这几个问题是Linux操作的入门问题，但是确实也会让刚上手Linux小伙伴头疼一阵，故特有此文，希望能对刚入门的小伙伴有一些帮助~

众所周知

在linux上在线安装软件需要用到yum命令，经常下述命令来安装

yum install [-y] 包名  #-y的意思就是确认安装，如果不添加-y，则后续还需要再确认一下

但是实际安装的时候经常遇到下述问题

报错没有可用的包

此时引出了一个概念

yum源是什么？

Yum源是指Yum软件包管理器在系统中使用的软件源。Yum（全称为Yellowdog Updater, Modified）是一款在Linux系统中常用的软件包管理器，用于自动化地下载、安装、更新和删除软件包。Yum源可以理解为存储软件包的仓库，用户可以通过Yum源获取和安装所需的软件包。Yum源包含了各种软件包的元数据信息，可以根据用户的需求搜索、安装和更新软件包。通过配置不同的Yum源，用户可以访问不同的软件仓库，以满足不同的需求。

所以对于日常用户来说要做的就是：修改yum源的配置文件

配置yum源

编辑yum源文件（只要是在/etc/yum.repos.d/路径下的.repo的文件都可以，名字可以随便起。例如当前的文件命名为：aliyun.repo）

vi /etc/yum/repos.d/aliyum.repo

输入以下内容（注意！！这个示例是centos操作系统的yum源，其他操作系统不能直接复制）：

# CentOS-Base.repo
#
# The mirror system uses the connecting IP address of the client and the
# update status of each mirror to pick mirrors that are updated to and
# geographically close to the client.  You should use this for CentOS updates
# unless you are manually picking other mirrors.
#
# If the mirrorlist= does not work for you, as a fall back you can try the 
# remarked out baseurl= line instead.
#
#
 
[base]
name=CentOS-$releasever - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/os/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/os/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#released updates 
[updates]
name=CentOS-$releasever - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/updates/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/updates/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/extras/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/extras/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/centosplus/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/centosplus/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7
 
#contrib - packages by Centos Users
[contrib]
name=CentOS-$releasever - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos/$releasever/contrib/$basearch/
        http://mirrors.aliyuncs.com/centos/$releasever/contrib/$basearch/
        http://mirrors.cloud.aliyuncs.com/centos/$releasever/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos/RPM-GPG-KEY-CentOS-7

也可以从阿里官网直接下载：

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

清理并重建缓存

yum clean all && yum makecache

重建缓存成功，继续安装

自动下载依赖，安装成功！