I have recently moved from RVM to Rbenv and when attempting to execute rails I am getting an error like the one below
Pauls-Air:~ $ rails rbenv: rails: comma
You need to install Rails for each Ruby version within rbenv. Try running rbenv version, I might expect that 2.1.2 is not the ruby version in use for the current project (local version) or maybe your global version.
rbenv
rbenv version