Comments on: HVC – SSH Direct for Linux VMs on Hyper-V

By: Brian

Brian — Thu, 21 Apr 2022 01:05:38 +0000

@Paul, I finally figured this out. In answer to your question “Do you have to do anything specific on either guest or host in order to get the Ubuntu VM to ‘listen’ for incoming SSH connections on the VMBus (as opposed to the TCP/IP stack).” the answer is yes! The SSH service needs to know to listen on the VMBus as well as the TCP/IP stack. On my Ubuntu system I edited, /usr/lib/systemd/system/ssh.socket and added

ListenStream=vsock::22

after the existing line that said,

ListenStream=22

You then need to restart the ssh.socket service for the change to take effect.

By: Clayms

Clayms — Mon, 23 Sep 2019 13:37:41 +0000

Hi Thomas,

Version info below:

Major Minor Build Revision
—– —– —– ——–
10 0 17763 0

However, I suspect `hvc` is calling `ssh` from the the install of [OpenSSH](https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_install_firstuse) which is installed in ‘C:\Program Files\OpenSSH\’ and that is what is causing the problem.

I don’t know why it only has a problem when I actually specify a username@vmname to ssh into.

How would I tell hvc to quote the path to the ssh executable?

By: Thomas Maurer

Thomas Maurer — Sun, 22 Sep 2019 15:49:59 +0000

In reply to Clayms. Hi Clayms This is strange, which version of Windows 10 are you running?

By: Clayms

Clayms — Wed, 18 Sep 2019 18:20:21 +0000

From PowerShell, `hvc id test_vm` correctly returns the VM’s ID and `hvc list` shows that the ‘test_vm’ `STATUS` is `running`.

Also, `hvc ssh` returns the ‘hvc ssh’ command usage options.

However, `hvc ssh root@test_vm` returns:
‘C:\Program’ is not recognized as an internal or external command, operable program or batch file.

Obviously, hvc is in the PATH variable, so what is going on here?

By: Alfredo

Alfredo — Tue, 19 Mar 2019 13:58:49 +0000

Hi Thomas,
thanks for the reply.
Yes, ssh over tcp/ip working properly.
Any other suggestions?

By: Thomas Maurer

Thomas Maurer — Tue, 12 Mar 2019 08:38:21 +0000

In reply to Alfredo. Did you configure SSH Server within the Linux machine?

By: Alfredo

Alfredo — Tue, 12 Mar 2019 08:32:37 +0000

Hi,
I created a linux vm on a hyper-v host (Windows 2019).
On the Linux vm (CentOS) I have installed and configured the integration services and I have
tried to connect via SSH Direct (HVC nc vm-name -t vsock port(??)) but I got the following error:

“No connection could be made because the target machine actively refused it.”

Any suggestions?

Thx

By: ben

ben — Fri, 01 Feb 2019 09:49:37 +0000

As this is the 1st result in Google et al., I’ll put my understanding here, hoping it helps.
I had the same issue and digging into it, hvc.exe does not connect to ssh through VMBus: if you add ‘-v’ to see what’s going on under the hood, you can see that hvc.exe will try vsock (VMBus) 1st but will fallback to ip (TCP/IP) in case it does not work. As OpenSSH does not support vsock and only listen on TCP/IP, hvc.exe ends up using regular TCP/IP. If you do not have IP connectivity between HyperV and you VM, you are screwed.
I ended up writing a quick&dirty VMBus-to-TCP proxy to be able to connect to my Linux VM through VMBus using socat: https://github.com/bganne/hvnc
HTH

By: István Nagy

István Nagy — Thu, 06 Dec 2018 15:38:27 +0000

@Paul I wouldn’t be surprised if this only works with Red Hat Enterprise Linux or CentOS as a guest. Vmbus Sockets is only supported on those according to Microsoft. I haven’t yet tried though.

By: Paul

Paul — Wed, 05 Dec 2018 22:58:31 +0000

Thx for the reply @István.

@Thomas mentions in this blog post that “to make this work, the SSH server inside the VM needs to be configured”.

Other than ensuring that SSH is installed within the guest OS, I’m wondering whether there is some additional configuration of SSH that is required to allow it to ‘bind to’ or ‘listen’ on the VMBus, as opposed to a normal TCP socket.