2. Positioning in the IT world

To comprehend the architecture of UCS, it’s important to understand the origin and where it locates in the world of IT.

2.1. Origin

UCS is a Linux distribution derived from Debian GNU/Linux. Among others, it benefits from the strong software package manager, the high quality maintenance and the long-term stability as operating system for servers. Over the years, Debian has been and is a solid basis for UCS.

UCS is part of the open source family and has strong relations to important projects like for example Samba and OpenLDAP.

2.1.1. History

Univention started UCS in 2002 as a collection of scripts that turn a Debian system into a Linux server that offers Windows domain capability. The goal was to offer companies and organizations a standardized Linux server as alternative to Microsoft Windows Server that implements Microsoft’s domain concept. Over the time it developed to an enterprise Linux distribution with maintenance cycles that better suited the needs of organizations.

2.1.2. Packages

On UCS software is managed in software packages. The packages on UCS use the deb file format. For more information on the deb file format, see Wikipedia about deb (file format) and Basics of the Debian package management system in the Debian FAQ.

UCS—like Debian—uses a package manager, which is a collection of software tools, to automate the process of installation, upgrade, configuration, and removal of computer programs. Packages organize such computer programs on UCS. In UCS the package manager is APT. For more information about APT, see the Debian package management chapter in the Debian reference.

Univention distributes most packages from Debian GNU/Linux for the amd64 and all architecture without changes for UCS. This includes the GNU/Linux kernel and over 98% of unchanged packages from the Debian project. Univention uses the default services from the Debian distribution and delivers custom configurations for UCS.

In the following circumstances, Univention builds and maintains derived packages:

• A later software version of a package is needed for UCS than Debian offers.

• Bug fixes or backports of a specific software are needed for a package.

Additionally, Univention develops own software responsible for UCS capability that is distributed as Debian package.

Nevertheless, UCS doesn’t include packages from the Debian games section, because it would require a content rating for video games. Univention doesn’t see added value in the distribution of video games with UCS for the product audience.

2.2. Identity management

The most important functional pillar of UCS is identity management.

Simplified, an IT environment consists of services and users. Services offer capability. Users use capability. Services can also behave as users when they use the capability of another service. Users identify themselves against services to proof that they’re eligible to use the capability.

The identification is done with user accounts to represent users. User accounts typically have properties like for example username, password, and email address. User accounts that digitally represent a person additionally have for example first name and last name.

Imagine a small IT environment with 20 persons and five systems. Without a central identity management, an administrator would have to maintain 20 user accounts on each of the five systems. The management effort sums up to 100 items. The number of items to manage is a linear function. The function’s slope increases with the number of systems that need to know user accounts.

With a central identity management, one service holds the information about the user accounts. All other services have access to that information. An administrator only has to maintain the user accounts on one system. The maintenance effort for the user accounts doesn’t anymore multiply with the number of systems that need to know the user accounts. The slope of this linear function is less steep.

Central identity management reduces the maintenance effort of user accounts for administrators.

UCS is a product for central identity management for user accounts, their permissions and the collection of user accounts in groups.

2.3. Infrastructure management

The second important functional pillar of UCS is IT infrastructure management.

IT infrastructure is a set of IT components like computer and networking hardware, various software and network components. It’s the foundation of an organization’s technology system and drives the organization’s success.

UCS provides important infrastructure services to create an IT network infrastructure and connect IT components. For example UCS assigns addresses to computers and other network components through DHCP and resolves hostnames through DNS, and much more. Administrators manage various IT components in their IT environment, like different kind of hosts, clients, and printers.

2.4. Connection to the world around

As an operating system that offers many services, UCS interacts with its surrounding peers. Users access the capability of UCS through the following ways:

Web

Persons like administrators and also end users use HTTPS to access the web based UCS management system. In many cases other web-based services provided by other software products delivered through apps are also available through HTTPS.

Console

Persons with more technical background and the appropriate permissions can access UCS through a console, either on a local terminal or through a remote secure shell (SSH) session.

Service protocols

As soon as users use any of the services that UCS offers, they access UCS through one of the service protocols. For example, a user’s client requests and IP address through DHCP and later asks for the IP address of the print server through DNS.

As a central system offering identity and infrastructure management UCS has to use and offer numerous ways of connections.