Using GuestStore to Deliver Content to Network-Isolated VMs in vSphere

When working with VMs that lack network connectivity, transferring files can be tricky. I recently explored the GuestStore feature a built-in vSphere feature that solves this challenge by allowing file delivery via VMware Tools—even without a network. This post walks through how I used GuestStore to push a script into a TinyCore Linux VM with no network, CD drive, or external storage options.

The vSphere documentation does a good job explaining what GuestStore is and how it can be used: Distributing Content with GuestStore – https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/8-0/vsphere-virtual-machine-administration-guide-8-0/managing-virtual-machinesvsphere-vm-admin/distributing-content-with-gueststorevsphere-vm-admin.html

Configuring ESXi Hosts for GuestStore

To begin, I configured all of the hosts in a cluster to use the same NFS datastore as a gueststore repository. The official docs linked above show how to do this per host with esxcli so I used that example to write a PowerCLI equilivant. This example uses one host has a reference to create the arguments, populates the URL value, then sets the value for each host in cluster NestedCluster03.

$setRepo = (Get-VMHost test-vesx-71* | Get-EsxCli -v2).system.settings.gueststore.repository.set.CreateArgs()
$setRepo.url = 'ds:///vmfs/volumes/ebb8ed5e-48fb2f0b/h045-gueststore'

foreach ($thisHost in (Get-Cluster NestedCluster03 | Get-VMHost | Sort-Object Name )) {
  ($thisHost | Get-EsxCli -v2).system.settings.gueststore.repository.set.Invoke($setRepo)
}

Preparing the Content / sample script

This sets a datastore folder named h045-gueststore as the base folder for my custom content. I then created a script file to demonstrate how to get this file to the VM. The full path of the test file would be [nfs-datastore-a] h045-gueststore/custom/myscript.sh. This script will write the current date/time value from the system, dot source the os-release file, and then write the ‘pretty name’ of the OS to the screen:

#!/bin/sh
echo "The current system time is $(date)"
. /etc/os-release
echo "This system is running ${PRETTY_NAME}."

This is a basic shell script. It is just a sample, we could use this same method to distribute any script or binary file that is 512MB or less.

Guest VM Retrieval with VMware Tools

I then deployed a TinyCore Linux VM, which is super small (my OVA is less than 30MB, including open-vm-tools) and perfect for this type of testing as it deploys very quickly. In this example, the TinyCore VM has no network adapter, CD/DVD drive, or floppy drive that could be used to access script files or other binaries. It does run in the NestedCluster03 which has GuestStore configured.

Inside the guest OS we’ll run the following command to retrieve the file:

/usr/local/bin/vmware-toolbox-cmd gueststore getcontent /custom/myscript.sh /tmp/myscript.sh

Since this file is only a few KB in size, we should see a complete progress bar almost immediately, with confirmation that ‘getcontent’ succeeded, as pictured below.

Running the Script

From here we can make our script executable (chmod +x /tmp/myscript.sh) and then run it (/tmp/myscript.sh).

This script creates a very basic output, but its just a starting point. The real key here isn’t the script, its the process of getting the script to the virtual machine which does not have an alternate method of file transfer.

Conclusion

Configuring GuestStore on ESXi hosts wasn’t difficult. Using VMware Tools to get these files into the guest OS was also straightforward. While there are many ways to get files into a virtual machine, this worked well in this specific case where the VM didn’t have a CD drive or functioning network connectivity.