Chapter 2. Configuring Unix

Although you may have heard of people recompiling their kernels (the lowest-level "core" of a Unix system), Unix's extreme configurability is accessible with just a text editor and an understanding of the files used to start the system's resident programs (the daemons).

After the kernel is finished initializing your system's hardware, it starts the init program. init is one of the few programs started directly by the kernel (it always gets process ID 1), and it launches the scripts that start the daemons during the normal boot process and then begins the system's normal multiuser operations.

Although we're considering Cygwin a Unix system for this book, it doesn't depend on the init system because the Windows host OS is already up and running before Cygwin processes can start.

When users log in to a Unix system, their preferred shell (listed in the /etc/passwd file) starts up and loads several scripts. These global shell-configuration scripts let the administrator specify application locations and other general settings, and give users a way of personalizing their shells with custom environment variables, shell functions, and command aliases.