I used the Software Updater and at the end it said
Failed to download repository information
Check your Internet connection
I saw an article said use sudo apt-get update
I tried and it said
Ign:1 cdrom://Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725) bionic InRelease
Err:2 cdrom://Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725) bionic Release
Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
Hit:3 http://mirror.ehost.vn/ubuntu bionic InRelease
Hit:4 http://mirror.ehost.vn/ubuntu bionic-updates InRelease
Hit:5 http://mirror.ehost.vn/ubuntu bionic-backports InRelease
Hit:6 http://mirror.ehost.vn/ubuntu bionic-security InRelease
Hit:7 http://archive.canonical.com/ubuntu bionic InRelease
Reading package lists... Done
E: The repository 'cdrom://Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725) bionic 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.
I also saw a post saying that I should go to Settings and select Select best server in Download from in the Ubuntu Software tab.
However, when I closed that window this appeared:
I pressed Reload and it ran a cache update, but when it finished it again said
Failed to download repository information
Check your Internet connectionDetails
E:The repository 'cdrom://Ubuntu 18.04.1 LTS _Bionic Beaver_ - Release amd64 (20180725) bionic Release' does not have a Release file.
My network is totally fine.
