Windows 7 / Getting Started

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Overview of Windows Server Core

In nearly all environments today, servers are designated for a single purpose. Often when you go to a client's site, the conversation is "these are the domain controllers, here are the file servers" and so on. Microsoft recognizes this specialization of servers. This recognition can be seen in the rolebased nature of Windows Server 2008. However, even though your domain controllers, for example, need only a limited number of services to function (and maybe domain name system [DNS]), the server has a plethora of unneeded components. These components bloat the server, requiring the server to have more resources to function than are needed for its main function. Most importantly, the more components the system has installed, the more possible vulnerabilities it has. The more components there are, the greater the attack surface and the more patches required, resulting in more management overhead.

The typical server has the full .NET Framework, Internet Explorer, Media Player, and Outlook Express, all of which will likely never be used but still have to be managed.

With Windows Server Core, the "extra" parts of Windows Server 2008 have been removed, leaving a much thinner core operating system than with a normal Windows Server 2008 full installation. Because it has far fewer components, you benefit from having a reduced attack surface and less to manage and maintain. Server Core has only the critical components of the operating system necessary to support the various roles and features made available on a Windows Server Core installation. Many of the nonvalue- add legacy and client components are missing from Server Core.

This much smaller footprint, and optimized installation based around specific roles such as a domain controller or file server, means the following:

• As already discussed, Server Core presents less attack surface because it involves fewer components with less possible vulnerabilities.
• Because you have fewer components installed, fewer patches apply to a Server Core installation than to a normal full installation. You often hear of an urgent patch related to an Internet Explorer vulnerability. If Internet Explorer is not installed, you don't need to apply that patch. Microsoft believes there will be a large reduction in the number of patches needed for a Server Core install compared to a full installation. It's not possible to know how many patches will be released for Windows Server 2008 or what components the patches will be applicable to. But if a core version had been available for Windows 2000, it would have required 60 percent fewer patches than a full installation, and if available for Windows 2003 there would have been a 40 percent reduction in patches. The servicing stack in Windows Server 2008 downloads and applies only fixes that apply to components installed on the system. No actions or special Windows Update site is required that is Server-Core-specific.
• Administrators can focus more on their technology area without having to be so worried about general Windows knowledge because all the extra parts are no longer installed.
• With fewer components running, the installation uses fewer system resources and becomes more reliable because the fewer different components executing, the less chance of problems occurring.
• Less disk space. A typical core installation uses 1GB of disk space for the install and additional disk space for its actual operation. In terms of other resources, there is not a great deal of difference, although obviously with fewer components, fewer resources are used overall. But remember: A Windows 2008 install alone requires 512MB of RAM.

The Server Core is available as an installation option for the Standard, Enterprise, and Datacenter editions of Windows Server 2008 and is available on both the x86 and x64 architectures.

Because the Server Core is a minimal installation of Windows, not all the full Windows Server components can run. For example, because the .NET Framework is not present in Server Core, which in turn means no Common Language Runtime (CLR), no managed code can run. That means no PowerShell. A Server Core installation has many "nots":

• There is no Explorer-based shell, so the Start button, taskbar notification area (system tray), and taskbar are eliminated. There are no fancy wall papers, screen savers (a default screen saver shows the Windows Server 2008 logo), and no Aero Glass. Explorer itself is not available, which means no My Computer. Because you have no system tray, you get no balloon notifications, which also means no password prompts because they are balloon notifications.
• No Explorer means no Internet Explorer, no Search, no Run, and no Help, but you do get Notepad.
• No .NET Framework. This is because the .NET Framework is monolithic, meaning all or nothing. And .NET has a lot of multimedia- related code and other components that do not fit the Server Core model. However, a "core" version of the .NET Framework is expected for the Windows Server 2008 R2 timeframe. This means no managed code, which requires .NET.
• No Microsoft Management Console (MMC), which means no snapins either. That is an issue because nearly everything is managed with the MMC.
• Only two Control Panel applets.

So let's get it clear. With Server Core, there is no graphical interface, no management tools, no Explorer, no Control Panel applets? Before you get freaked, this is a great feature. The advantages of the reduced overhead are worth a little hardship. You do have a shell, but it's the command prompt. However, if you think about it, nearly every MMC snap-in you have today can connect to a remote computer, which helps you manage your GUI-less Server Core installation.

What do you get? Much more than in the early builds of Johnsay when the only roles available were Active Directory Domain Servers (a domain controller), DNS, DHCP and File Servers. You are a lot further than that now. As you've seen, with Windows Server you have roles, which are important components of Windows Server 2008, and features, which are less important than their older, driving Role brothers. Table-1 provides a list of the roles and features available in Windows Server Core. Note there are no relationships between the roles and features; they are in a table only to save space.

Table-1 Windows Server Core Roles and Features

Server Core Roles 			Server Core Features
Active Directory Domain Services 	(ADDS) BitLocker Drive 
                                        Encryption (and remote
					admin tools)
Active Directory Lightweight Directory 	Failover Clustering
Services (formally known as ADAM)
DHCP Server 				Multipath I/O
DNS Server 				NAP Client
File Services 				QoS (Qwave)
Internet Information Services (IIS) 	Removable Storage Management
Print Services 				Simple Network Management
                                        Protocol (SNMP) Services
Streaming Media Services 		Subsystem for UNIX-based
                                        applications
Windows Server Virtualization (Hyper-V) Telnet Clients
					Windows Process Activation 
                                        Service
					Windows Server Backup
					WINS Server

Don't forget that Server Core is not a separate operating system. It just takes advantage of the highly componentized nature of Windows Server and deploys only the most critical components. Core still has the same kernel as a normal installation in addition to other core components such as the Hardware Abstraction Layer (HAL), memory manager, security subsystem, Winlogon, file systems, networking subsystem, Windows File Protection, Distributed Component Object Model (DCOM), and remote procedure call (RPC), and device drivers for NIC, disk, and basic video. Many of the other drivers have been removed from Core, such as audio drivers and modem drivers. However, you can add them manually. Imagine a print server, however; print drivers are also not included with Server Core because Windows Server 2008 has nearly 1GB of printer drivers. Instead of including drivers in Server Core for a role that might not be used, the print drivers are not included. When you enable the Print Server role, the spooler starts, and drivers need to be manually added using the Print Management Console remotely from a Windows Vista/Windows 2008 machine.

Also included are features such as the event log, which is critical to nearly all components of Windows, performance counters, WSManagement for remote management, and Windows Management Instrumentation (WMI).

Think of Server Core as a subset of the full Windows installation. If a core kernel patch is released, the same patch for Windows Server is applicable to a Server Core installation. How do you use this? What do you get to manage this Server Core environment? Let's look at installing Server Core, and then you can see the usable environment.