Bootability

Bootability refers to the ability of a computer or device to start from a powered-off state by loading and executing software from a bootable medium. In most systems, the process begins with firmware—BIOS in older hardware or UEFI in modern machines—that initializes hardware and selects a boot device according to a boot order. The firmware loads a boot loader, which then loads the operating system kernel into memory and hands control to it. The kernel starts the init system, mounts the root filesystem, and begins user-space operation.

Bootable media include internal hard drives, USB flash drives, optical discs, and network boot environments (PXE). A bootable USB or disc typically contains a boot loader, a minimal environment if needed, and an image of an operating system. On BIOS-based systems, boot information is stored in the Master Boot Record or the Volume Boot Record; on UEFI-based systems, bootloaders reside on an EFI System Partition and may require signatures for Secure Boot.

Creating bootable media often involves writing an image to a target device using tools such as Rufus, balenaEtcher, dd, or similar utilities. ISO, IMG, or other disk images are common formats. Verification via checksums or digital signatures helps ensure integrity and compatibility, particularly with Secure Boot.

Common issues include incorrect boot device selection, damaged media, missing or corrupted bootloaders, and Secure Boot preventing unsigned software from loading. Troubleshooting steps include adjusting boot order, repairing or reinstalling the bootloader, or temporarily disabling Secure Boot in some environments. Virtual machines and cloud environments frequently provide bootable images that can be tested without physical hardware.