ZFS: unsupported feature: com.klarasystems:vdev_zaps_v2

Note of caution:

Read the FreBSD Release Notes carefully at https://www.freebsd.org/releases/14.0R/relnotes/ especially the section called “Upgrading from Previous Releases of FreeBSD”.

If you recently upgraded to FreeBSD 14 but you get the above error displayed before the beastie logo (see image below), here’s a solution for those with the boot loader in the MBR and that use the GPT partition scheme.

• First figure if your machine bios is efi or mbr by running efibootmanager -v. If yours is not efi, the message will be “efibootmgr: efi variables not supported on this system. root? kldload efirt?”
• Run gpart show and note the disk (ada0, ada1) on which your MBR is written into. We’ll assume its ada0 for the next command below.
• Now run gpart bootcode -b /boot/pmbr -p /boot/gptzfsboot -i 1 ada0, where ada0 is your disk.

Running anything like the above on your freebsd box might cause loss of data. Please exercise caution.