Linux Shells by Example

1.3. System Startup and the Login Shell

When you start up your system, the first process is called init. Each process has a process identification number associated with it, called the PID. Because init is the first process, its PID is 1. The init process initializes the system and then starts another process to open terminal lines, and sets up the standard input (stdin), standard output (stdout), and standard error (stderr), which are all associated with the terminal. The standard input normally comes from the keyboard; the standard output and standard error go to the screen. At this point, a login prompt (Login:) appears at your console. After you type your login name, you are prompted for a password (you will be given up to 10 chances to enter ...