Red hat Linux is booting in Single user mode only even /etc/inittab contains runlevel 3

Adding "1" as a kernel parameter in /boot/grub/grub.conf will force linux to boot into SINGLE USER mode, discarding /etc/inittab default run level. Check "kernel" line in /boot/grub/grub.conf

Red hat Linux is booting in Single user mode if /etc/inittab contains runlevel1 as default runlevel not3.the runlevel3 is for multiuser mode .Also ,you can start Redhat in rescue mode when grub is displayed edit kernel option with pressing keyboard  "e" and write "1" after "quiet" word.if you want to return to graphical mode  edit /etc/inittab with default runlevel "5" and Ctrl+D from rescue mode.