We will now try to outline some minor technical differences (which are constantly being reduced) in the distributions (Fedora/Red Hat and Debian) used [Mor03], which we will examine in more detail throughout the modules as they appear.
Modifications to or particularities of Fedora/Red Hat:
Using the grub boot loader (a GNU utility); unlike previous versions of most distributions, which tend to use lilo, Fedora uses grub. GRUB (grand unified bootloader) has a text-mode configuration (usually in /boot/grub/grub.conf) that is quite simple and that can be modified when booting. It is possibly more flexible than lilo. Lately, distributions tend to use grub; Debian also includes it as an option.
Example 5-2. Note
It is important to know the details of a distribution, as they are essential for performing a task or resolving an issue (for example, if there are extra tools available).
Management of alternatives. If there is more than one equivalent program present for a specific task, the alternative that will be used must be indicated through a directory (/etc/alternatives). This system was borrowed from Debian, which uses it a lot in its distribution.
TCP/IP portscanning program based on xinetd; in /etc/xinetd.d we will find the modular configuration files for some of the TCP/IP services, along with the /etc/xinetd.conf. configuration file. In classic UNIX systems, the program used for this was inetd, which had a single configuration file in /etc/inetd.conf, which was the case, for example, in the Debian distribution, which uses inetd, leaving xinetd as an option.
Some special configuration directories: /etc/profile.d, files that are executed when a user opens a shell; /etc/xinetd.d, configuration of some net services; /etc/sysconfig, configuration data for various aspects of the system; /etc/cron., various directories where the tasks that have to be performed regularly are specified (through crontab); /etc/pam.d, where the authentication modules are known as PAM: the permissions for the particular service or program are configured in each of the PAM files; /etc/logrotate.d, rotation configuration (when it is necessary to clean, compress etc.) of some of the log files for different services.
There is a software library called kudzu, which examines the hardware at start-up to detect any possible changes (in some previous versions of Fedora) in the configuration and to create the appropriate elements or configurations. Although there is currently a progressive migration to API Hal that controls precisely this aspect.
In Debian's case:
In-house packaging system based on DEB packages, with tools at various levels for working with packages such as: dpkg, apt-get, dselect, tasksel.
Debian follows FHS, over the directories structure, adding some particulars in /etc, such as: /etc/default, configuration files and default values for some programs; /etc/network, data and network interfaces configuration scripts; /etc/dpkg y /etc/apt, information on the configuration of the package management tools; /etc/alternatives, links to the default programs, in which there are (or may be) various available alternatives.
Configuration system for many software packages using the dpkg-reconfigure tool. For example:
makes it possible to select the incoming manager for X, or:
allows us to configure the different elements of X.
Uses the TCP/IP services configuration through inetd; the configuration isin file /etc/inetd.conf; there is an update-inetd tool for disabling or creating services entries.
Some special configuration directories: /etc/cron., several directories where the tasks that have to be performed regularly are specified (though crontab); /etc/pam.d, where PAM are authentication modules.