Download/extract deployed wsp packages

When you are about to update a wsp solution it often would be nice to be able to get a backup of the existing.

This is how its done in 3 lines of  PowerShell:

$farm = Get-SPFarm
$file = $farm.Solutions.Item("mysolution.wsp").SolutionFile
$file.SaveAs("c:\Users\sp\Desktop\mysolution.wsp")

You need to be a farm administrator and have permissions to the configuration database.

See also: Extract a WSP Solution from SharePoint 2010