一、问题描述与原因
在使用 yum install 或者 yum update 时，均会报错如下：
Loaded plugins: fastestmirrorSetting up Update ProcessDetermining fastest mirrorsYumRepo Error: All mirror URLs are not using ftp, http[s] or file.Eg. Invalid release/repo/arch combination/removing mirrorlist with no valid mirrors: /var/cache/yum/i386/6/base/mirrorlist.txtError: Cannot find a valid baseurl for repo: base
出现这个错误的原因是官方自 2020 年 11 月底起不再维护 CentOS 6 了，所以之前的 yum 存储库也不能用了：
二、问题解决方法
解决方法很简单，就是修改 baseurl。
1、进入到 /etc/yum.repos.d目录下：
cd /etc/yum.repos.d
先备份原来的 CentOS-Base.repo 文件：
cp CentOS-Base.repo CentOS-Base.repo.old
修改 CentOS-Base.repo 文件：
vi CentOS-Base.repo
主要修改 baseurl 的值，包括 [base]、[updates] 和 [extras]：
[base]name=CentOS-$releasever - Base# mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os&infra=$infra# baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/baseurl=https://vault.centos.org/6.10/os/$basearch/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6# released updates[updates]name=CentOS-$releasever - Updates# mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra# baseurl=http://mirror.centos.org/centos/$releasever/updates/$basearch/baseurl=https://vault.centos.org/6.10/updates/$basearch/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6# additional packages that may be useful[extras]name=CentOS-$releasever - Extras# mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras&infra=$infra# baseurl=http://mirror.centos.org/centos/$releasever/extras/$basearch/baseurl=https://vault.centos.org/6.10/extras/$basearch/gpgcheck=1gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-6
清理yum 缓存
yum clean all
之后再执行 yum install 或者 yum update 就一切正常了！
