A spotter's guide to open-source Linux package formats
For the dead keen, it is possible to pull all the files out of a package and then manually install it. As said earlier, the rpm package format uses the cpio archive format internally. A simple command, rpm2cpio, will assist by dumping the internal archive. You can use the following command to extract all the files without actually installing them:
rpm2cpio examplepackage.rpm | cpio –i
Handily, in a similar fashion, the Debian package format is a collection of tarballs in an archive format called ar; as you might expect this is closely related to tar but is much more basic. One feature is it does not support folders.
Extract the contents of a Debian package like so:
ar –x examplepackage.deb
This will spill out two tarballs – control.tar.gz and data.tar.gz – and a single-lined text file called debian-binary.
debian-binary merely contains the Debian packaging version used; control.tar.gz contains install scripts and useful information. data.tar.gz holds the actual binary files and configuration items themselves, all the files needed for the program to work. At a pinch you could just extract this archive with tar –xf although if the app is complex the install scripts will be doing much more work than this.
Earlier, I said one of the great features of a package manager was its ability to keep your apps up-to-date as newer versions are released. The tools used will obviously vary based on your distro, but do check out Apt (Advanced Package Tool), Yum (Yellowdog updater modified), Synaptic (a graphical front-end on top of apt) and up2date.
Apt is a mature piece of software which came with Debian and related distros but now supports rpm also. It is not so much a single tool as a collection of utilities; the most commonly used parts of Apt are apt-get and apt-cache which pull down packages from available repositories and query what’s available, respectively. Synaptic offers no new functionality overall but bundles everything together in a single easy-to-use graphical tool.
Similar to Apt, Yum is a command-line utility for rpm packages. It can query what’s available, install packages, and perform all the other required functions like listing what’s been installed and uninstalling previously installed packages.
up2date is also an rpm tool, but it seeks to provide access to Yum and Apt repositories giving a richer suite.
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David has been computing since 1984 where he instantly gravitated to the family Commodore 64. He completed a Bachelor of Computer Science degree from 1990 to 1992, commencing full-time employment as a systems analyst at the end of that year. Within two years, he returned to his alma mater, the University of Newcastle, as a UNIX systems manager. This was a crucial time for UNIX at the University with the advent of the World-Wide-Web and the decline of VMS. David moved on to a brief stint in consulting, before returning to the University as IT Manager in 1998. In 2001, he joined an international software company as Asia-Pacific troubleshooter, specialising in AIX, HP/UX, Solaris and database systems. Settling down in Newcastle, David then found niche roles delivering hard-core tech to the recruitment industry and presently is the Chief Information Officer for a national resources company where he particularly specialises in mergers and acquisitions and enterprise applications.