How to Remove UEFI Boot in KVM Virtualization

Here is an example how you can test if a machine is online using ping:

#!/bin/bash
# test-online.sh
ret=1
while [ $ret != 0 ]
do
  ping -c 1 $1 2>/dev/null
  ret=$?
done
exit 0

You can adapt this to use ssh by replacing the ping line with something like ssh $1 "echo", assuming you can connect to the machine without a password.

Using the above script (let's call it test-online.sh), you can start the machine and then measure the time using GNU time (the first argument of this script is the machine name):

#!/bin/bash
# start-and-time.sh
start-vm $1
/usr/bin/time -f "%E" ./test-online.sh $1

The output will be something like 1:23.52 which means your machine took 1 minute 23 seconds to boot.

If you want to measure the boot time of many machines, you can just call start-and-time.sh for every machine:

#!/bin/bash
mymachines=(machine1 machine2 machine3)
for machine in "${machines[@]}"
do
  echo -n "$machine "
  ./start-and-time.sh $machine &
done

which will give the following exemplary output:

machine1 1:53.23
machine2 2:42.42
machine3 0:42.42

So with your question, "What is the right way to save and restore Running VMs?" you pretty much nailed it on the head. Saving with virsh save VM and restoring with virsh restore VM will do what you wanted it to do--that is save memory to disk and then stop the VM (see the first section of this link).

When your VM froze, I believe you would have been able to restore if you had not deleted the state file (depending on the root cause of the VM failure in the first place).

I generally do not save memory to state files because my use case runs persistent, stateless services that do not depend on memory. If I need to shut down I usually just run virsh destroy VM and then start it as necessary. But, this all depends on your own use case.

You may want to also look into backing up your VM with snapshots, if you are leery of losing your machine again. Something like:

virsh snapshot-create-as --domain {VM-NAME} --name "{SNAPSHOT-NAME}"

See NixCraft for more details.

In any case, for getting your VM running after it froze you could have simply undefined the broken VM and re-attached the originally existing image from it to a new VM by updating the newly created VM's XML configuration document. First, tear down the original VM:

:~$ virsh destroy OriginalVM
:~$ virsh undefine OriginalVM

After that build the new VM, stop it and access the config:

:~$ virt-install --virt-type kvm --name NewVM --memory 4096 --disk size=1 --vcpus 4 --location /yadda/yadda.iso --network bridge=br0 --os-type=linux --so-on-and-so-forth
:~$ virsh destroy NewVM
:~$ virsh edit NewVM

Then, when editing the XML file search for "disk" by typing /disk and update the path for the source file:

 <disk type='file' device='disk'>
  <driver name='qemu' type='raw'/>
  <source file='/update_to/path_of/OriginalVM.img'/>

After saving and exiting (:w, :q or simply :x) you should be able to execute a virsh start NewVM and then access the new VM running your image via VNC, console, or ssh.

You could also try to clone your VM, though I have not tried this myself:

virt-clone --connect=qemu:///system -o srchost -n newhost -f /path/to/newhost.qcow2