How to Increase GRUB Timeout in CentOS 7

• Edit the file /etc/default/grub by issuing the following command

      $ vim /etc/default/grub # Edit the GRUB_TIMEOUT field and set the new timeout

• Generate the new grub configuration file by issuing the following command

      $ grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg

Note: If Windows is installed before installing CentOS, running grub2-mkcondig should detect Windows boot loader too.