#ifconfig -a | grep inet6
#ip addr show | grep net6

#vi /etc/default/grub
GRUB_CMDLINE_LINUX----该行增加ipv6.disable=1

[root@centos8 ~]# grep CMDLINE /etc/default/grub
GRUB_CMDLINE_LINUX="ipv6.disable=1 crashkernel=auto resume=/dev/mapper/cl-swap rd.lvm.lv=cl/root rd.lvm.lv=cl/swap rhgb quiet"

#grub2-mkconfig -o /boot/grub2/grub.cfg

#vi /etc/sysctl.conf
net.ipv6.conf.all.disable_ipv6 =1
net.ipv6.conf.default.disable_ipv6 =1

[root@centos8 ~]# tail -n 2 /etc/sysctl.conf
net.ipv6.conf.all.disable_ipv6 =1
net.ipv6.conf.default.disable_ipv6 =1

#vi /etc/selinux/config
SELINUX=disabled


#reboot