(रेवंत) Revant Nandgaonkar wrote:
On 12/13/05, Amol Hatwar amol@hatwar.org wrote:
*chop*
and my question was whether Linux had the capability of FreeBSD kernel to load multiple kernels on top of it.
You do have User Mode Linux (UML) don't you? :). Why, this very mail you are reading now is being was sent through Qmail running in a virtual server (Not One, but many Linux Kernels running on top of another Linux Kernel).
Is this like VMWare? a single file handling filesystems and OS data?
Well, unlike they call it Virtual "Machine", UML is a kernel and can be called "Virtual OS". As the kernel itself provides its own system call interface to Kernels.
But you can achieve almost all the functionality VMWare can support except two major differences that I know.
1. You can port only Linux kernels on UML. 2. VMWare is not free (Freedom-wise and Money-wise), UML is *free*.
You can load multiple kernels simultaneously, run different applications/servers on different kernels. The UML kernel sits over the hardware and all other kernels are loaded into user space.
You can control the amount of Memory, Diskspace and CPU cycles utilized by the kernels sitting on top of UML. Each of these kernels are virtually "separate machines" but they don't have access to hardware directly. Instead they access virtual drives, virtual network adapters and Virtual X-windows displays provided by UML environment.
You can create filesystems that Linux supports (such as ext2, ext3, reiserfs..) and mount these UML filesystems.
Though UML is useful, it is not right for testing device drivers and it is currently ported only on x86 platform.
Regards,