Le vendredi 25 janvier 2008 à 09:18 -0600, Anthony Liguori a écrit : > Laurent Vivier wrote: > > Hi, > > > > this patch allows to mount qemu disk images on the host. > >
Sorry, I didn't see you did a similar work 19 months ago. > Note, the general problem with this approach is that mounting a NBD > device locally with write access can lead to dead locks. If you look > through the mailing list archives, you'll find a number of conversations > on the topic. Yes, I experimented some problems with heavily loaded I/O (2 * dbench 64 on a 4 CPUs SMP) But perhaps to edit config files or fsck partition of a virtual machine it is acceptable. What I'm wondering is how loop and device mapper can work ? > Regards, > > Anthony Liguori Thank you, Laurent > > It is based on the Network Block Device protocol and allows qemu-img to > > become an NBD server (Yes, Anthony, userspace block device is the right > > way to do that... :-P ). > > > > Once you've applied the attached patch to Qemu and build the binaries, > > you can use it like that: > > > > # ./qemu-img server -d 1234 etch.qcow2 > > > > This starts an NBD server on port 1234. This server will expose > > the disk image etch.qcow2. "-d" means it will be daemonize and will run > > in background. > > > > Then you need to connect the block device to the server: > > > > # nbd-client localhost 1234 /dev/nbd0 > > Negotiation: ..size = 4194304KB > > bs=1024, sz=4194304 > > > > This will link etch.qcow2 to /dev/nbd0. > > > > Then to see partitions, you can use kpartx, as explained Daniel, or my > > patched loop modules (I can send an updated and bug free version). > > ... > > # kpartx -a /dev/nbd0 > > ... > > or > > ... > > # rmmod loop > > # insmod drivers/block/loop.ko max_part=64 > > # losetup -f /dev/nbd0 > > ... > > # mount /dev/loop0p1 /mnt > > # ls /mnt > > bench cdrom etc initrd.img media proc selinux tmp vmlinuz > > bin clients home lib mnt root srv usr > > boot dev initrd lost+found opt sbin sys var > > # cd > > # umount /mnt > > # losetup -d /dev/loop0 > > # nbd-client -d /dev/nbd0 > > > > TODO: security/host client checking, device lock... > > > > As usual all comments are welcome, > > have fun, > > Laurent > > > > > > -- ----------------- [EMAIL PROTECTED] ------------------ "La perfection est atteinte non quand il ne reste rien à ajouter mais quand il ne reste rien à enlever." Saint Exupéry