HOW TO CHANGE RUN LEVEL IN UBUNTU

This is really tricky since ubuntu starts to use upstart. In the current start sequence, after all scripts in the S runlevel are processed, the system will execute /etc/init.d/rc-default to get into the next runlevel. With the /etc/init.d/rc-default shipped with Ubuntu, you don't really have any choice for anything other than runlevel 2 and single user mode. So in order to recorgonize the kernel runlevel parameter (a digit or letter S in the kernel parameter list), you will need to revise /etc/init.d/rc-default. Following is a simple implementation (I didn't test it because I don't have my ubuntu computer with me, but it should work)

# Before testing for single user runlevel in the kernel parameter list, add these lines:

RL=`sed -n -e "s/.*[ \t]\([S0-6]\)[ \t].*/\1/p" -e "s/.*[ \t]\([S0-6]\)$/\1/p" /proc/cmdline`

if [ 'x'$RL != 'x' ]; then
  telinit $RL;
elif ... (following the original script here to test "single" in the cmdline)

After this modification, you can add the runlevel parameter in grub to boot to the desired runlevel. You will probably want to change the /etc/rc*.d/ links for the runlevel you want, since by default, runlevel 2-5 are identical in Ubuntu.

Just want to add the following link in my blog:
http://plutino-cnotes.blogspot.com/2009/01/add-non-graphical-login-option-in.html
which details how to add an non-graphical boot option in Ubuntu

To switch runlevels easily, create an /etc/inittab file and add the line

id:3:initdefault:

Switch 3 to whatever run level you want.

Remember that Upstart emulates the old init system, including obeying an inittab file if one is present. I just tested and this works fine in 9.04 Alpha.