If a failure occurs, you can quickly fall back to the original boot environment with an activation and reboot. You need to fall back if the new boot environment cannot be booted, or if the new environment boots but does not work completely, or you are not satisfied with the results.
The use of fallback takes only the time to reboot the system, which is much quicker than backing up and restoring the original. The new boot environment that failed to boot is preserved. The failure can then be analyzed. You can only fall back to the boot environment that was used by luactivate to activate the new boot environment.
You fall back to the previous boot environment the following ways:
If the new boot environment boots successfully, but you are not happy with the results, you run the luactivate command with the name of the previous boot environment and reboot.
If the new boot environment does not boot, you boot the fallback boot environment in single-user mode and run the luactivate command and reboot.
If you cannot boot in single-user mode, you must boot from media or a net installation image, mount the root (/) file system on the fallback boot environment, run the luactivate command, and reboot.
For procedures to fall back, see Failure Recovery: Falling Back to the Original Boot Environment (Command-Line Interface).
Figure 30–7 shows the switch that is made when you reboot to fallback.