Powershell to list all site collections in farm with feature activated from ‘Farm’ definition scope

In SharePoint 2010, a Feature can be installed from a farm solution and from a sandbox solution. In case of farm solution, the Feature is installed on farm-level, and dependent on the feature scope, visible (unless hidden) for all webapplications, site-collections or webs to activate (by GUI, Powershell and yes, even stsadm). In case of sandboxed solution, only possible for scope = Site or Web, the feature is only visible within the site-collection, and can also only be activated in the site-collections to which added and activated.

Today we encoutered a situation in which a sandboxed solution was per accident also deployed on the farm. The result was that features within the solution were installed and visible twice in each site collection to which it also was added as sandbox. The remedy is to retract the per-accident farm deployment. But we must take into account that features from the SharePoint solution may have been activated from the farm-deployed version.

Powershell enables us to easily determine in which site collections in the farm the feature is activated from the farm-deployed solution:

$snapin = Get-PSSnapin | Where-Object {$_.Name -eq 'Microsoft.SharePoint.Powershell'}
if ($snapin -eq $null) {
    Add-PSSnapin "Microsoft.SharePoint.PowerShell"
}

$featureId = ".......-....-....-....-............";
$contentWebAppServices = (Get-SPFarm).services | ? {$_.typename -eq "Microsoft SharePoint Foundation Web Application"}
foreach($webApp in $contentWebAppServices.WebApplications) {
  foreach($site in $webapp.Sites) {
    Get-SPFeature -Site $site| where{$_.Id -eq $featureId}|%{
    if ($($site.QueryFeatures($featureId)).FeatureDefinitionScope -match "Farm"); {
        Write-Host $_.DisplayName " is Activated from Farm deployment on site : " $site.url
      }
    }
  }
}