Hi @Primesty!
Because the default username/password combination offered to you in the Marketplace instructions are quite insecure, we opted to make that user (rstudio-user) not a sudoer, so you wont be able able to perform sudo operations from the rstudio-server terminal by default.
Obviously, you've discovered that the default ubuntu user for this instance is, as the Ubuntu AMI standard, capable of performing sudo tasks.
In addition, the TensorFlow-GPU AMI does actually come with tensorflow-gpu installed in the default python environment (and even has the tensorflow/keras R packages installed with all existing R versions). I imagine you were looking to do something a little more nuanced with the tensorflow install, which is perfectly alright! Please let us know though if you had trouble using the default set of tensorflow tools installed in the AMI, we'd love to make this offering work great for everyone!
Thanks!
Steve