[H-GEN] User mode Linux

[David Jericho]

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On Fri, Jan 24, 2003 at 12:56:52PM +1000, Robert Brockway wrote:
> > redirect the system calls to the kernel process?  I guess it could use a
> 
> Traps them somehow and feeds them out (boy thats a non-technical answer :)

To quote from their intro pages (http://user-mode-linux.sourceforge.net)

"UML runs its scheduler independently of the host scheduler - the host 
scheduler simply implements the decisions made by the UML scheduler. Similarly, 
UML runs its own VM system, allocating backing memory from a pool that it 
considers to be physical memory, mapping that memory as needed into its 
process virtual address spaces and its own virtual memory. If needed, and 
it has swap configured, it will swap.

Basically, anything in Linux that's not hardware-specific just works. This 
includes kernel modules, the filesystems, software devices, and network 
protocols." 

> > which leads me to ask the question: do processes under the UML run as
> > seperate processes on the host machine or are they loaded into the
> > userspace of the UML kernel process?
> 
> As far as I can tell they are loaded into the userspace of the UML kernel
> process.  No modifications are made to the host system kernel so I can't
> see any trickery going on at that level - it must be a clean approach
> which holds the virual processes fully within the address space allocated
> to the UML kernel process.

As far as the global system process table is concerned, all
processes are userspace. You can kill off uml userspace applications
from the host system using a simple kill. You can also see all
applications in the uml userspace in the global process table.

-- 
David Jericho
Senior Systems Administrator, Bytecomm Pty Ltd


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