If GRUB was not installed during the Red Hat Linux installation process it can be installed afterward. Once installed, it automatically becomes the default boot loader.
Before installing GRUB, make sure to use the latest GRUB package available or use the GRUB package from the Red Hat Linux installation CD-ROMs. For instructions on installing packages, see the chapter titled Package Management with RPM in the Red Hat Linux Customization Guide.
Once the GRUB package is installed, open a root shell prompt and run the command /sbin/grub-install <location>, where <location> is the location that the GRUB Stage 1 boot loader should be installed.
The following command installs GRUB to the MBR of the master IDE device on the primary IDE bus: /sbin/grub-install /dev/hda
The next time the system boots, the GRUB graphical boot loader menu will appear before the kernel loads into memory.