[Impact]
When ubuntu 18.04 server is trying to do an OEM installation using oem-config-firstboot, the ubiquity breaks the symlink /etc/resolv.conf -> /run/systemd/resolv/stub-resolv.conf, replacing /etc/resolv.conf with a 0-byte file and thereby breaking name resolution.
[Test Case]
The reproducer steps:
1. Prepare ubuntu-server with d-i version
2. Install iso
3. apt install oem-config ubiquity-frontend-debconf oem-config-debconf
5. oem-config-prepare -q
6. reboot
7. enter oem-config and finish it
8. check if /etc/resolv.conf is broken (actually it becomes a zero-byte file)
[Regression potential]
The fix is simple, merely adding a service to oem-config.target's Wants=. Even if the service somehow fails to start or is not present on a system, the other functionality of oem-config will be unaffected.
Status changed to 'Confirmed' because the bug affects multiple users.