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UPDATING: update notes on EFI booting

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The notes on EFI booting and updating for ZFS had become dated and only
partially updated. Expand the notes with a few more details and a
pointer to laoder.efi(8) and uefi(8).

Sponsored by:		Netflix
Discussed with:		pauamma, karels
Differential Revision:	https://reviews.freebsd.org/D36629
This commit is contained in:
Warner Losh 2023-01-20 16:13:54 -07:00
parent 456f05756b
commit 0cd612664e
1 changed files with 37 additions and 9 deletions
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UPDATING
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@ -2528,22 +2528,50 @@ COMMON ITEMS:
ZFS notes
---------
When upgrading the boot ZFS pool to a new version, always follow
these two steps:
When upgrading the boot ZFS pool to a new version (via zpool upgrade),
always follow these three steps:
1.) recompile and reinstall the ZFS boot loader and boot block
1) recompile and reinstall the ZFS boot loader and boot block
(this is part of "make buildworld" and "make installworld")
2.) update the ZFS boot block on your boot drive
2) update the ZFS boot block on your boot drive (only required when
doing a zpool upgrade):
The following example updates the ZFS boot block on the
freebsd-boot partition of a GPT partitioned drive ada0:
"gpart bootcode -p /boot/gptzfsboot -i $N ada0"
The value $N will typically be 1 (if booting from BIOS) or 2 (if
booting from EFI).
When booting on x86 via BIOS, use the following to update the ZFS boot
block on the freebsd-boot partition of a GPT partitioned drive ada0:
gpart bootcode -p /boot/gptzfsboot -i $N ada0
The value $N will typically be 1. For EFI booting, see EFI notes.
3) zpool upgrade the root pool. New bootblocks will work with old
pools, but not vice versa, so they need to be updated before any
zpool upgrade.
Non-boot pools do not need these updates.
EFI notes
---------
There are two locations the boot loader can be installed into. The
current location (and the default) is \efi\freebsd\loader.efi and using
efibootmgr(8) to configure it. The old location, that must be used on
deficient systems that don't honor efibootmgr(8) protocols, is the
fallback location of \EFI\BOOT\BOOTxxx.EFI. Generally, you will copy
/boot/loader.efi to this location, but on systems installed a long time
ago the ESP may be too small and /boot/boot1.efi may be needed unless
the ESP has been expanded in the meantime.
Recent systems will have the ESP mounted on /boot/efi, but older ones
may not have it mounted at all, or mounted in a different
location. Older arm SD images with MBR used /boot/msdos as the
mountpoint. The ESP is a MSDOS filesystem.
The EFI boot loader rarely needs to be updated. For ZFS booting,
however, you must update loader.efi before you do 'zpool upgrade' the
root zpool, otherwise the old loader.efi may reject the upgraded zpool
since it does not automatically understand some new features.
See loader.efi(8) and uefi(8) for more details.
To build a kernel
-----------------
If you are updating from a prior version of FreeBSD (even one just