I want to be able to automatically restore login information when starting a disposable VM

[apparatus]

Then try this:

@unman

Put a line in /rw/.config/rc.local like this:
echo "nameserver 9.9.9.9 " > /etc/resolv.conf

How to overwrite Qubes Virtual DNS 10.139.1.1, 10.139.1.2

You asked a simple question - how do I overwrite /etc/resolv.conf from Qubes default? The simple answer is: Put a line in /rw/.config/rc.local like this: echo "nameserver 9.9.9.9 " > /etc/resolv.conf That is the simple answer to the question you asked. The difficult t you have is that your problem is not encompassed by that simple question. That is why I told you you would have to deal with the warning message that you received. etc/resolvconf/update.d/libc: Warning: /etc/resolv.conf …