you can permantelty change the server's runlevel by editing the /etc/inittab file. this file contains a linc like this:

id:3:initdefault:

this example shows a system configured for runlevel 3. to modify it, you can change the 3 to whatever value you want. after making the changes, you can make ther server to switch immediately to the new runlevel by running telinit. you can send this command for example:

telinit Q

this command will cause the server to read your chagnes directly, or you can use the runlevel in place of Q.

NOTE: do not et the default runlevel to 0 or 6 since this will cause the system to shutdown or reboot as soon as it boots, going into a loop