Am 14.06.2012 16:17, schrieb Dong Xu Wang: > On Thu, Jun 14, 2012 at 10:11 PM, Kevin Wolf <kw...@redhat.com> wrote: >> Am 14.06.2012 16:06, schrieb Dong Xu Wang: >>> On Thu, Jun 14, 2012 at 6:51 PM, Kevin Wolf <kw...@redhat.com> wrote: >>>> Am 13.06.2012 16:36, schrieb Dong Xu Wang: >>>>> add-cow file can't live alone, must together will image_file and >>>>> backing_file. >>>>> If we implement qemu-img convert operation for add-cow file format, we >>>>> must >>>>> create image_file and backing_file manually, that will be confused for >>>>> users, >>>>> so we just ignore add-cow format while doing converting. >>>>> >>>>> Signed-off-by: Dong Xu Wang <wdon...@linux.vnet.ibm.com> >>>> >>>> NACK. >>>> >>>> This stupid "let's drop the feature, it might confuse users" attitude is >>>> known from Gnome, but not from qemu. >>>> >>>> There's no technical reason to forbid it and anyone who manages to >>>> create a valid add-cow image will also be able to specify the very same >>>> options to a convert command. Also, having image format specific code in >>>> qemu-img is evil. >>>> >>> >>> If I implement add-cow convert command, I am wondering which method should >>> I use: >>> 1) create add-cow, and its backing_file, and its image_file, then we >>> need 3 files. >>> 2) create add-cow(with all bitmap marked to allocated), and its >>> image_file, then we >>> need 2 files. >>> >>> 2) will be easier, I should let .add-cow file can live only with >>> image_file, without backing_file. >>> >>> I think both 1) and 2) need add code to qemu-img.c. Or I will have to create >>> image_file automaticly in add_cow_create function. >>> >>> Can you give some comments on how to implement convert? Thanks. >> >> Just leave it alone and it will work. >> >> qemu-img convert takes the same options as qemu-img create. So like for >> any other image you specify the backing file with -b or -o backing_file, >> and for add-cow images to be successfully created you also need to >> specify -o image_file. >> > "-o image_file", the image_file should be precreated? Or I should created it > manually?
Yes, it must already exist. Just like with qemu-img create. To convert an existing qcow2 image that has a backing file 'base.img' to an add-cow image, you would use something like: $ qemu-img create -f raw target.img 4G $ qemu-img convert -O add-cow -o image_file=target.img -B base.img source.qcow2 target.add-cow Kevin
