The Unwanted Nag Screen
By default, Ubuntu runs a background daemon that periodically checks Canonical’s servers for available software updates. If it detects that security patches or new application versions are available, it automatically launches the graphical “Update Manager” utility on your desktop shortly after you boot the computer and log in. While this ensures casual users keep their systems secure, it is incredibly annoying for power users, developers, or system administrators who prefer to manage all their apt updates manually via the terminal at a time of their own choosing.
Silencing the Update Daemon
To stop the graphical update manager from spontaneously launching itself on your screen, you need to configure the software properties to never automatically check for updates. You can do this entirely through the graphical interface.
Press the Super (Windows) key on your keyboard, type Software & Updates, and press Enter to launch the utility. A window with several tabs will appear. Click on the Updates tab. Locate the dropdown menu labelled Automatically check for updates:. By default, this is likely set to “Daily.” Click the dropdown and change the setting to Never. You will immediately be prompted to enter your administrator password to confirm this system-wide change. Enter your password and click Authenticate. Finally, click the Close button on the main window. Ubuntu will no longer spontaneously launch the update manager upon boot; you are now solely responsible for running sudo apt update manually.