l i n u x - u s e r s - g r o u p - o f - d a v i s
L U G O D
 
Next Meeting:
August 5: Social gathering
Next Installfest:
TBD
Latest News:
Jul. 4: July, August and September: Security, Photography and Programming for Kids
Page last updated:
2003 Mar 31 16:29

The following is an archive of a post made to our 'vox-tech mailing list' by one of its subscribers.

Report this post as spam:

(Enter your email address)
[vox-tech] definition of a virtual machine
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[vox-tech] definition of a virtual machine



can someone tell me if this is a formally correct explanation of what a
virtual machine is?

pete


A "real computer" provides an operating system many things, including a
CPU, I/O channels, memory, a BIOS to provide low level access to
motherboard and I/O resources, etc.  When an operating system wants to
write to a hard drive, it communicates through a device driver that
interfaces directly with the hardware device memory.

However, it's possible to give a program all the hardware resources it
needs.  When it wants to access a hard drive, give it some memory to
write to.  When it wants to set an IRQ, give it some bogus instructions
that lets it think it set an IRQ.  If you do this correctly, then in
principle, there's no way for the application to know whether it's
really accessing hardware or tricked by being given resources which
simulate hardware.  A virtual machine is the environment which tricks
applications into believing they're running on a real computer.  It
provides all the services that a real computer would provide.
		
VM's were used initially in the 1960's to emulate time shared operating
systems, but these days we use them to run software which was written
for foreign operating systems, or more commonly, an entire operating
system.  Because of the nature of the VM, the foreign OS can't tell the
difference between operating in a VM or in a "real" machine.
_______________________________________________
vox-tech mailing list
vox-tech@lists.lugod.org
http://lists.lugod.org/mailman/listinfo/vox-tech



LinkedIn
LUGOD Group on LinkedIn
Sign up for LUGOD event announcements
Your email address:
facebook
LUGOD Group on Facebook
'Like' LUGOD on Facebook:

Hosting provided by:
Sunset Systems
Sunset Systems offers preconfigured Linux systems, remote system administration and custom software development.

LUGOD: Linux Users' Group of Davis
PO Box 2082, Davis, CA 95617
Contact Us

LUGOD is a 501(c)7 non-profit organization
based in Davis, California
and serving the Sacramento area.
"Linux" is a trademark of Linus Torvalds.

Sponsored in part by:
O'Reilly and Associates
For numerous book donations.