Transcript Booting
Booting Booting • Booting is the process of powering it on and starting the operating system. • power on your machine, and in a few minutes your computer will be ready to use. • To start your machine, you need to turn on the monitor and computer. • I usually turn on the monitor first so that I don't forget. If you have a printer you can turn that on as well. • If all goes well, you will see an image on your monitor, and your computer will start the boot process. • If you see no image, make sure the monitor cable is plugged in, and make sure that your computer and monitor are both plugged in and are turned on. Booting • Usually your computer will beep once or twice on bootup. • Repeated beeping combined with no display and/or error messages indicate that something might be wrong. • Otherwise, your computer will proceed to perform a power-on self test. Booting • When your computer first starts it will start counting its memory in the top left corner of the screen. • You may see the keyboard lights flash, see the floppy and/or CDROM lights turn on, and hear the floppy and hard drives spin. • Then your computer will beep (possibly a few times). • This process is called the POST: power on self test. • On most machines, the POST is followed by one or two screens of information about your hardware: the sizes of your hard drives, the extra cards that are on your system, and so on. • In a few seconds the GRUB menu should appear. • It is safe to power off your machine during this stage. Booting • GRUB Screen • GRUB stands for "GRand Unified Bootloader". • Its job is to start up the operating system on a computer. • After the POST screens you should see the GRUB screen. • If you had multiple operating systems on your computer, you would be able to choose which operating system to boot at this step. • Probably you will want to leave the GRUB screen alone. • In a few seconds it will start booting • It is safe to power off your computer at the GRUB screen. Booting • In order for a computer to successfully boot, its BIOS (Basic Input/Output System), operating system and hardware components must all be working properly; failure of any one of these three elements will likely result in a failed boot sequence. Booting • When the computer's power is first turned on, it look to the system's ROM BIOS for its first instruction in the startup program. • The ROM BIOS stores the first instruction, which is the instruction to run the power-on self test (POST), in a predetermined memory address. • POST begins by checking the BIOS chip and then tests CMOS RAM. • If the POST does not detect a battery failure, it then continues to initialize the CPU, checking the inventoried hardware devices (such as the video card), secondary storage devices, such as hard drives and floppy drives, ports and other hardware devices, such as the keyboard and mouse, to ensure they are functioning properly. Booting • Once the POST has determined that all components are functioning properly and the CPU has successfully initialized, the BIOS looks for an OS to load. • The BIOS typically looks to the CMOS chip to tell it where to find the OS, and in most PCs, the OS loads from the C drive on the hard drive even though the BIOS has the capability to load the OS from a floppy disk, CD or ZIP drive. • The order of drives that the CMOS looks to in order to locate the OS is called the boot sequence, which can be changed by altering the CMOS setup. • Looking to the appropriate boot drive, the BIOS will first encounter the boot record, which tells it where to find the beginning of the OS and the subsequent program file that will initialize the OS. Booting • Once the OS initializes, the BIOS copies its files into memory and the OS basically takes over control of the boot process. • Now in control, the OS performs another inventory of the system's memory and memory availability (which the BIOS already checked) and loads the device drivers that it needs to control the peripheral devices, such as a printer, scanner, optical drive, mouse and keyboard. This is the final stage in the boot process, after which the user can access the system’s applications to perform tasks. Booting • A