Because the system does not automatically reinstall the GRUB Legacy boot loader when you destroy the last GRUB 2 boot environment, if you want to reinstall the GRUB Legacy boot loader, you must first boot to the latest boot environment that includes the GRUB Legacy boot loader files (in /boot/grub/stage1 and /boot/grub/stage2).
The installgrub command is deprecated in this release and should only be used if you are running a release that supports the GRUB Legacy boot loader. See installgrub(1M).
The following procedure applies if you have upgraded your system from a release that supports GRUB Legacy to Oracle Solaris 11.3.
If you decide to revert your system to the older GRUB Legacy boot loader, use the following procedure.
Caution - Be sure to perform these steps from the boot environment that contains the Oracle Solaris release or a Support Repository Update (SRU) that you used to update to Oracle Solaris 11.3. Additionally, if you have upgraded the ZFS pool's capabilities by using the zpool upgrade command past version 33, you will not be able to downgrade to GRUB Legacy or complete Step 2 of this procedure. Forcibly downgrading to GRUB Legacy after the root pool has been upgraded past version 33 results in an unbootable system.
Performing this step ensures that you do not accidentally activate and install GRUB 2, as activating any boot environments that include the Oracle Solaris 11.3 release will replace the Legacy GRUB boot loader with GRUB 2.
# bootadm install-bootloader -f