I would like to show a consistent background image from grub2 boot up to unity's login screen for Ubuntu 16.04.3.
Instructions to show a background image I have found so far are:
After implementing them, I noticed that there is still a black screen shown between the grub2 and lightdm stages for a few seconds and a short flash (less than a second) of black screen when transiting between lightdm and unity-greeter.
I think there is a X11 or Xorg stage between grub2 and lightdm which needs setting up. I am also not sure how to avoid the black screen flash between lightdm and unity-greeter.
I have stored an image in /usr/share/backgrounds with root permission and I want to show this image.
How do show this image in X11 or Xorg background? How do I overcome the blackscreen flashing between lightdm and unity-greeter? Is there any stage(s) that I have not identified, and if so, what should I do in those stages to show the image?
Edit: @muru cited another question which asked specifically about customizing the Ubuntu Logo. Plymouth was recommended as a solution to that question. My question is unique to that because it involves a wider scope. Plymouth deals with the splash screen stage, but does not deal with showing an image past the display manager. I am getting a black screen during the splash screen stage and also getting 4 seconds of black between lightdm and unity-greeter (earlier I wrote "a short flash (less than a second)" and this was wrong). The latter issue is beyond the scope of plymouth. Also, I have tried using various plymouth themes and they did not work; I still get a black screen during the splash screen stage.
Edit2: I discovered that different GPU drivers give different results. Below are the drivers that I have tried with a Nvidia GPU connected with a monitor. I also report here the monitor appearances and time (in seconds) after Ubuntu was selected at the Grub2 stage.
dpkg -l | grep nouveau
ii libdrm-nouveau2:amd64 2.4.76-1~ubuntu16.04.1 amd64 Userspace interface to nouveau-specific kernel DRM services -- runtime
ii xserver-xorg-video-nouveau-hwe-16.04 1:1.0.14-0ubuntu1~16.04.1 amd64 X.Org X server -- Nouveau display driver
$ dpkg -l | grep nvidia-384
ii nvidia-384 384.90-0ubuntu0.16.04.1 amd64 NVIDIA binary driver - version 384.90
Nouveau
Grub2 | Blackscreen | Plymouth w/ image | Purple LoginScreen | LoginScreen w/ image
2s 14s 30s 36s
Nvidia-384
Grub2 | Blackscreen | lightdm w/ image | Blackscreen | LoginScreen w/ image
2s 20s 31s 37s
In addition, regardless of driver types, a blackscreen would consistently after selecting Ubuntu at the grub2 stage for 12s to 18s. Also my background image would not appear between 30s to 36s time range.
Question: How can I overcome these black and/or purple screens?
