Where can I find the default content of /etc/apt/sources.list in Ubuntu 18.04 LTS (Bionic Beaver)

cat /etc/apt/sources.list shows

# deb cdrom:[Ubuntu 16.04.2 LTS _Xenial Xerus_ - Release amd64 (20170215.2)]/ xenial main restricted
# See for how to upgrade to
# newer versions of the distribution.
deb bionic main restricted universe
deb-src bionic multiverse restricted universe main #Added by software-properties
# deb-src xenial main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb bionic-updates main restricted universe
deb-src bionic-updates multiverse restricted universe main #Added by software-properties
# deb-src xenial-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-src xenial universe
# deb-src xenial-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 bionic multiverse
# deb-src xenial multiverse
deb bionic-updates multiverse
# deb-src xenial-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 bionic-backports main restricted multiverse universe
deb-src bionic-backports main restricted multiverse universe #Added by software-properties
# deb-src xenial-backports main restricted universe 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 xenial partner
# deb-src xenial partner
deb bionic-security main restricted universe
deb-src bionic-security multiverse restricted universe main #Added by software-properties
# deb-src xenial-security main restricted
# deb-src xenial-security universe
deb bionic-security multiverse
# deb-src xenial-security multiverse
# deb binary/

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1 Answer

As you just want to remove unneeded lines from your sources.list, below is an example of what you could have in the contents of your file:

deb bionic main restricted universe multiverse
deb bionic-updates main restricted universe multiverse
deb bionic-backports main restricted universe multiverse
deb bionic-security main restricted universe multiverse
deb-src bionic main restricted universe multiverse
deb-src bionic-security main restricted universe multiverse
deb-src bionic-backports main restricted universe multiverse
deb-src bionic-updates main restricted universe multiverse

This is based on the contents of the sources.list you have provided which have not been commented out. Some things were combined to minimise lines. Additionally, if you don't require source, you can remove all the deb-src lines.

That said, there isn't much of a point to doing this, other than readability. The commented-out sections won't affect anything, and some lines provide information for you. If you definitely won't be needing them, go ahead and use the lines provided above.

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