Powershell - site-defintion installation

I had the following problem. I created a powershell script to install a solution, that contains a site-defintion to a web-application. The issue I ran into was, that the template I am using to create the SPSite in this web-application was not recognized. That means everytime I tried to use this custom template, I received the error ""

On the web I found the cause for this error. The template is not recognized in this session. When you open parallel another powershell window and list the templates (get-spwebtemplates), then you see your template. But not in the host window.

To avoid this error, you have to start another powershell process out of the host window. There you can work with the template.
Be aware to add a sleep function, because the install of the solution with the site-definition needs to be terminated before being able to work with it.

You can copy the host-script into a file called hostscript.ps1 and the new window script into a file called window.ps1

---- your host script ------- (rename the %% variables with your parameters)
#This function installs the solution
function InstallSolution([string] $solutionname, [string] $url)
{
#Check if solution already exists
$solution = Get-SPSolution | where-object {$_.Name -eq $solutionname}
if ($solution -eq $null)
{
#If it is not added yet. Add it and then deploy it.
Add-SPSolution -LiteralPath "%your solution directory%\$solutionname"
Install-SPSolution –Identity $SolutionName –WebApplication "http://$url" –GACDeployment
}
$solution = Get-SPSolution | where-object {$_.Name -eq $solutionname}
#Run the sleeper. It will wait until the solution is finally deployed
do
{
Start-Sleep -Seconds 10
}
until ($solution.Deployed -eq $true)
}

#Enter your parameters here
$webapplicationname = %webapplication-name%
$webapplicationport = %webapplication-port%
$hostheader = %host-header%
$url = %url%
$iisdirectory = %iis-directory%
$apppool = %app-pool%
$apppoolaccount = %app-pool-account%
$databasename = %database-name%
$databaseserver = %database-server%
$sitecollectionadmin = %site-collection-admin%

#Create a new web-application with the above mentioned parameters
New-SPWebApplication -Name $webapplicationname -Port $webapplicationport -AllowAnonymousAccess:$true -HostHeader $hostheader -URL "http://$url" -Path $iisdirectory -ApplicationPool $apppool -ApplicationPoolAccount (Get-SPManagedAccount $apppoolaccount) -DatabaseName $databasename -DatabaseServer $databaseserver

#Call the function above and overload the needed parameters
InstallSolution "%my solution name%", $url

#Here is your template-name. If you don't know yours, then just install the solution and run get-spwebtemplate. It lists all templates. Yours is then supposed to be there as well with the correct # value.
$mydefinitiontemplate = "%My Template%#0"

#Here the new console powershell-window opens.
$newwindow = New-Object system.Diagnostics.ProcessStartInfo
$newwindow.FileName = "powershell.exe"
#I am overloading some variables just to show, how this works
$newwindow.Arguments = "-noexit %your install directory%\window.ps1 $url $mydefinitiontemplate $sitecollectionadmin"
$process = [system.Diagnostics.Process]::Start($newwindow)
#The process will wait, until the window will exit and close
$process.waitforexit()

#Finally just reset the iis
iisreset
---- end host script -------


---- your new window script ------- (rename the %% variables with your parameters)
#Here you catch the overloaded parameters and fill some variables with it
$url = $args[0]
$mytemplatename = $args[1]
$sitecollectionadmin = $args[2]

#Create the new site-collection
New-SPSite -URL "http://$url" -OwnerAlias $sitecollectionadmin -Name %your site name% -Template $mytemplatename
#Tell the host-window, that this window closed
$Host.SetShouldExit(0)
---- end new window script -------

Then save those files somewhere and open powershell and type:
[your path of the hostscript.ps1 file]\hostscript.ps1

This script now creates the web-application, installs the solution with the site-definition and as soon as the solution is deployed, it opens a new console window, to run the second script, that creates a new site-collection in the web-application with the site-definition template you deployed. The window closes afterwards and the host-window then does an iisreset.

It took me quite long to find out about this speciality with site-definition solution deployment and using the template afterwards when creating a site-collection.