Robin Minto

Software development, security and miscellany

IIS configuration file contention

I’ve been automating the configuration of IIS on Windows servers using PowerShell. I’ll tell anyone who’ll listen that PowerShell is awesome and combined with source control, it’s my way of avoiding snowflake servers.

To hone the process, I’ll repeatedly build a server with all of it’s configuration from a clean image (strictly speaking, a Hyper-V checkpoint) and I’m occasionally getting an error in a configuration script that has previously worked:

new-itemproperty : Filename: \\?\C:\Windows\system32\inetsrv\config\applicationHost.config 
Error: Cannot write configuration file

Why is this happening? The problem is intermittent so it’s difficult to say for sure but it does seem to occur more often if the IIS Management Console is open. My theory is that if the timing is right, Management Console has a lock on the config file when PowerShell attempts to write to it and this error occurs.


I'm now blaming AppFabric components for this issue. I noticed the workflow service was accessing the IIS config file and also found this article on the IIS forums - AppFabric Services preventing programmatic management of IIS. The workflow services weren't intentionally installed and we're using the AppFabric Cache client NuGet package so I've removed the AppFabric install completely and haven't had a recurrence of the problem.