I'm in the process of installing a default 4.5.1_install installation onto IIS6.

My IIS server has its default security trust polict set to medium.

Having tried to install using the wizard I couldn't get past the permissions check as this would always fail completely (no boxes checked).  I therefore tried to use the auto-install/traditional method and half way through running the install I get the error below.

It seems that this is due to Medium trust not being granted the FileIOPermission by default.  I'm going to attempt to create a custom trust config file based on web_mediumtrust.config and include FileIOPermission as:

<IPermission
  class="FileIOPermission"
  version="1"
  Read="C:\SomeDir;$AppDir$"
  Write="$AppDir$"
  Append="$AppDir$"
  PathDiscovery="$AppDir$"
/>

Just thought I'd post this in case anyone else has similar issue.  I'll post back to report my results.

Error I received was:

Error: Error configuring Child PortalRequest for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) at System.Security.CodeAccessPermission.Demand() at System.IO.Directory.InternalCreateDirectory(String fullPath, String path, DirectorySecurity dirSecurity) at System.IO.Directory.CreateDirectory(String path, DirectorySecurity directorySecurity) at DotNetNuke.Entities.Portals.PortalController.CreatePortal(String PortalName, String FirstName, String LastName, String Username, String Password, String Email, String Description, String KeyWords, String TemplatePath, String TemplateFile, String HomeDirectory, String PortalAlias, String ServerPath, String ChildPath, Boolean IsChildPortal)
00:00:07.190 -   Portal failed to install:Error!

Hi Cathal,

Thanks for you reply.  Since posting my first message about Medium Trust I have now found the cause of my problem.

This is the first time I'd try to run DNN under Medium Trust and using a custom Windows server account (e.g. not Network Service) as the app pool identity.  When set to Full trust the install worked OK, but when set to medium trust it failed.  I therefore thought it must be a trust issue given I'd set the permissions on the webroot folder already.

However... it turned out that the problem was due to NTFS permissions.  I had previously set Modify permissions for the app pool identity account on the webroot directory of the DNN installation, however it was also necessary to grant read/executre, list and read privs to the account on the parent of the webroot folder.  E.g. my webroot where the DNN files where was set to d:\inetpub\websites\dnn.  I had to set read access to d:\inetpub\websites.

Something I've never had to do before but as I say, first time round with Medium trust and custom app pool identity, but suprised all the same.  I originally saw this post which lead be to believe I might be missing FileIOPermission in my medium trust file but as you said, this is already there.

It seems I may not have been the only one having seen this issue (see this post) so thought it best to post my reply to help anyone else in the future.  Maybe it's worth re-wording the advice in the wizard to reflect the above on the "Failed Permissions Test" page.

/W