Step1:
Encrypt a password in MD5 format:
# grub-md5-crypt Password: Retype password: $1$ENXcp$ahirbu0qZQR6SC9B7VCKI1
Copy encrypted password and add it in /etc/grub.conf or /boot/grub/grub.conf file, below “timeout” option. use format:
password --md5 $1$z3OXp$opU39tOqdiRfXz1QtsQzz/
For example:
#boot=/dev/sda default=0 timeout=5 password --md5 $1$z3OXp$opU39tOqdiRfXz1QtsQzz/ splashimage=(hd0,0)/grub/splash.xpm.gz hiddenmenu title CentOS (2.6.32-573.7.1.el6.x86_64) root (hd0,0) kernel /vmlinuz-2.6.32-573.7.1.el6.x86_64 ro root=/dev/mapper/VolGroup-lv_root nomodeset rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD rd_LVM_LV=VolGroup/lv_swap SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=VolGroup/lv_root KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet initrd /initramfs-2.6.32-573.7.1.el6.x86_64.img title CentOS (2.6.32-431.el6.x86_64) root (hd0,0) kernel /vmlinuz-2.6.32-431.el6.x86_64 ro root=/dev/mapper/VolGroup-lv_root nomodeset rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD rd_LVM_LV=VolGroup/lv_swap SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=VolGroup/lv_root KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet initrd /initramfs-2.6.32-431.el6.x86_64.img
Reboot your system and try to edit the grub parameters, it will ask you for password, before proceeding to edit.
