On Thu, Jan 08, 2009 at 08:15:25PM +0200, Uri Lublin wrote:
The purpose of this prefix is to
1. Provide a way to know the backing file format without probing
it (setting the format upon creation time).
2. Enable using qcow2 format (and others) over host block devices.
(only if the user specifically asks for it).
If no fmt:FMT: is provided we go back to probing.
I still don't like the fact that this is inventing a second syntax
for specifying format that's different to the syntax used for the
existing -drive parameter, which is
-drive file=/some/path,format=qcow2,....other disk options...
backing file format is qcow2 (even though it's on a host block device)
$ qemu-img create -b fmt:qcow2:/dev/loop0 -f qcow2 /tmp/uuu.qcow2
I'd prefer to see a '-F' flag to specify format of backing file and
leave syntax of existing -b arg alone
$ qemu-img create -F qcow2 -b /dev/loop0 -f qcow2 /tmp/uuu.qcow2
force backing file format to raw (no probing)
$ qemu-img create -f raw /tmp/image1.raw 10G
$ qemu-img create -b fmt:raw:/tmp/image1.raw -f qcow2 /tmp/image1.qcow2
$ qemu-img create -F raw -b /tmp/image1.raw -f qcow2 /tmp/image1.qcow2
Use together with other protocols, e.g. nbd
$ qemu-nbd -v -n --snapshot -t -k /tmp/uuu.socket
fmt:qcow2:/tmp/images/uuu.qcow2 &
Should just add a -f arg to qemu-nbd to specify format so it
follows qemu-img style, eg
$ qemu-nbd -v -n --snapshot -t -k /tmp/uuu.socket \
-f qcow2 /tmp/images/uuu.qcow2 &
$ qemu-img info nbd:unix:/tmp/uuu.socket
$ qemu-system-x86_64 -snapshot -hda nbd:unix:/tmp/uuu.socket
Or fat
$ qemu-system-x86_64 -hda fmt:qcow2:/tmp/uuu.qcow2 -hdb
fat:floppy:/tmp/images
This is unneccessary, since -hda is deprecated, and there's a
new -drive arg that already has ability to set format explicitly,
as well as many other flags that you need when setting up disks.
$ qemu-system-x86_64 \
-drive index=0,format=qcow2,file=/tmp/uuu.qcow2 \
-drive index=1,format=fat:floppy,file=/tmp/images
Regards,
Daniel