the GRUB boot menu lists a bunch of previous Linux kernels which you can boot into. While this can occasionally come in handy - like if you can't boot into the new kernel after an upgrade…

Ubuntu Cleanup: How to Remove All Unused Linux Kernel Headers, Images and Modules |
Ubuntu Genius's Blog

Submitted by michael on Thu, 01/01/2015 - 16:16

Unless you have a totally fresh install of Ubuntu, you have probably noticed that each
time you boot up, the GRUB boot menu lists a bunch of previous Linux kernels which you can
boot into. While this can occasionally come in handy - like if you can't boot into the new
kernel after an upgrade…