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The Challenge
of a Cross-Distribution Configuration Tool
All of the tools discussed in this chapter
work on a wide variety of Linux distributions. One difficulty in designing such
a configuration tool is that the details of what these tools must do varies
substantially from one distribution to another. For instance, as discussed in
Starting Servers, different distributions may use different methods of starting
the same servers. Some use inetd and others use xinetd , SysV startup script locations and numbers differ between
distributions, configuration file locations differ between distributions, and
so on. This isn't a problem for distribution-specific tools like SuSE's YaST,
but tools like Linuxconf and Webmin face a challenge in working with many
different distributions.The answer to this challenge, in the case of
both Linuxconf and Webmin, is to rely upon configuration modules. The configuration tool itself provides
nothing more than a frameworkcode to interact with network clients, ways to
allow users to select options and enter free-form strings for things like
hostnames, and so on. The configuration tool relies upon modules that fill in
the details, such as file locations, information on the format of server
configuration files, and specific information that must be collected to
configure the subsystem in question. Modules exist for general configuration,
such as configuring SysV startup scripts or /etc/inittab settings,
and for specific server packages, such as Apache, sendmail, and Samba. These
modules can be modified for specific distributions or for specific server
packages. When you install a distribution that comes with Linuxconf or Webmin,
the configuration package includes modules for the servers included with the
distribution, or the modules may come with the individual packages. When you
install a configuration program from its home Web site, you must obtain a set
of modules for your distribution. Fortunately, these module sets are readily
available for most distributions, and usually ship with the configuration tool
itself.The existence of configuration modules makes
tools like Linuxconf and Webmin extremely flexible, but they can also pose
challenges. Specifically, if modules aren't kept up to date to reflect changes
in the systems they're meant to administer, the tools can become unreliable. This
may manifest in terms of an inability to configure an updated server, as errors
in such a configuration, or even in unreliable operation of the configuration
tool itself. These problems have been particularly troublesome for Linuxconf,
and Red Hat (its main associated distribution) has ceased installing Linuxconf
by default, as of Red Hat 7.1.Server-specific configuration packages, such
as SWAT, have an easier time because they don't need to deal with so much
variability. For instance, SWAT needs to read just one configuration file
(Samba's smb.conf ). Although this file's location may vary from one system to
another, SWAT itself is generally compiled at the same time as Samba, so it can
be compiled with the same default location. (You may also specify a nonstandard
location when you launch SWAT.) Thus, tools like SWAT don't usually rely upon
configuration modules.
