我在运行 Windows 8 x64 的虚拟机中安装 Ubuntu 14.04.1 LTS x64。在运行安装程序时，我没有在要求设置某些必需代理的对话框中输入任何内容。默认情况下，虚拟机使用桥接网络连接网络。
此虚拟机用于测试安装程序脚本的一些内部开发。因此，我在基本安装程序完成后拍摄了快照。我可以正确启动该虚拟机，并且始终恢复到该快照以重试我们自己的安装程序。
这些测试总是以这种方式开始：
- 将虚拟机恢复到初始快照
- 使用远程托管的 SVN 克隆安装程序
git svn（始终成功） - 调用克隆的安装程序
该安装程序用于调用
apt-get update
首次启动时，以及每天重复调用时再次调用。此外，它还调用
apt-get upgrade
每天一次，使用
apt-get install <somepackage>
用于安装必需但缺少的依赖项。
- 安装程序当前未添加任何 PPA。
- 快照也没有列出任何 PPA。
但是，即使在刚刚恢复到该快照的 VM 中，安装程序的初始调用apt-get update偶尔也会失败，因为找不到某些存储库或选定存储库的哈希值总和不匹配。
由于这个问题，我们目前无法建议客户将现有安装升级到 Ubuntu 14.04 LTS，尽管它包含几个非常有益的改进（例如支持 LXC）。
目前已证实的解决方案是
- 等待30-60分钟
- 将虚拟机恢复到初始快照
- 重新启动安装程序检查更新存储库是否成功
我很确定这与我们办公室的网络连接无关，因为它发生在不同的地方、不同的时间和日期，同时从网络流式传输、通过 Skype 进行音频/视频通话等，没有任何问题。
这是我的/etc/apt/sources.list：
#
# deb cdrom:[Ubuntu-Server 14.04.1 LTS _Trusty Tahr_ - Release amd64 (20140722.3)]/ trusty main restricted
#deb cdrom:[Ubuntu-Server 14.04.1 LTS _Trusty Tahr_ - Release amd64 (20140722.3)]/ trusty main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://de.archive.ubuntu.com/ubuntu/ trusty main restricted
deb-src http://de.archive.ubuntu.com/ubuntu/ trusty main restricted
## Major bug fix updates produced after the final release of the
## distribution.
deb http://de.archive.ubuntu.com/ubuntu/ trusty-updates main restricted
deb-src http://de.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://de.archive.ubuntu.com/ubuntu/ trusty universe
deb-src http://de.archive.ubuntu.com/ubuntu/ trusty universe
deb http://de.archive.ubuntu.com/ubuntu/ trusty-updates universe
deb-src http://de.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://de.archive.ubuntu.com/ubuntu/ trusty multiverse
deb-src http://de.archive.ubuntu.com/ubuntu/ trusty multiverse
deb http://de.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
deb-src http://de.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://de.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://de.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
/etc/apt/sources.list.d/...中没有任何文件