Archive | May, 2020

Black screen when re-connect to VMware Horizon virtual desktop

27 May

We had an issue after we upgraded our EUC Stack, especially VMware App Volumes 2.14 to 2.18.1. Quite a few end-users started reporting black screen when they were trying to re-connect to their desktops post the original session launch. This would mean re-connect post breaks, endpoint screen locks, next working day re-connections, etc.

EUC Environment Details:
VMware Horizon 7.11
VMware App Volumes 2.18.1
VMware Dynamic Environment Manager 9.10
VMware Horizon Client 5.x
VMware Workspace One 3.3

Process of elimination

  • If we re-created the writable volumes of the problematic end-users the black screen issue would go away. This provided us with a clue that the problem lied with VMware App Volumes – Writable Volumes
  • No errors/failures observed within the VMware DEM/Horizon logs
  • Upgrade the Horizon Client to the latest 5.x version to remove any Client related issues
  • We already had the necessary anti-virus exclusion based on VMware Antivirus Considerations in a VMware Horizon 7 Environment

After trying out all the usual steps and avoid re-creating writable volumes for problematic end-users, we managed to open a VMware GSS case handled by Karan Ahuja(Very helpful support engineer), which ended been worked by the engineering team(Art Rothstein – Champ in AV Eng Team). Note quite alot of logs, memory dumps, and Procmon were exchanged from the problematic VM using various remote gathering techniques. Finally, the fix was determined as a writable volume snapvol.cfg exclusion. (In our case, the problem is caused by smss.exe using a copy of winlogon.exe that is on the writable volume). After putting this exclusion into all problematic end-users, they stopped seeing Black screen issues upon re-connect.

Path exclusion in writable volumes snapvol.cfg

In this blog, I am not outlining the steps on how to add the snapvol.cfg exclusion as my ex-colleague Daniel Bakshi outlines on a VMware blog post on how to do it step by step. I hope you will find this information useful if you encounter intermittent black screen issues.

Aresh Sarkari

Swagger-UI and Postman Collection for VMware Unified Access Gateway

6 May

I aimed to perform a particular VMware Unified Access Gateway (UAG) tasks programatically. After some guidance from Mark Benson he introduced me to the Swagger-UI that is available within the product.

To access the Swagger-UI on UAG open the following URL within the browser and enter your username and password.

Swagger-UI – UAG API Calls

One can do alot within the swagger-ui to make various GET, POST, PUT actions. However, my preferred tool is POSTMAN. I needed a way to figure out how to get all the swagger-ui converted to POSTMAN. Upon searching, I came across this method mentioned here.

To fetch all the swagger JSON output, go to this URL on the VMware UAG Appliance.


We have two options here. #Option1 – copy all the data from the webpage and paste it under Postman – Import – Paste Raw Text. You will have all the VMware UAG Access Gateway Rest API listed. #Option2 – Paste the above URL into Postman – Import – Import from link (This didn’t work for me maybe authentication was required)

Postman – Import

Please find attached the POSTMAN export for the VMware Unified Access Gateway Appliance 3.9.1. (Note I believe swagger-ui was availble post UAG 3.7 onwards).

Postman – API Calls UAG

I hope you will find this post useful to start using the Swagger-UI and Postman collections to begin working with UAG appliance. My request if you further create interesting scripts or perform cool activities with UAG appliance, I hope you can share it back with me?

Aresh Sarkari