Software update Error Mint 18 Cinnamon
 

I get an error when trying to do a software update. I will attach a screenshot of the error. Attachment 22682

domain.com is, as far as I am aware, an invalid repository-hosting domain. The repository name looks like one that would have been given as a dummy example for you to modify accordingly. Did you recently manually add a repository to your system?

In order to see which repositories your system is set up to use, please post the output of inxi -r here in CODE tags. Thanks.

Repositories
 

Repos: Active apt sources in file: /etc/apt/sources.list.d/additional-repositories.list
deb http://packages.domain.com/ xenial main
Active apt sources in file: /etc/apt/sources.list.d/nilarimogard-webupd8-xenial.list
deb http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu xenial main
deb-src http://ppa.launchpad.net/nilarimogard/webupd8/ubuntu xenial main
Active apt sources in file: /etc/apt/sources.list.d/nylas.list
deb [arch=i386,amd64] http://apt.nylas.com/ubuntu vivid main
Active apt sources in file: /etc/apt/sources.list.d/official-package-repositories.list
deb http://packages.linuxmint.com sarah main upstream import backport
deb http://archive.ubuntu.com/ubuntu xenial main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu xenial-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu xenial-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu/ xenial-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu/ xenial partner
Active apt sources in file: /etc/apt/sources.list.d/vivaldi.list
deb http://repo.vivaldi.com/stable/deb/ stable main

Thank you. You appear to have missed my question as to whether you recently manually added a repository to your system. You also missed my request that you paste the output using CODE tags (the # button on the Linux Questions advanced toolbar allows you to do this easily).

The line in /etc/apt/sources.list.d/additional-repositories.list is incorrect. You should delete this, either by editing the file as root, or through Synaptics Package Manager (Settings->Repositories->Additional Repositories).

Of more importance though is to work out how it got there so that you can make sure you add the correct repository for the software in question. It will have been something you did recently like manually add a repository, install a deb package etc.