x86: Falling Back to the Original Boot Environment

To fall back to the original boot environment, choose the procedure the best fits your circumstances.

x86: To Fall Back Despite Successful New Boot Environment Activation With the GRUB Menu
x86: To Fall Back From a Failed Boot Environment Activation With the GRUB Menu
x86: To Fall Back From a Failed Boot Environment Activation With the GRUB Menu and the DVD or CD

x86: To Fall Back Despite Successful New Boot Environment Activation With the GRUB Menu

Use this procedure when you have successfully activated your new boot environment but are dissatisfied with the results. You can quickly switch back to the original boot environment by using the GRUB.

Note - The boot environments that are being switched must be GRUB boot environments that were created with GRUB software. If a boot environment was created with the Solaris 8, Solaris 9, or Solaris 10 3/05 release, the boot environment is not a GRUB boot environment.

Reboot the system.

# init 6

The GRUB menu is displayed. The Oracle Solaris OS is the original boot environment. The second_disk boot environment was successfully activated and appears on the GRUB menu. The failsafe entries are for recovery if for some reason the primary entry does not boot.

GNU GRUB version 0.95 (616K lower / 4127168K upper memory)
+-------------------------------------------------------------------+
|Solaris                                                            |
|Solaris failsafe                                                   |
|second_disk                                                        |
|second_disk failsafe                                               |
+-------------------------------------------------------------------+
Use the ^ and v keys to select which entry is highlighted. Press
enter to boot the selected OS, 'e' to edit the commands before
booting, or 'c' for a command-line.

To boot to the original boot environment, use the arrow key to select the original boot environment and press Return.

x86: To Fall Back From a Failed Boot Environment Activation With the GRUB Menu

If you experience a failure while booting, use the following procedure to fall back to the original boot environment. In this example, the GRUB menu is displayed correctly but the new boot environment is not bootable. The device is /dev/dsk/c0t4d0s0. The original boot environment, c0t4d0s0, becomes the active boot environment.

Caution - For the Solaris 10 3/05 release, the recommended action to fall back if the previous boot environment and new boot environment were on different disks included changing the hard disk boot order in the BIOS. Starting with the Solaris 10 1/06 release, changing the BIOS disk order is unnecessary and is strongly discouraged. Changing the BIOS disk order might invalidate the GRUB menu and cause the boot environment to become unbootable. If the BIOS disk order is changed, reverting the order back to the original settings restores system functionality.

Before You Begin

The boot environment must have been created with GRUB software. A boot environment that was created before the Solaris 10 1/06 release is not a GRUB boot environment. If you do not have a bootable GRUB boot environment, then go to the procedure, x86: To Fall Back From a Failed Boot Environment Activation With the GRUB Menu and the DVD or CD.

To display the GRUB menu, reboot the system.

# init 6

The GRUB menu is displayed.

GNU GRUB version 0.95 (616K lower / 4127168K upper memory)
+-------------------------------------------------------------------+
|Solaris                                                            |
|Solaris failsafe                                                   |
|second_disk                                                        |
|second_disk failsafe                                               |
+-------------------------------------------------------------------+
Use the ^ and v keys to select which entry is highlighted. Press
enter to boot the selected OS, 'e' to edit the commands before
booting, or 'c' for a command-line.

From the GRUB menu, select the original boot environment.
Boot to single user mode by editing the GRUB menu.
1. Type e to display the GRUB edit menu.
```
root (hd0,2,a)
kernel /platform/i86pc/multiboot
module /platform/i86pc/boot_archive
```
2. Select the original boot environment's kernel entry by using the arrow keys.
3. Type e.
  The kernel entry is displayed in the GRUB edit menu.
```
grub edit>kernel /boot/multiboot
```
4. Type -s and press Enter.
  The following example notes the placement of the -s option.
```
grub edit>kernel /boot/multiboot -s
```
5. To begin the booting process in single user mode, type b.
(Optional) If necessary, check the integrity of the root (/) file system for the fallback boot environment.
```
# fsck mount- point
```
mount-point

A root (/) file system that is known and reliable
Mount the original boot environment root slice to some directory (such as /mnt).
```
# mount device-name /mnt
```
device-name

Specifies the location of the root (/) file system on the disk device of the boot environment you want to fall back to. The device name is provided in the form /dev/dsk/cwtxdysz.
From the active boot environment root slice, activate the previous working boot environment.
```
# /mnt/sbin/luactivate
```
Unmount the directory.
```
# umount /mnt
```
Reboot.
```
# init 6
```
The previous working boot environment becomes the active boot environment.

x86: To Fall Back From a Failed Boot Environment Activation With the GRUB Menu and the DVD or CD

If you experience a failure while booting, use the following procedure to fall back to the original boot environment. In this example, the new boot environment was not bootable. Also, the GRUB menu does not display. The device is /dev/dsk/c0t4d0s0. The original boot environment, c0t4d0s0, becomes the active boot environment.

Become superuser or assume equivalent role.
Roles contain authorizations and privileged commands. For more information about roles, see Configuring RBAC (Task Map) in System Administration Guide: Security Services.
Insert the Oracle Solaris Operating System for x86 Platforms DVD or the Oracle Solaris Software for x86 Platforms - 1 CD.

Boot from the DVD or CD.

# init 6

The GRUB menu is displayed.

GNU GRUB version 0.95 (616K lower / 4127168K upper memory)
+-------------------------------------------------------------------------+
|Oracle Solaris 10 8/11                                                   |
|Oracle Solaris 10 8/11 Serial Console ttya                               |
|Oracle Solaris 10 8/11 Serial Console ttyb (for lx50, v60x and v65x      |
+-------------------------------------------------------------------------+
Use the ^ and v keys to select which entry is highlighted. Press
enter to boot the selected OS, 'e' to edit the commands before
booting, or 'c' for a command-line.

Wait for the default option to boot or choose any option displayed.

The installation screen is displayed.

+-------------------------------------------------------------------+
|                                                                    |
|Select the type of installation you want to perform:                |
|                                                                    |
|         1 Solaris Interactive                                      |
|         2 Custom JumpStart                                         |
|         3 Solaris Interactive Text (Desktop session)               |
|         4 Solaris Interactive Text (Console session)               |
|         5 Apply driver updates                                     |
|         6 Single user shell                                        |
|                                                                    |
|        Enter the number of your choice followed by the <ENTER> key.|
|        Alternatively, enter custom boot arguments directly.        |
|                                                                    |
|         If you wait 30 seconds without typing anything,            |
|         an interactive installation will be started.               |
+----------------------------------------------------------------- --+

Choose the Single User Shell option.
The following message is displayed.
```
Do you wish to automatically update the boot archive? y /n
```
Type n.
```
Starting shell...
#
```
You are now in single user mode.
(Optional) If necessary, check the integrity of the root (/) file system for the fallback boot environment.
```
# fsck mount- point
```
mount-point

A root (/) file system that is known and reliable
Mount the original boot environment root slice to some directory (such as /mnt).
```
# mount device-name /mnt
```
device-name

Specifies the location of the root (/) file system on the disk device of the boot environment you want to fall back to. The device name is provided in the form of /dev/dsk/cwtxdysz.

From the active boot environment root slice, activate the previous working boot environment.

# /mnt/sbin/luactivate
Do you want to fallback to activate boot environment c0t4d0s0
(yes or no)? yes

Unmount the directory.
```
# umount device_name
```
Reboot.
```
# init 6
```
The previous working boot environment becomes the active boot environment.

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