ubuntu 14.04.1 linuxcnc help

That's almost too simple lol

But remember if you want to choose a different boot kernel say from Rtai to Rt you would have to uninstall Linuxcnc then reinstall with deb file made for Rt while booted into Rt kernel
To uninstall Linuxcnc (in linux mint) I would right click on Deb file used to to load currently installed Linuxcnc then choose open with Gedbi then uninstall

If Gedbi in not a option in Ubuntu choose to open deb file with Software Center then uninstall

If you notice in instructions when making deb files for Rtai and Rt kernels they are different commands and you have to be booted in the respective kernel when making deb file. But deb files can be saved and re-used for respective kernel.

To be changing from one boot kernel to to another as mentioned all dependencies would have to be there for both kernels also

I am setting in airport at the moment but if I remember correctly the only difference in 32bit scripts for Rt and Rtai dependencies besides image and header files is Rtai script loads a package called Rtai-moduals not exact name but you should be able to find it. And Rt kernel comes from different repository, (Debian, squeeze)

For ease you could use Rt script and add Rtai image package and Rtai header package and Rtai moduals package to section that loads packages and everything would install Rt and Rtai kernel