On Wed, Jan 23, 2019 at 15:19:53 -0600, Eric Blake wrote: > The existing qemu-nbd --partition code claims to handle logical > partitions up to 8, since its introduction in 2008 (commit 7a5ca86). > However, the implementation is bogus (actual MBR logical partitions > form a sort of linked list, with one partition per extended table > entry, rather than four logical partitions in a single extended > table), making the code unlikely to work for anything beyond -P5 on > actual guest images. What's more, the code does not support GPT > partitions, which are becoming more popular, and maintaining device > subsetting in both NBD and the raw device is unnecessary maintenance > burden. And nbdkit has just added code to properly handle an > arbitrary number of MBR partitions, along with its existing code > for handling GPT partitions. > > Note that obtaining the offsets of a partition can be learned by > using 'qemu-nbd -c /dev/nbd0 file.qcow2 && sfdisk --dump /dev/nbd0', > but by the time you've done that, you might as well just mount > /dev/nbd0p1 that the kernel creates for you. > > Start the clock on the deprecation cycle, with an example of how > to write device subsetting without using -P. > > Signed-off-by: Eric Blake <eblake redhat com> > --- > qemu-deprecated.texi | 27 +++++++++++++++++++++++++++ > qemu-nbd.texi | 6 ++++-- > qemu-nbd.c | 2 ++ > 3 files changed, 33 insertions(+), 2 deletions(-) Libvirt does not use qemu-nbd in any way so it's okay from our POV.
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