Authentication is only support in Rstudio Server Professional. If you are using Rstudio Server Pro you can use the PAM session API to initializeand destroy Kerberos tickets:
Login to Rstudio with your Unix credentials(using PAM authentication)
Open a shell in Rstudio(via 'Tools ---> Shell' menu item in RStudio)
Get Kerberos ticket(issue the command: 'kinit <user>" - this should prompt you for the users Kerberos password.
Now you should have a Kerberos ticket for that user until the lease expires(usually 24 hours). Commands that you execute using Rstudio will have a valid Kerberos credential.