Is there a virtual appliance for managing TLXOS devices?

Yes, but it is very out-of-date and is not currently maintained as it was diverting staff time away from higher priority work.  We hope to provide a new version of this based on CentOS 8 (rather than CentOS 7) when we have the resources to do so.

You can download the old TLXADM virtual appliance from http://archive.thinlinx.com/tlxadm/.  The "vmw_vbx_kvm" version is for VMware Workstation/ESX[i], Oracle VirtualBox, and Linux KVM; the "xen_hv" version is for Xen/XenServer/XCP-NG and Hyper-V.  For maximum compatibility with old virtualization software, the template is based on OVF 0.9 rather than OVF >= 1.0, and as such you will not be able to import it using vCenter 6.5.0 or later (which dropped support for OVF < 1.0).  You can still install it using VMware ESX[i]'s host UI, but this function will be disabled while the hypervisor is joined to a vCenter server, so you may temporarily need to remove the host from vSphere in order to do this.

The version of TMS provided on this virtual appliance is very old, but you can easily update it by opening a root shell and entering a command like "yum install http://mirrors.thinlinx.com/downloads/TMS-8.2.3-1.el7.centos.x86_64.rpm" (adjust filename as required, use the "el7" version of the relevant RPM).

There are several known bugs when using the old TLXADM appliance for session shadowing:

• /home/tlx/.ssh has incorrect permissions (rwxrwxr-x) and sshd refuses to have anything to do with its contents. If you chmod /home/tlx/.ssh to 0700 it will subsequently work, subject to the limitation below.
• /home/tlx/.ssh/authorized_keys only includes the [I]SFF/RePC keys. RPi and its variants have different key pairs than [I]SFF and RePC, which was a deliberate decision on my part because I was concerned about wider availability via NOOBS and the unlicensed VTOS and RPi MC variants.
• "vncviewer -listen" quits after a single connection. This does not happen on the even older CentOS 6 appliance, which is running the same software (TigerVNC) at a lower version (1.1.0), so behavior is different in the newer version (1.3.1) for some reason (bug?).