Running VBoxManage from guest vm? - ssh

Question

I have a need to disable host time syncing selectively on a vagrant/virtualbox vm. I can do that without issue on the host machine like so:
$ VBoxManage setextradata <name> \
> "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" "1"
The issue is that I only need to disable syncing while some work is done in the guest vm. Specifically, a unit test job needs to be able to toggle the GetHostTimeDisabled value programmatically, effectively giving full control of the vm system time to the test job.
I've considered running the VBoxManage command over ssh from within the unit test job but that brings up additional difficulty. Like, for example, setting up passwordless login to my local machine as the vagrant user.
I have ssh agent forwarding enabled for the vm and it's confirmed working. Unless anyone has suggestions for a "better" way, I'd appreciated some help figuring out how to ssh back to the host machine (OSX) from the vm (ubuntu linux) as the vagrant user. Ideally I'd like it to work the same for all users of the vagrant. Maybe using the forwarded agent somehow?
Perhaps there's a way to manipulate VBoxService on the guest to temporarily disable time sync?

Answer 1

I've solved this using ssh to run the VBoxManage command on the host machine.
Enable ssh forwarding in your Vagrantfile
e.g., config.ssh.forward_agent = true
Enable yourself to ssh to yourself as yourself ;)
In other words, copy your own public key to your own authorized_keys file
e.g., $ cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
Set the VM to ssh as you by default (instead of the vagrant user)
e.g., via the shell provisioner in your Vagrantfile:
require 'etc'
username = Etc.getlogin
config.vm.provision :shell, :inline => "echo \"Host *\n User #{username}\" > /home/vagrant/.ssh/config"
Freely ssh back to the host like so: (the default NAT IP of the host is 10.0.2.2)
$ ssh 10.0.2.2 'hostname'
$ ssh 10.0.2.2 'VBoxManage setextradata <your vm name> \
"VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" "1"'
$ echo "GetHostTimeDisabled is now " && \
ssh 10.0.2.2 'VBoxManage getextradata <your vm name> \
"VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled"'

Answer 2

I see that you have found an answer, but I've thought of a different way.
VirtualBox has a concept called "shared folders". This means that you can set up a folder on the host that will be available for mounting on the guest, and which stays the same between host & guest, meaning you can share data while the guest is running. You can even have it automatically mounted, in which case it will be mounted as /media/<folder>. Then, you can symlink it to wherever you want.
For my idea, you would put VBoxManage.exe into the shared folder from the host, then call it from wherever you put it in the guest, and possibly put it in your PATH. Then you'd call
$ /path/to/VBoxManage setextradata <guest name> \
> "VBoxInternal/Devices/VMMDev/0/Config/GetHostTimeDisabled" "1"
from your script or whatever.
I just tried this, and it didn't work, but I have a feeling that was because my host & guest are different OS's, specifically Windows & Linux, respectively. I suspect calling dos2unix on VBoxManage.exe might work, but I'm afraid to try it because it might break VirtualBox. It might work better for you, though.