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Linux boot partitions and how to set them up

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Re: Linux boot partitions and how to set them up

#81

Post by dottedmag »

saghm wrote: post #77
sagarun wrote: post #56

Meanwhile the apple firmware cannot read vFAT ESP. Apple wants ESP to be HFS.

Out of curiosity, how recent is this? I haven't owned my own macbook since the pre-touchbar era (I think the last model I had was the early 2015 Pro), and I had heard that Linux had gotten harder to boot since then due to newer firmware (I remember hearing for a time the newer models were yet to get wifi support on Linux, although I don't know how long that lasted), but at least up until then I was able to use a fair…

There is no UEFI on M1 macs. However boot protocol there is completely different and complicated.

Re: Linux boot partitions and how to set them up

#82

Post by still_grokking »

Almost everything makes sense, imho.

I have actually almost such a setup since some time.

The only thing I don't understand: Why add something like `systemd-boot` to the setup? It's completely unnecessary! All you need is an UKI on the EFI partition. UEFI has a perfectly sufficient bootloader already. I never found out what additional advantages `systemd-boot` would offer.

Maybe someone could clarify?

Re: Linux boot partitions and how to set them up

#84

Post by oxplot »

My humble boot installer, no explicit bootloader, straight to the kernel:

    #!/bin/bash
    set -ueo pipefail

    # Remount EFI partition read/write and restore to readonly when done

    trap 'mount /sys/firmware/efi/efivars/ -o ro,remount &>/dev/null || true' EXIT
    mount /sys/firmware/efi/efivars/ -o rw,remount &>/dev/null || true

    # Remove all existing Arch Linux entries

    efibootmgr | grep 'Arch Linux' | grep -Po 'Boot\K\d+' | while read -r bn; do
      efibootmgr --delete-bootnum -b "$bn" &> /dev/null
    done || true

    # Install boot entry

    efibootmgr --verbose \
      --create --disk /dev/disk/by-id/nvme-abcdef --part 1 --label "Arch Linux" \
      --loader /vmlinuz-${_linux} \
      --unicode "initrd=\\intel-ucode.img initrd=\\initramfs-linux.img OTHER-KERNEL-BOOT-PARAMS"
EDIT: added initrd boot params

Re: Linux boot partitions and how to set them up

#85

Post by still_grokking »

GauntletWizard wrote: post #49
candiddevmike wrote: post #6

How to make one boot partition to rule them all (debian, secure boot disabled for UEFI due to weird bug with how files are laid out with removable flag): parted -s "${diskpath}" mklabel gpt parted -s "${diskpath}" mkpart primary 1MiB 2MiB parted -s "${diskpath}" set 1 bios_grub on parted -s "${diskpath}" mkpart primary 2Mib 202MiB parted -s "${diskpath}" set 2 esp on sleep 1 mkfs.fat -F 32 -n "boot" "${diskpath}2" mo…

The symlinking .bat files for initrd ended up completely bricking my Ubuntu installation a few months ago, so... take heed? I am unimpressed by the quality and robustness of that whole stuff, though, but ended up writing essentially this article into my notes for the next Arch installation I make, where I think there's a fair chance that EFI will live in /efi but be symlinked in /boot. There's a whole other problem,…

Secure boot is super easy when using a UKI.

I have a setup that's almost like what Poettering proposes. Only that I don't use any external bootloader as it seems completely unnecessary.

All you need for secure boot in such a setup is signing the UKI with your keys.

That's the simplest boot setup ever!

It's only one file, so no moving parts. It just works. No LiLo and config, no grub and config, not systemd-boot, no nothing. Just the signed UKI on the EFI partition, and a efibootmgr entry pointing to that single file. That's all needed to boot a modern system.

Re: Linux boot partitions and how to set them up

#86

Post by hyperupcall »

amarshall wrote: post #68
hyperupcall wrote: post #65

This is excellent! Over the years, I've been pleased to see that more and more distributions are writing their disk images and the like to the ESP. (Previously, dd'd USB images for distro installing _required_ the creation of a /boot partition) The logical next step would be to standardize everything through systemd, and ensure all boot images are autodiscoverable and automatically bootable. It's been somewhat frustr…

> through systemd, and ensure all boot images are autodiscoverable and automatically bootable. See systemd-boot and BootLoaderSpec, both mentioned in OP. https://www.freedesktop.org/wiki/Software/systemd/systemd-bo... https://systemd.io/BOOT_LOADER_SPECIFICATION/

yes - not all Linux distros do this

Re: Linux boot partitions and how to set them up

#87

Post by Volundr »

adrian_b wrote: post #54
Volundr wrote: post #42

Earlier quoted context omitted.

This sounds like work to me > For booting the computers, I either boot them from Ethernet or I boot them from a small USB memory that uses a FAT file system for storing the OS kernel, either in the format required by UEFI booting, or, when booting Linux in legacy BIOS mode, together with syslinux, which loads the kernel. Creating boot USB drives (which I think need partitions don't they?) or setting up a PXE boot ser…

If the USB drives were bought formatted as FAT, which is always true for those smaller than 32 GB, they already have the required partition. For booting with UEFI, you just need to create the directories with the names expected by the firmware. For legacy booting, you just need to install syslinux, which takes a second. Then the USB drive can be used to boot any computer, without any other work, for many years. When…

Yeah I don't see it. I don't really have any investment in how you boot your machines, but I can't see this being anything but significantly more work than just using the tooling that's already there for you. When I buy I computer I set it up once and then it lasts 3-6 years. Even setting the system you've got up once would likely take me more time that I've spent adding partitions to disks in the last 20 years. Heck that's probably true even if you include all the servers I've administered in that time as well as my personal machines, especially since those all ran Ubuntu or RedHat where the installer just does it for me, vs my personal Arch machines.

I partition a new computer once every few years. I upgrade the kernel a few times a month. With the normal way that's a simple `pacman -Syu` or `apt get dist-upgrade` and it's handled, no mounting thumb drives or sftp needed.

Re: Linux boot partitions and how to set them up

#88

Post by krylon »

cesarb wrote: post #26

> 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 f…

> 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.

Re: Linux boot partitions and how to set them up

#89

Post by csdvrx »

hyperupcall wrote: post #65

This is excellent! Over the years, I've been pleased to see that more and more distributions are writing their disk images and the like to the ESP. (Previously, dd'd USB images for distro installing _required_ the creation of a /boot partition) The logical next step would be to standardize everything through systemd, and ensure all boot images are autodiscoverable and automatically bootable. It's been somewhat frustr…

> Over the years, I've been pleased to see that more and more distributions are writing their disk images and the like to the ESP. (Previously, dd'd USB images for distro installing _required_ the creation of a /boot partition)

Same. The boot partition is a relic of the past, and you can easily do without it when you remove other relics like grub2: simply make EFI payloads the Arch way: https://wiki.archlinux.org/title/Unified_kernel_image#Manual...

> The logical next step would be to standardize everything through systemd, and ensure all boot images are autodiscoverable and automatically bootable.

As much as I like systemd, I think it's not necessary here: I have a EFISP that's about 16G: it also contains a few .ISO that can be loaded in case system maintenance or a full reinstall is needed. GrubFM and others like Ventoy let you boot directly on say Windows11-22H2.ISO, Ubuntu22-10.iso etc.

When I buy a new drive or computer, I just copy this partition: it's much faster than playing with thumbdrives or PXE Boot.

Re: Linux boot partitions and how to set them up

#90

Post by csdvrx »

oxplot wrote: post #84

My humble boot installer, no explicit bootloader, straight to the kernel: #!/bin/bash set -ueo pipefail # Remount EFI partition read/write and restore to readonly when done trap 'mount /sys/firmware/efi/efivars/ -o ro,remount &>/dev/null || true' EXIT mount /sys/firmware/efi/efivars/ -o rw,remount &>/dev/null || true # Remove all existing Arch Linux entries efibootmgr | grep 'Arch Linux' | grep -Po 'Boot\K\d+' | whil…

If you want to add an initrd, create an EFI payload: https://wiki.archlinux.org/title/Unified_kernel_image#Manual...

$ stub_line=$(objdump -h "/usr/lib/systemd/boot/efi/linuxx64.efi.stub" | tail -2 | head -1)

$ stub_size=0x$(echo "$stub_line" | awk '{print $3}')

$ stub_offs=0x$(echo "$stub_line" | awk '{print $4}')

$ osrel_offs=$((stub_size + stub_offs))

$ cmdline_offs=$((osrel_offs + $(stat -c%s "/usr/lib/os-release")))

$ splash_offs=$((cmdline_offs + $(stat -c%s "/etc/kernel/cmdline")))

$ linux_offs=$((splash_offs + $(stat -c%s "/usr/share/systemd/bootctl/splash-arch.bmp")))

$ initrd_offs=$((linux_offs + $(stat -c%s "vmlinuz-file")))

$ objcopy \

    --add-section .osrel="/usr/lib/os-release" --change-section-vma .osrel=$(printf 0x%x $osrel_offs) \

    --add-section .cmdline="/etc/kernel/cmdline" \

    --change-section-vma .cmdline=$(printf 0x%x $cmdline_offs) \

    --add-section .splash="/usr/share/systemd/bootctl/splash-arch.bmp" \

    --change-section-vma .splash=$(printf 0x%x $splash_offs) \

    --add-section .linux="vmlinuz-file" \

    --change-section-vma .linux=$(printf 0x%x $linux_offs) \

    --add-section .initrd="initrd-file" \

    --change-section-vma .initrd=$(printf 0x%x $initrd_offs) \

    "/usr/lib/systemd/boot/efi/linuxx64.efi.stub" "linux.efi"
The resulting linux.efi" can be added directly with efibootmgr, and contains the kernel boot parameters (cmdline)
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