this post was submitted on 30 Apr 2024
223 points (97.9% liked)

linuxmemes

21126 readers
1185 users here now

Hint: :q!

Sister communities:

Community rules (click to expand)

1. Follow the site-wide rules

2. Be civil
  • Understand the difference between a joke and an insult.
  • Do not harrass or attack members of the community for any reason.
  • Leave remarks of "peasantry" to the PCMR community. If you dislike an OS/service/application, attack the thing you dislike, not the individuals who use it. Some people may not have a choice.
  • Bigotry will not be tolerated.
  • These rules are somewhat loosened when the subject is a public figure. Still, do not attack their person or incite harrassment.
    • 3. Post Linux-related content
  • Including Unix and BSD.
  • Non-Linux content is acceptable as long as it makes a reference to Linux. For example, the poorly made mockery of sudo in Windows.
  • No porn. Even if you watch it on a Linux machine.
    • 4. No recent reposts
  • Everybody uses Arch btw, can't quit Vim, and wants to interject for a moment. You can stop now.

    • Please report posts and comments that break these rules!

    founded 1 year ago
    MODERATORS
    [email protected]
    [email protected]
    [email protected]
    223
    What is your experience with btrfs snapshots? (lemmy.world)
    submitted 6 months ago by [email protected] to c/[email protected]
    33 comments fedilink hide all child comments
     
    you are viewing a single comment's thread
    view the rest of the comments
    [–] [email protected] 2 points 6 months ago (2 children)

    Thanks for explaining it! So systemd-boot finds the kernel in the EFI partition, which it then loads, and then that kernel loads another kernel from the main partition, which is then the full OS.

    Is there a reason it's done this way, and not just the bootloader loads the main kernel?

    Also, are the two kernels the same, or does this use two different kernels?

    [–] [email protected] 2 points 5 months ago (1 children)

    Sorry for the late reply btw, responses were broken for me

    [–] [email protected] 1 points 5 months ago

    No problem, thanks for replying.

    [–] [email protected] 2 points 5 months ago* (last edited 5 months ago) (1 children)

    In the case of Dracut, I'm not sure what it does exactly, but the kernels will almost definitely not be identical. In the "EFI kernel", uneeded modules (meaning most of them) are usually omitted.

    You could probably also have different kernels in terms of version number, although it might complicate things. Kinda depends on whether they recycle data structures from the first kernel and whether those remain compatible. I don't really know whether this is actually done tho.

    The reason why multiple kernels (or bootloaders for that matter) are used is that there are different levels of "readiness" in your system. Say you have LVM and a LUKS encrypted partition (in whatever order). Systemctl-boot will load the kernel and it's initramfs, but can't be bothered to deal with complicated file system shenanigans. That would complicate the whole program significantly.

    So it just loads a Linux kernel which has these capabilities. That kernel can deal with LVM, decrypt the LUKS partition (or ask for a password), mount whatever btrfs nonsense is inside and then hand it over to the proper kernel. The proper kernel can in turn rely on having all its stuff mounted and ready, instead of having to worry about all this.

    You could do with just one kernel, but Dracut allows you to rapidly create bootable kernel + initramfs pairs of which you might need multiple (e.g. for dual booting, backup). Moreover, you probably wouldn't really want it to fiddle with your kernel all the time, especially when it's customised already.

    [–] [email protected] 1 points 5 months ago

    That makes sense. It looks like a really clever way of letting the boot process allow for basically any arangement. Thanks!