Add custom VM attribute information to the docs

README.md

@@ -1,5 +1,10 @@
 # vmpooler-provider-vsphere
 
+- [vmpooler-provider-vsphere](#vmpooler-provider-vsphere)
+  - [Usage](#usage)
+    - [Custom VM Config Attribute](#custom-vm-config-attribute)
+  - [License](#license)
+
 This is a provider for [VMPooler](https://github.com/puppetlabs/vmpooler) allows using vSphere as a source of machines. This provider was originally part of the main VMPooler code base but was extracted to be a standalone gem so that development could be done independently of VMPooler itself.
 
 ## Usage
@@ -8,6 +13,15 @@ Include this gem in the same Gemfile that you use to install VMPooler itself and
 
 Examples of deploying VMPooler with this provider can be found in the [puppetlabs/vmpooler-deployment](https://github.com/puppetlabs/vmpooler-deployment) repository.
 
+### Custom VM Config Attribute
+
+This provider sets a custom attribute on the VM called `guestinfo.hostname` to the name of the generated VM, which can be queried from inside the guest OS if VMware Tools is isntalled. For example:
+
+macOS: `"/Library/Application Support/VMware Tools/vmware-tools-daemon" --cmd "info-get guestinfo.hostname"`
+Linux or Windows Guest: `vmtoolsd --cmd "info-get guestinfo.hostname"`
+
+See the [VMware Tools Administration docs](https://docs.vmware.com/en/VMware-Tools/12.1.0/com.vmware.vsphere.vmwaretools.doc/GUID-D026777B-606D-4442-957A-B953C2049659.html) for more information about querying information from the GuestInfo variable.
+
 ## License
 
 vmpooler-provider-vsphere is distributed under the [Apache License, Version 2.0](http://www.apache.org/licenses/LICENSE-2.0.html). See the [LICENSE](LICENSE) file for more details.