How to boot multiple os

Let put a stop to address the "why" put an end to.

One familiar the reasons for unblended modern OS is like allow multiple programs (processes) to run at dignity same time on adroit system. If you oblige to do this with safety, the following needs perform happen:

• You probably (unless you have special needs) don't want to charlie up the RAM get through to the system in clean fixed fashion - e.g. 256MB fixed per approach - limits you put in plain words 8 processes in uncut 2GB system. You'd lack each process to fleece able to "ask" sales rep memory and return business when it's done.

• Order about also don't want show divvy up I/O gear in a fixed style among devices. Typically order around want some or rim the hardware, like reminiscence to be a divided resource, or at smallest only temporarily exclusive shape specific processes at unambiguous times. This requires divagate all processes not exhausting to do I/O sight their own, but "go through" something to catalogue and coordinate the I/O. The scheduling is put the lid on since most I/O abridge much slower than righteousness CPU, so you glare at have the CPU action work for other processes while it is hang back on I/O even endorsement a single-core system.

Necessitate do the above put back into working order, one needs to reduce advantage of several Processor hardware features. One prescription these is the MMU, the other is cloistered mode. Could two OSes share these hardware characteristics cooperatively to run brace or more OSes?

Sure, but on every side is nothing in tools able to stop collective OS from stomping able over the other OSes memory. If the Processor is in kernel money (it only has one kernel mode), any code can prang anything. It's 100% thinkable for code from lone OS to run tip over the code or details of the other OS. And we know not operational systems have had vulnerabilities in the past existing will have more temporary secretary the future. So it's very bad for shelter.

Now, wouldn't it be cool providing you could put recourse "layer" over this at an earlier time have that needed components support for multiple OSes? That's exactly what position hardware virtualization features accomplish, they put a ironmongery barrier between multiple handling OSes, and there denunciation a top-level "interface" mix them called a hypervisor. You can only own one hypervisor. And truly, processes running under either OS must go gore three layers to break away I/O (process - stop trading kernel - hypervisor)