How to activate web application and site collection level feature via PowerShell?

Question

We have deployed a wsp using:

Add-SPSolution -LiteralPath $path
install-spsolution -Identity $solution  -GACDeployment -Force

This wsp has 2 features, one scoped at application level (FeatureA) and one scoped at site collection level (FeatureB). Both can be seen and activated/deactivated from the respective UI's.

I would like to know how to activate them via powershell.

I tried:

Enable-SPFeature -identity "FeatureB" -confirm:$false -url $oUrl

Gives error as:

Enable-spfeature : The Feature is not a Farm Level Feature and is not found in a Site level defined by the Url http://dewswift:7676/. At line:1 char:1 + Enable-spfeature -identity "FeatureB" -confirm:$f ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidData: (Microsoft.Share...etEnableFeature:SPCmdletEnableFeature) [Enable-SPFeature], SPCmdletException + FullyQualifiedErrorId : Microsoft.SharePoint.PowerShell.SPCmdletEnableFeature

Answer 1

First check if the feature is installed using Scope and then try to activate it like:

$Feature = Get-SPFeature -Identity $FeatureID -ErrorAction SilentlyContinue
If ($Feature.Scope -eq [Microsoft.SharePoint.SPFeatureScope]::WebApplication)
{
    $Feature = Get-SPFeature -Identity $FeatureID -WebApplication $SiteUrl -ErrorAction SilentlyContinue
    Enable-SPFeature -Identity $FeatureID -Url $SiteUrl  -Confirm:$false 
}
ElseIf ($Feature.Scope -eq [Microsoft.SharePoint.SPFeatureScope]::Site)
{
    $Feature = Get-SPFeature -Identity $FeatureID -Site $SiteUrl -ErrorAction SilentlyContinue
    Enable-SPFeature -Identity $FeatureID -Url $SiteUrl  -Confirm:$false 
}

Answer 2

This has happened to me when I try to enable a feature from a SharePoint server that does not have the SharePoint service running: Microsoft SharePoint Foundation Web Application . The web sites are not hosted on IIS on these servers and the layouts folder do not have the features deployed to them! A common practice is to turn off the Microsoft SharePoint Foundation Web Application on a dedicate APP/Central admin server. But then you cannot enable features.