käynnistyslevyt

Käynnistyslevy, often referred to as a boot disk or startup disk, is a storage medium containing the necessary files and instructions to initiate the startup process of a computer. When a computer is powered on, it typically looks for a bootable device to load the operating system. This device is usually the primary hard drive, but it can also be a USB drive, CD, DVD, or a network location.

The boot process begins with the BIOS or UEFI firmware, which performs a Power-On Self-Test (POST) and then searches for a bootable device according to a predefined boot order. Once a bootable device is found, the firmware loads the boot sector from that device into the computer's random-access memory (RAM). The boot sector contains a small program, known as the boot loader, which is responsible for loading the operating system kernel and other essential system files.

Käynnistyslevyt are crucial for several reasons. They allow users to install or reinstall an operating system, recover a system from a crash or corruption, run diagnostic tools, or even operate a computer without a main hard drive. In the past, floppy disks were commonly used as käynnistyslevyt. Today, USB drives and optical media are more prevalent, offering larger storage capacities and faster transfer speeds. Creating a bootable USB drive involves formatting the drive and copying specific boot files and the desired operating system image onto it.