Chapter 10. Customizing your installation of Debian GNU/Linux

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10.4 How can I configure an X11 program's application defaults?

Debian's

X

programs

will

install

their

application

resource

data

in

the

/etc/X11/app defaults/

directory.

If you want to customize X applications glob 

ally, put your customizations in those files. They are marked as configuration files, so their

contents will be preserved during upgrades.

10.5 Every distribution seems to have a different boot up method.

Tell me about Debian's.

Like all Unices, Debian boots up by executing the program

init

. The configuration file

for

init

(which is

/etc/inittab

) specifies that the first script to be executed should be

/etc/init.d/rcS

. This script runs all of the scripts in

/etc/rcS.d/

by sourcing or forking

subprocess depending on their file extension to perform initialization such as to check and to

mount file systems, to load modules, to start the network services, to set the clock, and to per 

form other initialization. Then, for compatibility, it runs the files (except those with a `.'in the

filename) in

/etc/rc.boot/

too. Any scripts in the latter directory are usually reserved for

system administrator use, and using them in packages is deprecated.

After completing the boot process,

init

executes all start scripts in a directory specified by

the default runlevel (this runlevel is given by the entry for

id

in

/etc/inittab

). Like most

System V compatible Unices, Linux has 7 runlevels:

  0 (halt the system),

  1 (single user mode),

  2 through 5 (various multi user modes), and

  6 (reboot the system).

Debian systems come with id=2, which indicates that the default runlevel will be '2' when the

multi user state is entered, and the scripts in

/etc/rc2.d/

will be run.

In fact, the scripts in any of the directories,

/etc/rcN.d/

are just symbolic links back to scripts

in

/etc/init.d/

. However, the names of the files in each of the

/etc/rcN.d/

directories

are selected to indicate the way the scripts in

/etc/init.d/

will be run. Specifically, before

entering any runlevel, all the scripts beginning with 'K' are run; these scripts kill services. Then

all the scripts beginning with 'S' are run; these scripts start services. The two digit number

following the 'K' or 'S' indicates the order in which the script is run. Lower numbered scripts

are executed first.

This approach works because the scripts in

/etc/init.d/

all take an argument which can be

either `start', `stop', `reload', `restart' or `force reload' and will then do the task indicated by the

argument. These scripts can be used even after a system has been booted, to control various

processes.