From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sun, 11 Aug 2013 20:27:13 +0100 From: "Richard W.M. Jones" Message-ID: <20130811192713.GT5918@redhat.com> References: <20130809204355.GA10864@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [uml-devel] Using UML in libguestfs To: Geert Uytterhoeven Cc: user-mode-linux-devel@lists.sourceforge.net List-ID: On Sun, Aug 11, 2013 at 09:05:08PM +0200, Geert Uytterhoeven wrote: > On Fri, Aug 9, 2013 at 10:43 PM, Richard W.M. Jones wrote: > > * UML is pretty fast! It's certainly faster (by a factor of > 5) than > > spinning up a lightweight KVM VM. > This is interesting. Typically people say you have to use KVM or XEN > for good virtualization performance. But for that you need > sufficient privileges. I think this is true of Xen, but to be fair to KVM it doesn't require special privileges, with one exception. If you want KVM to use a tunX network interface then you have to start it as root (or use a setuid helper). I think this is probably true of UML too although I've not explored UML's networking yet. Basically it's a restriction in Linux itself. > With UML, all you need is to be able to compile and run your own > executables. With libguestfs we specifically don't want people to use root, so UML not requiring root was one reason why it's possible to write a UML-based libguestfs backend. I now have a UML backend for libguestfs working, with a significant part of the testsuite passing too. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming blog: http://rwmj.wordpress.com Fedora now supports 80 OCaml packages (the OPEN alternative to F#)