This section contains basic information about concepts and objects used when managing Virtual Machines.
When using REVEN with QEMU VMs, you will have to switch between two virtual machine mode, because recording is restricted to full emulation mode:
|Mode||Technology||Speed||What we use it for|
|KVM||Virtualization with hardware support||Fast||Installation, heavy configuration|
|Emulation (TCG)||Full software: code for each instruction||Slower||Recording, simple configuration|
From the point of view of the guest OS running, these two modes are completely different hardware. Going from one to the other is akin to moving a physical hard disk between two machines, and as a consequence requires properly shutting down the VM before making the switch.
Note: the same is true when changing most other hardware options, you must do it while the VM is shut down.
REVEN uses the native disk / live snapshot mechanism from QEMU which might differ from what users expect. Two different objects are called "snapshots", so to avoid any confusion we need to differentiate:
|Name||What it is||Support switching VM modes|
|Disk snapshot||The living VM's hard disk||Yes, by shutting the VM down|
|Live snapshot||A frozen state of a running VM,|
to be restored anytime
|No: must be restored using the same|
mode it has been created with
Live snapshots are very handy, because they provide a very quick way to restore a VM from a known good VM state, instead of having to wait for the VM to boot up. This is even more true in Emulation mode, where booting a VM takes a few minutes.
Finally, note that the above table is a simplification. Notably, live snapshots are stored within the
qcow disk snapshot file itself, and this is reflected in the Project Manager's organisation.
You can now head over to the Adding VMs section.