On Tue, Oct 13, 2015 at 10:39:58AM +0800, justlibvirt(a)gmail.com wrote: Hi, Firstly, please don't post the same message multiple times in a row. If someone hasn't responded, they're either busy, or haven't noticed this message. As near as I know, 'blockcommit' hasn't yet gotten offline support. As you note there's the 'qemu-img commit' primitive that allows you to commit the changes in an overlay back into its base image: If you have: base.qcow2 <-- overlay1.qcow2 <-- overlay2.qcow2 And, if you do: $ qemu-img commit overlay2.qcow2 It'll commit the contents of overlay2.qcow2 into overlay1.qcow2. And, indeed use the 'qemu-img rebase' to modify the backing file is the only method I know of, for offline operations. Though I haven't tested this recently, why would it lead to VM filesystem becoming read-only? -- /kashyap

Hi Kashyap Chamarthy: thank you very much for answer my question: 一： lead to VM filesystem becoming read-only 1： test case it lead to VM filesystem becoming read-only test case as follows: we want to snapshot for VM , to obtain VM incremental data，and use virsh blockcommit，qemu-img commit，qemu-img rebase to shorten snapshot chain. Details are as follows（when VM running state， we perform the following operations）: (1) the host machine control VM test virsh snapshot-create-as mix snap1 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap1-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap2 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap2-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap3 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap3-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap4 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap4-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap1-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap2-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap1-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap3-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap1 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap1-mix.img virsh snapshot-delete mix snap2 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap2-mix.img virsh snapshot-create-as mix snap5 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap5-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap6 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap6-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap7 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap7-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap8 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap8-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap3-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap6-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap3-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap7-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap3 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap3-mix.img virsh snapshot-delete mix snap4 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap4-mix.img virsh snapshot-delete mix snap5 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap5-mix.img virsh snapshot-delete mix snap6 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap6-mix.img virsh snapshot-create-as mix snap9 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap9-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap10 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap10-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap11 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap11-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap12 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap12-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap7-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap10-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap7-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap11-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap7 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap7-mix.img virsh snapshot-delete mix snap8 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap8-mix.img virsh snapshot-delete mix snap9 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap9-mix.img virsh snapshot-delete mix snap10 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap10-mix.img virsh snapshot-create-as mix snap13 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap13-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap14 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap14-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap15 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap15-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap16 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap16-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap11-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap14-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap11-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap15-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap11 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap11-mix.img virsh snapshot-delete mix snap12 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap12-mix.img virsh snapshot-delete mix snap13 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap13-mix.img virsh snapshot-delete mix snap14 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap14-mix.img 。。。。。。。。。。。。。。。。。。。。。。。。。。。。(the cycle test continue) (2) the VM test in the VM, loop write data and delete data operations。 2： test result when the test run for a while(8 hour or 10 hour or 20 hour or 30 hour and so on), the VM filesystem becoming read-only! 3： We are not sure the problem （1）when VM running, whether it can be used to modify snapshot's backingfile by qemu-img rebase(can only be used in vm offline？)? （2）when VM running，whether it can be used to commit the snapshot's changes by qemu-img commit(can only be used in vm offline？)？ 二： Run normal(ok) test 1： test case in order to eliminate potential problems，we only use virsh blockcommit shorten snapshot chain. (1) the host machine control VM test virsh snapshot-create-as length snap1 --diskspec vda,file=/tmp/testsnapshot/image/snap1-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap2 --diskspec vda,file=/tmp/testsnapshot/image/snap2-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap3 --diskspec vda,file=/tmp/testsnapshot/image/snap3-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap4 --diskspec vda,file=/tmp/testsnapshot/image/snap4-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap3-length.img --wait --verbose virsh snapshot-delete length snap1 --metadata rm -fr /tmp/testsnapshot/image/snap1-length.img virsh snapshot-delete length snap2 --metadata rm -fr /tmp/testsnapshot/image/snap2-length.img virsh snapshot-delete length snap3 --metadata rm -fr /tmp/testsnapshot/image/snap3-length.img virsh snapshot-create-as length snap5 --diskspec vda,file=/tmp/testsnapshot/image/snap5-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap6 --diskspec vda,file=/tmp/testsnapshot/image/snap6-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap7 --diskspec vda,file=/tmp/testsnapshot/image/snap7-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap8 --diskspec vda,file=/tmp/testsnapshot/image/snap8-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap7-length.img --wait --verbose virsh snapshot-delete length snap4 --metadata rm -fr /tmp/testsnapshot/image/snap4-length.img virsh snapshot-delete length snap5 --metadata rm -fr /tmp/testsnapshot/image/snap5-length.img virsh snapshot-delete length snap6 --metadata rm -fr /tmp/testsnapshot/image/snap6-length.img virsh snapshot-delete length snap7 --metadata rm -fr /tmp/testsnapshot/image/snap7-length.img virsh snapshot-create-as length snap9 --diskspec vda,file=/tmp/testsnapshot/image/snap9-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap10 --diskspec vda,file=/tmp/testsnapshot/image/snap10-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap11 --diskspec vda,file=/tmp/testsnapshot/image/snap11-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap12 --diskspec vda,file=/tmp/testsnapshot/image/snap12-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap11-length.img --wait --verbose virsh snapshot-delete length snap8 --metadata rm -fr /tmp/testsnapshot/image/snap8-length.img virsh snapshot-delete length snap9 --metadata rm -fr /tmp/testsnapshot/image/snap9-length.img virsh snapshot-delete length snap10 --metadata rm -fr /tmp/testsnapshot/image/snap10-length.img virsh snapshot-delete length snap11 --metadata rm -fr /tmp/testsnapshot/image/snap11-length.img virsh snapshot-create-as length snap13 --diskspec vda,file=/tmp/testsnapshot/image/snap13-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap14 --diskspec vda,file=/tmp/testsnapshot/image/snap14-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap15 --diskspec vda,file=/tmp/testsnapshot/image/snap15-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap16 --diskspec vda,file=/tmp/testsnapshot/image/snap16-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap15-length.img --wait --verbose virsh snapshot-delete length snap12 --metadata rm -fr /tmp/testsnapshot/image/snap12-length.img virsh snapshot-delete length snap13 --metadata rm -fr /tmp/testsnapshot/image/snap13-length.img virsh snapshot-delete length snap14 --metadata rm -fr /tmp/testsnapshot/image/snap14-length.img virsh snapshot-delete length snap15 --metadata rm -fr /tmp/testsnapshot/image/snap15-length.im (2) the VM test in the VM, loop write data and delete data operations。 2： test result the test run 200 hours， the test ok！！ Waiting for your reply, thank you very much! justlibvirt(a)gmail.com From: justlibvirt(a)gmail.com Date: 2015-10-19 19:51 To: Kashyap Chamarthy CC: libvirt开发邮件列表libvir-list; libvirt使用者邮件列表libvirt-users; libvirt快照大牛eblake Subject: Re: Re: [libvirt-users] virsh can't support VM offline blockcommit Hi Kashyap Chamarthy: thank you very much for answer my question: 一： lead to VM filesystem becoming read-only 1： test case it lead to VM filesystem becoming read-only test case as follows: we want to snapshot for VM , to obtain VM incremental data，and use virsh blockcommit，qemu-img commit，qemu-img rebase to shorten snapshot chain. Details are as follows（when VM running state， we perform the following operations）: (1) the host machine control VM test virsh snapshot-create-as mix snap1 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap1-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap2 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap2-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap3 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap3-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap4 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap4-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap1-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap2-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap1-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap3-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap1 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap1-mix.img virsh snapshot-delete mix snap2 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap2-mix.img virsh snapshot-create-as mix snap5 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap5-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap6 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap6-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap7 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap7-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap8 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap8-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap3-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap6-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap3-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap7-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap3 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap3-mix.img virsh snapshot-delete mix snap4 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap4-mix.img virsh snapshot-delete mix snap5 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap5-mix.img virsh snapshot-delete mix snap6 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap6-mix.img virsh snapshot-create-as mix snap9 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap9-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap10 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap10-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap11 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap11-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap12 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap12-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap7-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap10-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap7-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap11-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap7 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap7-mix.img virsh snapshot-delete mix snap8 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap8-mix.img virsh snapshot-delete mix snap9 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap9-mix.img virsh snapshot-delete mix snap10 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap10-mix.img virsh snapshot-create-as mix snap13 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap13-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap14 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap14-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap15 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap15-mix.img --disk-only --atomic --quiesce virsh snapshot-create-as mix snap16 --diskspec vda,file=/tmp/mul/loop-mix-commit-rebase/snap16-mix.img --disk-only --atomic --quiesce virsh blockcommit mix vda --base /tmp/mul/loop-mix-commit-rebase/snap11-mix.img --top /tmp/mul/loop-mix-commit-rebase/snap14-mix.img --wait --verbose qemu-img commit -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap11-mix.img qemu-img rebase -f qcow2 /tmp/mul/loop-mix-commit-rebase/snap15-mix.img -b /tmp/mul/loop-mix-commit-rebase/mix.img -F qcow2 -p virsh snapshot-delete mix snap11 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap11-mix.img virsh snapshot-delete mix snap12 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap12-mix.img virsh snapshot-delete mix snap13 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap13-mix.img virsh snapshot-delete mix snap14 --metadata rm -fr /tmp/mul/loop-mix-commit-rebase/snap14-mix.img 。。。。。。。。。。。。。。。。。。。。。。。。。。。。(the cycle test continue) (2) the VM test in the VM, loop write data and delete data operations。 2： test result when the test run for a while(8 hour or 10 hour or 20 hour or 30 hour and so on), the VM filesystem becoming read-only! 3： We are not sure the problem （1）when VM running, whether it can be used to modify snapshot's backingfile by qemu-img rebase(can only be used in vm offline？)? （2）when VM running，whether it can be used to commit the snapshot's changes by qemu-img commit(can only be used in vm offline？)？ 二： Run normal(ok) test 1： test case in order to eliminate potential problems，we only use virsh blockcommit shorten snapshot chain. (1) the host machine control VM test virsh snapshot-create-as length snap1 --diskspec vda,file=/tmp/testsnapshot/image/snap1-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap2 --diskspec vda,file=/tmp/testsnapshot/image/snap2-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap3 --diskspec vda,file=/tmp/testsnapshot/image/snap3-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap4 --diskspec vda,file=/tmp/testsnapshot/image/snap4-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap3-length.img --wait --verbose virsh snapshot-delete length snap1 --metadata rm -fr /tmp/testsnapshot/image/snap1-length.img virsh snapshot-delete length snap2 --metadata rm -fr /tmp/testsnapshot/image/snap2-length.img virsh snapshot-delete length snap3 --metadata rm -fr /tmp/testsnapshot/image/snap3-length.img virsh snapshot-create-as length snap5 --diskspec vda,file=/tmp/testsnapshot/image/snap5-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap6 --diskspec vda,file=/tmp/testsnapshot/image/snap6-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap7 --diskspec vda,file=/tmp/testsnapshot/image/snap7-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap8 --diskspec vda,file=/tmp/testsnapshot/image/snap8-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap7-length.img --wait --verbose virsh snapshot-delete length snap4 --metadata rm -fr /tmp/testsnapshot/image/snap4-length.img virsh snapshot-delete length snap5 --metadata rm -fr /tmp/testsnapshot/image/snap5-length.img virsh snapshot-delete length snap6 --metadata rm -fr /tmp/testsnapshot/image/snap6-length.img virsh snapshot-delete length snap7 --metadata rm -fr /tmp/testsnapshot/image/snap7-length.img virsh snapshot-create-as length snap9 --diskspec vda,file=/tmp/testsnapshot/image/snap9-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap10 --diskspec vda,file=/tmp/testsnapshot/image/snap10-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap11 --diskspec vda,file=/tmp/testsnapshot/image/snap11-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap12 --diskspec vda,file=/tmp/testsnapshot/image/snap12-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap11-length.img --wait --verbose virsh snapshot-delete length snap8 --metadata rm -fr /tmp/testsnapshot/image/snap8-length.img virsh snapshot-delete length snap9 --metadata rm -fr /tmp/testsnapshot/image/snap9-length.img virsh snapshot-delete length snap10 --metadata rm -fr /tmp/testsnapshot/image/snap10-length.img virsh snapshot-delete length snap11 --metadata rm -fr /tmp/testsnapshot/image/snap11-length.img virsh snapshot-create-as length snap13 --diskspec vda,file=/tmp/testsnapshot/image/snap13-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap14 --diskspec vda,file=/tmp/testsnapshot/image/snap14-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap15 --diskspec vda,file=/tmp/testsnapshot/image/snap15-length.img --disk-only --atomic --quiesce virsh snapshot-create-as length snap16 --diskspec vda,file=/tmp/testsnapshot/image/snap16-length.img --disk-only --atomic --quiesce virsh blockcommit length vda --base /tmp/testsnapshot/image/length.img --top /tmp/testsnapshot/image/snap15-length.img --wait --verbose virsh snapshot-delete length snap12 --metadata rm -fr /tmp/testsnapshot/image/snap12-length.img virsh snapshot-delete length snap13 --metadata rm -fr /tmp/testsnapshot/image/snap13-length.img virsh snapshot-delete length snap14 --metadata rm -fr /tmp/testsnapshot/image/snap14-length.img virsh snapshot-delete length snap15 --metadata rm -fr /tmp/testsnapshot/image/snap15-length.im (2) the VM test in the VM, loop write data and delete data operations。 2： test result the test run 200 hours， the test ok！！ Waiting for your reply, thank you very much! justlibvirt(a)gmail.com From: Kashyap Chamarthy Date: 2015-10-13 21:55 To: justlibvirt(a)gmail.com CC: libvir-list; libvirt-users; eblake Subject: Re: [libvirt-users] virsh can't support VM offline blockcommit On Tue, Oct 13, 2015 at 10:39:58AM +0800, justlibvirt(a)gmail.com wrote: Hi, Firstly, please don't post the same message multiple times in a row. If someone hasn't responded, they're either busy, or haven't noticed this message. As near as I know, 'blockcommit' hasn't yet gotten offline support. As you note there's the 'qemu-img commit' primitive that allows you to commit the changes in an overlay back into its base image: If you have: base.qcow2 <-- overlay1.qcow2 <-- overlay2.qcow2 And, if you do: $ qemu-img commit overlay2.qcow2 It'll commit the contents of overlay2.qcow2 into overlay1.qcow2. And, indeed use the 'qemu-img rebase' to modify the backing file is the only method I know of, for offline operations. Though I haven't tested this recently, why would it lead to VM filesystem becoming read-only? -- /kashyap