LiveCDs

LiveCD is a bootable operating system that resides on removable media such as a CD, DVD, or USB flash drive and can run independently of a computer’s installed hard disk. The term originated with optical discs, but many modern Live environments are delivered on USB sticks as well. A typical LiveCD includes a Linux kernel, a set of user-space applications, and the necessary system tools to perform common tasks, such as web browsing, document editing, and system maintenance, without permanent installation.

How it works: The media contains a bootloader that loads a compressed kernel and initramfs into memory. The operating system runs primarily in RAM, using the removable media as a read-only root filesystem, often with a writable overlay to let users save temporary changes. Some distributions offer persistence, allowing user data, installed programs, and settings to be stored on another device so the session can be reused on subsequent boots.

Common uses include testing hardware compatibility, performing system recovery and backups, data rescue, malware analysis, privacy-conscious computing, and educational demonstrations. Notable examples historically include Knoppix, and more recently Ubuntu Live, Debian Live, Fedora Live, and SystemRescueCD. Today, Live USBs have largely supplanted optical LiveCDs due to faster speeds and greater storage, while remaining a convenient means to run a temporary OS without installation.

Limitations and considerations: because the OS mostly runs in memory, performance depends on available RAM, and clever overlays are required for writeable changes. A LiveCD is not a full replacement for a hard-disk installation, and some hardware or software may not be supported out of the box. Windows environments also offer recovery options based on Windows PE that function similarly, though they are not typically referred to as LiveCDs.