What version of kernel should be available for running Ubuntu 14.04.3? I have 3 machines with different kernel versions. Would like to know how an upgrade would be performed
When Ubuntu 14.04 was first released, it came with the 3.13.X kernel version. Then came the point releases. Point releases are versions of LTS systems that come with some newer software in the repositories, such as the kernel, but do not sacrifice stability.
- Ubuntu 14.04 and 14.04.1 both had the 3.13.X kernel.
- Ubuntu 14.04.2 brought the 3.16.X kernel.
- Ubuntu 14.04.3 brought the 3.19.X kernel.
When you're in a point release and another one is released you won't get an automatic kernel upgrade, even though you can get it, as explained in How do I upgrade from 14.04 to 14.04.2?.
That's probably the reason why you have different 14.04 machines with different kernel versions.