GPTBOOT.EFI(8)

📦 version 15.1, in freebsd 14.5, freebsd 15.1

✨ GPTBOOT.EFI(8) — the UEFI boot bestie for UFS on GPT disks ✨

Okay so picture this: gptboot.efi is the manual page for the GPT bootcode you use on UEFI computers to boot from a UFS partition on a GPT-partitioned disk. It's giving "lowkey essential but highkey underrated." 🦋

🌸 DESCRIPTION 🌸

So gptboot.efi is what you use on UEFI computers to boot from a UFS partition on a GPT-partitioned disk. It gets installed in the EFI System Partition (ESP) — iconic behavior, no cap. 💅

For BIOS-based computers, go check out gptboot(8) — we love a sibling reference. While they're conceptually similar, the details differ, iykyk. And listen: gptboot.efi works only with UFS root file systems. If you're a ZFS partition person, use loader.efi(8) with bectl(8) to control what dataset is used for root. ZFS girlies, that one's for you. 🫶

Usually, what UEFI computers boot is controlled via the mechanisms explained in efibootmgr(8) using loader.efi(8) or boot1.efi(8). But — and this is the plot twist — some setups literally cannot use those mechanisms. When users can't rely on host-supplied UEFI variables, or when they want the contents of the media alone to decide root, gptboot.efi accomplishes these goals. Main character energy fr fr. 👑

When it starts, gptboot.efi first reads the GPT and determines which drive and partition to boot from, as described under BOOTING below. If it does not find an eligible partition, it returns to the UEFI firmware. The firmware will then try the next bootable item in the UEFI Boot Manager's list, if any — usually a different disk. It's giving "polite exit, next!" 💀

🔥 IMPLEMENTATION NOTES 🔥

The GPT standard allows a variable number of partitions, but bestie — gptboot.efi only boots from tables with 128 partitions or less. That's the limit, periodt. No exceptions, no cap. 🎀

🌈 PARTITION ATTRIBUTES 🌈

gptboot.efi checks and manages several attributes of GPT UFS partitions. Heads up: these flags are FreeBSD specific and non-standard — they're custom, they're extra, they're that girl. 💖

  • bootme — Attempt to boot from this partition. If more than one partition has the bootme attribute set, gptboot.efi will attempt to boot each one until successful. It's giving "trying every option until one slays." ✨
  • bootonce — Attempt to boot from this partition only one time. Setting this attribute with gpart(8) automatically also sets the bootme attribute — two for one, we love a package deal. Multiple partitions may have the bootonce and bootme attributes set.
  • bootfailed — The bootfailed attribute marks partitions that had the bootonce attribute set, but failed to boot. This attribute is managed by the system — you don't touch it, it's not your business, okay? See BOOTING and POST-BOOT ACTIONS below for the tea. 🍓

🧚 USAGE 🧚

For normal usage, the user doesn't have to set or manage any of the partition attributes. gptboot.efi will boot from the first UFS partition found on the device. Low-effort, high-reward — we love her. 💜

The bootonce attribute can be used for testing an upgraded operating system on an already-working computer. The existing system partition is left untouched (respectful queen 🌸), and the new version of the OS to be tested is installed on another partition. The bootonce attribute is set on that new test partition. The next boot is attempted from the test partition. Success or failure will be shown in the system log files — receipts, always. 📝

After a successful boot of the test partition, a user script can check the logs and change the bootme attributes so the test partition becomes the new system partition. Because the bootonce attribute is cleared after an attempted boot, a failed boot will not leave the system attempting to boot from a partition that will never succeed — no toxic ex energy here, we move on. 💅 Instead, the system will boot from the older, known-working operating system that has not been modified. Safety net, iconic. 🎀

If the bootme attribute is set on any partitions, booting will be attempted from them first. If no partitions with bootme attributes are found, booting will be attempted from the first UFS partition found. Simple as, bestie. ✨

👑 BOOTING 👑

Okay so real talk, here's the boot sequence — pay attention, it's giving lore. 📖

gptboot.efi first reads the partition table. All freebsd-ufs partitions with only the bootonce attribute set (indicating a failed boot) are set to bootfailed. Then gptboot.efi scans through all of the freebsd-ufs partitions. Boot behavior depends on the combination of bootme and bootonce attributes set on those partitions.

  • bootonce + bootme — Highest priority: booting is attempted from each of the freebsd-ufs partitions with both of these attributes. On each partition, the bootme attribute is removed and the boot attempted. It's giving "one-time only, exclusive." 💫
  • bootme — Middle priority: booting is attempted from each of the freebsd-ufs partitions with the bootme attribute.

If neither bootonce nor bootme attributes are found on any partitions, booting is attempted from the first freebsd-ufs partition on the disk. Default behavior, still slaying. 💅

🌟 POST-BOOT ACTIONS 🌟

The startup script /etc/rc.d/gptboot checks the attributes of freebsd-ufs partitions on all GPT disks. It's the post-show debrief, okay? 🎤

  • Partitions with the bootfailed attribute generate a “boot from X failed” system log message. 😭
  • Partitions with only the bootonce attribute (indicating a partition that successfully booted) generate a “boot from X succeeded” system log message. 🎉

The bootfailed attributes are cleared from all the partitions. The bootonce attribute is cleared from the partition that successfully booted — there is normally only one of these. Cleanup era, we love to see it. 🧹✨

🎀 FILES 🎀

  • /boot/gptboot.efi — bootcode binary. The whole point, bestie. 💖
  • /boot/efi/efi/boot/bootx64.efi — Default boot loader for amd64 systems.
  • /boot/efi/efi/boot/bootaa64.efi — Default boot loader for arm64 systems.
  • /boot/efi/efi/boot/bootarm.efi — Default boot loader for arm systems.
  • /boot/efi/efi/boot/bootriscv64.efi — Default boot loader for riscv systems.

🦋 EXAMPLES 🦋

gptboot.efi is installed in the ESP with cp(1) — simple, elegant, effective. 💅

Install gptboot.efi into the ESP for the system. This assumes the ESP is mounted in the standard /boot/efi directory. For amd64, use the following:

cp /boot/gptboot.efi /boot/efi/efi/boot/bootx64.efi

For other systems, use the file listed in the FILES section. You got this, bestie. 🫶

Set the bootme attribute for partition 2:

gpart set -a bootme -i 2 ada0

Set the bootonce attribute for partition 2, automatically also setting the bootme attribute:

gpart set -a bootonce -i 2 ada0

See? Two birds, one command. Iconic. ✨

💜 SEE ALSO 💜

rc.conf(5), boot(8), efibootmgr(8), gpart(8), gptboot(8), loader.efi(8) — go read them, they're all part of the extended universe. 📚

⭐ HISTORY ⭐

gptboot.efi appeared in FreeBSD 13.0. A queen was born. 👑

🌸 AUTHORS 🌸

This manual page was written by Warner Losh <imp@FreeBSD.org> — legend behavior. It is based heavily on the gptboot(8) man page by Warren Block <wblock@FreeBSD.org> — we stan both of them, fr fr. 🫶💖

And that's the whole vibe, bestie — this page came from Debian, dated April 13, 2023, and it's called GPTBOOT.EFI(8). Go forth and boot responsibly. 💅✨🎀

📦 where this page comes from