Не мог обновить 3.13.0-36-универсальное Ядро в Ubuntu 14.04.5

У меня есть капелька Ubuntu 14.04.5 на digitalocean выполнение 3.13.0-36-универсального ядра. Я читал на digitalocean, что моя версия ядра уязвима, таким образом, я пытался обновить свое ядро путем выполнения

sudo apt-get update && sudo apt-get dist-upgrade

Но это всегда говорило, что нет никакого доступного обновления. Это говорит, что я уже выполняю последнюю версию. Но когда я работаю uname -rv

Это всегда возвращается

3.13.0-36-generic #63-Ubuntu SMP Wed Sep 3 21:30:07 UTC 2014

Я попробовал другие терминальные команды такой как

apt-get install linux-generic

и перезагружая сервер, но это все еще имеет 3.13.0-36-универсальный.

Я пропустил что-то?

ОБНОВЛЕНИЕ: Согласно просьбе @mikewhatever вот результат cat /etc/apt/sources.list

# deb cdrom:[Ubuntu-Server 14.04 LTS _Trusty Tahr_ - Release amd64 (20140416.2)]/ trusty main restricted

#deb cdrom:[Ubuntu-Server 14.04 LTS _Trusty Tahr_ - Release amd64 (20140416.2)]/ trusty main restricted

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

## Major bug fix updates produced after the final release of the
## distribution.
deb http://mirrors.digitalocean.com/ubuntu/ trusty-updates main restricted
deb-src http://mirrors.digitalocean.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://mirrors.digitalocean.com/ubuntu/ trusty universe
deb-src http://mirrors.digitalocean.com/ubuntu/ trusty universe
deb http://mirrors.digitalocean.com/ubuntu/ trusty-updates universe
deb-src http://mirrors.digitalocean.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://mirrors.digitalocean.com/ubuntu/ trusty multiverse
deb-src http://mirrors.digitalocean.com/ubuntu/ trusty multiverse
deb http://mirrors.digitalocean.com/ubuntu/ trusty-updates multiverse
deb-src http://mirrors.digitalocean.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://mirrors.digitalocean.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://mirrors.digitalocean.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