Hi,
You are not supposed to enter "sudo apt-get update" or "sudo apt-get install -y nginx" into the cloud shell window. These commands are run automatically in the vm you created when you copy/paste the az vm extension set...
command in the code block. They mention these commands to you for informational purposes so that you know what the command is doing.
If there is still time remaining on your sandbox go ahead and continue through the module and complete the Configure network access exercise in Unit 9. If your sandbox has expired, please Activate a new sandbox and complete Unit 3 exercise as well as Unit 9 exercise. These two exercises are intended to be completed in sequence using the same sandbox.
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Thanks.
-TP