PowerShell Core for Linux Administrators Cookbook

By : Prashanth Jayaram, Ram Iyer

PowerShell Core for Linux Administrators Cookbook

By: Prashanth Jayaram, Ram Iyer

Overview of this book

PowerShell Core, the open source, cross-platform that is based on the open source, cross-platform .NET Core, is not a shell that came out by accident; it was intentionally created to be versatile and easy to learn at the same time. PowerShell Core enables automation on systems ranging from the Raspberry Pi to the cloud. PowerShell Core for Linux Administrators Cookbook uses simple, real-world examples that teach you how to use PowerShell to effectively administer your environment. As you make your way through the book, you will cover interesting recipes on how PowerShell Core can be used to quickly automate complex, repetitive, and time-consuming tasks. In the concluding chapters, you will learn how to develop scripts to automate tasks that involve systems and enterprise management. By the end of this book, you will have learned about the automation capabilities of PowerShell Core, including remote management using OpenSSH, cross-platform enterprise management, working with Docker containers, and managing SQL databases.

Preface

Who this book is for

What this book covers

To get the most out of this book

Sections

Get in touch

Free Chapter

Introducing PowerShell Core

Introduction

Installing PowerShell

Updating and using Help

Exploring about_ topics

Discovering cmdlets

Finding and installing PowerShell modules

Listing the various providers in PowerShell

Understanding objects

Parsing input from text to object

Comparing the outputs of Bash and PowerShell

Comparing Windows PowerShell and PowerShell Core

Working with aliases

Dissecting a .NET Core object

Listing out the execution policies and setting a suitable one

Preparing for Administration Using PowerShell

Introduction

Installing Visual Studio Code

Configuring automatic variables

Changing shell behavior using variables

Enabling automated execution of commands for each load

Customizing the Terminal prompt

Understanding standard redirection in PowerShell

Calling native Linux commands from PowerShell

Understanding cmdlets and parameters

Running cmdlets with minimal keystrokes

Finding parameter aliases

Calling a PowerShell script

Dot-sourcing a PowerShell script

Calling a PowerShell cmdlet from outside of PowerShell

Recording the cmdlets run on the PowerShell console

First Steps in Administration Using PowerShell

Introduction

Working with date properties

Working with date and time methods

Working with currently-running processes to measure resource consumption

Launching and stopping a process

Finding the owner of a process

Invoking an application based on the file type

Installing the CronTab PowerShell module

Scheduling jobs in PowerShell

Removing scheduled jobs in PowerShell

Passing Data through the Pipeline

Introduction

Selecting columns from the output

Limiting the number of output objects

Expanding the properties within properties

Filtering objects

Grouping the output

Sorting the output

Taking actions on the returned objects

Understanding pipeline-enabled parameters

Importing content into PowerShell

Using Variables and Objects

Introduction

Using environment variables

Storing the output of an instance of a .NET Core object

Adding custom properties to an object

Creating a custom object from a returned object

Understanding the extension of type data

Retaining object modifications across sessions

Removing custom type data

Understanding variables

Working with Strings

Introduction

Creating a literal string

Creating an expanding string

Understanding Here-Strings

Using basic string methods

Performing string matching operations

Replacing substrings within strings

Splitting and combining strings

Using the formatting operator

Flow Control Using Branches and Loops

Introduction

Using If–ElseIf–Else conditions to control script flow

Using Switch–Case conditions to control script flow

Learning to use delays

Writing a basic looping construct

Writing a more complex loop on a predefined array

Using the For loop construct

Using the While loop construct

Cleaning empty directories using the Do–While construct

Cleaning empty directories using the Do–Until construct

Performing Calculations

Introduction

Performing arithmetic operations

Performing calculations on the output

Working with administrative constants

Working with calculated properties

Working with binary numbers

Performing base conversions

Using Arrays and Hashtables

Introduction

Creating and working with a simple array

Accessing and manipulating array items

Sorting an array

Searching for an item in an array

Combining arrays

Item matching in an array

Removing elements from an array

Comparing arrays

Creating a simple hashtable

Performing simple tasks on a hashtable

Handling Files and Directories

Introduction

Reading content from a file

Sending output to a file

Adding and setting content to a file

Searching for content

Working with locations

Working with files and directories

Listing files and directories

Working with structured and unstructured files

Building Scripts and Functions

Introduction

Writing a simple script

Reading input from the host

Displaying an interactive menu

Showing progress of execution

Defining arguments for a script

Writing a simple function

Working with a script block

Measuring running duration

Important points to remember

Advanced Concepts of Functions

Introduction

Defining parameters

Working with parameter aliases

Working with parameter sets

Adding default values to the parameter

Adding validation to parameter input

Handling dependencies and prerequisites

Adding safety switches to functions

Adding help to functions

Adding support for pipeline input

Using the Main function

Writing a script module

Handling module cleanup

Debugging and Error Handling

Introduction

The Debug tab of Visual Studio Code

Writing debug output

Running a script in Debug mode

Tracing errors

Using breakpoints

Using conditional breakpoints

Using exit codes

Working with the Error variable

Controlling flow based on errors

Sending verbose output to a file

Enterprise Administration Using PowerShell

Introduction to OpenSSH

Installing OpenSSH on Windows

Configuring OpenSSH using sshd_config on Windows

Installing and configuring OpenSSH on Linux

Testing PowerShell remoting using OpenSSH

Testing PowerShell remoting with OpenSSH using keys between Linux machines

Testing PowerShell remoting with OpenSSH using keys between Linux and Windows machines

Running cmdlets on remote computers

Managing the administration of remote machines with PowerShell Jobs

Generating HTML reports

Sending email messages

PowerShell and Cloud Operations

Introduction to PowerShell for Cloud operations on Azure and AWS

Installation of the AzureRM.Netcore PowerShell module on Linux machines

Installation of the AWSPowerShell.NetCore module on Linux machines

Discovering AzureRM cmdlets discovery functions

Azure Cloud Shell in action

Provisioning a Ubuntu 18.04 LTS VM using AzureRM.Netcore cmdlets on the Azure Cloud

Provisioning Linux Docker containers using Docker Machine on Azure

Provisioning Linux VM using PowerShell script

Performing management tasks using ARM PowerShell cmdlets

PowerShell remoting to Azure VM using OpenSSH

Managing AWS credentials

Connecting an EC2 Linux instance using SSH from PowerShell

Using PowerShell for SQL Database Management

Introduction to PowerShell, SQL Server, and Python

Technical requirements

Installing .Net Core on Linux

Installing the SqlServer module

Overview of SQL Server SMO

Running cross-platform T-SQL queries

Running cross-platform T-SQL queries on multiple servers

Creating a repository for Get-Process in the SQL database

Data formatting examples with PowerShell

Overview of PowerShell, Bash, and Python integration

Using PowerShell with Docker

Introduction to Docker

Installation of Docker on Linux

Getting and listing the Docker management cmdlets

Overview of Docker Hub and its operations

Building an image from a Dockerfile using PowerShell

Pulling a Docker container image from the repository

Listing Docker containers and the images

Starting and stopping Docker containers

Removing containers and container images

Working with a container using miscellaneous Docker PowerShell cmdlets

Running a PowerShell script to set up Docker containers

Finding Docker tags using PowerShell cmdlets from the remote registry

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Comparing Windows PowerShell and PowerShell Core

Windows PowerShell and PowerShell Core are two different implementations. The former is based on a larger framework, the .NET Framework. The latter, on the other hand, is a more modern framework, the .NET Core. PowerShell Core is cross-platform since its parent is. Windows PowerShell, on the other hand, is Windows-only, but has more capabilities than PowerShell at the time of writing this book.

The PowerShell that this book talks about is the cross-platform PowerShell Core. This is referred to as PowerShell. The PowerShell that is Windows-specific is referred to as Windows PowerShell.

Windows PowerShell leverages the internal components and the architectural model of Windows, with its capabilities enhanced by WinRM as well as Windows Management Instrumentation. In fact, most of the differences exist because of the inherent differences between Windows and Unix-like operating systems.

Support for snap-ins

PowerShell will not support the legacy version of modules, also known as snap-ins. Many of the snap-ins of old have been repackaged to be binary modules. Therefore, the unavailability of snap-ins should not be of much concern. Future development of these binary modules should, in theory, work on either PowerShell, provided that the host supports the API calls that are part of the binaries. For example, let's imagine that the Windows Active Directory module was repackaged into a binary PowerShell module. This module would run on Windows PowerShell as well as PowerShell on Windows. However, since Windows Active Directory does not run on Linux, the module would not work with PowerShell on Linux.

Convenience aliases

One important point to note is that commands such as ls and mkdir are aliases in Windows PowerShell, which means that running ls on Windows PowerShell would run Get-ChildItem in the background (this is also true for PowerShell on Windows). In Linux, however, running ls from within PowerShell would run the actual ls command; ls is not an alias in PowerShell on Linux—it is the command itself, whose output would be plain text. You can validate this by running ls | Get-Member on PowerShell on Linux, and comparing it with PowerShell on Windows as well as Windows PowerShell (it is, therefore, good to stick to the best practice of not using aliases in scripts):

PowerShell knows whether it is running on Linux, Windows, or macOS by means of the values of the automatic variables IsLinux, IsWindows, and IsMacOS. On any system, only one of these variables has the value True. When PowerShell sees that IsLinux is True, it would run Linux commands instead of the convenience aliases that were initially created to facilitate Linux administrators. For more information on these automatic variables, read the Configuring built-in variables recipe.

PowerShell Workflows

Windows administrators who are used to PowerShell Workflows in Windows PowerShell need to note that they are absent in PowerShell. PowerShell Workflows were a little advanced (to put it nicely) and were used in specific scenarios where multiple cmdlets were to be run in parallel, or activities had to, say, survive a reboot. Workflows work on the Windows Workflow Foundation, which is not cross-platform. Therefore, PowerShell Workflows will not run on PowerShell. However, the unavailability of PowerShell Workflows is no deal-breaker. Workflows were not used much either.

PowerShell Desired State Configuration

Desired State Configuration (DSC) is a work in progress at the time of writing this book. As of now, there are two code bases of DSC resources: LCM for Linux, which is managed by Microsoft's Unix team, and DSC Resources for Windows PowerShell, which was written by the PowerShell team. It could be some time before the DSC code base becomes cross-platform.

PowerShell Core for Linux Administrators Cookbook

By : Prashanth Jayaram, Ram Iyer

PowerShell Core for Linux Administrators Cookbook

By: Prashanth Jayaram, Ram Iyer

Overview of this book

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