In Linux, during boot up, the system looks for the boot sector on the hard disk. Once it finds the boot sector, it then searches for a boot loader. In turn, the boot loader loads the boot manager. In Linux, this will usually be either GRUB or GRUB2. After this stage, the user is presented with a boot menu. Finally, the user is given the opportunity to either select an operating system to load or edit an existing entry. The options available are usually going to be different versions of the Linux kernel. Sometimes, it might be an entirely different Linux distribution. However, in mixed environments, you may come into contact with another operating system, such as Microsoft Windows.
After the user selects a Linux kernel, depending on the Linux distribution release, a single process is started, known as init, which stands for initialization. init is often...