I ran sudo apt-get install… and got this error when setting up a new Ubuntu machine to run Ruby 1.9.2…
“Package build-essential is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package build-essential has no installation candidate”
Turns out, simply running “sudo apt-get update” fixes it.