Open kmcrl value of 5 , and can verify in /proc/ cmdline

# vim /boot/grub/grub.conf

kernel/vmlinuz-2.6.32-71.el6.x86_64 ro root=/dev/mapper/GLSvg-GLSrootrd_LVM_LV=GLSvg/GLSroot

rd_LVM_LV=GLSvg/GLSswaprd_NO_LUKSrd_NO_MDrd_NO_DM

LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us crashkernel=auto rhgb quiet kmcrl=5

Restart to take effect and verification:

# cat /proc/cmdline

ro root=/dev/mapper/GLSvg-GLSroot rd_LVM_LV=GLSvg/GLSroot rd_LVM_LV=GLSvg/GLSswap rd_NO_LUKS rd_NO_MD rd_NO_DM

LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us rhgb quiet kmcrl=5