elementary.list

==> /etc/apt/sources.list.d/elementary.list <==
deb http://ppa.launchpad.net/elementary-os/stable/ubuntu trusty main
deb-src http://ppa.launchpad.net/elementary-os/stable/ubuntu trusty main

lsb-release

==> /etc/lsb-release <==
DISTRIB_ID="elementary OS"
DISTRIB_RELEASE=0.3.2
DISTRIB_CODENAME=freya
DISTRIB_DESCRIPTION="elementary OS Freya"

os-release

==> /etc/os-release <==
NAME="elementary OS"
VERSION="0.3.2 Freya"
ID="elementary OS"
ID_LIKE=ubuntu
PRETTY_NAME="elementary OS Freya"
VERSION_ID="0.3.2"
HOME_URL="http://elementary.io/"
SUPPORT_URL="http://elementary.io/support/"
BUG_REPORT_URL="https://bugs.launchpad.net/elementary/+filebug"

patches.list

==> /etc/apt/sources.list.d/patches.list <==
deb http://ppa.launchpad.net/elementary-os/os-patches/ubuntu trusty main
deb-src http://ppa.launchpad.net/elementary-os/os-patches/ubuntu trusty main

sources.list

==> /etc/apt/sources.list <==
# deb cdrom:[elementary OS 0.3 _Freya_ - Stable amd64 (20150411)]/ trusty main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://us.archive.ubuntu.com/ubuntu/ trusty main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ trusty universe
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty universe
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://us.archive.ubuntu.com/ubuntu/ trusty multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty multiverse
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu trusty-security main restricted
deb-src http://security.ubuntu.com/ubuntu trusty-security main restricted
deb http://security.ubuntu.com/ubuntu trusty-security universe
deb-src http://security.ubuntu.com/ubuntu trusty-security universe
deb http://security.ubuntu.com/ubuntu trusty-security multiverse
deb-src http://security.ubuntu.com/ubuntu trusty-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu trusty partner
# deb-src http://archive.canonical.com/ubuntu trusty partner

## Uncomment the following two lines to add software from Ubuntu's
## 'extras' repository.
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
# deb http://extras.ubuntu.com/ubuntu trusty main
# deb-src http://extras.ubuntu.com/ubuntu trusty main

Yay! Thanks! I did something absolutely stupid: deleting elementary.list by mistake. I thought this was of little consequence, since surely the PPA repository link would be somewhere, right? Well — wrong. Just to make matters incredibly confusing, Elementary has tons of PPAs on launchpad, and getting the right URL to them was next to impossible! Also, it seems to be buried very deep in Elementary's published source code on GitHub — wherever it might be, I couldn't find it.

Anyway, I just wanted to say my thanks — I'm well-aware that this Gist is a decade old, but still useful! — and to suggest a new version of it. The whole packaging system used by apt has been updated — progressively! — to be more secure, by storing the repository's PGP keys differently. The whole structure of /etc/apt/ has changed as a consequence; the 'old way' is still accepted, but raises warnings (as it should). Given the proper URLs, it's very easy to change the list format to the new sources format; and storing the PGP keys in separate keyrings — one per repo, as opposed to a unified keyring for all repos) is also trivial. While ElementaryOS is still struggling with the necessary changes and somehow mid-way of implementing all of them, Ubuntu's apt, which is pulled in by Elementary, already 'expects' all keys to be in the right place, and complains otherwise. Thus, moving to the 'new' format is a good idea, and maybe will last another decade or so! 😁