Re: EFI boot partition overwritten

From: Thomas Laus <>
Date: Fri, 16 Jul 2021 19:55:11 +0000
On 7/16/21 1:35 PM, Warner Losh wrote:
> There should be. Yes. Last time I went hunting for a place to shoe-horn it
> in, I got distracted by something else.
> The instructions are relatively straight forward. I'm writing them here for
> your benefit, and also in case someone wants to send me a diff/pull request
> to include them. Or better yet, put this in the handbook and we can
> reference
> a location from there.
> WARNING: This is a quick run-through of how to do this if you need to.
> The example commands given might not be exactly right for all installations
> as differing numbers of partitions will change the '-i' parameters.
> Frist, you need a partition that's of the right type. For GPT that type is
> `efi`
> as shown in `gpart show <boot-device>` eg
> # gpart show ada0
> =>        40  2000409184  ada0  GPT  (954G)
>           40        1600        - free -  (800K)
>         1640  1992292792     2  freebsd-ufs  (950G)
>   1992294432     7000000     3  freebsd-swap  (3.3G)
>   1999294432     1114792     4  efi  (544M)
It looks like the default layout from the install media is 200M
=>       40  488397088  ada0  GPT  (233G)
         40     409600     1  efi  (200M)
     409640       1024     2  freebsd-boot  (512K)
     410664        984        - free -  (492K)
     411648    4194304     3  freebsd-swap  (2.0G)
    4605952  483790848     4  freebsd-zfs  (231G)
  488396800        328        - free -  (164K)

> If you don't have one, you'll need to create one. In the above exmaple,
> I had installed the system with a tiny partition for booting with legacy
> BIOS, but then moved to booting with UEFI. I did this by turning off
> swapping and doing the following:
> # gpart resize -i 3 -s 7000000 ada0
> I then created a new efi partition:
> # gpart add -t efi ada0
> and I let it autosize.
> Next, I needed a FAT32 filesystem on that device. FAT16 usually will
> work and often FAT12, but there are known examples of system integrators
> that omit support for these last two (more the latter than the former since
> it's viewed as a floppy only thing, and who uses floppies).  I just used
> newfs_msdos and mounted it:
> # newfs_msdos -F 32 /dev/ada0p4
> # mount -t msdos /dev/ada0p4 /boot/efi
> Next, you need to put a bootloader on the system. Unless you have
> special needs, loader.efi is that loader.
> # mkdir -p /boot/efi/efi/boot
> # cp /boot/loader.efi /boot/efi/efi/boot/bootx64.efi
All of the forums use uppercase for mountpoint/EFI/BOOT/BOOTX64.efi.  Is
that directory structure standard across motherboard manufacturers or is
lower case allowed?

> If you are using efibootmgr to set a location to boot from, generally people
> create a freebsd directory (we've registered /efi/freebsd with the proper
> folks
> to avoid conflicts):
> # mkdir -p /boot/efi/efi/freebsd
> # cp /boot/loader.efi /boot/efi/efi/freebsd
> # efibootmgr -c -a -k /boot/kernel/kernel -l
> /boot/efi/efi/freebsd/loader.efi -L "FreeBSD Boot"
> though some vendors impose limits on how many boot envs you can create
> and some do not allow any at all.

Thanks for getting this effort rolling.  I think that the best place for
is in the Handbook since it is something that is not performed often.
The /usr/src/UPDATING section can just refer to the section in the
Handbook for the times the loader.efi is updated or requires


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Received on Fri Jul 16 2021 - 19:55:11 UTC

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