Hitchhiker's Guide to Openbsd

15.2.1 - How does it work?
Packages are the pre-compiled binaries of some of the most used third party software. Packages can be 
managed easily with the help of several utilities, also referred to as the pkg* tools: 
http://www.openbsd.org/faq/faq15.html (2 of 27)9/4/2011 10:02:29 AM

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15 - The OpenBSD packages and ports system
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pkg_add(1)
 - a utility for installing and upgrading software packages. 
●
pkg_delete(1)
 - a utility for deleting previously installed software packages. 
●
pkg_info(1)
- a utility for displaying information about software packages. 
●
pkg_create(1)
 - a utility for creating software packages. 
In order to run properly, an application X may require that other applications Y and Z be installed. 
Application X is said to be dependent on these other applications, which is why Y and Z are called 
dependencies of X. In turn, Y may require other applications P and Q, and Z may require application R 
to function properly. This way, a whole dependency tree is formed. 
Packages look like simple 
.tgz
bundles. Basically they are just that, but there is one crucial difference: 
they contain some extra packing information. This information is used by 
pkg_add(1)
 for several 
purposes: 
●
Different checks: has the package already been installed or does it conflict with other installed 
packages or file names? 
●
Dependencies which are not yet present on the system, are automatically fetched and installed, 
before proceeding with the installation of the package. 
●
Information about the package(s) is recorded in a central repository, by default located in 
/var/
db/pkg/
. This will, among other things, prevent the dependencies of a package from being 
deleted before the package itself has been deleted. This helps ensure that an application cannot be 
accidentally broken by a careless user.