Changing the Default Run Level

Oracle Database Tips by Donald Burleson

As discussed in Chapter 3, the run level of a Linux computer describes whether the system will boot to a graphical interface (level 5) or a command line (level 3).  

It can be very useful to change the run level from 5 to 3. When booting up, instead of a graphical login, a command line login will be seen. All that is needed at that point is the command used to launch the desired windows manager. Quitting a windows manager will bring the user back to the command prompt. Compare that to level 5, in which the only way to change windows managers is to run the command init 3 as root, which will reboot the machine.

To change the default run level, edit the file /etc/inittab and change the line that describes the default run level so it reads:

id:3:initdefault:

Then, reboot the machine. When the machine finishes rebooting, login at the command prompt, and issue the startx command to launch the gnome interface. To return to the command prompt, logout of gnome.

Trivial Windows Manager (TWM)

The trivial windows manager is the ultimate in lightweight windows managers. Its strength is it has almost no features at all, which means it requires very little of CPU and RAM. About the only things a user will be able to do is to move, minimize and resize various windows.

Use the command xinit /usr/X11R6/bin/twm to launch the trivial windows manager. At first, all that appears is a black screen with an X for the mouse cursor in the middle. Click on the desktop, and the options menu appears. Launch a terminal by selecting xterm. From the terminal, any program can be launched.

FVWM

Another windows manager that is worthy of mention is fvwm, a lightweight windows manager with more features than twm. Download fvwm at http://fvwm-themes.sourceforge.net/rpm/.

At the bottom of that page is a link to required packages. Click it and download libstroke-0.4-1mdk.i586.rpm. Install the packages in the order shown in Figure E.2.

Once fvwm is installed, exit twm and use the command xinit /usr/bin/fvwm to launch fvwm. The initial screen will be very bare. Click the desktop and run the setup form. Select all the available modules and click to copy the config files and restart fvwm. This will create text configuration files in the directory ~/.fvwm for the current user only. These files can be edited to change the fvwm desktop appearance and functionality.

Fvwm can be an excellent desktop manager for installing Oracle software or creating databases. Figure E.3 shows the dbca running in the fvwm window with the CPU monitor below it showing the CPU activity as the database nears completion.

FVWM's CPU monitor is a fast and easy method to ensure that database creation is not hanging. If the CPU is being utilized, then database creation is still ongoing.

Using the Alias Command to Simplify Launching Windows Managers

To make launching the desired windows manager a simple, easy to remember command, add the following lines to the ~/.bashrc file of each user who desires it:

alias fvwm="xinit /usr/bin/fvwm"
alias gnome="xinit /usr/bin/gnome-session"
alias twm="xinit /usr/X11R6/bin/twm"

Launching a WM without Tying up the Command Prompt

Use the ampersand at the end of the command to launch a windows manager. By doing so, the terminal login can be returned to by typing [ctl+alt+F1] without having to quit the windows manager to free up the command prompt. To return to the windows manager, type [ctl+alt+F7].

Launching a GUI Program without a Windows Manager

It is possible to launch an Oracle GUI program without being in a windows manager interface. For example, the command xinit $ORACLE_HOME/bin/dbca will launch the database configuration assistant alone with no window around the application. This is not advised because control will be lost over which windows appear on top and whether the windows that appear can be moved or minimized.