在 CentOS 8 环境下安装 docker 遇到的一些问题

因为 CentOS 8 已经停止维护了，如果原来系统中的软件源已经被改的乱七八糟了，推荐全部删掉重新下载：

# 阿里云
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo

或者自行创建 CentOS-Base.repo，如清华的：

# CentOS-Base.repo
#
[BaseOS]
name=CentOS-$releasever - Base
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/8.5.2111/BaseOS/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=BaseOS&infra=$infra
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

[AppStream]
name=CentOS-$releasever - AppStream
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/8.5.2111/AppStream/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=AppStream&infra=$infra
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

[PowerTools]
name=CentOS-$releasever - PowerTools
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/8.5.2111/PowerTools/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=PowerTools&infra=$infra
enabled=0
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

#additional packages that may be useful
[extras]
name=CentOS-$releasever - Extras
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/8.5.2111/extras/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=extras
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-$releasever - Plus
baseurl=https://mirrors.tuna.tsinghua.edu.cn/centos-vault/8.5.2111/centosplus/$basearch/os/
#mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=centosplus
gpgcheck=1
enabled=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial

如果遇到错误 Failed to start docker: Access denied，可以尝试执行命令

kill -TERM 1

参考：https://superuser.com/questions/1125250/systemctl-access-denied-when-root/1130976