在 Ubuntu 的更新中几个小问题的总结

有一台 Ubuntu 服务器，由于一直运行很正常，就很久没有去打理它了。某一天上面提示

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

的字样，看来很久没有更新了。如是就打算使用

sudo apt-get update

和

sudo apt-get upgrade

来更新一下，刷了半天，报错如下：

E: Some index files failed to download. They have been ignored, or old ones used instead.

嗯，换一个国内的源试试。听说中国科学技术大学的源很不错，找来试试。

sudo mv /etc/apt/sources.list /etc/apt/sources.list.old

然后把 /etc/apt/sources.list 内容按 https://lug.ustc.edu.cn/wiki/mirrors/help/ubuntu 提示换成如下：

# 默认注释了源码镜像以提高 apt update 速度，如有需要可自行取消注释
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial main main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-updates main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse
deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-security main restricted universe multiverse
 
# 预发布软件源，不建议启用
# deb https://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse
# deb-src https://mirrors.ustc.edu.cn/ubuntu/ xenial-proposed main restricted universe multiverse

然后再 sudo apt-get update 就没有问题了。
再使用 sudo apt-get upgrade 也都正常了。

另外，如果在使用过程中提示：

N: Ignoring file '50unattended-upgrades.ucf-dist' in directory '/etc/apt/apt.conf.d/' as it has an invalid filename extension  

将这个文件重命名

mv /etc/apt/apt.conf.d/50unattended-upgrades.ucf-dist /etc/apt/apt.conf.d/50unattended-upgrades.ucf-dist.old

就可以了。