POWERCLI IN THE ENTERPRISE: BREAKING THE MAGICIAN’S CODE

@jonathanmedd

PowerShell and PowerCLI

Other programming languages are available………

…but the principles in this session can typically be applied to most of them.

…move your code from the equivalent of this….

…to this………

From Command to Script…..

….to Function

Reasons for functions:

Primary: Break up code to manageable, reusable chunks

Also:

1. No cmdlet exists for a task

2. Existing cmdlet doesn’t behave like you want it to

3. String multiple cmdlets together

Functions…….

function Get-Something {

Take some input

Do something with it

Produce some output

}

function Set-Something {

Take some input

Change the configuration of something

}

Function Recommendations

1) Name Your Functions Verb-Noun

Get-VMHostLicense & Set-VMHostLicense

Get-Verb | Sort Verb

….will give you a list of approved verbs

Function Recommendations

2) Use Built-In Help

Function Recommendations

3) Generalise everything!

No hardcoded data in functions (or scripts)! Data should always come from an external source…CSV, XML, SQL database….etc

Function Recommendations

4) Parameters

Function Recommendations

5) Pipeline Support

ValueFromPipeline = $true

and

Function Flexibility

You need to be able to cater for pipeline support:

Get-VMHost | Get-VMHostSomething

as well as

Get-VMHostSomething –VMHost ESXi01,ESXI02

Function Templates

Build up templates for Get-Something and Set-Something, then to create say Get-VMHostiSCSIBinding, all you need is this:

….to Module

A method to organise your functions into collections of functions

Easy to distribute via file copy / XCOPY Easy to access all functions via:

Import-Module MyModule

Tip: Use a Module Manifest to make your module professional: New-ModuleManifest

Modules

Typically will contain at least 2 files*.psm1 - containing your functions*.psd1 – the manifest

$env:PSModulePath contains the path Import-Module will look for modules○ Typically this is your user profile\Documents\

WindowsPowerShell\Modules and○ C:\Windows\system32\WindowsPowerShell\v1.0\

Modules\ - use this one for deployment!

Modules

Modules: PSM1

Difficult to find individual functions

Hassle to maintain to keep them in a particular order

Nested Modules

Break each module down into Nested Modules each containing a single function

Reference the Nested Modules in the *.psd1

Import-Module vSphereTools

Module: Search

Search for string patterns

dir * -Recurse | Select-String 'PSBoundParameters'

Module: Search

Search for metadata

Search-ModuleTag -Module vSphereTools -Tag ‘iscsi’

Modules: Considerations

Module Dependencies – One module may requires functions from another module

Generic module with standard tools for other modules

Flexibility Now you have code broken down into

Functions and Modules you can pick out various functions or entire modules to plug into:Command line useScriptsAutomation and Orchestration systems

Backup / Source Control

Internal File Share Dropbox or other….

Git / Atlassian StashFree Atlassian SourceTree client for Windows and

OSX. Works with all Git repositories (not just Stash), including GitHub

Source Control – Version History

Template Functions

Will be available on my blog after this presentation

○ Get-Something○ Set-Something○ Get-VMSomething○ Set-VMSomething○ Get-VMHostSomething○ Set-VMHostSomething

Template SnippetsAnd also these….Ctrl-J in PowerShell ISE

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