package nvidia-340 (not installed) failed to install/upgrade: trying to overwrite '/lib/udev/rules.d/71-nvidia.rules', which is also in package nvidia-kernel-common-390 390.48-0ubuntu3. sudo password correct. if something else info necessary mail me.

[EJolloX]

i had the latest nVidia driver installed. the 390. proprietary and tested.
Well... I have ported my system from a fresh install ubuntu 17.10 64bit.
On that system, I istalled the latest drivers because with xOrg drivers games where unplayable.
Now i have 18.04 lts 64bit. latest drivers remained checked in Software & updates>Adds drivers.
From that menu i tryed downporting drivers to the 340 version. Failed. I was looking at a youtube video while done this. Maybe could be affected the procedure somehow.
Video on youtube are lagghy.
Games on steam are smooth.
My hardware is
250 ssd
gtx770
i7-7700k
32 ddr4

Yes, the gpu is old. Bad economy in italy.

I'll add some other information, as the guideline below. Hope it can help you.

#lsb_release -rd
Description: Ubuntu 18.04 LTS
Release: 18.04

I think my system it's pretty up to date 'cause I've done sudo apt update -> upgrade. And updated everything...

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: nvidia-340 (not installed)
ProcVersionSignature: Ubuntu 4.15.0-29.31-generic 4.15.18
Uname: Linux 4.15.0-29-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.3
Architecture: amd64
Date: Wed Jul 25 21:07:19 2018
DuplicateSignature:
 package:nvidia-340:(not installed)
 Unpacking nvidia-340 (340.106-0ubuntu3) ...
 dpkg: error processing archive /var/cache/apt/archives/nvidia-340_340.106-0ubuntu3_amd64.deb (--unpack):
  trying to overwrite '/lib/udev/rules.d/71-nvidia.rules', which is also in package nvidia-kernel-common-390 390.48-0ubuntu3
ErrorMessage: trying to overwrite '/lib/udev/rules.d/71-nvidia.rules', which is also in package nvidia-kernel-common-390 390.48-0ubuntu3
InstallationDate: Installed on 2018-07-20 (5 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Release amd64 (20180105.1)
Python3Details: /usr/bin/python3.6, Python 3.6.5, python3-minimal, 3.6.5-3ubuntu1
PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2
 apt 1.6.3
SourcePackage: nvidia-graphics-drivers-340
Title: package nvidia-340 (not installed) failed to install/upgrade: trying to overwrite '/lib/udev/rules.d/71-nvidia.rules', which is also in package nvidia-kernel-common-390 390.48-0ubuntu3
UpgradeStatus: Upgraded to bionic on 2018-07-23 (1 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.