OpenBoot 3.x Command Reference Manual

Booting Your System

The most important function of OpenBoot firmware is to boot the system. Booting is the process of loading and executing a stand-alone program such as an operating system. Booting can either be initiated automatically or by typing a command at the User Interface.

The boot process is controlled by a number of configuration variables. (Configuration variables are discussed in detail in Chapter 3, Setting Configuration Variables) The configuration variables that affect the boot process are:

This variable controls whether or not the system automatically boots after a system reset or when the power is turned on. This variable is typically true.

This variable specifies the command to be executed when auto-boot? is true. The default value of boot-command is boot with no command line arguments.

If the value is true, run in the Diagnostic mode. This variable is false by default.

This variable contains the name of the default boot device that is used when OpenBoot is not in diagnostic mode.

This variable contains the default boot arguments that are used when OpenBoot is not in diagnostic mode.

This variable contains the name of the default diagnostic mode boot device.

This variable contains the default diagnostic mode boot arguments.

Based on the values of the above configuration variables, the boot process can proceed in a number of different ways. For instance:

Booting for the Casual User

Typically, auto-boot? will be true, boot-command will be boot, and OpenBoot will not be in diagnostic mode. Consequently, the system will automatically load and execute the program and arguments described by boot-file from the device described by boot-device when the system is first turned on or following a system reset.

If you want to boot the default program when auto-boot? is false, simply type boot at the ok prompt.

Booting for the Expert User

Booting is the process of loading and executing a client program. The client program is normally an operating system or an operating system's loader program, but boot can also be used to load and execute other kinds of programs, such as diagnostics. (For more details about loading programs other than the operating system, see Chapter 5, Loading and Executing Programs").

Booting usually happens automatically based on the values contained in the configuration variables described above. However, the user can also initiate booting from the User Interface.

OpenBoot performs the following steps during the boot process:

Often, the program loaded and executed by the boot process is a secondary boot program whose purpose is to load yet another program. This secondary boot program may use a protocol different from that used by OpenBoot to load the secondary boot program. For example, OpenBoot might use the Trivial File Transfer Protocol (TFTP) to load the secondary boot program while the secondary boot program might then use the Network File System (NFS) protocol to load the operating system.

Typical secondary boot programs accept arguments of the form:

filename -flags

where filename is the name of the file containing the operating system and where -flags is a list of options controlling the details of the start-up phase of either the secondary boot program, the operating system or both. Please note that, as shown in the boot command template immediately below, OpenBoot treats all such text as a single, opaque arguments string that has no special meaning to OpenBoot itself; the arguments string is passed unaltered to the specified program.

The boot command has the following format:


ok boot [device-specifier] [arguments]

The optional parameters for the boot command are described in Table 2-1.

Table 2-1 Optional boot Command Parameters

Parameter 

Description 

[device-specifier]

The name (full path name or devalias) of the boot device. Typical values include:

cdrom (CD-ROM drive)

disk (hard disk)

floppy (3-1/2" diskette drive)

net (Ethernet)

tape (SCSI tape)

If device-specifier is not specified and if diagnostic-mode? returns false, boot uses the device specified by the boot-device configuration variable.

If device-specifier is not specified and if diagnostic-mode? returns true, boot uses the device specified by the diag-device configuration variable.

[arguments]

The name of the program to be booted (e.g. stand/diag) and any program arguments.

If arguments is not specified and if diagnostic-mode? returns false, boot uses the file specified by the boot-file configuration variable.

If arguments is not specified and if diagnostic-mode? returns true, boot uses the file specified by the diag-file configuration variable.


Note -

Most commands (such as boot and test) that require a device name accept either a full device path name or a device alias. In this manual, the term device-specifier indicates that either an appropriate device path name or a device alias is acceptable for such commands.


Since a device alias cannot be syntactically distinguished from the arguments, OpenBoot resolves this ambiguity as follows:

Consequently, boot command lines have the following possible forms.


ok boot

With this form, boot loads and executes the program specified by the default boot arguments from the default boot device.


ok boot device-specifier

If boot has a single argument that either begins with the character / or is the name of a defined devalias, boot uses the argument as a device specifier. boot loads and executes the program specified by the default boot arguments from the specified device.

For example, to explicitly boot from the primary disk, type:


ok boot disk

To explicitly boot from the primary network device, type:


ok boot net 

If boot has a single argument that neither begins with the character / nor is the name of a defined devalias, boot uses all of the remaining text as its arguments.


ok boot arguments

boot loads and executes the program specified by the arguments from the default boot device.


ok boot device-specifier arguments

If there are at least two space-delimited arguments, and if the first such argument begins with the character / or if it is the name of a defined devalias, boot uses the first argument as a device specifier and uses all of the remaining text as its arguments. boot loads and executes the program specified by the arguments from the specified device.

For all of the above cases, boot records the device that it uses in the bootpath property of the /chosen node. boot also records the arguments that it uses in the bootargs property of the /chosen node.

Device alias definitions vary from system to system. Use the devalias command, described in Chapter 1, Overview", to obtain the definitions of your system's aliases.