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Solaris Open Boot

News Recommended Links Forth Getting Help in OpenBoot NVRAM variables OpenBoot Diagnostics
Forcing Solaria into OK prompt System Run States PROM Device Tree The nvedit Line Editor Humor Etc

The primary function of the OpenBoot firmware is to start up the system. Starting up is the process of loading and executing a standalone program (for example, the operating system or the diagnostic monitor). In case of Solaris the standalone program that is being started is the two-part operating system kernel. After the kernel is loaded, the kernel starts the Solaris OS, mounts the necessary file systems, and runs /sbin/init  to bring the system to the initdefault  state that is specified in /etc/inittab. Stages of this process is known as "System Run States".

The OpenBoot architecture consists of the following components:

The normal Solaris boot process has five main phases:

  1. Basic hardware detection (memory, disk, keyboard, mouse, and the like) and executing the firmware system initialization program .  In Solaris this is called Boot PROM phase—After you turn on power to the system, the PROM displays system identification information and runs self-test diagnostics to verify the system's hardware and memory. PROM chip contains Forth OpenBoot firmware, and it is executed immediately after you turn on the system. The primary task of the OpenBoot firmware is to boot the operating system either from a mass storage device or from the network. OpenBoot contains a program called the monitor that controls the operation of the system before the kernel is available. When a system is turned on, the monitor runs a power-on self-test (POST) that checks such things as the hardware and memory on the system.  If no errors are found, the automatic boot process begins. OpenBoot contains a set of instructions that locate and start up the system's boot program and eventually start up the Unix operating system.

  2. Locating and running the initial boot program (IPL or bootloader) from a predetermined location on the disk (MBR in PC). In Solaris the primary boot program, called bootblk, is loaded from its location on the boot device (usually disk) into memory.

  3. Locating and starting the Unix kernel. The kernel image file to execute may be determined automatically or via input to the bootloader. In Solaris the bootblk  program finds and executes the secondary boot program (called ufsboot) from the Unix file system (UFS) and loads it into memory. After the ufsboot  program is loaded, the ufsboot  program loads the two-part kernel.

  4. The kernel initializes itself and then performs final, high-level hardware checks, loading device drivers and/or kernel modules as required.  In Solaris the kernel initializes itself and begins loading modules, using ufsboot  to read the files. When the kernel has loaded enough modules to mount the root file system, it unmaps the ufsboot  program and continues, using its own resources.

  5. The kernel starts the init process, which in turn starts system processes (daemons) and initializes all active subsystems. When everything is ready, the system begins accepting user logins. In Solaris kernel starts the Unix operating system, mounts the necessary file systems, and runs /sbin/init  to bring the system to the initdefault  state specified in /etc/inittab. The kernel creates a user process and starts the /sbin/init  process, which starts other processes by reading the /etc/inittab  file. The /sbin/init  process starts the run control (rc) scripts, which execute a series of other scripts. These scripts (/sbin/rc*) check and mount file systems, start various processes, and perform system maintenance tasks.

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PCI System Commands

The following user query and control commands (forth words) are available on PCI based systems.

Use the show-pci-devs command to show all devices on a specific PCI bus.

ok show-pci-devs /pci@1f,2000 (show pcia devices)
ok show-pci-devs /pci@1f,4000 (show pcib devices)
Use the show-pci-devs-all command to show all PCI devices.
ok show-pci-devs-all (show all pci devices)
Use the show-pci-config command to show configuration space registers for a given PCI device.
ok show-pci-config /pci@1f,4000/network@1,1
Use the show-pci-configs command to show configuration space registers for all PCI devices on a PCI bus.
ok show-pci-configs /pci@1f,4000
Use the show-pci-configs-all command to show configuration space registers for all PCI devices on all PCI busses.
ok show-pci-configs-all /pci@1f,4000
Use the probe-pci command to probe all devices on a specific PCI bus.
ok probe-pci /pci@1f,4000
probing /pci@1f,4000 at Device 3 scsi disk tape
probing /pci@1f,4000 at Device 3 nothing there
Use the probe-pci-slot command to probe a specific PCI slot on a specific PCI bus.
ok 3 probe-pci-slot /pci@1f,4000
probing /pci@1f,4000 at Device 3 scsi disk tape

Updating OpenBoot PROM for Sun Workstations and Workgroup Servers ...

Having the latest version of OpenBoot PROM (OBP) on a SPARC processor-based workstation or workgroup server can be critical when adding new applications or hardware, or when upgrading the machine's Solaris Operating System (OS). Updating may also save some time and difficulty by resolving any latent bugs that have been detected and fixed since the previous releases. The paragraphs that follow guide you through the steps required to do the update.

Note: This Tech Tip does not cover larger servers; for those systems, see SunSolve document #41723

How to Perform System Boot and Shutdown Procedures for Solaris 10 ...

[PDF] Debugging Solaris using Open Boot Prom

Solaris 9 System Startup and Shutdown > The OpenBoot Architecture

OpenBoot > OpenBoot Environment

Open Boot Parameters

The firmware in Sun's boot PROM is called OpenBoot. The main features of openboot are initial program loading, & debugging features to assist kernel debugging .OpenBoot supports plug-in device drivers which are written in language Forth. . This plug in feature allows Sun or any third-party vendors to develop new boot devices but without making any changes to boot PROM.

See also Solaris Booting problems error messages & solutions

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OpenBoot > OpenBoot Environment

Sun's "OpenBoot 3.x Command Reference Manual", Chapter 1. (Used to be at

Solaris 9 System Startup and Shutdown


The following objectives for the Solaris System Administrator Exam are covered in this chapter:

Explain how to execute boot PROM commands to

You need to understand the primary functions of the OpenBoot environment, which includes the programmable read-only memory (PROM. You need to have a complete understanding of how to use many of the OpenBoot commands and how to set and modify all the configuration parameters that control system bootup and hardware behavior.

You must understand the entire boot process, from the proper power-on sequence to the steps you perform to bring the system into multiuser mode.

You must be able to identify the devices connected to a system and recognize the various special files for each device.

Occasionally, conventional shutdown methods might not work on an unresponsive system or on a system that has crashed. This chapter introduces when and how to use these alternative shutdown methods to bring the system down safely.

You must understand how the system run levels define which processes and services are started at various stages of the boot process. You need to understand all the run levels that are available in Solaris.

You need to understand how to add and modify run control scripts to customize the startup of processes and services on Solaris systems. You need to have a detailed understanding of the programs and configuration files involved at the various run levels.



Booting a System

The OpenBoot Environment

The OpenBoot Architecture

The OpenBoot Interface

Getting Help in OpenBoot

PROM Device Tree (Full Device Pathnames)

OpenBoot NVRAM

OpenBoot Security

OpenBoot Diagnostics

OpenBoot PROM Versions

Booting a System

The Kernel

System Run States

System Shutdown

Stopping the System for Recovery Purposes

Turning Off the Power to the Hardware


Apply Your Knowledge

Study Strategies

The following study strategies will help you prepare for the exam:


System startup requires an understanding of the hardware and the operating system functions that are required to bring the system to a running state. This chapter discusses the operations that the system must perform from the time you power on the system until you receive a system logon prompt. In addition, it covers the steps required to properly shut down a system. After reading this chapter, you'll understand how to boot the system from the OpenBoot programmable read-only memory (PROM) and what operations must take place to start up the kernel and Unix system processes.

Plagiarism?By David, Feb 3, 2004 05:11 PM
Much of this seems to be copied, with minor modification, from Sun's "OpenBoot 3.x Command Reference Manual", Chapter 1. (Currently at

For example, the Sun documentation says: "OpenBoot deals directly with hardware devices in the system. Each device has a unique name representing the type of device and where that device is located in the system addressing structure."

In the this article, it's been changed slightly to read: "OpenBoot deals directly with the hardware devices in the system. Each device has a unique name that represents both the type of device and the location of that device in the device tree."

Sometimes, the minor changes alter the meaning. For example, the Sun doc says: "A full device path name is a series of node names separated by slashes (/). The root of the tree is the machine node, which is not named explicitly but is indicated by a leading slash (/). Each node name has the form:


In the copied version posted here, though, it's: "A device tree is a series of node names separated by slashes (/).The top of the device tree is the root device node. Following the root device node, and separated by a leading slash /, is a bus nexus node. Connected to a bus nexus node is a leaf node, which is typically a controller for the attached device. Each device pathname has this form:


The first sentence is incorrect, and the last sentence is confusing. It's each nodename that has that form, not the pathname, which is a series of slash delimited nodenames.



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