Ubuntu 18.04 LTS shows that update cannot be done securely due to lack of Release File
65
What can I do if a repository/PPA does not have a Release file?
22164
Problem with sudo apt get update: The repository cdrom... does not have a Release file
13970
Why am I not getting the Ubuntu 18.04 upgrade?
31506
How do I update Ubuntu manually?
30068
Update: Failed to lock /var/cache/apt/archives/lock
95593
sudo apt-get update returns an error
100494
Update Manager asking me to update kernel but apt-get upgrade does not?
105715
Security updates for the universe repository for LTS releases?
82035
Debian: The repository does not have a Release file
52190
How and when is old-releases.ubuntu.com updated?
56150
Can't upgrade/update ubuntu 18.04 as apt/dpkg error is showing up
9578
Are security.ubuntu.com updates eventually merged into normal updates?
8525
Error Updating: izx/askubuntu/ubuntu xenial Release' does not have a Release file
105335
How do I upgrade my Ubuntu server from one LTS version to another? Is this safe?
42634
How do I upgrade to the development release (aka. Ubuntu+1)?
15687
How do I resume a release upgrade?
144507
No facility exists in Update Manager to upgrade to a new version, why?