1.2. 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. Since 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 set 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 would appear on your terminal.
After you type your login name, you will be prompted for a password. The /bin/login program then verifies your ...
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