3 ms·

> For example, it’s probably worth mentioning that some distributions decided to put kernels onto the root file system of the OS itself. For this setup to work

by cesarb 4y ago

> For example, it’s probably worth mentioning that some distributions decided to put kernels onto the root file system of the OS itself. For this setup to work the boot loader itself [sic!] must implement a non-trivial part of the storage stack. IIRC, older bootloaders like LILO used a simpler approach: after each kernel update, a userspace program asked the kernel for the list of sectors which contained the kernel file, and wrote the list to a map file; the bootloader then read that map file (its sector hardcoded into the bootloader by the same userspace program), and loaded the kernel by reading the sectors directly. Neither the bootloader nor its userspace installer needed to know anything about filesystems or other parts of the storage stack, and it worked perfectly with RAID 1.

yjftsjthsd-h 4y ago
That only works with simple filesystems, though; it'll fall apart if your root filesystem uses, say, compression, encryption, or possibly any RAID except mirroring (depending on the details and what the bootloader can handle).
krylon 4y ago
> LILO Ah, that stirs memories. That 1,024 something boundary the kernel image had to reside in, hence the need for a separate /boot partition. And every time there was a new kernel available, I had to re-run some command to recreate that map file. Things have become a lot more convenient since then.
- akira2501 4y ago
  Pardon the snark, but I'm old. And more complex at the same time. Now I need to do a silly dance to register a GUID with my BIOS so it can find an executable and run it for me (you did remember to add efivars to your kernel, right?), hold a vFAT partition around specifically for this case (what package has mkvfat again?), and worry about how the system maintainers will decide to "improve" what they think is wrong with this hierarchy. Previously.. the BIOS would find a particular sector on what I told it was the "boot drive" and run it without too much concern over what, if anything, happened next. And for this change, do I get a BIOS that's more helpful when there's a frustrating boot misconfiguration? A log to show me what precisely went wrong? The ability to save debug information in any relevant format? I could, but zero vendors in the consumer space are going to do that. Now.. essentially, I just don't have to specify a "boot drive" anymore. Other than that, if you're bringing a system up from scratch, EFI has just as much "janky magic" in it that the old boot sector method did.
  - krylon 4y ago
    You are correct, the good old BIOS was not pretty, but it worked and was simple enough one could understand it and its common failure modes. All the complexity we keep piling up is going to come back and bite us eventually. I was just speaking of LILO vs grub, though. (I heard that grub is not pretty internally, but as a mere user, it has not given me trouble.)

by cesarb 4y ago

yjftsjthsd-h 4y ago

That only works with simple filesystems, though; it'll fall apart if your root filesystem uses, say, compression, encryption, or possibly any RAID except mirroring (depending on the details and what the bootloader can handle).

krylon 4y ago

> LILO Ah, that stirs memories. That 1,024 something boundary the kernel image had to reside in, hence the need for a separate /boot partition. And every time there was a new kernel available, I had to re-run some command to recreate that map file. Things have become a lot more convenient since then.

akira2501 4y ago
Pardon the snark, but I'm old. And more complex at the same time. Now I need to do a silly dance to register a GUID with my BIOS so it can find an executable and run it for me (you did remember to add efivars to your kernel, right?), hold a vFAT partition around specifically for this case (what package has mkvfat again?), and worry about how the system maintainers will decide to "improve" what they think is wrong with this hierarchy. Previously.. the BIOS would find a particular sector on what I told it was the "boot drive" and run it without too much concern over what, if anything, happened next. And for this change, do I get a BIOS that's more helpful when there's a frustrating boot misconfiguration? A log to show me what precisely went wrong? The ability to save debug information in any relevant format? I could, but zero vendors in the consumer space are going to do that. Now.. essentially, I just don't have to specify a "boot drive" anymore. Other than that, if you're bringing a system up from scratch, EFI has just as much "janky magic" in it that the old boot sector method did.
- krylon 4y ago
  You are correct, the good old BIOS was not pretty, but it worked and was simple enough one could understand it and its common failure modes. All the complexity we keep piling up is going to come back and bite us eventually. I was just speaking of LILO vs grub, though. (I heard that grub is not pretty internally, but as a mere user, it has not given me trouble.)