x86: Solaris Support for the GRUB Bootloader
The following sections contain additional reference information for administering GRUB in the Solaris
OS
x86: GRUB Terminology
To thoroughly grasp GRUB concepts, an understanding of the following terms is essential.
Note - Some of the terms that are described in this list are not
exclusive to GRUB based booting.
- boot archive
A collection of critical files that is used to boot the Solaris OS. These files are needed during system startup before the root file system is mounted. Multiple boot archives are maintained on a system:
A primary boot archive is used to boot the Solaris OS on an x86 based system.
Note - On the x86 platform, when you install the Solaris OS, two primary boot archives are created, one 32-bit archive and one 64-bit archive.
A failsafe boot archive that is used for recovery when a primary boot archive is damaged. This boot archive starts the system without mounting the root file system. On the GRUB menu, this boot archive is called failsafe. The archive's primary purpose is to regenerate the primary boot archives, which are usually used to boot the system.
- boot loader
The first software program that runs after you power on a system. This program begins the booting process.
- failsafe archive
See boot archive.
- GRUB
GNU GRand Unified Bootloader (GRUB) is an open-source boot loader with a menu interface. The menu displays a list of the operating systems that are installed on a system. GRUB enables you to easily boot these various operating systems, such as the Solaris OS, Linux, or Windows.
- GRUB main menu
A boot menu that lists the operating systems that are installed on a system. From this menu, you can easily boot an operating system without modifying the BIOS or fdisk partition settings.
- GRUB edit menu
A submenu of the GRUB main menu. GRUB commands are displayed on this submenu. These commands can be edited to change boot behavior.
- menu.lst file
A configuration file that lists all the operating systems that are installed on a system. The contents of this file dictate the list of operating systems that is displayed in the GRUB menu. From the GRUB menu, you can easily boot an operating system without modifying the BIOS or fdisk partition settings.
- miniroot
A minimal, bootable root (/) file system that resides on the Solaris installation media. A miniroot consists of the Solaris software that is required to install and upgrade systems. On x86 based systems, the miniroot is copied to the system to be used as the failsafe boot archive. See boot archive for details about the failsafe boot archive.
- primary boot archive
See boot archive.
x86: Functional Components of GRUB
GRUB consists of the following functional components:
You cannot use the dd command to write stage1 and stage2 images
to disk. The stage1 image must be able to receive information about the
location of the stage2 image that is on the disk. Use the installgrub
command, which is the supported method for installing GRUB boot blocks.
Naming Conventions That Are Used for Configuring GRUB
GRUB uses conventions that are slightly different from previous Solaris releases. Understanding the
GRUB device-naming conventions can assist you in correctly specifying drive and partition information
when you configure GRUB on your system.
The following table describes the GRUB device-naming conventions for this Solaris release.
Table 15-1 Conventions for GRUB Devices
Device Name |
Description |
|---|
(fd0) |
First
diskette |
(fd1) |
Second diskette |
(nd) |
Network device |
(hd0,0) |
First fdisk partition on first hard disk |
(hd0,1) |
Second fdisk partition on
first hard disk |
(hd0,0,a), |
Slice a on first fdisk partition on first hard disk |
(hd0,0,b) |
Slice b
on first fdisk partition on first hard disk |
Note - All GRUB device names must be enclosed in parentheses.
For more information about fdisk partitions, see Guidelines for Creating an fdisk Partition in System Administration Guide: Devices and File Systems.
Naming Conventions That Are Used by the findroot Command
Starting with the Solaris 10 10/08 release, the findroot command replaces the root
command that was previously used by GRUB. The findroot command provides enhanced capabilities
for discovering a targeted disk, regardless of the boot device. The findroot
command also supports booting from a ZFS root file system This command replaces
the root command that was formerly used by GRUB.
The following is a description of the device naming convention that is used
by the findroot command for various GRUB implementations:
Solaris Live Upgrade:
findroot (BE_x,0,a)
The x variable is the name of the boot environment.
Standard system upgrades and new installations for systems with ZFS support:
findroot(pool_p,0,a)
The p variable is the name of the root pool.
Standard system upgrades and new installations for systems with UFS support:
findroot (rootfsN,0,a)
The N variable is an integer number that starts at 0.
How Multiple Operating Systems Are Supported by GRUB
This section describes how multiple operating systems that are on the same disk
are supported with GRUB. The following is an example of an x86
based system that has the Solaris 10 10/08 OS, the Solaris 9 OS,
Linux, and Windows installed on the same disk.
Table 15-2 Sample GRUB Menu Configuration
Operating System |
Location on Disk |
|---|
Windows |
fdisk partition 0 |
Linux |
fdisk
partition 1 |
Solaris |
fdisk partition 2 |
Solaris 9 OS |
Slice 0 |
Solaris 10 10/08 OS |
Slice 3 |
Based on the preceding information, the GRUB menu would look like the following:
title Solaris 10
findroot (pool_rpool,0,a)
kernel$ /platform/i86pc/multiboot -B $ZFS-BOOTFS
module /platform/i86pc/boot_archive
title Solaris 9 OS (pre-GRUB)
root (hd0,2,a)
chainloader +1
makeactive
title Linux
root (hd0,1)
kernel <from Linux GRUB menu...>
initrd <from Linux GRUB menu...>
title Windows
root (hd0,0)
chainloader +1
Note - The Solaris slice must be the active partition. Also, do not indicate
makeactive under the Windows menu. Doing so causes the system to boot Windows
every time. Note that if Linux has installed GRUB on the master boot
block, you cannot access the Solaris boot option. The inability to access the
Solaris boot option occurs whether or not you designate it as the
active partition.
In this case, you can do one of the following:
Chain-load from the Linux GRUB by modifying the menu on Linux.
Chain-loading is a mechanism for loading unsupported operating systems by using another boot loader.
Replace the master boot block with the Solaris GRUB by running the installgrub command with the -m option:
# installgrub -m /boot/grub/stage1 /boot/grub/stage2 /dev/rdsk/root-slice
See the installgrub(1M) man page for more information.
For information about the Solaris Live Upgrade boot environment, see Solaris Express Installation Guide: Solaris Live Upgrade and Upgrade Planning.
x86: Supported GRUB Implementations
In the Solaris Express release, GRUB uses the direct boot implementation. The contents
of the menu.lst file varies, depending on the Solaris release you are running,
the installation method that is used, and whether you are booting the system
from a ZFS root or a UFS root.
Note - In this implementation of GRUB, the multiboot module is no longer used.
Description of the menu.lst File (ZFS Support)
The following are various examples of a menu.lst file for a boot environment that
contains a ZFS boot loader:
Note - Because the miniroot is mounted as the real root file system, the entry
for failsafe booting in the menu.lst file does not change to the
ZFS bootfs property, even if the failsafe archive is read from a ZFS
dataset. The ZFS dataset is not accessed after the boot loader reads the
miniroot.
Example 15-1 Default menu.lst File (New Installation or Standard Upgrade)
title Solaris 11 s10x_90 X86
findroot (pool_rpool,0,a)
kernel$ /platform/i86pc/kernel/$ISADIR/unix -B $ZFS-BOOTFS
module$ /platform/i86pc/$ISADIR/boot_archive
title Solaris 11 failsafe
findroot (pool_rpool,0,a)
kernel /boot/platform/i86pc/kernel/unix -s -B console=ttyb
module /boot/x86.miniroot-safe
Example 15-2 Default menu.lst File (Solaris Live Upgrade)
title be1
findroot (BE_be1,0,a)
bootfs rpool/ROOT/szboot_0508
kernel$ /platform/i86pc/kernel/$ISADIR/unix -B $ZFS-BOOTFS
module$ /platform/i86pc/$ISADIR/boot_archive
title be1 failsafe
findroot (BE_be1,0,a)
kernel /boot/platform/i86pc/kernel/unix -s -B console=ttyb
module /boot/x86.miniroot-safe
Description of the menu.lst File (UFS Support)
The following are examples of a menu.lst file on a system that supports
booting from UFS.
Example 15-3 Default GRUB menu.lst File (New Installation or Standard Upgrade)
title Solaris 10 5/08 s10x_nbu6wos_nightly X86
findroot (pool_rpool,0,a)
kernel /platform/i86pc/multiboot
module /platform/i86pc/boot_archive
title Solaris failsafe
findroot (rootfs0,0,a)
kernel /boot/multiboot kernel/unix -s -B console-ttyb
module /boot/x86.miniroot-safe
Example 15-4 Default GRUB menu.lst File (Solaris Live Upgrade)
title be1
findroot (BE_be1,0,a)
kernel$ /platform/i86pc/kernel/$ISADIR/unix
module$ /platform/i86pc/$ISADIR/boot_archive
title be1 failsafe
findroot (BE_be1,0,a)
kernel /boot/platform/i86pc/kernel/unix -s -B console=ttyb
module /boot/x86.miniroot-safe
Description of a menu.lst File That Supports Hypervisor Technology
You can run the Solaris OS as a virtualized control domain, with
the hypervisor. To run the Solaris release with this support, there must be
an entry in menu.lst file that specifies the hypervisor. This entry can either be
the default boot menu item, or you can select this entry manually at
boot time. After you upgrade your system for the first time to
a Solaris release that includes this support, the bootadm command automatically adds a
GRUB menu.lst entry for the hypervisor.
The following are menu.lst entries for this GRUB implementation:
title Solaris on xVM
kernel$ /boot/$ISADIR/xen.gz
module$ /platform/i86xpv/kernel/$ISADIR/unix /platform/i86xpv/kernel/$ISADIR/unix -B $ZFS-BOOTFS
module$ /platform/i86pc/$ISADIR/boot_archive
The kernel$ line specifies a path to xen.gz file, followed by optional hypervisor arguments.
The first module$ line includes the path to UNIX twice, followed by any arguments for the Solaris dom0 kernel.
The second module$ line provides the path to the boot archive.
Note that the path to UNIX in the menu.lst entry for the hypervisor
uses i86xpv, not i86pc. The options that are interpreted by the hypervisor
are added to end of the kernel$ line, after the xen.gz file information.
If you choose to run the Solaris release as a stand-alone OS,
you can continue to use the same GRUB menu entries that you used
previously.
For example:
title Solaris Nevada ... X86
kernel$ /platform/i86pc/kernel/$ISADIR/unix -B $ZFS-BOOTFS
module$ /platform/i86pc/$ISADIR/boot_archive
For more information about how to modify GRUB menu.lst entries, see x86: How to Modify Boot Behavior by Editing the menu.lst File.
