Steps of live migration under QEMU&&KVM.

A is the source host, B is the destination host.

1. launch source VM on A

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<qemu-command-line>
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#! /bin/bash -x
    qemu-system-x86_64 \
    -enable-kvm \
    -m 4096 \
    -smp 2 \
    -cpu host \
    -drive format=raw,file=laag.img \
    -serial mon:stdio \
    -vnc :3

2. launch destination VM on B

Start the VM on B with the exact same parameters as the VM on A, in migration-listen mode:

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<qemu-command-line> -incoming tcp:0:4444
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#! /bin/bash -x
    qemu-system-x86_64 \
    -enable-kvm \
    -m 4096 \
    -smp 2 \
    -cpu host \
    -drive format=raw,file=laag.img \
    -serial mon:stdio \
    -vnc :4 \
    -incoming tcp:0:4444

3. start the migration (on A only)

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(qemu)migrate -d tcp:<host B IP>:4444
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(qemu)migrate -d tcp:localhost:4444

4. check the status (on A only)

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(qemu) info migrate

When completed, get can the info: Migration status: completed. The source VM will stop at the end.

5. misc

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(qemu) help migrate
migrate [-d] [-b] [-i] [-r] uri -- migrate to URI (using -d to not wait for completion)
                         -b for migration without shared storage with full copy of disk
                         -i for migration without shared storage with incremental copy of disk (base image shared between src and destination)
                         -r to resume a paused migration

The ‘-d’ will let you query the status of the migration. With no ‘-d’ the monitor prompt returns when the migration completes.

参考资料:

  1. page/Migration
  2. qemu热迁移简介