Introducing process basics

A running instance of a program is called a process. A program stored in the hard disk or pen drive is not a process. When that stored program starts executing, then we say that process has been created and is running.

Let's very briefly understand the Linux operating system boot-up sequence:

1. In PCs, initially, the BIOS chip initializes system hardware, such as PCI bus, and display device drivers.
2. Then the BIOS executes the boot loader program.

3. The boot loader program then copies the kernel in the memory and, after basic checks, it calls a kernel function start_kernel().
4. The kernel then initializes the OS and creates the first process called init.
5. You can check the presence of this process with the following command:

$ ps -ef

6. Every process in the OS has one numerical identification associated with it. It is called a process ID. The process ID of the init process is 1. This process is the parent process of all user space processes.
7. In the Linux OS, every new process is created...