Powershell provisioning new site with unique permissions but uses existing owners group - sharepoint

Question

Currently run in to a bit of a stumbling block and i don't know if i am searching for the right thing on google to get the correct results to help me.
The situation....
1)In sharepoint via the GUI i can use unique permissions when setting up a site.
2)You are then presented with a page showing 3 possibilities(Read, Contribute and owner) of groups.
3)In these possibilities you can select to use an existing group or create a new one.
The setup i am looking for is use existing group for owner and create 2 new groups for contribute and read. How do i do this in powershell?
The other way i have thought about doing this is to not break permissions, Delete all the groups apart from the owners groups, Create 2 new groups, assign them contrbute and read and add them to the site. <- this sounds like it would work but also sounds like a workaround!
Cheers
Truez

Answer 1

Do you want to create custom permission levels, or custom groups but give them one of the exisiting permission levels? In the case of the former, the easiest way would be to create your custom permission levels in the GUI by copying and then modifying the existing Contribute and Read groups and then to assign these to your groups in your PowerShell script.
Here's the code you need to set your custom permissions on a site.
# Function to create role assignment variable for SharePoint group
#-----------------------------------------------------------------
Function CreateGroupRoleAssignment {
Param(
[parameter(Mandatory = $true)]
[string]
$RaName,
[parameter(Mandatory = $true)]
[string]
$GroupName
)
# Delete role assignment variable if it already exists
if(Test-Path "variable:global:$RaName") {
Write-Host "-- Removing existing Role Assignment variable: $RaName"
Remove-Variable -Name $RaName -Scope Global
}
# Create role assignment object variable in the global scope (to persist outside of the function)
Write-Host "-- Creating Role Assignment variable for SharePoint group: $GroupName"
New-Variable -Name $RaName -Value ([Microsoft.SharePoint.SPRoleAssignment] $RootWeb.SiteGroups[$GroupName]) -Scope Global
} # End Function CreateGroupRoleAssignment
# Script body
#------------
# Get your site
$Web = Get-SPWeb http://yoursiteurl
# Stop your site from inheriting permissions
$Web.BreakRoleInheritance($false)
# Create Role Definitions from the "Permission Levels" in your site
# Pick from the list in http://yoursiteurl/_layouts/role.aspx
$FullControlRD = $Web.RoleDefinitions | Where {$_.Name -eq "Full Control"}
$ContributeRD = $Web.RoleDefinitions | Where {$_.Name -eq "Contribute"}
$ReadRD = $Web.RoleDefinitions | Where {$_.Name -eq "Read"}
# Call function to create role assignments from your SharePoint site groups
# SharePoint groups inc. built-in Your Site Owners/Members/Visitors plus any you create
# See list of groups in http://yoursiteurl/_layouts/user.aspx
CreateRoleAssignment -RAName "OwnersRA" -GroupName "Your Site Owners"
CreateRoleAssignment -RAName "Group1RA" -GroupName "Your Custom Group 1"
CreateRoleAssignment -RAName "GRoup2RA" -GroupName "Your Custom Group 2"
# Bind the role definition to the role assignment to assign the desired permission level to each group
$OwnersRA.RoleDefinitionBindings.Add($FullControlRD)
$Group1RA.RoleDefinitionBindings.Add($ContributeRD)
$Group2RA.RoleDefinitionBindings.Add($ReadRD)
# Add the role assignment with the custom permission to your site
$Web.RoleAssignments.Add($OwnersRA)
$Web.RoleAssignments.Add($Group1RA)
$Web.RoleAssignments.Add($Group2RA)

Answer 2

I managed to find a solution.
I created the site so all the groups were inherited.
Broke inheritance
Once broken i looped through all the groups and removed any that didn't contain owner. This meant that the owner group still updated when you placed a member in the owner group at the root level site.
I then created a Members and readers group.
$businessUnitWeb = New-SPweb -Url "My Site" -Name "Test" -UseParentTopNav
$businessUnitWeb.BreakRoleInheritance($true)
$groupsToRemove = $businessUnitWeb.Groups| WHERE-OBJECT{$_.Name -ne "XXXXXXXXX Portal Owners"} | $businessUnitWeb.Groups.Remove($_)
$groupsToRemove | FOREACH-OBJECT{$businessUnitWeb.Groups.Remove($_)}
$usersToRemove = $businessUnitWeb.Users| WHERE-OBJECT{$_.Name -ne "XXXXXXXXXX Portal Owners"}
$usersToRemove | FOREACH-OBJECT{$businessUnitWeb.Users.Remove($_)}
}
$businessUnitWeb.SiteGroups.Add("$businessUnitWeb Read", $businessUnitWeb.Site.Owner, $businessUnitWeb.Site.Owner, "The read group for $businessUnitWeb")
$newGroup = $businessUnitWeb.SiteGroups["$businessUnitWeb Read"]
$newGroupAssign = New-Object Microsoft.SharePoint.SPRoleAssignment($newGroup)
$newGroupAssign.RoleDefinitionBindings.Add($businessUnitWeb.RoleDefinitions.GetByType("Reader"))
$businessUnitWeb.RoleAssignments.Add($newGroupAssign)
$businessUnitWeb.update()
$businessUnitWeb.SiteGroups.Add("$businessUnitWeb Contributor", $businessUnitWeb.Site.Owner, $businessUnitWeb.Site.Owner, "The Contributor group for $businessUnitWeb")
$newGroup = $businessUnitWeb.SiteGroups["$businessUnitWeb Contributor"]
$newGroupAssign = New-Object Microsoft.SharePoint.SPRoleAssignment($newGroup)
$newGroupAssign.RoleDefinitionBindings.Add($businessUnitWeb.RoleDefinitions.GetByType("Contributor"))
$businessUnitWeb.RoleAssignments.Add($newGroupAssign)
$businessUnitWeb.update()
Write-Host "Creating $businessAreaURL..... "
$businessUnitWeb.ApplyWebTemplate(Template stuuf")
If there are some typo's i've had to remove company tie's from the code.