1.前言

在CentOS 8上用yum安装wget时，出现错误：Error: Failed to synchronize cache for repo 'AppStream'，如下图所示：

想着可能需要升级一下yum，结果还是同样的错误。

2.解决方法

其实就是因为默认的源不行了，换个源就完事了，这里演示的是换阿里云的源。具体来说，需要修改/etc/yum.repos.d下的四个文件：“CentOS-AppStream.repo”，“CentOS-Base.repo”，“CentOS-Extras.repo”，“CentOS-PowerTools.repo”。

这里推荐用FinalShell，文件修改只需要下载到本地，编辑完了后，按Ctrl+S保存就会自动上传覆盖，简单快速。

分别将对应文件替换为下面的内容，建议复制后直接覆盖原来文件里面的所有内容就行。

2.1 CentOS-AppStream.repo

# CentOS-AppStream.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.
#
#

[AppStream]
name=CentOS-$releasever - AppStream
baseurl=https://mirrors.aliyun.com/centos/8-stream/AppStream/$basearch/os/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

2.2 CentOS-Base.repo

# 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.
#
#

[BaseOS]
name=CentOS-$releasever - Base
baseurl=https://mirrors.aliyun.com/centos/8-stream/BaseOS/$basearch/os/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

2.3 CentOS-Extras.repo

# CentOS-Extras.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.
#
#

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=https://mirrors.aliyun.com/centos/8-stream/extras/$basearch/os/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

2.4 CentOS-PowerTools.repo

# CentOS-PowerTools.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.
#
#

[PowerTools]
name=CentOS-$releasever - PowerTools
baseurl=https://mirrors.aliyun.com/centos/8-stream/PowerTools/$basearch/os/
gpgcheck=1
enabled=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

3.检验

重新执行命令：

yum -y install wget

可以看到能够正常安装了。