Kernel updates

Occasionally your distro’s package manager will want to install a newer version of the Linux kernel, the very heart of the operating system. The kernel package is unlike any other in that you can have multiple versions installed. Each package puts its own kernel and initramfs file in /boot with a corresponding set of modules in /lib/modules. It also adds a separate entry to the boot menu, so installing a new kernel leaves your old kernel available for use. This is important if you use third party drivers – those that are not included with the kernel. These often include proprietary graphics card and wireless network adaptor drivers. If you find that your wireless doesn’t work after a kernel upgrade, or you boot to a command prompt instead of your beautifully themed desktop, then you can select the previous kernel from the boot menu to go back to the old kernel while you fix the problem. This is especially useful if your network adaptor is affected, as you usually need a network connection to install network card drivers (which makes sense from a technical standpoint if not from a practical one).

Some distros hide the boot menu, in which case you have a few seconds to hold down the appropriate key – usually Shift but sometimes Esc – to pop up the menu before the boot process continues. One consequence of this method of installing kernel packages is that as time goes on you will accumulate more and more kernel packages, so if your boot directory contains a lot of vmlinux-* files, you can free up some space by uninstalling the older packages for kernels that you no longer use.