Understanding the Intel Boot Process

The OBP is specific to SPARC-based computers. Most commonly, you will see the OBP on Sun-manufactured computers, although other vendors that use the SPARC platform can also use OBP. Because the OpenBoot PROM does not work with Intel-manufactured chips (or Intel clones), there needs to be a substitute for OBP. Intel-based computers use the system BIOS instead.

One of the new features of the Solaris 9 Intel Platform Edition is the support of booting from the Preboot Execution Environment (PXE) network booting protocol. If your computer has a network card that is PXE compliant, as well as a BIOS that supports PXE, you can boot Solaris from over the network without a boot disk.

To use PXE, you must first configure your BIOS to recognize that it can boot from the network card. Then, during the boot process, your BIOS will tell you to press a certain key (it varies, depending on the BIOS, but N is a popular choice) to boot from the network. If you've configured a network boot server, the computer will get its necessary boot information from the boot server.

Booting Solaris 9 Intel Platform Edition

During the discussion of the OpenBoot PROM, you learned that the OBP loads and configures devices, and stops at an ok prompt, waiting for you to type boot to load Solaris. If you're using a default configuration, then variables in OBP execute the boot command automatically, and you're presented with the Solaris 9 login screen.

Instead of seeing an ok prompt on Intel Architecture (IA) computers, you will be given a menu presenting the current boot parameters and asking you to make a boot decision. It will look similar to this:

                <<< Current Boot Parameters >>> Boot path: /pci@0,0/pci-ide@7,1/ide@0/cmdk@0,0:a Boot args: Type    b [file-name] [boot-flags] <ENTER>   to boot with options or      i <ENTER>                            to enter boot interpreter or      <ENTER>                              to boot with defaults                <<< timeout in 5 seconds >>> Select (b)oot or (i)nterpreter: 

At this screen, you have two choices. You can either boot Solaris (with or without options) or enter the boot interpreter. To boot Solaris, either press Enter, or type b and press Enter. You will then be taken to the Solaris login screen.

Booting with the defaults will take you to run level 3 (described later in this chapter). If you want to boot to an alternate run level, use the run level as an argument for the boot command. For example, to boot to run level S, you would use b-s.

Changing BIOS Configuration and Boot Parameters

During the boot phase of Solaris, the Solaris Device Configuration Assistant scans for installed devices and displays identified devices. The Device Configuration Assistant is also used to make changes to hardware configurations, as opposed to using the OBP on a SPARC computer. You can access the Device Configuration Assistant by booting from either a Solaris boot disk or the Solaris installation CD-ROM, or by interrupting the auto-boot process. If your BIOS does not support booting from CD-ROM, you will need to use the Solaris boot disk.

To create a Solaris boot disk, go to http://soldc.sun.com/support/drivers/dca_diskettes. Booting or rebooting Solaris with the installation CD-ROM or boot disk inserted will automatically activate the Device Configuration Assistant.

Upon entering the Solaris Device Configuration Assistant, you will get a menu similar to the following:

 Solaris Device Configuration Assistant The Solaris(TM) (Intel Platform Edition) Device Configuration Assistant scans to identify system hardware, lists identified devices, and can boot the Solaris software from a specified device. This program must be used to install the Solaris operating environment, add a driver, or change the hardware on the system. > To perform a full scan to identify all system hardware, choose Continue. > To diagnose possible full scan failures, choose Specific Scan. > To add new or updated device drivers, choose Add Driver. About navigation...     - The mouse cannot be used.     - If the keyboard does not have function keys or they do not respond,       press ESC. The legend at the bottom of the screen will change to       show the ESC keys to use for navigation.     - The F2 key performs the default action. F2_Continue    F3_Specific Scan    F4_Add Driver    F6_Help 

Pressing the appropriate function key will invoke the option you want. To continue booting, press the F2 key.

Alternate Boot Scenarios

When you're at the Current Boot Parameters menu, you can either boot Solaris (with options, if you want) or enter the boot interpreter. Listed here are ways you can boot into different modes of Solaris, such as booting interactively or with the kernel debugger.

Choosing to boot interactively is necessary if you want to specify an alternate system kernel or /etc/system file. To boot interactively, type b-a at the Current Boot Parameters prompt. You will then be required to provide information on the directories to load modules from, the name of the system file, the file system type for the root file system (/), and the physical boot device.

If you are having kernel problems, you will want to boot by using the kernel debugger. At the Current Boot Parameters menu, type b kadb. After the login screen is displayed, press the F1 and A keys at the same time, and you should get a kadb[0]: prompt. You are now in the kernel debugger.

One of the reasons you might want to use the kernel debugger is to force a crash dump of system memory (for troubleshooting purposes) and a system reboot. To force a crash dump and system reboot, first boot into the kernel debugger. Then, follow this command sequence:

 kadb[0]: vfs_syncall/W ffffffff kadb[0]: 0>eip kadb[0]: :c kadb[0]: :c kadb[0]: :c 

This will force a crash dump, and the computer will reboot. For more information on crash dumps, see Chapter 11, "Virtual File Systems and NFS."

Details about the Intel Boot Phases

By now, you should understand that the boot processes for SPARC and IA platforms are different. One of the main differences is that on an IA computer, you will be presented with a Primary Boot Subsystem menu (also called the Boot Partition menu) if you have multiple operating systems installed on your computer. If you choose an alternate operating system, the Solaris boot process ceases. If you choose to boot into Solaris, you will be given additional options, such as to interrupt the auto-boot process and enter the Solaris Device Configuration Assistant. The final menu you will see during the boot process is the Current Boot Parameters menu. That's where you can boot Solaris with or without options, or just wait five seconds for Solaris to boot automatically.

After Solaris begins its boot process, you will see a short series of screens, such as the Scanning Devices screen and the Identified Devices screen. Solaris is merely detecting and displaying devices. If the computer appears to hang for a long time, use the reset button to restart the computer.

Like the SPARC edition of Solaris, the Intel edition has four generalized boot phases: BIOS, boot programs, kernel initialization, and init. Unlike the SPARC version, though, different files are used during the boot phases. Here's an overview of what happens during each phase:

  1. During the BIOS phase, the system BIOS runs diagnostic tests to ensure that the system's hardware and memory are running properly. Then, the BIOS reads the first physical sector on the boot device, looking for the master boot record mboot. If mboot is not found, the boot process will stop with an error message.

  2. The loading of mboot starts the boot programs phase. The mboot program looks for the Solaris boot program, pboot. After pboot loads, pboot looks for and loads the primary boot program, bootblk. If you have more than one bootable partition, bootblk reads the fdisk table and displays a menu enabling you to choose which operating system to boot into. You will have 30 seconds to make this choice. Choosing Solaris will cause bootblk to find the secondary boot program, boot.bin in the root file system (/). During this time, you will have a five-second pause in which you can choose to execute the Device Configuration Assistant. The secondary boot program will load the /etc/bootrc script, which displays the Current Boot Parameters menu. You will have five seconds to make a boot choice, or Solaris will load with the default options.

  3. The kernel will initialize and use boot.bin, the secondary boot program, to load kernel modules. When enough modules are loaded to mount the root file system (/), the secondary boot program is unloaded, and the kernel continues to initialize. The kernel then loads the /sbin/init program, which reads the /etc/inittab file, and loads other processes.

  4. The final phase, init, is when the /sbin/init process begins to load run control (rc) scripts, in turn loading other scripts. These scripts mount file systems, load services, and perform other miscellaneous tasks.

Overall, this four-phase process is very similar to the SPARC boot process. However, more files are needed to complete the boot process, meaning that there is more room for problems to occur.

Tip 

For test purposes, know the SPARC boot process well.




Solaris 9. Sun Certified System Administrator Study Guide
Solaris 9 Sun Certified System Administrator Study Guide
ISBN: 0782141811
EAN: 2147483647
Year: 2003
Pages: 194

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