Assistance needed with: The repository cdrom://... does not have a Release file

Question

Why do I continue to receive this error message:

The repository 'cdrom://Kubuntu 20.04.3 LTS _Focal Fossa_ - Release amd64 (20210819.1) focal Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

...and just exactly how does one go about correcting it?

Any information provided on the issue at hand is greatly appreciated.

Answer 1

As mentioned by Archisman Panigrahi, You need to open the software and update app and disable the CDrom repository.

1. Open the software sources file known as sources.list:

   sudo nano /etc/apt/sources.list
   

2. 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.

3. 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.

4. 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:

1. First, open Software & updates app.

   sudo apt install software-properties-gtk
   sudo software-properties-gtk
   

2. 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.

3. Uncheck it or remove it.

4. Update:

   sudo apt update
   

That's it!
Good Luck!