When to Shut Down a System

Turning 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)

Changing kernel parameters in the /etc/system file

Run level 6 (reboot the system) 

Chapter 9, Shutting Down a System (Tasks)

Performing file system maintenance, such as backing up or restoring system data 

Run level S (single-user mode) 

Chapter 9, Shutting Down a System (Tasks)

Repairing a system configuration file such as /etc/system

See "When to Boot a System"

N/A 

Adding or removing hardware from the system 

Reconfiguration boot (plus turning off power when adding or removing hardware) 

Chapter 24, Device Management (Overview)

Repairing an important system file which is causing system boot failure 

See "When to Boot a System"

N/A 

Booting the kernel debugger (kadb) to track down a system problem

Run level 0, if possible 

Chapter 9, Shutting Down a System (Tasks)

Recovering from a hung system and you want to force a crash dump 

See "When to Boot a System"

N/A