Programmatically break permission level inheritance

I would like to create a subsite that has its own custom Permission Levels. At the moment, when I visit the Permission Levels screen at http://servername/subsite1/_layouts/role.aspx I see all the permission levels but these are ones from the rootweb. How can I break the inheritance here and add my own custom permission level?

The purpose is because开发者_如何学JAVA the role would have no use outside of this site so I would prefer not to put it on the root.

This question is the same as asked here: http://social.technet.microsoft.com/Forums/en-US/sharepoint2010setup/thread/32ad2700-8009-4636-880e-07acfca98a06 but Shah Mehul replied saying it could be done programmatically. Is he mistaken? I've read through the parameter descriptions at SPWeb.BreakRoleInheritance(Boolean, Boolean) but they don't describe Permission Levels.

You can still break permission level inheritance in sharepoint 2010, albeit only programatically (reference: http://technet.microsoft.com/en-us/library/ff607713.aspx , section Permissions for sub-webs)

To break it programmatically you can use the SPRoleDefinitionCollection.BreakInheritance Method (http://msdn.microsoft.com/en-us/library/ee547386.aspx)

Powershell sample:

$web = Get-SPWeb "your site URL"
$web.RoleDefinitions.Delete("Some Custom Perm Level") # will not work, because perm levels are inherited
$web.RoleDefinitions.BreakInheritance(true,true)
$web.RoleDefinitions.Delete("Some Custom Perm Level") #will work