Understanding the general principles of a package manager is the foundation to utilize package managers. The package manager provides a repository of software stored in a dedicated file system location – even for different versions. A specific software and version may depend on another software or libraries forming a tree of dependencies. Software might be incompatible with another software, too.

The user can query available software via commands and loads software using a program of the package manager via the shell command line interface. A package manager then makes it available by manipulating shell variables. Understanding these variables helps to understand system behavior and to debug issues.

• To describe the principles of a package manager and how it interfaces with the shell.

• Describe the general dependency structure of software
• Describe how a package manager makes software available
• Using the export command to print shell variables
• Understand shell variables relevant for executing software and for building software
  1. PATH for executables
  2. LD_LIBRARY_PATH for libraries
  3. MANPATH for manual pages (man command)
  4. PKG_CONFIG_PATH for pkg-config
• Manipulate shell variables to include additional software
  1. Setting shell variables for a single program by prefixing or by using export