The Boot PROM Chap' 12

1
The Boot PROM (Chap. 12)

• ICE System Consultant 2nd
• 2002? 8? 7?

2
Objectives

• Describe the main functions of the boot
  programmable read-only memory (PROM) chip and
  NVRAM
• The basic elements of the power-on self test
  (POST)
• The boot command options
• Show-devs command
• Probe- commands to identify the currently
  connected devices
• Devalias command
• Create a custom device alias name for a new boot
  device
• Eeprom command for change the NVRMA parameters

3
The Boot PROM Concept

• 8Kbyte chip is located on the same board as the
  CPU
• Test the system hardware boot the operating
  system
• Perform system initialization at power-on and
  provide a user interface
• The state of OK prompt called as
• PROM mode
• OK mode
• Hardware test mode
• Verify the version of PROM
• prtconf V
• The boot PROM handles hardware devices

4
The Boot PROM Concept (Cont.)

• The NVRAM component
• 8Kbytes of nonvolatile random access memory
• Stores the Ethernet address, host ID, time-of-day
  clock
• Contains the EEPROM for the storage of
  user-configurable parameters

5
The Boot PROM Concept (Cont.)

• Power-On Self Test (POST)
• A low-level power-on self test is initiated
• Stored in the boot PROM
• High-level POST
• Initializes the system
• Check the memory and then the CPU
• Check bus devices, drivers, and builds a device
  tree
• Installs the console

6
Controlling The POST Phase

• Stop key
• Stop key only to skip the POST phase
• Stop d key to run extensive POST diagnostics
• Stop n key to reset the NVRAM parameter
• Stop a key to force the initialization
• Ok go command restart the open window
  environment
• Ok ctrl d boot from default run level

7
Control the Stop-a key

• kbd a disable
• Edit the /etc/default/kbd file
• vi /etc/default/kbd
• KEYBOARD_ABOARTdisable
• remove the comment modify the enable to
  disable
• reboot
• Edit the /etc/system file
• vi /etc/system
• Type following
• set abort_enable0
• reboot

8
Basic Boot PROM Commands

• Ok banner
• Information about the system
• Model name, amount of memory, host ID, Ethernet
  address, and the boot PROM version
• Ok boot
• Boot
• Option
• -s single mode
• -a boots the system interactively
• -r reconfigure the devices
• -v display more detailed information

9
Basic Boot PROM Commands (Cont.)

• Ok help
• To obtain help on the main categories
• Ok printenv parameter-name
• List all or one of the NVRAM parameters
• List the default current settings
• Ok setenv
• Change the NVRAM parameters
• Ok setenv auto-boot? False
• Ok reset command needed

10
Basic Boot PROM Commands (Cont.)

• Ok reset
• Halts the system, clears all buffers, registers
  the system, and ..
• Reboot or ok prompt according to auto-boot
  parameter
• Ok set-default parameter-name
• Reset one of the parameters to default value
• Ok set-defaults
• Reset all of the parameters to default values

11
Device Tree

• The organization of devices
• The OpenBoot firmware builds the device tree from
  information gathered at the POST
• Each node in the device tree represents a device
• Nodes with children usually represent buses and
  their associated controllers
• Form
• name_at_addressarguments

12
Identify Devices with probe- command

• Before using the probe- command, execute
  following step
• Ok setenv auto-boot? False
• Ok reset
• Ok probe-scsi
• Identify the peripheral devices(disks, tape
  drives, CD-ROM) attached to the on-board SCSI
  controller by their target address
• Ok probe-scsi-all
• Identify all peripheral devices
• Ok probe-ide
• For IDE controller

13
Boot Device

• Set in the NVRAM as the boot-device parameter
• Ok devalias
• Identify the current boot device for the system
  device
• Print alias physical address of each device
• The disk device alias identifies the default boot
  device for the system
• Ok nvalias
• Create a new device alias name to access the
  newly attached external device
• Example) create custom device alias
• Ok show-disks
• Ok nvalias mydisk /pci_at_1f,0/pci_at_1/SUNW,isptwo_at_4/sd

14
Boot Device (Cont.)

• Change the boot device
• Ok setenv boot-device mydisk
• Ok boot
• Ok nvunalias
• Remove the custom device alias

15
Boot Device (Cont.)

• Access the NVRAM parameter with command
  /usr/sbin/eeprom for remote environment
• eeprom
• List all parameters
• eeprom boot-devicemydisk
• Change the boot disk
• eeprom auto-boot?true