Revert back from xfce to classic ubuntu gnome desktop [duplicate]

To change between the installed themes you should do:

sudo update-alternatives --config default.plymouth
sudo update-initramfs -u

The first will list available themes to choose from, the second command with update initramfs with a new theme.

Getting Started Guide

Editing Plymouth

You can edit Plymouth with a simple text editor for animations and images. This is Ubuntu version agnostic.

Original to New

Get Template
Customize Template
Set Custom Theme

Make a template

First you will get a template that covers all the basic aspects of a Plymouth. Change my-theme to your own personal them name.

sudo cp --recursive /lib/plymouth/themes/ubuntu-logo ~/themes/my-theme

Customize file names

Now you can change some names to help identify our theme from others.

sudo mv ubuntu-logo.plymouth my-theme.plymouth
sudo mv ubuntu-logo.script my-theme.script
sudo mv ubuntu-logo.grub my-theme.grub
sudo mv ubuntu_logo16.png my_theme16.png
sudo mv ubuntu_logo.png my_theme.png

Edit image files

Use your image editor of choice to alter the png images. I like GIMP for quick edits.

gimp my_theme.png my_theme16.png 
gimp progress_dot_on.png progress_dot_off.png 
gimp progress_dot_on16.png progress_dot_off16.png

Here is an example of my alterations:

Edit the configuration files.

Set up theme information file.

gedit my-theme.plymouth

Edit lines 2, 7, and 8 and change ubuntu logo to you theme name.

[Plymouth Theme]
Name=My Theme
Description=A theme that features a blank background with a logo.
ModuleName=script

[script]
ImageDir=/lib/plymouth/themes/my-theme
ScriptFile=/lib/plymouth/themes/my-theme/my-theme.script

Start-up terminal color. (Optional)
```
gedit my-theme.grub
```
Change it from purple to something else.

Edit line 1 with RGB color code.

A good site to help you is Color-Hex. I am just going to make mine black.
```
if background_color 0,0,0; then
  clear
fi
```

The script file to apply theme changes

gedit my-theme.script

There is many different aspects to this file that you can change to customize your plymouth boot theme. If you wish to do more advanced changes you should study it. I am only showing how to change the background color, logo, and status indicator.

Edit lines 169, 170, 174, and 180 to change the background gradient and images you edited earlier.

Window.SetBackgroundTopColor (0.66, 0.66, 0.66);       #top 
Window.SetBackgroundBottomColor (0.146, 0.146, 0.146); #bottom

bits_per_pixel = Window.GetBitsPerPixel ();
if (bits_per_pixel == 4) {
    logo_filename = "my_theme16.png";
    progress_dot_off_filename = "progress_dot_off16.png";
    progress_dot_on_filename = "progress_dot_on16.png";
    password_field_filename = "password_field16.png";
    question_field_filename = "password_field16.png";
} else {
    logo_filename = "my_theme.png";
    progress_dot_off_filename = "progress_dot_off.png";
    progress_dot_on_filename = "progress_dot_on.png";
    password_field_filename = "password_field.png";
    question_field_filename = "password_field.png";
}

Send your theme folder

cp --recursive ~/themes/my-theme /lib/plymouth/themes

Set Plymouth configuration to use theme.

sudo ln -sf /lib/plymouth/themes/my-theme/my-theme.plymouth /etc/alternatives/default.plymouth
sudo ln -sf /lib/plymouth/themes/my-theme/my-theme.grub /etc/alternatives/default.plymouth.grub

18.04+

sudo update-initramfs -u