SPARC systems rely on OpenBoot (IEEE-1275).
The environment behind is a configurable and programmable session run by the OpenBoot PROM (OPB).
The OPB utility sets up a SPARC system to accept and execute the kernel.
The boot process reduces to four phases:
- OpenBoot PROM
- Booter
- Ramdisk
- Kernel
The OpenBoot PROM starts by looking for a file system reader.
If you’re booting from a disk, you first need its layout. The boot disk stores a partition map (VTOC) at sector 0.
OBP will find and load a file reader from sector 1-15 (boot block), then it can find and read the boot archive, a collection of configuration files and drivers.
The boot utility will pass the OPB environment variables to the kernel.
By calling boot -a, you can invoke an interactive session to override the values passed as defaults.
boot -m will override the default running state or logging level:
boot -m milestone=<milestone>
Values for milestones are:
- none (point where you can repair the services facility)
- all
- single-user
- multi-user
- multi-user-server
The second option for boot -m is:
boot -m [quiet | verbose | debug]
reboot -f will apply the Fast Reboot feature (default on x86 but not on SPARC).