Under Red Hat Enterprise Linux, it is possible to change the
default runlevel at boot time.
To change the runlevel of a single boot session, use the
When the GRUB menu bypass screen appears at boot time, press any
key to enter the GRUB menu (within the first three seconds).
Press the [a] key to append to the
Add <space><runlevel> at the end of the boot
options line to boot to the desired runlevel. For example, the
following entry would initiate a boot process into runlevel 3:
grub append> ro root=/dev/VolGroup00/LogVol00 rhgb quiet 3