> From: Prasad Joshi > Sent: 10 November 2010 13:01 > To: Stefan Hajnoczi > Cc: Keqin Hong; kvm@xxxxxxxxxxxxxxx > Subject: RE: Unable to start VM using COWed image > From: Stefan Hajnoczi [stefanha@xxxxxxxxx] > Sent: 10 November 2010 12:47 > To: Prasad Joshi > Cc: Keqin Hong; kvm@xxxxxxxxxxxxxxx > Subject: Re: Unable to start VM using COWed image > On Wed, Nov 10, 2010 at 12:40 PM, Prasad Joshi <P.G.Joshi@xxxxxxxxxxxxxxxxxxxxx> wrote: >> From: Stefan Hajnoczi [stefanha@xxxxxxxxx] >> Sent: 10 November 2010 11:12 >> To: Prasad Joshi >> Cc: Keqin Hong; kvm@xxxxxxxxxxxxxxx >> Subject: Re: Unable to start VM using COWed image > > On Wed, Nov 10, 2010 at 10:08 AM, Prasad Joshi > <P.G.Joshi@xxxxxxxxxxxxxxxxxxxxx> wrote: >> Where can I get the code of the qemu-kvm program? >> I cloned the qemu-lvm git repository and compiled the code. But it looks like qemu-kvm program is not part of this code.-- > >> qemu-kvm.git contains the qemu-kvm codebase but the binary is built in >> x86_64-softmmu/qemu-system-x86_64. Distro packages typically rename >> it to qemu-kvm. > > Thanks Stefan for your reply. > > I guess you pointed out the problem in the first mail. QEMU places a restriction on location of the COWed file. The source image and COWed image should be in the same drectory. > > In my case the source image was in directory /var/lib/libvirt/images/ and the COWed image was in /home/prasad/Virtual directory. > While debuging the source code using gdb I realized this limitation. It would be good to fix this problem. I will see if I can solve this problem. > This behavior is a feature. You chose to use a relative backing file > path when you used qemu-img create -b <relative-path>. > If you want an absolute path you need to use qemu-img create -b > /home/prasad/Virtual/... (i.e. specify an absolute path instead of a > relative path). > Oh I see. I am such a stupid. ha ha ha ha > Thanks a lot for letting me know. > It worked after using absolute paths. Gr8 Thanks a lot. Though specifying the absolute path for source image worked for me. Can any one please let me know the situation in which one would not want to specify the absolute path? How does relative path help? Advantage of using relative path rather than absolute path. I think using the absolute path would always work. >> One more question on the same lines, >> How does QEMU detect the file is COWed and the name of the file (not whole path) from it is COWed? > COW support comes from the image file format that you choose. A qcow > file is not just a raw image file like the kind you can dd from a real > disk. Instead it has its own file format including a header and > metadata for tracking allocated space. The header contains the name > of the backing file. > Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
