Terminology

This section describes the terminology used in shutting down and booting a system.

• Run levels and init states - A run level is a software configuration of processes and available services that describes how a system is shut down or booted. Run levels are also referred to as init states because the init process starts and stops the system processes that are available at each run level. This book refers to init states as run levels.
• Boot Types - A boot type describes how a system is booted, which may include a shut down of the operating system as well. Different boot types include:

  · Interactive boot - You are prompted to provide information about how the system is booted, such as the kernel and device path name.

  · Reconfiguration boot - The system is reconfigured to support newly added hardware or new pseudo devices.

  · Recovery boot - The system is hung or an invalid entry is prohibiting the system from booting successfully or from allowing users to log in.

Guidelines for Shutting Down a System

Keep the following in mind when shutting down a system:

• Use the init and shutdown commands to shut down a system. Both commands perform a clean system shutdown, which means all system processes are services are terminated normally.
• Use the shutdown command to shut down a server, because logged-in users and systems mounting resources from the server are notified before the server is shut down. Additional notification of system shutdowns via electronic mail is also recommended so that users can be prepared for system downtime.

• You need root privileges to use the shutdown or init command to shut down a system.
• Both shutdown and init commands take a run level as an argument. The three most common run levels are:

  · Run level 3 - Means that all system resources are available and users can login. By default, booting a system brings it to run level 3, which is used for normal day-to-day operations. Also known as multiuser level with NFS resources shared.

  · Run level 6 - Reboots the system from run level 3 (multiuser level with NFS resource shared) to run level 0, and back to run level 3. Rebooting is used to enable certain system configuration changes and to activate newly added software services.

  · Run level 0 - Means the operating system is shut down and it is safe to turn off power. Bringing a system to run level 0 is needed whenever the system is moved or hardware is added or removed.

  Run levels are fully described in Chapter 6, "Run Levels and Boot Files."

Guidelines for Booting a System

Keep the following in mind when booting a system:

• After a system is shut down, it is brought to a new run level using the boot command.
• A system can be rebooted by turning the power off and then back on. This is not a clean shutdown because system services and processes are terminated abrubtly. However, turning a system's power off and back is an alternative for emergency situations.
• SPARC and x86 systems use different hardware components for booting. These differences are described in Chapter 10, "The Boot Process."

Performing a Reconfiguration Boot

Perform a reconfiguration boot when adding new hardware to the system or configuring support for pseudo devices, such as increasing the number of pseudo devices (ptys). Table 5-1 to determine which reconfiguration procedure to use.

Table 5-1

If You Are Reconfiguring the System To ...	See ...
Add a secondary disk	Chapter 29, "SPARC: Adding a Disk" or Chapter 30, "x86: Adding a Disk"
Add some other peripheral device	"How to Add a Peripheral Device" on page 391
Change the number of pseudo devices	"Managing System Performance" in System Administration Guide, Volume II

When to Shut Down a System

Table 5-2 provides a list of system administration tasks and the type of shut down needed to initiate the task.

Table 5-2

If You Are ...	Change to this Run Level ...	See a Example on ...
Turning off system power due to anticipated power outage.	Run level 0, where it is safe to turn off power.	page 140
Changing kernel parameters in the /etc/system file.	Run level 6 (reboot the system)	page 141
Performing file system maintenance, such as performing a backup or restoring system data.	Run level S (single-user mode)	page 139
Repairing a system configuration file such as /etc/system.	N/A	N/A
Changing pseudo device parameters in the /etc/system file.	Reconfiguration boot	"Managing System Performance" in System Administration Guide, Volume II
Adding or removing hardware from the system.	Reconfiguration boot (plus turning off power when add-ing or removing hardware)	page 465
Repairing an important system file which is causing system boot failure.	N/A	N/A
Booting the kernel debugger (kadb) to track down a system problem.	Run level 0, if possible	page 140
Recovering from a hung system and you want to force a crash dump.	N/A	N/A

See Chapter 7, "Shutting Down a System," for examples of shutting down a server or standalone system.

When to Boot a System

Table 5-3 provides a list of system administration tasks and the corresponding boot type used to complete the task.

Table 5-3

If You Are Rebooting the System After ...	Use This Boot Type ...	See a procedure for a SPARC System on ...	See a procedure for an x86 System on ...
Turning off system power due to anticipated power outage.	Turn system power back on	page 145	page 145
Changing kernel parameters in the /etc/system file.	Reboot the system to run level 3 (multiuser mode with NFS resources shared)	page 153	page 167
Performing file system maintenance, such as performing a backup or restoring system data.	Use Control-d from run level S to bring the system back to run level 3	page 155	page 168
Repairing a system configuration file such as /etc/system.	Interactive boot	page 156	page 170
Changing pseudo device parameters in the /etc/system file.	Reconfiguration boot	"Managing System Performance" in System Administration Guide, Volume II	"Managing System Performance" in System Administration Guide, Volume II
Adding or removing hardware from the system.	Reconfiguration boot (plus turning on system power after adding or removing hardware)	page 465	page 483
Booting the kernel debugger (kadb) to track down a system problem.	Booting kabd	page 162	page 175
Repairing an important system file which is causing system boot failure.	Recovery boot	page 172	page 172
Recovering from a hung system and you want to force a crash dump.	Recovery boot	See example on page 175	See example on page 175

See Chapter 8, "Booting a SPARC System," or Chapter 9, "Booting an x86 System," for examples of booting a system.