiving.
 .shar  application/x-shar  Shell archive  A self-extracting archive that use the Bourne shell (sh).
 .iso  ISO-9660 image  An archive format originally used mainly for archiving and distributing the exact, nearly exact, or custom-modified contents of an optical storage medium (CD-ROM or DVD-ROM). This archive file can also be burned to a CD using appropriate tools.
 .mar  Mozilla archive  Archive format used by Mozilla for storing binary diffs. Used in conjunction with bzip2 (like popular .tar archive)
 .tar  Tape archive  A common archive format. Generally used in conjunction such as gzip, bzip2, xz, etc.

Compressing Only

File Extension MIME type Official Name Description
 .bz2  application/x-bzip2  bzip2  Open Source compression format using Burrows-Wheeler transform followed by a move-to-front transform and finally Huffman coding.
 .gz  application/x-gzip  gzip  GNU Zip, using DEFLATE algorithm.
 .lz  application/x-lzip  lzip  An alternate LZMA algorithm implementation with support for checksums and ident bytes.
 .lzma  application/x-lzma  lzma  Using LZMA compression.
 .lzo  application/x-lzop  lzop  An implementation of the LZO data compression algorithm.
 .rz  rzip  A compression designed to do particularly well on very large files containing long distance redundancy.
 .xz  application/x-xz  xz  Compression format using LZMA2 to yield very high compression ratios.
 .z  application/x-compress  pack  Old Huffman coding compression format.
 .Z  application/x-compress  compress  Traditional LZW compression format.

Archiving and Compressing

File Extension MIME type Official Name Description
 .7z  application/x-7z-compressed  7z  Open source file format used by 7-zip
 .afa  application/x-astrotite-afa  AFA  Compress and doubly encrypt the data (AES256 and CAS256)
 .arc  ARC
 .arj  application/x-arj  ARJ
 .ba  Scifer  Binary Archive with external header
 .cfs  application/x-cfs-compressed  Compact File Set  Open source file format
 .dar  Disk Archiver  Open source file format. Files are compressed individually with either gzip, bzip2, or lzo
 .kgb  KGB Archiver  Open sourced archiver with compression using the PAQ family of algorithm and optional compression
 .rar  application/x-rar-compressed
 .sitx  application/x-stuffitx  Stuffit X  Compression format common on Apple Macintosh computer.
 .sqx  SQX  Royalty free compressing format
 tar.gz, .tgz, .tar.Z, .tar.bz2, tbz2, .tar.lzma, .tlz  application/x-gtar  Tar with gzip, compress, bzip2, or lzma  Tarball format combines tar archives with a file-based compression scheme which is common used on Unix.
 .xar  XAR
 .yz1  YZ1  Yamazaki Zipper Archive. Compression format used in DeepFreezer archiver utility.
 .zip, .zipx  application/zip  ZIP
 .zz  Zzip  Use compression algorithm based on Burrows-Wheeler transform method.

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