Windows Server 2008 R2 : Automating Tasks Using PowerShell Scripting - Introduction to PowerShell

Luckily, Jeffrey Snover (the architect of PowerShell) and others on the PowerShell team realized that Windows needed a strong, secure, and robust CLI shell for systems management. Enter PowerShell. PowerShell was designed as a shell with full access to the underpinnings of Windows via the .NET Framework, Component Object Model (COM) objects, and other methods. It also provided an execution environment that’s familiar, easy, and secure. PowerShell is aptly named, as it puts the power into the Windows shell. For users wanting to automate their Windows systems, the introduction of PowerShell was exciting because it combined “the power of WSH with the warm-fuzzy familiarity of a CLI shell.”

PowerShell provides a powerful native scripting language, so scripts can be ported to all Windows systems without worrying about whether a particular language interpreter is installed. In the past, an administrator might have gone through the rigmarole of scripting a solution with WSH in Perl, Python, VBScript, JScript, or another language, only to find that the next system that they worked on didn’t have that interpreter installed. At home, users can put whatever they want on their systems and maintain them however they see fit, but in a workplace, that option isn’t always viable. PowerShell solves that problem by removing the need for nonnative interpreters. It also solves the problem of wading through websites to find command-line equivalents for simple GUI shell operations and coding them into .cmd files. Last, PowerShell addresses the WSH security problem by providing a platform for secure Windows scripting. It focuses on security features such as script signing, lack of executable extensions, and execution policies (which are restricted by default).

For anyone who needs to automate administration tasks on a Windows system or a Microsoft platform, PowerShell provides a much-needed injection of power. As such, for Windows systems administrators or scripters, becoming a PowerShell expert is highly recommended. After all, PowerShell can now be used to efficiently automate management tasks for Windows, Active Directory, Terminal Services, SQL Server, Exchange Server, Internet Information Services (IIS), and even a number of different third-party products.

As such, PowerShell is the approach Microsoft had been seeking as the automation and management interface for their products. Thus, PowerShell is now the endorsed solution for the management of Windows-based systems and server products. Over time, PowerShell could even possibly replace the current management interfaces, such as cmd.exe, WSH, CLI tools, and so on, while becoming even further integrated into the Windows operating system. The trend toward this direction can be seen with the release of Windows Server 2008 R2 and Windows 7, in which PowerShell is part of the operating system.

PowerShell Uses

In Windows, an administrator can complete a number of tasks using PowerShell. The following list is a sampling of these tasks:

• Manage the file system— To create, delete, modify, and set permissions for files and folders.

• Manage services— To list, stop, start, restart, and even modify services.

• Manage processes— To list (monitor), stop, and start processes.

• Manage the Registry— To list (monitor), stop, and start processes.

• Use Windows Management Instrumentation (WMI)— To manage not only Windows, but also other platforms such as IIS and Terminal Services.

• Use existing Component Object Model (COM) objects— To complete a wide range of automation tasks.

• Manage a number of Windows roles and features— To add or remove roles and features.

PowerShell Features

PowerShell is a departure from the current management interfaces in Windows. As such, it has been built from the ground up to include a number of features that make CLI and script-based administration easier. Some of PowerShell’s more key features are as follows:

• It has 240 built-in command-line tools (referred to as cmdlets).

• The scripting language is designed to be readable and easy to use.

• PowerShell supports existing scripts, command-line tools, and automation interfaces, such as WMI, ADSI, .NET Framework, ActiveX Data Objects (ADO), and so on.

• It follows a strict naming convention for commands based on a verb-noun format.

• It supports a number of different Windows operating systems: Windows XP SP2 or later, Windows Server 2003 SP1 or later, Windows Vista, Windows Server 2008, and now Windows Server 2008 R2 and Windows 7.

• It provides direct “access to and navigation of” the Windows Registry, certificate store, and file system using a common set of commands.

• PowerShell is object based, which allows data (objects) to be piped between commands.

• It is extensible, which allows third parties (as noted earlier) to build upon and extend PowerShell’s already rich interfaces for managing Windows and other Microsoft platforms.

PowerShell 2.0 Enhancements

Windows Server 2008 R2 has the Windows PowerShell 2.0 version built in to the operating system. In this version of PowerShell, a number of enhancements have been made to both PowerShell itself and the ability for managing Windows Server 2008 R2’s roles and features. The following is a summary for some of the improvements in PowerShell 2.0 :

• The number of built-in cmdlets has nearly doubled from 130 to 240.

• PowerShell 2.0 now includes the ability to manage a number of roles and features such as the Active Directory Domain Services, Active Directory Rights Management Services, AppLocker, Background Intelligent Transfer Service [BITS], Best Practices Analyzer, Failover Clustering [WSFC], Group Policy, Internet Information Services [IIS], Network Load Balancing [NLB], Remote Desktop Services [RDS], Server Manager, Server Migration, and Windows Diagnostics roles and features.

• PowerShell 2.0 also includes the introduction of the Windows PowerShell debugger. Using this feature, an administrator can identify errors or inefficiencies in scripts, functions, commands, and expressions while they are being executed through a set of debugging cmdlets or the Integrated Scripting Environment (ISE).

• The PowerShell Integrated Scripting Environment (ISE) is a multi-tabbed GUI-based PowerShell development interface. Using the ISE, an administrator can write, test, and debug scripts. The ISE includes such features as multiline editing, tab completion, syntax coloring, selective execution, context-sensitive help, and support for right-to-left languages.

• Background jobs enable administrators to execute commands and scripts asynchronously.

• Also through the inclusion of script functions, administrators can now create their own cmdlets without having to write and compile the cmdlet using a managed-code language like C#.

• PowerShell 2.0 also includes a new powerful feature, called modules, which allows packages of cmdlets, providers, functions, variables, and aliases to be bundled and then easily shared with others.

• The lack of remote command support has also been addressed in PowerShell 2.0 with the introduction of remoting. This feature enables an administrator to automate the management of many remote systems through a single PowerShell console.

However, with all of these features, the most important advancement that is found in PowerShell 2.0 is the focus on what is called the Universal Code Execution model. The core concept in this model is flexibility over how expressions, commands, and scriptblocks are executed across one or more machines.