To turn off system power due to anticipated power outage

Run level 0, where it is safe to turn off power

Chapter 9, Shutting Down a System (Tasks)

To change kernel parameters in the /etc/system file

Run level 6 (reboot the system)

Chapter 9, Shutting Down a System (Tasks)

To perform file system maintenance, such as backing up or restoring system data

Run level S (single-user level)

Chapter 9, Shutting Down a System (Tasks)

To repair a system configuration file such as /etc/system

See When to Boot a System

N/A

To add or remove hardware from the system

Reconfiguration boot (also to turn off power when adding or removing hardware)

Adding a Peripheral Device to a System in System Administration Guide: Devices and File Systems

To repair an important system file that is causing system boot failure

See When to Boot a System

N/A

To boot the kernel debugger (kmdb) to track down a system problem

Run level 0, if possible

Chapter 9, Shutting Down a System (Tasks)

To recover from a hung system and force a crash dump

See When to Boot a System

N/A

Reboot the system by using the kernel debugger (kmdb), if the debugger can't be loaded at runtime.

Run level 6 (reboot the system)

How to Boot the System With the Kernel Debugger (kmdb), Solaris Express 6/05: How to Boot a System With the Kernel Debugger in the GRUB Based Boot Environment (kmdb) Solaris 10: How to Boot a System With the Kernel Debugger (kmdb)