Thank you!
The thing I tried to do is to create a VM of volumio to use as a server and snapcast receivers to play the music (without local audio DAC)
About the “injection process”:
Booted a VM with a Knoppix Live CD, from then , execute netcat and set it up to listen in a port for data and redirection to dev/sda.
From another machine I sent the img of Volumio as raw data by using netcat to the VM.
This was done by others with success, but in my case, when I boot up, the machine shows the splash logo an then the “cannot find UUID blabla” error and the terminal.
I have observed that it doesnt take so long, so I suspect that maybe not everything is written to the virtual disk, but I don’t know why because netcat has no feedback whatsoever.
Let’s see if there’s somebody with the same issue and can pour some light .
Thank you again.