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For the Host-Initiated snapshot, we have to have an agent running in the virtual machine as a daemon. There is no way
around it. Fortunately, qemu comes with qemu-guest-agent software, which is available on Linux and Windows.
The agent is running as a daemon and communicates with the host via a virtio serial. From the host side commands can
be sent to the guest agent via the QMP socket.
Qemu-guest-agent fsfreeze command
Once such a command is received by the daemon, it would flush the guest file system and temporarily freeze it. That
would ensure that the snapshot is consistent and once we are rolled back to it, there will be no fsck problems.
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