ubuntu-19.10更换国内镜像源

ubuntu用sudo apt-get update和sudo apt-get upgrade更新软件库等下载速度慢的问题可能是由于访问国外源网站造成的，可以更换国内镜像源解决该问题。

国内有很多镜像源，像阿里云镜像源、163网易镜像源、清华大学镜像源、中科大镜像源等，我这里采用阿里云镜像源，其他的镜像源可自行查找，更换方法是一样的。

这是阿里云镜像源：

#阿里云镜像源
deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse

注意源中的代码bionic是ubuntu-18.04版本的发行好
如果是ubuntu-19.10，则要将bionic更换为eoan
即：

#阿里云镜像源
deb http://mirrors.aliyun.com/ubuntu/ eoan main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ eoan-security main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-security main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ eoan-updates main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-updates main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ eoan-proposed main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-proposed main restricted universe multiverse

deb http://mirrors.aliyun.com/ubuntu/ eoan-backports main restricted universe multiverse
deb-src http://mirrors.aliyun.com/ubuntu/ eoan-backports main restricted universe multiverse

打开ubuntu终端，ctrl+alt+t

依次输入以下命令：
备份源文件：sudo cp /etc/apt/sources.list /etc/apt/sources_init.list
(由于使用sudo命令，所以要输入用户密码，密码是隐式的，不要以为没敲进去)
更改source.list文件内容，用vim编辑或者gedit编辑
这里使用gedit编辑:sudo gedit /etc/apt/sources.list

可以将里面的全部内容注释掉或删掉，然后将阿里云镜像源copy进去，注意跟自己的版本号对应。
保存后关闭

然后输入以下命令更新源和下载相关的包
sudo apt-get update
sudo apt-get upgrade

输入sudo apt-get update可能出这样的错

这里将那个lock删掉就可以了：sudo rm /var/lib/apt/lists/lock
然后执行：sudo aot-get update和sudo apt-get upgrade