Correct the apt configuration.

apt/apt.conf.d/00configperso

@@ -1,20 +1,28 @@
 // Cache size
 APT::Cache-Limit 100000000;
-// Default Debian to manage: Unstable/Sid
-APT::Default-Release "unstable";
 
 APT
 {
-  # Configure behavior of apt periodic updates
-  # Done by /etc/cron.daily/apt
+  // Configure behavior of apt periodic updates
+  // Done by /etc/cron.daily/apt
   Periodic
   {
+    // Run a apt-get autoclean every x days
     AutocleanInterval "7";
     Update-Package-Lists "1";
     Download-Upgradeable-Packages "1";
   }
 
-  autoclean       "1";
-  clean-installed "1";
+  // Options for apt-get only (not aptitude!)
+  Get
+  {
+    Purge "true";
+  }
 
+  // General options
+
+  // Remove from the cache, any packages which can no longer be downloaded.
+  Clean-Installed "true";
+  // Default Debian to manage: Unstable/Sid
+  Default-Release "unstable";
 }