一、安装

1. 下载yum安装包并解压

   wget http://yum.baseurl.org/download/3.2/yum-3.2.28.tar.gz
   tar xvf yum-3.2.28.tar.gz 

2. 进入目录并install

cd yum-3.2.28
sudo apt install yum

参考引用：linux中安装yum简单方法 - 简书

3. 配置yum repo

创建文件

touch /etc/yum/repo.d/CentOS-Base.repo 

（我的/etc/yum/repo.d下没有文件）

下载Centos-7.repo（根据你的Centos version选择对应的）

wget -O /etc/yum/repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

 4. 更新

yum check-update
yum update
yum clean all

参考：centos镜像-centos下载地址-centos安装教程-阿里巴巴开源镜像站

二、可能遇到的问题

1. apt install  yum 时报：E: Unable to locate package yum

 搜了下，解决方案是用：sudo apt-get update

但是发现我的apt 的软件源配置的有问题，故重新配了软件源

2. 修改软件源

vi /etc/apt/sources.list

deb https://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty main restricted universe multiverse
deb https://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty-security main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty-updates main restricted universe multiverse

deb https://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src https://mirrors.aliyun.com/ubuntu/ trusty-backports main restricted universe multiverse

参考：https://zhuanlan.zhihu.com/p/15087295

3. 更新apt软件源后，再次 sudo apt-get install yum，发现：        

 很明显，没装python-sqlitecachec和python-sqlitecachec， 用apt install

sudo apt-get install python-sqlitecachec
sudo apt-get install python-urlgrabber

4. 使用yum repolist时报：

https://mirrors.aliyun.com/centos/%24releasever/AppStream/x86_64/os/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 "

发现url中有%24releasever，这个是变量，没有被系统识别，故用了简单粗暴的方法，将CentOS-Base.repo用$releasever变量的地方全部替换成对应的版本号，我用的是7

查看版本号命令：

lsb_release -a

vim CentOS-Base.repo
:%s/$releasever/7/g

参考：yum源中$releasever不能被系统识别_9t night的博客-CSDN博客