Zenbot/Gecko/LinuxCNC?

I didn't md5sum the image but I doubt that is the issue. I used and identical USB thumb drive (both recent and new) to download and boot an Ubuntu image, and it works perfectly. I could try that. But in any case Gmoccapy will still be broken.

You are using an experimental ISO. You are so close, don't give up yet.

This thread might help
forum.linuxcnc.org/9-installing-linuxcnc...ter-2-8?limitstart=0
So from the buildbot page, there is a statement that says

This is the stanza you need to use (read the page carefully and find it):
You may be lucky and find that the ISO has been configured to access master branch but I doubt it.

You can choose to edit that file with gedit or similar (you'll need to have root privileges or use sudo) or use Synaptics..

The Synaptics package manager is used to install/uninstall programs and is a GUI wrapper around the lInux shell. Find it in your menu system. Open it and enter your root password. Search for LinuxCNC and see if there is an entry for master or version 2.8. If so you are in luck otherwise you will need to add those lines to that file referenced above either using gedit or the provided menu option in Synaptics.Then it will show.

Then follow Tommy's simple instructions in the thread above. I was stunned how easy it was to do this in synaptics and was quite gobsmacked by the smorgasboard of software available to install at the click of a button. You don't get that kind of central repository in Windows.

Despite your problems with crappy ISO's, your journey has been much easier than I experienced. I ended up compiling the PREMPT_RT kernel from source and I tried several distributions to get my hardware supported (After I had purchased the Mesa hardware). I settled on Mint which is very nice. Once I got that far, I compiled LinuxCNC from source as it was not that much more effort. But lets leave that for another day.

If I want to follow rodw's instructions above, which ISO do I start with ("the ISO" referred to in the post). Also, what buildbot page has these instructions about "stanzas"?

Probably more questions to follow. The instructions are still far from clear. The thread referred to is awfully terse as well. But it may make sense once I'm sitting in front of a working base OS.

If I can get this working, I'm going to need to know how to create my own ISO from my working install. I'll be configuring all of this on my Mac in a VM. I'm not going to turf the Windows install on my CNC laptop until I get much closer to a working setup. So once I get Gmoccapy working in sim mode on the Mac VM, I need to create an ISO from that. If that is not straightfoward, I've got a problem.

I've already given you the link to the buildbot on this post earlier in this thread. Did you look at it?
forum.linuxcnc.org/38-general-linuxcnc-q...xcnc?start=30#108237
You don't need to worry about ISOs any more as you have the right OS with a preemptive kernel installed (based on a previous post of yours)
To save your LinuxCNC configs to move to a new machine, all you need to do is to copy the ~/linuxcnc/config folder.
Creating your own ISO is not trivial and is not necessary. Leave that to the dev team.

All you have to do is to do a software upgrade in Linux. This is done with apt_get from the command line or Synaptics from the GUI.
Linux software is stored in various repositories around the world. Whilst the Linux distro you have installed will keep all of its own files on its own repository, some projects (like LinuxCNC) are not part of the distro so you need to tell your copy of Linux where to look to find LinuxCNC which is the purpose of the stanza I quoted. (stanza is the buildbot term, not mine)

Sorry, I reread this thread and had forgotten that you were just running from the ISO without having installed Linux on a PC.
Lets start again.
The only ISO you could get to boot happened to be an experimental image. This will be good to use on real hardware with Mesa ethernet cards. However, it does not support the older v 2.7 version of gmoccappy.

For evaluation purposes, running from the USB stick, you really should be using the official V 2.7 iso on this page under the heading normal download
linuxcnc.org/docs/2.7/html/getting-start...etting-linuxcnc.html

On this version, the dependency issue will not be a problem and Gmoccapy will work fine.

As posted earlier, I think the solution to getting this to boot is to find a Windows machine, install win32diskimager, download the official ISO, rename it so it has a .IMG extension and burn to a USB stick using win32diskimager. That should boot reliably and is the way I create all of my bootable images becasue I've had so many problems getting things to boot in the past (not just Linuxcnc).

Give it a go and report back. If it fails, you really need to take your own advice and find another PC.

The first thing that happens after I install wheezy (I'm doing this first on my Mac in a VM, I'll get to real HW later) is that I'm asked whether I want to install 293 updates. Yes, no, or some of them?

Didn't know you could modify a configuration and save back to a USB stick and have that new USB be bootable. Is it obvious how to do that?

And in any case, what about the 293 potential updates to the wheezy from the Getting Started page?