Linux comes with many packages. Most of these packages depend on some other packages installed on your system. In RPM terms, packages provide capabilities and depend on capabilities that other packages provide. When the rpm command checks the RPM database for dependencies, it checks to ensure that all the capabilities that a given package requires are met by other installed packages.

You can trace the capabilities a package requires with the --requires option to the rpm command. You can see what capabilities a package provides for others with the --provides option.

Once you know a capability, you can query which package provides that capability with the --whatprovides option to the rpm command. And you can see which packages require that capability with the --whatrequires option.

Triggers are an extended form of dependencies. A trigger is a script that gets executed when other packages are installed or removed. This allows a package with a high dependence on another package to track changes in that package and reconfigure itself as needed.

The next chapter delves into transactions, which provide a safe means to install a set of packages. With transactions, either all the packages get installed, or none.