In this first post of the ‘What The Package’ series, I am trying to understand what a bunch of kernel-* packages installed on my Fedora 39 system are meant for. It only makes sense since, in itself, Linux is just the kernel. All the GUI on top of it is a part of the distro (or the distrubution) we use.

In today’s run of dnf update, a few packages related to kernel were updated, namely:

  • kernel
  • kernel-core
  • kernel-modules
  • kernel-core-modules

OK that’s interesting. I’m curious what’s different between kernel and kernel-core. Based on the dnf info outputs for the two packages, the difference between the two is that kernel-core is the package containing the actual kernel, while kernel package is a “meta” package for the kernel (which is kernel-core). Also, the size of the kernel-core package is 66MB while that of kernel is 0 (zero)! Maybe it’s just a few bytes so it’s rounded to zero?

Rather than having answers, I have questions like:

  • What’s a “meta” package and why is it needed?
  • How can a package be of zero size?

Upon asking a question on the r/fedora subreddit I learned that a meta package refers to other packages as dependency. And it’s helpful in uninstalling whatever dependencies it pulled in.

Anyway, I don’t want to try and go too deep into understanding RPM itself, but rather what they provide. So I did rpm -ql kernel-core-6.6.6-200.fc39.x86_64 which provides a list of files installed by the package being queried:

$ rpm -ql kernel-core-6.6.6-200.fc39.x86_64

The file /boot/vmlinuz-6.6.6-200.fc39.x86_64 is the actual kernel that’s booted into when the machine starts. An initramfs (/boot/initramfs-6.6.6-200.fc39.x86_64.img) is used for loading a temporary root file system into the memory when the system starts. A pretty good description of what other files in /boot are meant for can be found here.

Taking a look at list of files for kernel-modules using rpm -ql kernel-modules-6.6.6-200.fc39.x86_64 shows up a tonne of files under /lib/modules/6.6.6-200.fc39.x86_64/kernel/drivers/. Same is the case when I do rpm -ql kernel-modules-core-6.6.6-200.fc39.x86_64. These are the drivers for the various hardware supported by the Linux kernel. The difference between the two packages is the kind of drivers they provide. A quick dnf info indicates that kernel-modules package provides the “commonly” used kernel modules, while kernel-modules-core provides the “essential” kernel modules for the core kernel package. So it’s basically “common” vs. “essential”.

That’s it Link to heading

Looking up what various files under /boot mean was a good refresher. It’s been long since I worked on or looked into things revolving around the Linux boot process. At some point, it was something I used to discuss with my fellow mentees.