For some reason, running the 11.4 boot code on my system fails. That's under investigation[1], but in the meantime, I'm trying to recover my system back to 11.3.

I'm trying to figure out the right way to restore my old boot code. I imagine it will ultimately be some invocation of gpart bootcode -b xxx ..., but I am not sure what is correct. Or maybe it is bsdlabel -b ... that is needed?

Here's the brief timeline of events:

  1. I had a running 11.3 system
  2. Compiled 11.4 source (make buildworld, make kernel)
  3. Rebooted into the 11.4 kernel successfully
  4. Prep for install new userland (adjkerntz -i, mergemaster -p)
  5. Installed new userland (make installworld)
    • My understanding is that this applies any new bootcode as well. Is that true? I haven't found the exact invocation from the makefile that would do it, yet.
  6. Reboot into the new system
    • FAILURE - got "BTX halted" error

So, while I'm trying to track down the actual problem, my first concern is to get the system bootable gain.

I'm trying to avoid a "reinstall from backup" nuclear option. I already know how to do that (:

Instead, I'm trying to just get the boot code working again.

  • Maybe I can install the 11.3 boot code manually and still run my 11.4 system?
  • I still have the 11.3 source saved; maybe I can re-install that?

Any advice would be appreciated.

[1] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=257722

1 Answer 1


There are gory details at the bug link, but essentially, I just needed to do:

  • boot via LiveCD USB stick
  • in there, run cp /boot/loader MOUNTPOINT/boot/loader
    • where MOUNTPOINT is the real system's root partition, mounted inside the LiveCD. So, no MBR updates or anything, it's just the plain file in /boot/loader that needed updating.

With that (and after figuring out that the BIOS was choosing the wrong drive), it is back to booting correctly in the 11.4 system.

Still need to figure when that regression got introduced, though — see the bug report for that progress.

  • I seem to be hitting a very similar problem. However, my EIP when I get to "BTX halted" is 0003e3dd, which doesn't match your samples...
    – torek
    Commented Sep 22, 2021 at 14:42
  • Putting the old /boot/loader back did get it to boot, but unfortunately it then crashes shortly after booting up. No idea what's wrong, yet.
    – torek
    Commented Sep 22, 2021 at 15:17
  • Looks like the crash is from loading /boot/modules/radeonkms.ko, which makes some sense. Progress...
    – torek
    Commented Sep 22, 2021 at 15:33

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