After running qvm-backup-restore, starts a terminal for your VM:
$ qvm-run mytemplate gnome-terminal
In the VM,
- Rename /etc/apt/sources.list.d/qubes-r3.list to /etc/apt/sources.list.d/qubes-r4.list
- Replace mention of "3.2" to "4.0" qubes-r4.list
Now we will import the new GPG keys used to sign the packages.
- Start one of the official template:
$ qvm-run debian-8 gnome-terminal
In the debian-8 VM:
$ apt-ket exportall > /tmp/keys.txt
$ qvm-copy-to-vm /tmp/keys.txt
Choose "mytemplate" as destination.
In the mytemplate VM:
$ apt-key import ~/QubesIncoming/debian-8/keys.txt
Now enable networking in the mytemplate settings by specifying sys-net as a network VM.
Updates the packages:
$ apt-get update
$ apt-get upgrade
When prompted, choose to use the qubes-r4.list from the maintainer (or merge manually).
Disable network in the mytemplate VM.
Restart.
Now the proxy updates should work again.
Good luck.