Linked by David Adams on Wed 13th Aug 2008 16:57 UTC, submitted by irbis
"I recently had the opportunity to interview Andrew S. Tanenbaum, creator of the extremely secure Unix-like operating sytem MINIX 3. Andrew is also the author of Operating Systems Design and Implementation, the must-have book on programming and designing operating systems, and the man whose work inspired Linus Torvalds to create Linux. He has published over 120 works on computers (that's including manuals, second and third editions, and translations), and his works are known all over the world, being translated into a variety of different languages for educational use universally. He is currently a professor of computer science at Vrije University in Amsterdam, the Netherlands."
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Member since:
2008-06-24
Yes. It's a true microkernel using only a mere 4000 line of code or so. Everything including file server, device drivers, UNIX Server, etc all run in userspace versus Kernel space. This means that nearly everything can be upgraded while the system is live.
The Kernel itself only handles basic hardware IPC (inter-process communication) which allows the kernel what 'modules' can access what piece of hardware and pieces from other modules. The end result is that buffer overflows are a thing of the past (in theory)
With Linux, most BSDs, Windows... etc all run with drivers compiled and running in Kernel space. This allowed ANY driver to access ANY piece of hardware or pieces of other drivers. The fundamental flaw going this route is that any single piece of code-error (even 1 line) in a driver can bring down an whole system. Running drivers in userspaces allows the reincarnation server to kill the running driver, restart it and log what driver did what without taking the whole system down. Windows crashes, about 60-80% of the time or so, are caused by bad driver code. It's also believed that drivers carry about 3-7x more bugs than ANY other piece of code in the OS.
Windows NT had tried going this route when it was first released, but failed miserably. Vista is another example of Windows going this route (to each his own on how well they are doing). DragonflyBSD and Darwin(Mac OSX Kernel) are examples of "Hybrid" kernels where some parts (like certain drivers) are run in kernelspace, leaving other parts running in userspace.
Hope that helps.
edit .. FUSE on linux is running Filesystem in Userspace.
Linus seems to dislike microkernels considerably, claiming they cause much unnecessary overhead. 5000 IPC calls, on a 2.2ghz Athlon, expect to only use about 1% of the CPU (not very much at all). Each person has their opinion on performance:security/stability. I'm not campaigning against Monolithic kernels (as I'm a big believer in OpenBSD and how the project is run/audited), but as more and more drivers and features are added to kernels, the more and more code is added along with more and more bugs.
Edited 2008-08-13 19:01 UTC