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I’ve recently been interested in creating a TinyCore Linux virtual appliance. This OVA would allow for some customization, like hostname, IP address, default gateway, and DNS settings.

I’ve posted about TinyCore Linux before, most recently 2 years ago: https://enterpriseadmins.org/blog/scripting/tinycore-15-virtual-machine-very-small-vm-for-testing/. I really enjoy this very lightweight VM as it works perfectly for demos. In a very small (~28MB in this example) package, we can have a running virtual machine with VMware Tools.

I’ve recently started storing virtual machines that I need to deploy, like the Nested ESXi Fling, as OVAs in a content library. These OVAs are typically customized with OVF properties. I’ve never created my own OVA with custom properties, but found a great guide here: https://williamlam.com/2019/02/building-your-own-virtual-appliances-using-ovf-properties-part-1.html.

I wanted to take these steps and apply them to a TinyCore Linux appliance.

At a high level, this appliance works by exposing VMware OVF properties as guestinfo.* values. During boot, a startup script running inside TinyCore Linux reads those values through VMware Tools and applies the requested network and hostname configuration automatically.

Creating Virtual Machine

I started by creating a minimal virtual machine, with hardware compatibility going back to ESXi 7.0u2 and later (vmx-19), Other 5.x or later Linux (32-bit), 1vCPU, 1GB RAM, and configured the VM to boot using BIOS instead of EFI. I typically choose BIOS as I’ve had issues with VMs booting from the CD for the initial install with EFI.

In the VM, I installed TinyCore command line only to the entire disk. I then installed a few dependencies, copied a script from a webserver, and set that script to run when the system boots (by appending to the builtin /opt/bootlocal.sh script). Note: VMware Tools specifically are required for the mechanisms later in this post to function.

tce-load -wi curl pcre open-vm-tools
sudo wget http://www.example.com/build/tc-ova.txt -O /opt/tc-ova.sh
sudo chmod +x /opt/tc-ova.sh
echo "/opt/tc-ova.sh > /tmp/tc-ova-boot.log 2>&1" | sudo tee -a /opt/bootlocal.sh
echo y | backup

The tc-ova.txt file on my webserver (www.example.com) can be found on GitHub here: https://github.com/bwuch/code-snips/blob/master/build/tc-ova.txt. This file has a .txt extension, but that is so I don’t need to create a .sh mime type on my web server. The file is a generic shell script that retrieves OVF properties using VMware Tools and the vmtoolsd --cmd "info-get guestinfo.*" interface. It is renamed to have a .sh extension by the wget command. The script allows the guest operating system to read values provided during deployment without requiring cloud-init or additional provisioning frameworks. After reading those values, the script will apply them to set IP & subnet mask, default gateway, DNS servers, and hostname, if any of those values are found as OVF properties. By keeping all OVF properties optional, the appliance remains flexible. A deployment can use DHCP with minimal input, or fully specify static networking when needed.

Creating OVF Properties

The guide I used for initial setup (https://williamlam.com/2019/02/building-your-own-virtual-appliances-using-ovf-properties-part-1.html) shows how to create these OVF properties in the UI. I needed to create a handful of properties, with specific names, and was interested in setting some default values. While I could have done this in the UI, I decided to automate the creation of OVF properties with PowerCLI. The script below documents my property names in a CSV file embedded into the script, loops through them to apply them to the VM, and finally exports the VM as an OVA.

$applianceVersion = 'TinyCore_17.0_Appliance'
$vmName = 'h461-tinycore-01'

$ovfProperties = @"
Key,Label,Type,Description,DefaultValue
guestinfo.hostname,Hostname,string,Optional: Short hostname,
guestinfo.domain,DNS Domain,string,Optional: Will be appended to Hostname to set FQDN.,lab.enterpriseadmins.org
guestinfo.dns,DNS Server,string,Optional: Space or comma separated list of DNS servers,192.168.127.30 192.168.32.30
guestinfo.ipaddress,IP Address,string,Optional: IPv4 address to assign to VM
guestinfo.netmask,Netmask,string,"Optional: IPv4 Netmask, please specify if IP Address has been set."
guestinfo.gateway,Default Gateway,string,Optional: IPv4 default gateway
"@ | ConvertFrom-Csv


$spec = New-Object VMware.Vim.VirtualMachineConfigSpec         # Main VM config spec
$spec.vAppConfig = New-Object VMware.Vim.VmConfigSpec          # vApp config container

$propertySpecs = @()

$keyId = 0
foreach ($prop in $ovfProperties) {

    # Create property info object
    $propertyInfo = New-Object VMware.Vim.VAppPropertyInfo
    $propertyInfo.Key = $keyId
    $propertyInfo.Id = $prop.Key
    $propertyInfo.Category = "Guestinfo"
    $propertyInfo.Label = $prop.Label
    $propertyInfo.Type = $prop.Type
    $propertyInfo.DefaultValue = $prop.DefaultValue
    $propertyInfo.UserConfigurable = $true
    $propertyInfo.Description = $prop.Description

    # Create property spec wrapper
    $propertySpec = New-Object VMware.Vim.VAppPropertySpec
    $propertySpec.Operation = "add"
    $propertySpec.Info = $propertyInfo

    # Add to array
    $propertySpecs += $propertySpec
    $keyId++
}

# Attach property specs to vApp config
$spec.vAppConfig.Property = $propertySpecs

$spec.VAppConfig.Product = New-Object VMware.Vim.VAppProductSpec[] (1)
$spec.VAppConfig.Product[0] = New-Object VMware.Vim.VAppProductSpec
$spec.VAppConfig.Product[0].Operation = 'add'
$spec.VAppConfig.Product[0].Info = New-Object VMware.Vim.VAppProductInfo
$spec.VAppConfig.Product[0].Info.VendorUrl = 'http://tinycorelinux.net'
$spec.VAppConfig.Product[0].Info.Vendor = 'TinyCoreLinux'
$spec.VAppConfig.Product[0].Info.Name = $applianceVersion
$spec.VAppConfig.Product[0].Info.ProductUrl = 'http://tinycorelinux.net'
$spec.VAppConfig.Product[0].Info.Key = -1
$spec.VAppConfig.OvfEnvironmentTransport = New-Object String[] (1)
$spec.VAppConfig.OvfEnvironmentTransport[0] = 'com.vmware.guestInfo'

(Get-VM $vmName).ExtensionData.ReconfigVM_Task($spec)
Start-Sleep -Seconds 5  # allow the previous task to complete, we could make this more robust by checking for actual completion of previous task.
Get-VM $vmName | Export-VApp -Destination D:\tmp -Name $applianceVersion -Format:Ova -Description $applianceVersion

The resulting OVA file was very small, approximately 28MB on disk.

Testing the Deployment

When deploying this appliance through the UI, all properties have valid values by default, since all fields are optional. I’ve confirmed that this works as expected and the VM gets its IP from DHCP and the host name is set to the default value (box).

For another test, I deployed the OVA using PowerCLI. I’ll include that script below as well.

$file="D:\tmp\TinyCore_17.0_Appliance.ova"
$vmName=   'h461-tinycore-03'

# Get OVF Config
$ovfConfig = Get-OvfConfiguration -Ovf $file

# Set OVF Properties
$ovfConfig.NetworkMapping.dvportgroup_34861.Value = '192.168.10.0'
$ovfConfig.common.guestinfo.hostname.value  = $vmName
$ovfConfig.common.guestinfo.ipaddress.value = '192.168.10.222'
$ovfConfig.common.guestinfo.netmask.value   = '255.255.255.0'
$ovfConfig.common.guestinfo.gateway.value   = '192.168.10.1'

$newVmSettings = @{
  Source            = $file
  OvfConfiguration  = $ovfConfig
  Name              = $vmName
  VMHost            = 'core-esxi-34.lab.enterpriseadmins.org'
  Location          = '30-Greenfield'
  Datastore         = (Get-Datastore core-tier1-nfs1)
  InventoryLocation = 'Testing'
  DiskStorageFormat = 'thin'
  Confirm           = $false
  Force             = $true
}
$newVM = Import-VApp @newVmSettings
$newVM | Start-VM

You may notice that we did not set the dns or domain properties, as those already had default values. After powering on the VM , we can confirm that the settings were updated and networking is functioning as expected.

Changing the deployment

Once our settings have been set, we can browse to the VM > Configure > vApp Options tab (while the VM is powered off) and adjust our values with the SET VALUE button. When the virtual machine is powered on, the script will automatically run at startup, read the updated OVF properties, and set the values as desired.

Conclusion

I originally started this project because I wanted an extremely small appliance that could be stored in a Content Library and deployed quickly whenever I needed a Linux VM for testing or demos. The result is a TinyCore Linux appliance that occupies only about 28MB on disk while still supporting deployment-time customization through standard OVF properties.

This approach has already proven useful in my lab, and I expect it will become my default “utility VM” going forward. The same techniques could easily be expanded to support additional configuration options or application-specific appliances, making TinyCore Linux a surprisingly capable foundation for custom VMware virtual appliances.

About a year ago, I published a post covering how to monitor a Raspberry Pi using the open source Telegraf agent and VMware Aria Operations: https://enterpriseadmins.org/blog/virtualization/monitoring-a-raspberry-pi-with-telegraf-and-aria-operations

Recently, while rebuilding this configuration in a VCF 9.1 environment, I encountered a couple of changes that required updates to the original process:

• Updated InfluxData repository signing and package installation requirements
• Authentication workflow changes when using VCF 9.1 API tokens with the Telegraf Open Agent integration

The good news is that the remainder of the original workflow still functioned as expected after making these updates.

Although the original article focused on Raspberry Pi monitoring, these updates apply more broadly to Linux-based Telegraf Open Agent deployments, including x64 virtual machines and other supported systems.

Updated Telegraf Repository Configuration

When attempting to install or update Telegraf, apt update now produces the following error:

W: GPG error: https://repos.influxdata.com/ubuntu stable InRelease:
The following signatures couldn't be verified because the public key is not available:
NO_PUBKEY DA61C26A0585BD3B

E: The repository 'https://repos.influxdata.com/ubuntu stable InRelease' is not signed.

This occurs because older repository signing methods commonly used in previous installation examples have been deprecated.

The updated installation process now uses a dedicated keyring file under /etc/apt/keyrings.

Cleanup / Removal Steps

Before adding the new repository, we may need to clean up the bad entries we have (assuming we started with the old post). That fix is rather straightforward, we just need to delete two files:

sudo rm /etc/apt/keyrings/influxdata-archive_compat.key
sudo rm /etc/apt/sources.list.d/influxdata.list

With the optional cleanup complete, we can proceed to the updated installation steps.

Updated Installation Steps

The following commands successfully configured the repository and installed Telegraf in my testing:

curl --silent --location -O https://repos.influxdata.com/influxdata-archive.key

gpg --show-keys --with-fingerprint --with-colons ./influxdata-archive.key 2>&1 \
| grep -q '^fpr:\+24C975CBA61A024EE1B631787C3D57159FC2F927:$' \
&& cat influxdata-archive.key \
| gpg --dearmor \
| sudo tee /etc/apt/keyrings/influxdata-archive.gpg > /dev/null

echo 'deb [signed-by=/etc/apt/keyrings/influxdata-archive.gpg] https://repos.influxdata.com/debian stable main' \
| sudo tee /etc/apt/sources.list.d/influxdata.list

After configuring the repository:

sudo apt-get update
sudo apt-get install telegraf

Worked as expected.

Why This Changed

Modern Debian and Ubuntu-based distributions are moving away from the legacy apt-key approach for repository trust management. Instead, repository signing keys are now commonly stored individually under: /etc/apt/keyrings/. This provides better isolation and improved repository handling.

Using VCF 9.1 API Tokens with the Telegraf Open Agent

With VCF 9.1, I also wanted to test using an API key-based authentication workflow instead of relying on a previously obtained Aria Operations token.

This process works as follows

• Generate an API token from VMware Identity Broker (VIDB)
• POST the API token to VIDB
• Receive a Bearer token
• Present the Bearer token to VCF Operations

We can generate the API token in Manage > Identity & Access > VCF SSO > select identity broker instance > API Access tab, or by created a personal access token under our profile > Generate API token > Generate.

Once we have an API Token we need to present it to VIDB. We can do this with the following POST command:

vidbExtraLongToken=vidb_ZmVlMzM5ZGYtYWZkYS00OTkzLTkxMW<redatcted>

curl --request POST \
  --url https://vcf479-vidb-01.lab.enterpriseadmins.org/acs/t/CUSTOMER/token \
  --header 'content-type: application/x-www-form-urlencoded' \
  --data grant_type=urn:custom:vcf:params:oauth:grant-type:api-token \
  --data "api_token=$vidbExtraLongToken" \
  --insecure

During testing, I discovered that the token parameter handling within telegraf-utils.sh expected a traditional Aria Operations token format directly.

In the script, I could see (around like 378) an entry that showed:

377-    #set Authorization header for on-prem
378-    AUTHORIZATION_HEADER="Authorization: OpsToken $VROPS_TOKEN"

(Line numbers added for reference)

Proof of Concept Modification

As a proof of concept, I modified the authorization header handling to expect and present a standard Bearer token instead.

Example modification:

AUTHORIZATION_HEADER="Authorization: Bearer $VROPS_TOKEN"

Disclaimer: This modification should be considered a proof of concept only. Directly modifying bundled or vendor-provided scripts is generally not recommended. Use at your own risk.

After making this change, the remainder of the workflow from the original article functioned as expected in my VCF 9.1 environment.

Installing Telegraf

This is the command line I used to install telegraf:

sudo ./telegraf-utils.sh opensource -c 192.168.10.21 -t "<crazy_long_bearer_token_from_prior_curl_command>" -v 192.168.10.21 -d /etc/telegraf/telegraf.d -e /usr/bin/telegraf -k 1

Where 192.168.10.21 was the IP address of my Operations Collector / Cloud Proxy appliance. As before, I needed to change permissions of files in the /etc/telegraf/telegraf.d directory to be owned by telegraf:telegraf and restart the service with systemctl restart telegraf.

Final Thoughts

Outside of the repository signing changes and API token handling updates, the remainder of the original integration process still worked well in my testing.

If you previously implemented the Telegraf Open Agent integration and encounter:

• repository signing errors
• NO_PUBKEY DA61C26A0585BD3B
• or authentication issues with VCF 9.1 API tokens

the updates above should help with the deployment for current environments.