on 06-Jul-2021 (Tue)

A monolithic kernel is an operating system architecture where the entire operating system is working in kernel space.

The monolithic model differs from other operating system architectures (such as the microkernel architecture)^[1][2] in that it alone defines a high-level virtual interface over computer hardware.

A set of primitives or system calls implement all operating system services such as process management, concurrency, and memory management. Device drivers can be added to the kernel as modules.

Modular operating systems such as OS-9 and most modern monolithic operating systems such as OpenVMS, Linux, BSD, SunOS, AIX, and MULTICS can dynamically load (and unload) executable modules at runtime.

Practically speaking, dynamically loading modules is simply a more flexible way of handling the operating system image at runtime—as opposed to rebooting with a different operating system image. The modules allow easy extension of the operating systems' capabilities as required.^[3] Dynamically loadable modules incur a small overhead when compared to building the module into the operating system image.

The Linux kernel is a free and open-source,^[5][6] monolithic, modular,^[7] multitasking, Unix-like operating system kernel.^[8]

-source , ^{[5] [6]} monolithic , modular , ^[7] multitasking , Unix-like operating system kernel . ^[8] It was conceived and created in 1991 by Linus Torvalds^[9] for his i386-based PC, and it was soon adopted as the kernel for the GNU operating system,^[10] which was created as a free replacement for UNIX.^[11] Since then, it has spawned a plethora of operating system distributions, commonly also called Linux.

Linux is deployed on a wide variety of computing systems, such as embedded devices, mobile devices (including its use in the Android operating system), personal computers, servers, mainframes, and supercomputers.^[12]

Most of the Linux kernel code is written using the GNU extensions of GCC^[19][20] to the standard C programming language and with the use of architecture specific instructions (ISA). This produces a highly optimized executable (vmlinux) with respect to utilization of memory space and task execution times.^[21]

Day-to-day development discussions take place on the Linux kernel mailing list (LKML). Changes are tracked using the version control system git, which was created by Torvalds as a bespoke replacement for BitKeeper. Linux as a whole is released under the GNU General Public License version 2 (GPLv2),^[22] but it also contains several files under other compatible licenses,^[4] and an ad hoc exemption for the user space API header files (UAPI).

Linux is a monolithic kernel with a modular design (e.g., it can insert and remove loadable kernel modules at runtime), supporting most features once only available in closed source kernels of non-free operating systems.

a virtual filesystem on top of several concrete filesystems (ext4, Btrfs, XFS, JFS, FAT32, and many more);