[UI] Ubuntu 20.04 crashes during snapshot false launch

[activeshadow]

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Originally created by @eric-c-wood on Thu, 25 Feb 2021 15:29:00 GMT

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Describe your environment

minimega version: 2.7
Linux distro/version: Ubuntu 20.04.1 LTS/5.8.0-38-generic
Go compiler version:1.14.2
VM types:kvm
Qemu Version: 4.2.1

Describe the bug

After setting a VM's snapshot flag to false, Phenix will crash when starting the experiment. The qemu instances all get created and the VMs actually start but the running experiment page will fail to load.

To Reproduce
Steps to reproduce the behavior:

1. Set at least one VM's snapshot flag to false
2. Start an experiment via the Web UI

Notes
I understand that this issue is almost identical to this closed issue. https://github.com/activeshadow/phenix/issues/20 I was not sure if it was better to create a new issue or simply comment on the old closed issue. The operating system is slightly different from the old issue. If there is a preferred method for future issues, that would be good to know.

From what I can tell, here is why Phenix is crashing.

When the minimega disk info <disk path> command is issued, minimega runs qemu-img info <disk path>. With the way that qemu-img info is being ran, qemu-img returns the following error

Failed to get shared "write" lock

Here is a brief description of the issue https://bugs.launchpad.net/qemu/+bug/1721788

When qemu-img info returns an error, minimega's disk info command returns an error which causes this line to crash https://github.com/activeshadow/phenix/blob/main/src/go/internal/mm/minimega.go#L175