I want to install a new stable Linux kernel without removing the older one, as I see there is an option in Ubuntu to switch on whichever kernel I want to use.
- To get a listing of the latest packages available for upgrade use
sudo apt-get update
- Instead of running
sudo apt-get upgradeand selecting "Y" for "Yes"
sudo apt-get install "linux-image-###" to install the newest version alongside the old one.
Make sure to select the appropriate version when at the GRUB screen.
Shiftafter bios boot to get the GRUB screen to load if your installation is set to skip it.
I think the easiest way to install a new kernel using Ubuntu is using the Ukuu kernel Update Utility, you can launch it from your apps amd choose to install whatever kernel version Ubuntu supports. Each time you install a new one it creates an entry in GRUB so you can boot into an older kernel in case the new one doesn't work.
This link: How to update kernel to the latest mainline version without any Distro-upgrade? will answer all your questions on how to install a new kernel.
You can install kernels outside your distribution chain such as
4.14.xxx LTS which you will have to manually remove when unwanted.
Regular system updates will install new kernels from time to time. They may auto remove older kernels but will always keep the latest kernel plus the previous version for fall-back purposes in case a bug is discovered in the new version.
Ubuntu doesn't switch on the different kernel versions. You do this using grub's Advanced Options menu at boot time.