On Sat, Jan 12, 2013 at 12:00:45PM +0000, Blue Swirl wrote: > On Fri, Jan 11, 2013 at 7:27 AM, 马磊 <aware....@gmail.com> wrote: > > > > > > On Fri, Jan 11, 2013 at 2:28 PM, Wanlong Gao <gaowanl...@cn.fujitsu.com> > > wrote: > >> > >> On 01/11/2013 11:39 AM, 马磊 wrote: > >> > > >> > > >> > On Thu, Jan 10, 2013 at 8:20 PM, Daniel P. Berrange <berra...@redhat.com > >> > <mailto:berra...@redhat.com>> wrote: > >> > > >> > On Wed, Jan 09, 2013 at 09:37:54PM +0000, Blue Swirl wrote: > >> > > On Wed, Jan 9, 2013 at 7:31 AM, 马磊 <aware....@gmail.com > >> > <mailto:aware....@gmail.com>> wrote: > >> > > > > >> > > > > >> > > >>> Hi, > >> > > >>> The final effect is as follows: > >> > > >>> > >> > > >>> > >> > > >>> [malei@xentest-4-1 Fri Dec 28 ~/honeypot/xen/xen-4.1.2]$ > >> > qemu-img-xen cat > >> > > >>> -f /1/boot.ini ~/vm-check.img > >> > > >>> [boot loader] > >> > > >>> timeout=30 > >> > > >>> default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS > >> > > >>> [operating systems] > >> > > >>> multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows > >> > XP > >> > > >>> Professional" /noexecute=optin /fastdetect > >> > > >>> > >> > > >>> [malei@xentest-4-1 Fri Dec 28 ~/honeypot/xen/xen-4.1.2]$ > >> > qemu-img-xen ls > >> > > >>> -l -d /1/ ~/vm-check.img > >> > > >>> 【name size(bytes) dir? date > >> > > >>> create-time】 > >> > > >>> AUTOEXEC.BAT 0 file 2010-12-22 17:30:37 > >> > > >>> boot.ini 211 file 2010-12-23 > >> > 01:24:41 > >> > > >>> bootfont.bin 322730 file 2004-11-23 > >> > 20:00:00 > >> > > >>> > >> > > >>> > >> > > >>> > >> > > >>> As you see above, the patch add two sub-commands for > >> > qemu-img-xen:cat and > >> > > >>> ls. > >> > > >>> > >> > > >>> For details in the patch, please check the attachment. > >> > > >>> > >> > > >>> > >> > > > > >> > > > Does anyone prefer this feature?! > >> > > > >> > > Nice feature, but this approach would just clutter QEMU and give > >> > only > >> > > readonly FAT or NTFS support. I think a more generally useful > >> > approach > >> > > would be to use NBD or iSCSI to export the block device data from > >> > the > >> > > image file (qemu-nbd already exists) and then make a tool that > >> > uses > >> > > some combination of NBD/iSCSI client, all GRUB file systems and > >> > FUSE > >> > > or other user space methods to access the contents of the > >> > filesystem. > >> > > Probably also UML with a simple guest agent could provide > >> > read/write > >> > > access to any file system that Linux supports. > >> > > >> > The latter is what libguestfs already provides. It boots a Linux > >> > kernel > >> > and mini initrd containing a guest agent, to provide APIs to do > >> > arbitrary > >> > manipulation of guest OS images. > >> > > >> > The reason libguestfs used a linux guest was precisely to avoid > >> > having > >> > to re-implement drivers for every filesystem in existance like this > >> > patch is trying todo. > >> > > >> > I don't think QEMU wants to be in the business of maintaining > >> > filesystem > >> > drivers, so I'd reject this proposed patch. > >> > > >> > Regards, > >> > Daniel > >> > -- > >> > |: http://berrange.com -o- > >> > http://www.flickr.com/photos/dberrange/ :| > >> > |: http://libvirt.org -o- > >> > http://virt-manager.org :| > >> > |: http://autobuild.org -o- > >> > http://search.cpan.org/~danberr/ :| > >> > |: http://entangle-photo.org -o- > >> > http://live.gnome.org/gtk-vnc :| > >> > > >> > > >> > > >> > This feature could be configured to be optional in make file > >> > configuration according to individual preference. > >> > _In addition, the fat32 and ntfs filesystem driver will not change for a > >> > long time so it needs no much maintainence once implemented._ > >> > >> As Daniel and Stefan said, you can try to use libguestfs [libguestfs.org] > >> and qemu-nbd. > >> In libguestfs, we provide virt-cat, virt-ls, etc. And support all the disk > >> type which QEMU supported. > >> > >> Thanks, > >> Wanlong Gao > >> > > > > I used libguest, it's startup takes too long to meet specific requirements > > under some time-sensitive circumstance. > > For maximum speed, the backing formats (QCOW etc) should be > implemented in the kernel directly, somewhat like device mapper or > /dev/loop device. > > A very simple and fast approach without any changes would be to > convince the guest to not to use partitions and instead use one file > system for an entire block device, then the backing file (in raw > format, no QCOW etc) could be manipulated by mounting it with the > loopback device. > > Alternatively, we could implement in QEMU a way to concatenate several > separate files into one, each of the files containing a partition or > some space for partition table. Then the files could be again accessed > with loopback mount. The partition table could be also synthesized. > > I don't know why the loopback mount in the kernel does not support > partitions, that would also solve the problem when using raw files.
The loop module supports partitions through the offset= parameter. For example: # fdisk -lu /dev/sda [...] Device Boot Start End Blocks Id System /dev/sda1 * 2048 1026047 512000 83 Linux /dev/sda2 1026048 500117503 249545728 83 Linux # mount -o loop,offset=$((2048 * 512)) /dev/sda /mnt/boot # mount sda1 Stefan