Although boot is normally used to boot the operating system, it can be used to load and execute any client program. Although booting usually happens automatically, the user can also initiate booting from the User Interface.
The boot process is as follows:
The machine may be reset if a client program has been executed since the last reset. (The execution of a reset is implementation dependent.)
A device is selected by parsing the boot command line to determine the boot device and the boot arguments to use. Depending on the form of the boot command, the boot device and/or argument values may be obtained from configuration variables.
The bootpath and bootargs properties in the /chosen node of the device tree are set with the selected values.
The selected program is loaded into memory using a protocol that depends on the type of the selected device. For example, a disk boot might read a fixed number of blocks from the beginning of the disk, while a tape boot might read a particular tape file.
The loaded program is executed. The behavior of the program may be further controlled by the argument string (if any) that was either contained within the selected configuration variable or was passed to the boot command on the command line.
boot [device-specifier] [arguments]
where device-specifier and arguments are optional. For a complete discussion of the use of the boot command, see "Booting for the Expert User".