1.错误信息

已加载插件：langpacks, product-id, search-disabled-repos,
subscription-manager This system is not registered with an entitlement
server. You can use subscription-manager to register. There are no
enabled repos. Run “yum repolist all” to see the repos you have. To
enable Red Hat Subscription Management repositories:
subscription-manager repos --enable To enable custom repositories:
yum-config-manager --enable

2.解决步骤

在安装gcc的时候出现下面信息:

如果出现上面问题,只需要输入下面命令即可:
进入到/etc/yum.repos.d/目录,下载Centos-7.repo
下载的官网 http://mirrors.aliyun.com,复制下载链接

然后通过wget进行下载,如果没有wget可以直接下载Centos-7.repo,然后把Centos-7.repo文件上传到/etc/yum.repos.d/中即可

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

查看Centos-7.repo是否已经下载了

使用 yum clean all 和 yum makecache 命令

如果 yum makecache 报 256错误,修改CentOS-Base.repo文件即可:

vim /etc/yum.repos.d/CentOS-Base.repo

修改内容为(先删除原有内容,然后把替换为下面的内容,然后键盘esc键进入底行模式,输入 :wq 进行保存):

# 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-7 - Base - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os
baseurl=http://mirrors.163.com/centos/7/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

#released updates
[updates]
name=CentOS-7 - Updates - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates
baseurl=http://mirrors.163.com/centos/7/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

#additional packages that may be useful
[extras]
name=CentOS-7 - Extras - 163.com
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
baseurl=http://mirrors.163.com/centos/7/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-7 - Plus - 163.com
baseurl=http://mirrors.163.com/centos/7/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.163.com/centos/RPM-GPG-KEY-CentOS-7

再次执行 yum makecache 命令

最后再次使用 yum install gcc 命令安装gcc,就可以成功安装了