As mentioned by Archisman Panigrahi, You need to open the software and update app and disable the CDrom repository.
Open the software sources file known as sources.list
:
sudo nano /etc/apt/sources.list
Find the line which looks similar to:
deb cdrom:[Ubuntu Desktop <version> <codename> - x86] <code name> <reponames>
Most likely it will be the first line.
Comment the line by putting a #
after it.
# deb [<foo> <foo> blah blah whatever] foobar whatever...
You can also remove the line if you want.
Run update:
sudo apt update
Alternatively, you can change the /etc/apt/sources.list
to:
deb http://archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ focal-backports main restricted universe multiverse
deb http://archive.canonical.com/ubuntu focal partner
deb-src http://archive.canonical.com/ubuntu focal partner
And run apt update
:
sudo apt update
An alternate GUI way to do the same:
First, open Software & updates app.
sudo apt install software-properties-gtk
sudo software-properties-gtk
Then navigate to other sources → Kubuntu CDrom.
The name may not be the same, you just need to uncheck anything which says "CDrom" or similar to it.
Uncheck it or remove it.
Update:
sudo apt update
That's it!
Good Luck!