Exploring Tags and PowerCLI

Tags were added to vSphere back in version 5.1 so they’re not a new feature but are still often overlooked. One or more tags can be applied to items (entities) in the inventory and then used as a search term or metadata not only in the GUI but also through tools such as PowerCLI. This post covers a few useful cmdlets for working with tags.

CmdLets

There are a number of cmdlets which deal with tags, here’s a quick list using Get-Command.

Notice that there’s three Nouns used here- “Tag” represents the tag itself. “TagAssignment” represents a relationship between a tag and another object (for example “This VM has been assigned This (or These) tags). Finally there’s “TagCategory” which represents the category that a tag belongs to.

Getting Tags

So, what can we do with tags in PowerCLI? Well, first we can look at a list of all the tags using Get-Tag. This returns a lot of information, particularly if you have assigned tags already, so we can neaten the quick view using the PowerShell “Select” function to show just the tag name and description:

1Get-Tag | Select Name, Description
2
3Name                 Description
4--                   ------
5UrlShortener         URL Shortener Service
6Documents            Document Management Service
7Change               Change Management Service

In this example, I’ve created three tags to represent three different services operating in my environment. We can carry on from here and find out which entities have been assigned the “Documents” tag- i.e. what VMs form the Document Management Service.

1(Get-TagAssignment |
2Where {$_.Tag.Name -eq 'Documents'}).Entity
3
4
5Name                 PowerState Num CPUs MemoryGB
6--                   -------    ------   ------
7DocuWebServ          PoweredOn  1        4.000
8DocuDBServ           PoweredOn  2        16.000
9DocuFileServ         PoweredOn  1        4.000

Or we could flip that and ask the question- “What tags does this VM have assigned?”

1Get-VM "DocuWebServ" |
2     Get-TagAssignment | Select Tag
3
4
5Tag
6---
7Documents
8WebServers

Getting Bigger

As we’re using PowerCLI we can join more and more functions together and make bigger and bigger queries. For example, we can  list all VMs with their tags in a table.

 1Select Name,@{Name="Tags";Expression={(Get-TagAssignment -Entity $_).Tag.Name}} |
 2Where {$_.Tags} |
 3Format-Table - Autosize
 4
 5Name         Tags
 6----         ---
 7DocuWebServ  {Documents, WebServers}
 8DocuDBServ   Documents
 9DocuFileServ Documents
10URLShort1    {UrlShortener, WebServers}
11URLShort2    {UrlShortener, WebServers, TestAndDev}

This is only scratching the surface of the possibilities- by having useful metadata that lives with the VM and can be accessed programmatically we have plenty of avenues to explore in automation and reporting.