1. Open the APT sources.list File

sudo nano /etc/apt/sources.list

2. Remove any cdrom entries

• Sometimes Debian Adds the Install CD (aka. the Install USB) as a source for apt packages
• If apt can't access an entry it just throws errors
• Should the sources.list contain Lines starting with deb cdrom:[Debian... comment it out by adding a # to the start of the Line

3. Update APT

After Saving the sources.list file Update apt by running

sudo apt update