User space in the context of Hypervisor

In computer operating systems, a light-weight process (LWP) is a means of achieving multitasking. In the traditional meaning of the term, as used in Unix System V and Solaris, a LWP runs in user space on top of a single kernel thread and shares its address space and system resources with other LWPs within the same process. Multiple user-level threads, managed by a thread library, can be placed on top of one or many LWPs - allowing multitasking to be done at the user level, which can have some performance benefits.

In some operating systems, there is no separate LWP layer between kernel threads and user threads. This means that user threads are implemented directly on top of kernel threads. In those contexts, the term "light-weight process" typically refers to kernel threads and the term "threads" can refer to user threads. On Linux, user threads are implemented by allowing certain processes to share resources, which sometimes leads to these processes to be called "light weight processes". Similarly, in SunOS version 4 onwards (prior to Solaris) "light weight process" referred to user threads.

The Linux console is a system console internal to the Linux kernel. A system console is the device which receives all kernel messages and warnings and which allows logins in single user mode. The Linux console provides a way for the kernel and other processes to send text output to the user, and to receive text input from the user. The user typically enters text with a computer keyboard and reads the output text on a computer monitor. The Linux kernel supports virtual consoles – consoles that are logically separate, but which access the same physical keyboard and display. The Linux console (and Linux virtual consoles) are implemented by the VT (virtual terminal) subsystem of the Linux kernel, and do not rely on any user space software. This is in contrast to a terminal emulator, which is a user space process that emulates a terminal, and is typically used in a graphical display environment.

The Linux console was one of the first features of the kernel and was originally written by Linus Torvalds in 1991 (see history of Linux). There are two main implementations: framebuffer and text mode. The framebuffer implementation is the default in modern Linux distributions, and together with kernel mode setting, provides kernel-level support for display hardware and features such as showing graphics while the system is booting. The legacy text mode implementation was used in PC-compatible systems with CGA, EGA, MDA and VGA graphics cards. Non-x86 architectures used framebuffer mode because their graphics cards did not implement text mode. The Linux console uses fixed-size bitmap, monospace fonts, usually defaulting to 8x16 pixels per character.