Lguest vs. KVM

Lguest allows for the simultaneous operation of multiple instances of a 32-bit kernel, and you can start it by executing the command modprobe lg followed by Documentation/lguest/lguest to create a new guest. I highly recommend trying it out because lguest is incredibly easy to set up and use. Its advantages are noteworthy: I can boot kernels for testing in under a second, which is about ten times faster than qemu and a hundred times quicker than traditional boot methods. Furthermore, by utilizing a pty for console access, you can perform operations like piping outputs through grep. Lguest includes a full kernel patch, featuring the launcher, and is compatible with versions 2.6.23-git13 and newer. The main purpose of lguest is to maintain the isolation of guests, preventing them from directly accessing the host system, except via virtual devices provided by the host, even in cases where the guest may pose a security threat. However, a potentially dangerous guest kernel can still pin host memory, but this is restricted to the amount allocated for the guest itself. While many images are set up to create virtual consoles such as (/dev/tty0, etc.), lguest designates its console as /dev/hvc0, which enhances its functionality. This unique console setup, along with its rapid boot times, makes lguest an invaluable resource for developers looking to efficiently test kernel modifications without the complexities associated with full virtualization environments. Thus, lguest stands out as both a practical tool for quick testing and a means to ensure the integrity of the host system.

KVM, or Kernel-based Virtual Machine, is a robust virtualization platform designed for Linux systems that run on x86 hardware with virtualization support, such as Intel VT or AMD-V. It consists of a loadable kernel module named kvm.ko, which forms the core of the virtualization framework, and a processor-specific module, either kvm-intel.ko or kvm-amd.ko, tailored for Intel or AMD processors respectively. With KVM, users can create and manage multiple virtual machines that can execute unmodified operating systems like Linux or Windows. Each of these virtual machines is equipped with its own allocated virtual hardware, which includes components such as network interface cards, storage devices, and graphics adapters. As an open-source initiative, KVM has been part of the mainline Linux kernel since version 2.6.20, and its userspace has been integrated into the QEMU project since version 1.3, facilitating broader adoption and compatibility across various virtualization tasks. This seamless integration allows for a diverse range of applications and services to leverage KVM’s capabilities effectively. Additionally, the continuous development of KVM ensures that it keeps pace with advancements in virtualization technology.