Booting a System to a Specified State (Run Level)

A system's run level (also known as an init state) defines what services and resources are available to users when the system is in that state. A system can be in only one run level at a time. Oracle Solaris has eight run levels, which are described in the following table. The default run level is specified in the /etc/inittab file as run level 3.

Besides using typical boot commands to boot the system to a specified state, the svcadm command can be used to change the run level of a system by selecting a milestone at which to run. The following table shows how run levels correspond to milestones.

Table 4-2 Oracle Solaris Run Levels

Run Level	Init State	Type	Purpose
0	Power-down state	Power-down	To shut down the operating system so that it is safe to turn off power to the system.
s or S	Single-user state	Single-user	To run as a single user with some file systems mounted and accessible.
1	Administrative state	Single-user	To access all available file systems. User logins are disabled.
2	Multiuser state	Multiuser	For normal operations. Multiple users can access the system and all file systems. All daemons are running except for the NFS server daemons.
3	Multiuser level with NFS resources shared	Multiuser	For normal operations with NFS resources shared. This is the default run level.
4	Alternative multiuser state	Multiuser	Not configured by default, but available for customer use.
5	Power-down state	Power-down	To shut down the operating system so that it is safe to turn off power to the system. If possible, automatically turns off power on systems that support this feature.
6	Reboot state	Reboot	To shut down the system to run level 0, and then reboot to a multiuser level with NFS resources shared (or whatever run level is the default in the `inittab` file).

Determining a System's Current Run Level

To determine a system's current run level, use the who -r command.

Example 4-1 Determining a System's Run Level

The output of the who -r command displays information about a system's current run level, as well as previous run levels.

$ who -r
 .    run-level 3  Dec 13 10:10  3  0 S
$

SPARC: How to Boot a System to a Multiuser State (Run Level 3)

Use this procedure to boot a SPARC based system that is currently at run level 0 to run level 3. For instructions on booting an x86 based system to run level 3, see Booting an x86 Based System to a Multiuser State (Run Level 3) in Booting and Shutting Down Oracle Solaris on x86 Platforms.

Bring the system to the ok PROM prompt.
Boot the system to run level 3.
```
ok boot
```
The automatic boot procedure displays a series of startup messages and brings the system to run level 3. For more information, see the boot(1M) man page.
Verify that the system has booted to run level 3.
The login prompt is displayed when the boot process has finished successfully.
```
hostname console login:
```

Example 4-2 SPARC: Booting a System to a Multiuser State (Run Level 3)

The following example shows the messages from booting a system to run level 3.

ok boot
Probing system devices
Probing memory
ChassisSerialNumber FN62030249
Probing I/O buses

.
.
.
.
OpenBoot 4.30.4.a, 8192 MB memory installed, Serial #51944031.
Ethernet address 0:3:ba:18:9a:5f, Host ID: 83189a5f.
Rebooting with command: boot
Boot device: /pci@1c,600000/scsi@2/disk@0,0:a  File and args:
SunOS Release 5.11 Version fips_checksum_nightly 64-bit
Copyright (c) 1983, 2011, Oracle and/or its affiliates. All rights reserved.
DEBUG enabled
misc/forthdebug (455673 bytes) loaded
Hardware watchdog enabled
Hostname: portia-123
NIS domain name is solaris.us.oracle.com

portia-123 console login: NIS domain name is solaris.us.oracle.com

x86: How to Boot a System to a Single-User State (Run Level S)

The following procedure describes how to boot an x86 based system to a single-user state (run level S). For instructions on booting a SPARC based system to run level S, see How to Boot a System to a Single-User State (Run Level S) in Booting and Shutting Down Oracle Solaris on SPARC Platforms

Reboot the system.
```
# reboot
```
If the system displays the Press any key to reboot prompt, press any key to reboot the system.
You can also use the Reset button at this prompt. If the system is shut down, turn the system on with the power switch.
When the boot sequence begins, the GRUB main menu is displayed.
When the GRUB main menu is displayed, type e to edit the GRUB menu.
Depending on the release you are running, use the arrow keys to select the kernel$ line.
If you cannot use the arrow keys, use the caret (^) key to scroll up and the letter v key to scroll down.
Type e again to edit the boot entry.
From here, you can add options and arguments to the kernel or kernel$ line.
To boot the system to a single-user state, type -s at the end of the boot entry line, then press Return to go back to the previous screen.
Note - To specify other boot behaviors, replace the -s option with the appropriate boot option.

The following alternate boot behaviors can be specified in this manner:
- Perform a reconfiguration boot
- Boot the system with the kernel debugger
- Redirect the console
For more information, see the boot(1M) man page.
To boot the system to a single-user state, type b.
When prompted, type the root password.

Verify that the system is at run level S.

# who -r
.       run-level S  Jun 13 11:07     S      0  0

Perform the system maintenance task that required the run level change to S.
After you complete the system maintenance task, reboot the system.

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