idempotency

scripts/prepare-machine.ps1

@@ -466,10 +466,20 @@ function Install-Dotnet {
     }
 
     Write-Host "Installing dotnet"
-    # known issue https://learn.microsoft.com/en-us/dotnet/core/install/linux-package-mixup?pivots=os-linux-ubuntu
-    sudo bash -c "echo 'Package: dotnet* aspnet* netstandard*' >> /etc/apt/preferences"
-    sudo bash -c "echo 'Pin: origin packages.microsoft.com' >> /etc/apt/preferences"
-    sudo bash -c "echo 'Pin-Priority: -10' >> /etc/apt/preferences"
+
+    # Check /etc/apt/preperences whether it has the known issue workaround
+    if (Test-Path /etc/apt/preferences) {
+        $hasKnownIssueWorkaround = (Get-Content /etc/apt/preferences | Select-String -Pattern "Package: dotnet* aspnet* netstandard*") -ne $null
+        if (!$hasKnownIssueWorkaround) {
+            # known issue https://learn.microsoft.com/en-us/dotnet/core/install/linux-package-mixup?pivots=os-linux-ubuntu
+            sudo bash -c "echo 'Package: dotnet* aspnet* netstandard*' >> /etc/apt/preferences"
+            sudo bash -c "echo 'Pin: origin packages.microsoft.com' >> /etc/apt/preferences"
+            sudo bash -c "echo 'Pin-Priority: -10' >> /etc/apt/preferences"
+        } else {
+            Write-Host "Known issue workaround already applied"
+        }
+    }
+
     sudo apt-get update -y
     sudo apt-get install dotnet-sdk-6.0 aspnetcore-runtime-6.0 dotnet-runtime-6.0
 }