go-hvkvp: Hyper-V Data Exchange using Go

This is used by the Minishift project.

Installation

A Copr project is available. Installation can be done as follows:

CentOS 7 (or older versions of Fedora)

$ yum install yum-plugin-copr 
$ yum copr enable gbraad/go-hvkvp
$ yum install go-hvkp

Fedora

$ dnf copr enable gbraad/go-hvkvp
$ dnf install go-hvkvp

LiveCD Creator

repo --name=base --baseurl=http://mirror.centos.org/centos/7/os/x86_64/
repo --name=updates --baseurl=http://mirror.centos.org/centos/7/updates/x86_64/
repo --name=hvkvp --baseurl=https://copr-be.cloud.fedoraproject.org/results/gbraad/go-hvkvp/epel-7-x86_64/

%packages
@core
go-hvkvp

From source / development

$ git clone https://github.com/gbraad/go-hvkvp.git
$ cd go-hvkvp
$ go install -v ./cmd/hvkvp

Build RPM package

$ dnf install -y rpm-build go-compilers-golang-compiler
$ rpmbuild -ba hvkvp.spec

Usage

Prepare and send Key-Value pair

$VmMgmt = Get-WmiObject -Namespace root\virtualization\v2 -Class Msvm_VirtualSystemManagementService  
$vm = Get-WmiObject -Namespace root\virtualization\v2 -Class Msvm_ComputerSystem -Filter {ElementName = 'MyVM'}

$kvpDataItem = ([WMIClass][String]::Format("\\{0}\{1}:{2}", $VmMgmt.ClassPath.Server, $VmMgmt.ClassPath.NamespacePath, "Msvm_KvpExchangeDataItem")).CreateInstance()

$kvpDataItem.Name = "IpAddress"
$kvpDataItem.Data = "10.0.75.128"
$kvpDataItem.Source = 0

$VmMgmt.AddKvpItems($Vm, $kvpDataItem.PSBase.GetText(1))

Note

With $kvpDataItem.Source = 0 the KVP gets stored as /var/lib/hyperv/.kvp_pool_0.

Receive/Read on the host:

All records

$ ./hvkvp
Key: IpAddress, Value: 10.0.75.128

Record by specific key

$ ./hvkvp --key Hostname
fedora-vm%

Note

When dealing with special characters, consider using base64 encoding.

For example, the value of the message might contain:

REVWSUNFPWV0aDAKVVNFREhDUD15Cg==

This can be received on the host as:

$ hvkvp -key PROVISION_NETWORKING | base64 --decode > /var/lib/minishift/networking
$ cat /var/lib/minishift/networking
DEVICE=eth0
USEDHCP=y