Monolithic kernel: Difference between revisions
imported>Alexvsbudder The DragonFly BSD wiki page says it has a hybrid kernel. |
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{{Short description|OS that runs entirely in kernel-mode}} | {{Short description|OS that runs entirely in kernel-mode}} | ||
{{Use dmy dates|date=September 2022}} | {{Use dmy dates|date=September 2022}} | ||
{{More citations needed|23 October 2025|date=October 2025}} | |||
[[File:OS-structure2.svg|thumb|right|Structure of monolithic kernel, [[microkernel]] and [[hybrid kernel]]-based operating systems|580px]] | [[File:OS-structure2.svg|thumb|right|Structure of monolithic kernel, [[microkernel]] and [[hybrid kernel]]-based operating systems|580px]] | ||
A '''monolithic kernel''' is an [[operating system]] [[software architecture|architecture]] with the entire operating system running in [[kernel space]]. The monolithic model differs from other architectures such as the [[microkernel]]<ref>{{cite web |title=Modular system programming in Minix3 |url=http://www.usenix.org/publications/login/2006-04/openpdfs/herder.pdf}}</ref><ref>{{cite web |title=Server-Client, or layered structure |url=http://www.gridbus.org/~raj/microkernel/chap2.pdf |publisher=The Design of PARAS Microkernel |access-date=15 July 2009 |archive-url=https://web.archive.org/web/20100717085530/http://www.gridbus.org/~raj/microkernel/chap2.pdf |archive-date=17 July 2010 |url-status=dead }}</ref> in that it alone defines a high-level virtual interface over [[computer hardware]]. A set of primitives or [[system call]]s implement all operating system services such as [[Process (computing)|process management]], [[Concurrency (computer science)|concurrency]], and [[memory management]]. | A '''monolithic kernel''' is an [[operating system]] [[software architecture|architecture]] with the entire operating system running in [[kernel space]]. The monolithic model differs from other architectures such as the [[microkernel]]<ref>{{cite web |title=Modular system programming in Minix3 |url=http://www.usenix.org/publications/login/2006-04/openpdfs/herder.pdf}}</ref><ref>{{cite web |title=Server-Client, or layered structure |url=http://www.gridbus.org/~raj/microkernel/chap2.pdf |publisher=The Design of PARAS Microkernel |access-date=15 July 2009 |archive-url=https://web.archive.org/web/20100717085530/http://www.gridbus.org/~raj/microkernel/chap2.pdf |archive-date=17 July 2010 |url-status=dead }}</ref> in that it alone defines a high-level virtual interface over [[computer hardware]]. A set of primitives or [[system call]]s implement all operating system services such as [[Process (computing)|process management]], [[Concurrency (computer science)|concurrency]], and [[memory management]]. | ||
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**[[AIX]] | **[[AIX]] | ||
**[[Oracle Solaris]] | **[[Oracle Solaris]] | ||
*[[ | *[[DOS]] | ||
**[[Windows 1.0]] to [[Windows 3.1]] | |||
**[[Windows 9x]] | **[[Windows 9x]] | ||
*[[OpenVMS]] | *[[OpenVMS]] | ||
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==Loadable modules== | ==Loadable modules== | ||
Modular operating systems such as [[OS-9]] and most modern monolithic-kernel operating systems such as [[OpenVMS]], [[Linux kernel|Linux]], [[FreeBSD]], [[NetBSD | Modular operating systems such as [[OS-9]] and most modern monolithic-kernel operating systems such as [[OpenVMS]], [[Linux kernel|Linux]], [[FreeBSD]], [[NetBSD]], [[Oracle Solaris|Solaris]], and [[AIX]] can dynamically load (and unload) executable [[loadable kernel module|kernel modules]] at runtime. | ||
This modularity of the operating system is at the binary (image) level and not at the architecture level. Modular monolithic operating systems are not to be confused with the architectural level of modularity inherent in [[microkernel|server-client]] operating systems (and its derivatives sometimes marketed as [[hybrid kernel]]) which use microkernels and servers (not to be mistaken for modules or daemons). | This modularity of the operating system is at the binary (image) level and not at the architecture level. Modular monolithic operating systems are not to be confused with the architectural level of modularity inherent in [[microkernel|server-client]] operating systems (and its derivatives sometimes marketed as [[hybrid kernel]]) which use microkernels and servers (not to be mistaken for modules or daemons). | ||
Latest revision as of 12:36, 30 October 2025
Template:Short description Template:Use dmy dates Template:More citations needed
A monolithic kernel is an operating system architecture with the entire operating system running in kernel space. The monolithic model differs from other architectures such as the microkernel[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 loadable kernel modules.
Examples
Loadable modules
Modular operating systems such as OS-9 and most modern monolithic-kernel operating systems such as OpenVMS, Linux, FreeBSD, NetBSD, Solaris, and AIX can dynamically load (and unload) executable kernel modules at runtime.
This modularity of the operating system is at the binary (image) level and not at the architecture level. Modular monolithic operating systems are not to be confused with the architectural level of modularity inherent in server-client operating systems (and its derivatives sometimes marketed as hybrid kernel) which use microkernels and servers (not to be mistaken for modules or daemons).
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.
However, in some cases, loading modules dynamically (as-needed) helps to keep the amount of code running in kernel space to a minimum; for example, to minimize operating system footprint for embedded devices or those with limited hardware resources. Namely, an unloaded module need not be stored in scarce random access memory.