配置镜像源的主要作用是优化软件下载速度、提升系统更新稳定性，并确保软件包获取的可靠性
我这里配置阿里云镜像源
镜像的具体内容参考此文:
文章链接
以防万一,先备份一下
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
然后开始修改
sudo nano /etc/apt/sources.list
将里面原有的加#全部注释掉
并复制黏贴参考博文里的镜像内容,我的ubuntu是18.04，对应的镜像是
deb https://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse
# deb https://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
# deb-src https://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse
然后退出保存
测试一下有无生效
#更新软件列表：
sudo apt update
#检查软件源：
apt policy curl
配置成功