Init Runlevels - Red Hat LINUX 7.2 Reference Manual

54
• VNCSERVERS= <value> , where <value> is set to something like "1:fred", to indicate
that a VNC server should be started for user fred on display :1. User fred must have set a VNC
password using vncpasswd before attempting to connect to the remote VNC server.
Note that when you use a VNC server, your communication with it is unencrypted, and so it
should not be used on an untrusted network.
SSH to secure the VNC communication, please read the information found at http://www.uk.re-
search.att.com/vnc/sshvnc.html. To find out more about SSH, see Chapter 10, SSH Protocol or
Official Red Hat Linux Customization Guide.

3.4 Init Runlevels

The idea behind operating different services at different runlevels essentially revolves around the fact
that different systems can be used in a different ways. Some services cannot be used until the system
is in a particular state, or mode, such as ready for more than one user or has networking available.
There are times in which you may want to operate the system at a lower mode, such as fixing disk
corruption problems in runlevel 1 so no other users can possibly be on the system or leaving a server
in runlevel 3 without an X session running. In these cases, running services that depend upon a higher
system mode to function does not make sense because they will not work correctly anyway. By already
having each service assigned to start when its particular runlevel is reached, you ensure an orderly start
up process and can quickly change the mode of the machine without worrying about which services
to manually start or stop.
Generally, Red Hat Linux operates in runlevel 3 — full multi-user mode. The following runlevels are
defined in Red Hat Linux:
• 0 — Halt
• 1 — Single-user mode
• 2 — Not used (user-definable)
• 3 — Full multi-user mode
• 4 — Not used (user-definable)
• 5 — Full multi-user mode (with an X-based login screen)
• 6 — Reboot
The default runlevel for a system to boot to and stop is configured in /etc/inittab. For more
information on /etc/inittab, see Section 3.2.3, SysV Init.
Feel free to configure runlevels 2 and 4 as you see fit. Many users configure those runlevels in a way
that makes the most sense for them while leaving the standard runlevels 3 and 5 alone. This allows
Chapter 3:Boot Process, Init, and Shutdown
For specific instructions concerning the use of