The following information is provided in this section:
GRUB 2 is a powerful and more modular boot loader that supports a wider range of platforms and firmware types, including booting from Unified Extensible Firmware Interface (UEFI) firmware, and booting from GUID Partition Table (GPT) partitioned disks of any size, on systems with BIOS or UEFI firmware. GRUB 2 also supports the UEFI-specified, GPT partitioning scheme.
Like GRUB Legacy, GRUB 2 uses a two-stage boot process. The key difference between GRUB 2 and GRUB Legacy is that GRUB 2 places many facilities in dynamically loaded modules, which enables the core GRUB 2 (second-stage boot loader) image to be smaller and therefore load faster and be more flexible. As a result, GRUB functionality is loaded on demand at boot time.
GRUB 2 introduces the following key changes:
Configuration changes
The GRUB 2 configuration differs syntactically from the GRUB Legacy configuration. The menu.lst file that is used by GRUB Legacy has been replaced by a new configuration file, grub.cfg. Unlike the menu.lst file, the grub.cfg file is automatically regenerated by boot management commands. Therefore, this file should never be directly edited. as any edits are immediately destroyed when the grub.cfg file is regenerated. See Description of the GRUB 2 Configuration.
Partition and device naming changes
Instead of 0-based indexes, GRUB 2 uses 1-based indexes for partitions and a changed device naming scheme. See GRUB 2 Partition and Device Naming Scheme.
Boot loader and GRUB menu administration changes
You administer the grub.cfg file through the bootadm command. Modified subcommands and new subcommands enable you to perform most of the administrative tasks that were previously accomplished by editing the menu.lst file. Two examples include setting boot attributes (such as kernel arguments) for an Oracle Solaris boot instance and managing boot loader settings. See Administering the GRUB Configuration by Using the bootadm Command.
GRUB menu and screen changes
The various GRUB menus and some tasks, for example, adding kernel arguments by editing the GRUB menu at boot time, work somewhat differently now. These differences are documented in the various tasks within this document, where appropriate.
Other boot loader related command changes
The installgrub command is deprecated in this release. Do not use this command to install the boot loader on systems that support GRUB 2, as doing so can prevent the system from booting. Instead, if you are running a release that supports GRUB 2, use the bootadm install-bootloader command. This command supersedes the functionality of the installgrub command on x86 platforms and the installboot command on SPARC platforms. See Installing GRUB 2 by Using the bootadm install-bootloader Command.
You can use the installgrub command to install GRUB Legacy on a system, but only after you have verified that the version of GRUB Legacy you are installing supports the ZFS pool version of your root pool, and that there are no remaining GRUB 2 boot environments on the system. For instructions, see How to Install GRUB Legacy on a System That Has GRUB 2 Installed.