I installed Kubuntu 11.04 once, although version 14.04 was already available for downloading on the official website, but there were no other carriers at hand, so I decided to install the old one and then upgrade.
And after installing and executing the command:
sudo apt-get update
noticed the error “404 Not Found …”, as well as the same error when performing the update through the settings.
Similar errors will be displayed in other similar outdated Linux systems, such as Ubuntu, Xubuntu, Debian, etc.
The solution to this problem is an indication of the correct update sources for outdated versions.
Let’s make just in case a copy of the list of update sources:
sudo cp -i /etc/apt/sources.list /etc/apt/sources.list.old
Now open the file in any editor, for example nano:
sudo nano /etc/apt/sources.list
And replace in the lines of the address “archive.ubuntu.com” and “security.ubuntu.com” with “old-releases.ubuntu.com”.
In the nano editor to save using the key combination Ctrl+O and then Enter, and to exit Ctrl+X.
Finally, do the update:
sudo apt-get update sudo apt-get upgrade
Errors “404 Not Found …” are no longer displayed.