Appendix A: Development and advanced configuration

Importing configuration data

Although Zentyal UI interface greatly eases the system administrator work, some configuration tasks through the interface can be tedious if you have to perform them repeatedly. For example, adding 100 new user accounts or enabling an e-mail account for all 100 users.

These tasks can be automated easily through the Application Programming Interface (API) which is provided by Zentyal. You only need a basic knowledge of Perl [1], and to know the public methods exposed by the Zentyal modules you want to use. In fact, Zentyal web interface uses the same programming interface.

[1]Perl is a high-level, general-purpose, interpreted, dynamic programming language. http://www.perl.org/

An example on how to create a small utility is shown below, using the Zentyal API to automatically add an arbitrary number of users defined in a Comma Separated Values (CSV) file

#!/usr/bin/perl

use strict;
use warnings;

use EBox;
use EBox::Samba::User;
use File::Slurp;

my @lines = read_file('users.csv');
chomp (@lines);

EBox::init();

my $parent = EBox::Samba::User->defaultContainer();

for my $line (@lines) {
    my ($username, $givenname, $surname, $password) = split(',', $line);
    EBox::Samba::User->create(
        samAccountName => $username,
        parent => $parent,
        givenName => $givenname,
        sn => $surname,
        password => $password
    );
}

1;

Save the file with the name bulkusers and grant it execution permission using the following command: chmod +x bulkusers.

Before running the script, you must have a file called users.csv in the same directory. The appearance of this file should be as follows:

jfoo,John,Foo,jfoopassword,
jbar,Jack,Bar,jbarpassword,

Finally, you must be in the directory where the files are placed and run:

sudo ./bulkusers

This section has shown a small example of task automation using the Zentyal API, but the possibilities are almost unlimited.

Advanced Service Customization

You may need to extend Zentyal’s modules functionality to suit your needs. Zentyal offers you two different mechanisms to do so in such a way that you can still benefit from the abstraction, automation and context offered by the framework.

stubs: Templates that will be used to generate the configuration files used by the daemons. Modifying or creating a stub, you can customize the behaviour of any module, for example, adding a safe port to squid (HTTP Proxy) configuration.

hooks: Scripts that will be triggered during specific checkpoints of the life cycle of a module, for example adding a rule that marks certain types of traffic in the firewall after refreshing Zentyal’s rules.

Stubs

The Zentyal modules, once enabled, overwrite the original system configuration files for the services they manage. Modules do this through templates that essentially contain the structure of a configuration file for the service. Some parts of the resulting file are parametrized through variables provided by the framework.

How the configuration template system works

Configuration file from stub

Modifying the configuration files directly is incorrect, because these files will be overwritten each time the templates are processed (saving changes, for example). Zentyal’s own configuration templates can be found in /usr/share/zentyal/stubs, and their names are the original configuration file, plus the .mas extension, for example /usr/share/zentyal/stubs/dns/named.conf.mas. Modifying these templates is not a good solution either, because they will be overwritten if the software package is updated or reinstalled.

Therefore, to make your changes persistent, you can copy the original template file to a directory in /etc/zentyal/stubs/ with the name of the module.

For example:

sudo mkdir /etc/zentyal/stubs/dns
sudo cp /usr/share/zentyal/stubs/dns/named.conf.options.mas
/etc/zentyal/stubs/dns

Another advantage of copying the templates to /etc/zentyal/stubs/ is that you can keep control of the modifications that you have done over the original templates, and you will always be able to check these differences using the ‘diff’ tool. For example, for the former case:

diff /etc/zentyal/stubs/dns/named.conf.options.mas
/usr/share/zentyal/stubs/dns/named.conf.options.mas

For the next example, let’s suppose you don’t want to allow the DMZ network, which is internal but not so trusted, to perform DNS full zone transfers.

You will create the directory /etc/zentyal/stubs/dns and copy the files named.conf.local.mas and named.conf.options.mas.

You add the DMZ group containing the desired network ranges in named.conf.local.mas:

acl "DMZ" {
    192.168.200.0/24;
    192.168.201.0/24;
};

And then forbid zone transfers to this object in named.conf.options.mas:

allow-transfer { !DMZ; internal-local-nets; };

Remember to restart the module after modifying the files:

sudo service zentyal dns restart

Hooks

It is possible that you need to perform certain additional actions at some point of the execution state of a module. For example, when Zentyal saves changes related to the firewall, the first thing the firewall module does is to remove all existing rules, and then add the ones configured in Zentyal. If you manually add a custom iptables rule that is not covered by Zentyal interface, it will disappear when saving firewall module changes. To tweak that behavior, Zentyal lets you run scripts while the saving changes process is being performed. There are six points during the process when you may execute these scripts, also known as hooks. Two of them are general and the remaining four are per module:

  • Before saving changes: In /etc/zentyal/pre-save directory all scripts with running permissions are run before starting the save changes process.
  • After saving changes: Scripts with running permissions in /etc/zentyal/post-save directory are executed when the process is finished.
  • Before saving module configuration: Writing /etc/zentyal/hooks/<module>.presetconf file being <module> the module name you want to tailor, the hook is executed prior to overwriting the module configuration.
  • After saving module configuration: /etc/zentyal/hooks/<module>.postsetconf file is executed after saving <module> configuration.
  • Before restarting the service: /etc/zentyal/hooks/<module>.preservice is executed. This script could be useful to load Apache modules, for instance.
  • After restarting the service: /etc/zentyal/hooks/<module>.postservice is executed. For the firewall case, all the extra rules can be added here.

Let’s suppose your server has a transparent proxy, but you wish to exclude a certain network segment from the automatic redirection of HTTP connections. You will create the file /etc/zentyal/hooks/firewall.postservice with the following content:

#!/bin/bash
iptables -t nat -I premodules -s 192.168.200.0/24 \
-p tcp -m tcp --dport 80 -j ACCEPT

after that, you will give execution permissions to the file and restart the service:

sudo chmod +x firewall.postservice
sudo service zentyal firewall restart

These options have great potential and allow highly customizable Zentyal operations.

Development environment of new modules

Zentyal is designed with extensibility in mind and it is relatively simple to create new Zentyal modules.

Anyone with Perl language knowledge may take advantage of the Zentyal development framework to create web interfaces, and also benefit from the integration with the rest of the modules and the common features from the vast Zentyal library.

Zentyal design is completely object-oriented and it takes advantage of the Model-View-Controller (MVC) design pattern [2], so the developer only needs to define those features required by the data model. The remaining parts are generated automatically by Zentyal.

You can follow the development tutorial [3] to get started with some code examples.

[2]http://en.wikipedia.org/wiki/Model_View_Controller.
[3]https://wiki.zentyal.org/wiki/Tutorial

Zentyal is designed to be installed on a dedicated machine. This recommendation is also extended to the developing scheme. Developing on the same host is highly discouraged. The recommended option is to deploy a virtual system to develop as Appendix A: Test environment with VirtualBox explains in depth.

Commercial Edition Release Policy

Major Commercial Zentyal Server versions (such as 6.0 or 5.0) are published every two years, when a new Ubuntu Server LTS version becomes available. Minor Commercial Zentyal Server versions (such as 6.1 or 6.2) are published between mayor releases, introducing usually new features. Zentyal Server releases are solely based on Ubuntu Server LTS.

Zentyal offers 4.5 years of official support for Commercial Zentyal Editions. This ensures that since the release of a new major Zentyal Commercial Edition version, support for all security issues as well as commercial technical support and subscription services will be granted for this version during the next 4.5 years. After this time period, the Commercial Zentyal Edition version reaches the end of its life cycle and becomes unsupported.

Development Edition Release Policy

The general release cycle of the Development Edition is similar to that of the Commercial Edition: Major Zentyal Server versions (such as 6.0 or 5.0) are published every two years and minor Zentyal Server versions (such as 6.1 or 6.2) are published between mayor releases, introducing usually new features. All releases are always based on the Ubuntu Server LTS.

It is important to note that the Development Edition is the laboratory were new experimentations and features are first being deployed. Only when a new feature or a fix has been stabilized in the Developmen Edition, it will be back ported to the Commercial Edition. Also, only the latest Development Edition version is maintained.

Bug management policy

Zentyal uses [4] Github to manage the issues and requests for new features that the users create. Any user with an account in GitHub can create and answer to any issue or request.

[4]Zentyal Github: https://github.com/zentyal/zentyal/issues

It is highly recommendable to report a bug when you are fairly sure that your problem is really a bug and not just an expected result of the program under determined circumstances.

To report a bug, check first in the GitHub if the bug was reported already. If not, report the bug via the Zentyal web interface (if the crash appears there) or manually via the Zentyal bug tracker. If the bug was reported already, you can still help by confirming that you have reproduced it and giving additional details about the issue.

It is absolutely necessary to include detailed steps to reproduce the issue so that the Zentyal Development Team can fix it. If you are reporting manually, include at least the ‘/var/log/zentyal/zentyal.log‘ file or any other useful information you think it’s related with your issue. Screenshots are also welcome if you think they will help to see the problem.

Community support

Community support is provided mainly on the Internet. There are many occasions in which the community is able to support itself. That is, the users help each other.

The community members are an important, even fundamental, providers of information for the product development. Users contribute by discovering hidden bugs and help developers to improve the product so it becomes more attractive to more users.

This voluntary support, logically, does not offer any guarantees. If a user asks a question, it is possible that no reply is given depending on the question format, timing or any other circumstances.

Zentyal community support channels is centered on the forum [5], although IRC channels [6] are also available.

[5]http://forum.zentyal.org
[6]irc.freenode.net server, #zentyal (English) and #zentyal-es (Spanish) channels.

All this information is available, with further documentation, in the community section of Zentyal Wiki (http://wiki.zentyal.org).