[root@gymp ~]# cat /etc/default/grub.old
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(se{d}^{\prime }s,release.\ast$,g’ /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT=“console”
GRUB_CMDLINE_LINUX=“crashkernel=auto rhgb quiet”
GRUB_DISABLE_RECOVERY=“true”
[root@gymp ~]#

修改GRUB_CMDLINE_LINUX,即添加参数：ipv6.disable=1
例子：
GRUB_CMDLINE_LINUX=“ipv6.disable=1 crashkernel=auto rhgb quiet”

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