升級到 Ubuntu 14.04.3 LTS 後，MOTD 總是說 0 個新包可以更新

我不是伺服器專家，所以我在使用 Ubuntu 時遇到了一些升級問題。一點歷史：我的 Digital Ocean droplet 執行的是 Ubuntu 12.04 LTS，然後幾個月前我升級到更新的 HWE 以繼續接收 12.04 的安全更新。最近我將 Ubuntu 升級到 14.04 LTS。一切似乎都工作正常，除了我沒有收到任何通知有要更新的軟體包。登錄到我的伺服器後，每日消息繼續顯示：

0 packages can be updated.
0 updates are security updates.

現在 3 週內不可能是正確的……？

執行sudo apt-get update沒有錯誤並sudo apt-get upgrade說0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

我有一種感覺，/etc/apt/sources.list在升級到新的 HWE 核心和新的 LTS 之後，我的系統被破壞了。以下是目前列出的來源。有人看到這個列表有什麼問題嗎？任何意見，將不勝感激。

$ cat /etc/apt/sources.list

#

# deb cdrom:[Ubuntu-Server 12.04.3 LTS _Precise Pangolin_ - Release i386 (20130820.2)]/ precise main restricted

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

## Major bug fix updates produced after the final release of the
## distribution.
## DigitalOcean mirrors for blazing speed!
deb http://mirrors.digitalocean.com/ubuntu/ trusty-updates main restricted
deb-src http://mirrors.digitalocean.com/ubuntu/ trusty-updates main restricted
# deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-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.
## DigitalOcean mirrors for blazing speed!
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
# deb http://us.archive.ubuntu.com/ubuntu/ precise universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise universe
# deb http://us.archive.ubuntu.com/ubuntu/ precise-updates universe
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-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.
## DigitalOcean mirrors for blazing speed!
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
# deb http://us.archive.ubuntu.com/ubuntu/ precise multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise multiverse
# deb http://us.archive.ubuntu.com/ubuntu/ precise-updates multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-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.
## DigitalOcean mirrors for blazing speed!
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://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse
# deb-src http://us.archive.ubuntu.com/ubuntu/ precise-backports main restricted universe multiverse

## DigitalOcean mirrors for blazing speed!
deb http://mirrors.digitalocean.com/ubuntu/ trusty-security main restricted
deb-src http://mirrors.digitalocean.com/ubuntu/ trusty-security main restricted
deb http://mirrors.digitalocean.com/ubuntu/ trusty-security universe
deb-src http://mirrors.digitalocean.com/ubuntu/ trusty-security universe
deb http://mirrors.digitalocean.com/ubuntu/ trusty-security multiverse
deb-src http://mirrors.digitalocean.com/ubuntu/ trusty-security multiverse
# deb http://security.ubuntu.com/ubuntu precise-security main restricted
# deb-src http://security.ubuntu.com/ubuntu precise-security main restricted
# deb http://security.ubuntu.com/ubuntu precise-security universe
# deb-src http://security.ubuntu.com/ubuntu precise-security universe
# deb http://security.ubuntu.com/ubuntu precise-security multiverse
# deb-src http://security.ubuntu.com/ubuntu precise-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 precise partner
# deb-src http://archive.canonical.com/ubuntu precise 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 precise main
# deb-src http://extras.ubuntu.com/ubuntu precise main

Ubuntu LTS 版本沒有很多更新。事實上，您在 LTS 版本中看到的唯一更新是

1. 安全更新
2. 主要錯誤的錯誤修復（文件失去錯誤等）

請參閱https://wiki.ubuntu.com/StableReleaseUpdates#When了解 LTS 版本何時獲得更新。

引用自：https://serverfault.com/questions/746477