I tried to log into my Rstudio on the cloud server through :8787, only to find that I forget the password. I could log in the Rstudio on my other computer, because somehow the computer remembers the password. What can I do to change the password from inside the Rstudio from my other computer, or from the Ubuntu system on which the Rstudio was built?
"Rstudio on the cloud server through :8787" is a bit confusing, but I'm assuming youre talking about RStudio Server?
There, it depends on how you've set up authentication on your rstudio server. From What is my username on my RStudio Server?, "By default, RStudio Server uses PAM authentication. If you haven't done anything to configure authentication, you should be able to log in with the username and password you use on your Linux server. If you are using a different authentication system, you'll need to either create local PAM accounts, or if you're using RStudio Server Pro, you can set up RStudio Server Pro to use your external authentication system - see the Admin Guide for more."
(RStudio.cloud is in alpha and focused on serving education right now. In the off-chance you or others are curious about resetting your password there, currently go to https://login.rstudio.cloud/login)