Fail-safe Rollback

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Administrators can execute a fail-safe rollback of the system software from the serial console by selecting one of the other boot menu entries, if present. Although rollback can also be requested from the BUI or CLI, rollback is offered from the boot menu because it is possible that rollback will be needed in scenarios where the new system software has completely failed, i.e., has failed to even boot.

To rollback from the console, access the serial console as usual, and during boot, before the ten second timeout, use the arrow key to move the menu selection down to one of the earlier entries.

   GNU GRUB  version 0.97  (639K lower / 2620352K upper memory)
+-------------------------------------------------------------------------+
| Sun ZFS Storage 7120 2013.06.05.0.0,1-1.6                               |  
| Sun ZFS Storage 7120 2011.04.24.4.2,1-1.28                              |
|                                                                         |  
+-------------------------------------------------------------------------+
     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.

After the rollback boot menu entry is selected, the system boots the old kernel software, but the rollback must be manually confirmed on the console to commit the rollback, which effectively removes all changes to the system that have happened since, as described above. The confirmation step looks like this:

SunOS Release 5.11 Version ak/generic@2011.04.24.4.2,1-1.28 64-bit
Copyright (c) 1983, 2010, Oracle and/or its affiliates. All rights reserved.

System rollback in progress.
Rollback to: ak/nas@2011.04.24.4.2,1-1.28

Proceed with system rollback [y,n,?]

When prompted to proceed with system rollback, enter one of the following:
1. Enter "y" to proceed with the rollback.
  The system reboots using the prior snapshot.
2. Enter "n" to cancel the rollback and immediately reboot the system.
  This action allows the administrator to select the current software version or an older snapshot boot image.