Fedora And Red Hat System Administration/Archives And Compression

Compressing Data

gzip and gunzip

Under Construction

bzip2 and bunzip2

Under Construction

tar - *NIX Archives

Under Construction

Creating a tar archive

To create an uncompressed tar archive, the c and f options are provided (think 'c' for create and 'f' for filename):

[user@station user]$ tar cf foo.tar file1 file2 file3

The first argument is the name of the archive, in this case foo.tar. Any following arguments are the files that are being archived (e.g. file1 file2 file3). Usually globbing is used to archive all files of a particular type (e.g. tar cf foo.tar *.cpp will archive all of the .cpp files in the current directory):

To archive all files and subdirectories within a directory, the same options are provided, but the second argument is the . character which symbolizes the current working directory:

[user@station user]$ tar cf foo.tar .

To compress the contents of the archive one of the z, J, or j options are used. Each option corresponds to a different compression algorithm, which in order are: gzip, xz, and bzip2.

For example, to create a gzip compressed archive of the current directory the following would be run:

[user@station user]$ tar cfz foo.tar.gz .

Inspecting a tar archive

Under Construction

Extracting a tar archive

Under Construction

cpio - Flexible Archiving Tool

In general, tar is the preferred method for creating archives, but in some cases a particular archive format may be desired and cpio provides a greater degree of control over how the archive is generated at the cost of greater complexity.

Creating a cpio archive

To create a cpio archive, the -o option is provided (think 'o' for "The archive is being written out"). cpio expects a list of files to be provided to its standard input. The list of files is usually provided by piping results from the find command. The -H option can be used to specify the archive format, see the man page for more information.

[user@station user]$ find playground/
playground/
playground/AUTHORS
playground/ChangeLog
playground/COPYING
playground/foo.txt
playground/newfile
[user@station user]$ find playground/ | cpio -o >archive
1212 blocks
[user@station user]$ ls -l archive
-rw-rw-r--    1 user     user       620544 Jan  5 08:49 archive
[user@station user]$ file archive
archive: cpio archive

Listing contents of an archive with cpio

To view the contents of an archive the -i option is provided to tell cpio to expect the archive data on its standard input. The -t option is also used then to tell cpio to not extract, but rather simply list the contents of the archive.

[user@station user]$ cpio -it <archive
playground/
playground/AUTHORS
playground/ChangeLog
playground/COPYING
playground/foo.txt
playground/newfile
1212 blocks

Extracting an archive with cpio

The -i option is used with a combination of options to tell it how to extract. Common choices include -d to tell cpio to create directories as needed. -m to reset file modification times. -R to change file ownership.

[user@station user]$ cd /tmp
[user@station tmp]$ cpio -idm <archive
1212 blocks
[user@station tmp]$ find playground/
playground/
playground/AUTHORS
playground/ChangeLog
playground/COPYING
playground/foo.txt
playground/newfile

zip - PKZIP style archives

Creating a zip archive

[user@station user]$ zip -r playground.zip playground
  adding: playground/ (stored 0%)
  adding: playground/AUTHORS (deflated 63%)
  adding: playground/COPYING (deflated 62%)
  adding: playground/foo.txt (stored 0%)
  adding: playground/newfile (deflated 39%)
  adding: playground/ChangeLog (deflated 70%)
[user@station user]$ ls -l playground.zip
-rw-r--r--  1 user     user     71607 Jan 11 14:33 playground.zip

Listing contents of a zip archive

[user@station user]$ unzip -l playground.zip
Archive:  playground.zip
  Length     Date   Time    Name
 --------    ----   ----    ----
        0  01-11-05 14:33   playground/
     2110  01-11-05 14:32   playground/AUTHORS
    17992  01-11-05 14:33   playground/COPYING
       22  01-11-05 14:33   playground/foo.txt
       44  01-11-05 14:33   playground/newfile
   212169  01-11-05 14:32   playground/ChangeLog
 --------                   -------
   232337                   6 files

Unpacking a zip archive

[user@station user]$ rm -rf playground
[user@station user]$ unzip playground.zip
Archive:  playground.zip
   creating: playground/
  inflating: playground/AUTHORS
  inflating: playground/COPYING
 extracting: playground/foo.txt
  inflating: playground/newfile
  inflating: playground/ChangeLog

dump - Filesystem Level Backup

Under Construction