On Mon, Jan 14, 2013 at 9:13 AM, Stefan Hajnoczi <stefa...@gmail.com> wrote: > 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
Doesn't this make also the space after sda1, up to end of the device accessible via the partition? It could be a problem if the file system in sda1 (due to a bug) referenced blocks in sda2, or someone did dd if=/dev/zero of=/dev/loop0 to clear the partition. > > Stefan
