Re: virsh blockcopy: doesn't seem to flatten the chain by default

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On 07/03/2014 03:12 AM, Kashyap Chamarthy wrote:
Versions
--------

(Libvirt locally built from a recent git commit -ec7b922):

     $ rpm -q libvirt-daemon-kvm qemu-system-x86
     libvirt-daemon-kvm-1.2.6-1.fc20.x86_64
     qemu-system-x86-2.0.0-1.fc21.x86_64


Test
----

[All images are qcow2 files.]


We have this simple chain:

     base <- snap1

Let's quickly examine the contents of 'base' and 'snap1' images:

'base' has just a single file: foo

     $ guestfish --ro -a base.qcow2
     [. . .]
     ><fs> ls /
     ><fs> run
     ><fs> mount /dev/sda1 /
     ><fs> ls /
     foo
     lost+found
     ><fs> quit

'snap1' has files: bar, baz, jazz

     $ guestfish --ro -a snap1.qcow2
     [. . .]
     ><fs> run
     ><fs> mount /dev/sda1 /
     ><fs> ls /
     bar
     baz
     jazz
     lost+found
     ><fs>

Now, let's do a live blockcopy (with a '--finish' to graecully finish
the mirroring):

     $ virsh blockcopy --domain testvm2 vda \
         /export/dst/copy.qcow2 \
         --wait --verbose --finish


Examine the contents of the above 'copy':

     $ guestfish --ro -a copy.qcow2
     [. . .]
     ><fs> run
     ><fs> mount /dev/sda1 /
     ><fs> ls /
     bar
     baz
     jazz
     lost+found
     ><fs> quit

If I'm reading the man page of 'blockcopy' correctly, shouldn't it
'flatten' the entire chain, by also copying the contents of base into
copy.qcow2? i.e. the 'copy' should have files (including the file foo
from 'base':

     foo, bar, baz, jazz
I do test on my fedora20 with libvirt build from libvirt.git

# cd libvirt && git describe
v1.2.6-9-g5098f67
# rpm -q qemu-kvm
qemu-kvm-2.0.0-7.fc20.x86_64

It work well for me. I can see the file 'foo'(from base.qcow2) in copy file "copy.qcow2"

I also boot guest with image copy.qcow2, login guest and found file "foo" is existing.


True or false?


PS: I've tested the cases of --pivot, --shallow and --reuse-external,
will post my notes about them on a wiki.


--
Regards
shyu

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