Chapter 10. Customizing your installation of Debian GNU/Linux

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For example, with the argument `reload' the command

/etc/init.d/sendmail reload

sends the sendmail daemon a signal to reread its configuration file.

10.6 It looks as if Debian does not use

rc.local

to customize the

boot process; what facilities are provided?

Suppose a system needs to execute script

foo

on start up, or on entry to a particular (System

V) runlevel. Then the system administrator should:

  Enter the script

foo

into the directory

/etc/init.d/

.

  Run the Debian command

update rc.d

with appropriate arguments, to set up links

between the (command line specified) directories rc?.d and

/etc/init.d/foo

. Here,

'?' is a number from 0 through 6 and corresponds to each of the System V runlevels.

  Reboot the system.

The command

update rc.d

will set up links between files in the directories rc?.d and the

script in

/etc/init.d/

. Each link will begin with a 'S' or a 'K', followed by a number, fol 

lowed by the name of the script. Scripts beginning with 'S' in

/etc/rcN.d/

are executed

when runlevel

N

is entered. Scripts beginning with a 'K' are executed when leaving runlevel

N

.

One might, for example, cause the script

foo

to execute at boot up, by putting it in

/etc/init.d/

and installing the links with

update rc.d foo defaults 19

. The ar 

gument 'defaults' refers to the default runlevels, which are 2 through 5. The argument '19'

ensures that

foo

is called before any scripts containing numbers 20 or larger.

10.7 How does the package management system deal with packages

that contain configuration files for other packages?

Some users wish to create, for example, a new server by installing a group of Debian packages

and a locally generated package consisting of configuration files. This is not generally a good

idea, because

dpkg

will not know about those configuration files if they are in a different

package, and may write conflicting configurations when one of the initial  group  of packages

is upgraded.

Instead, create a local package that modifies the configuration files of the  group  of Debian

packages of interest. Then

dpkg

and the rest of the package management system will see that

the files have been modified by the local  sysadmin  and will not try to overwrite them when

those packages are upgraded.