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handbook: The freebsd-boot 512KB limit is for legacy BIOS
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Authored by emaste on Aug 5 2025, 2:35 PM.
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imp
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R9:2238c247d4a4: handbook: The freebsd-boot 512KB limit is for legacy BIOS
Summary

Handbook partitioning doc has no reference to EFI right now, and says that the freebsd-boot partition should not be bigger than 512KB. Clarify that this is the partition used for legacy BIOS booting to avoid confusion about EFI's default 200MB partition.

Ref: https://www.reddit.com/r/freebsd/comments/1mia9z6/boot_partition_over_512kb_works_fine/

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emaste requested review of this revision.Aug 5 2025, 2:35 PM
emaste updated this revision to Diff 159784.
emaste created this revision.
emaste added reviewers: imp, Installer.

Explicitly mention that EFI boot does not have an issue

imp added a comment.Aug 5 2025, 3:52 PM

So you *CAN* have boot partitions larger than 512k. We just don't read more than 512k bytes.

documentation/content/en/books/handbook/bsdinstall/_index.adoc
637

While here, s/current boot code/boot code/. There's no chance we'll ever fix it to be anything significantly larger. Otherwise it's fine.

emaste added inline comments.Aug 5 2025, 4:01 PM
documentation/content/en/books/handbook/bsdinstall/_index.adoc
637

Or how about "... for BIOS booting should be no larger than 512K due to legacy boot code limitations."?

imp accepted this revision.Aug 5 2025, 4:16 PM
imp added inline comments.
documentation/content/en/books/handbook/bsdinstall/_index.adoc
637

even better.

This revision is now accepted and ready to land.Aug 5 2025, 4:16 PM
emaste closed this revision.Aug 5 2025, 5:02 PM
emaste added a commit: R9:2238c247d4a4: handbook: The freebsd-boot 512KB limit is for legacy BIOS.

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handbook/
bsdinstall/
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documentation/content/en/books/handbook/bsdinstall/_index.adoc

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