System startup, inittab, and run levels

When we power on the Linux system, the Shell scripts are run one after another and the Linux system is initialized. These scripts start various services, daemons, start databases, mount discs, and many more applications. Even during the shutting down of the system, certain Shell scripts are executed so that important system data and information can be saved to the disk and the applications are properly shut down. These are called boot, startup, and shutdown scripts. These scripts are copied during installation of the Linux operating system in your computer. As a developer or administrator, understanding these scripts may help you in understating and debugging the Linux system. If required, you can customize these scripts if the need arises.

The kernel startup and init process

In our computers, there is one EPROM chip called BIOS, which is situated on the motherboard or main board of our computers. When we power on, the processor starts executing a...