Fundamentals of the Solaris Boot Design
The Solaris boot design, for both the SPARC and x86 platforms, includes the
Use of a boot archive
The boot archive is a ramdisk image that contains all of the files that are required for booting a system. When you install the Solaris OS, two boot archives are created, one primary archive and one failsafe archive. For more information, see Implementation of the Boot Archives on Solaris SPARC.
The bootadm command has also been modified for use on the SPARC platform. This command functions the same way that it does on the Solaris x86 platform. The bootadm command handles the details of archive update and verification automatically. During an installation or system upgrade, the bootadm command creates the initial boot archive. During the process of a normal system shutdown, the shutdown process checks the boot archive contents against the root file system. If there are any inconsistencies, the system rebuilds the boot archive to ensure that on reboot, the boot archive and root (/) file system are synchronized. You can also use the bootadm command to manually update the boot archives. See Using the bootadm Command to Manage the Boot Archives.
Note - Some options of the bootadm command cannot be used on SPARC based systems.
For more information, see the bootadm(1M) and boot(1M) man pages.
Use of a ramdisk image as the root file system during installation and failsafe operations
This process is now the same on the Solaris SPARC and Solaris x86 platforms. The ramdisk image is derived from the boot archive and is then transferred to the system from the boot device.
Note - On the SPARC platform, the OpenBootTM PROM continues to be used to access the boot device and to transfer the boot archive to the system's memory. Conversely, on the x86 platform, the system is initially controlled by the BIOS. The BIOS is used to initiate a transfer of the boot archive from a network device or to run a boot loader. In the Solaris OS, the x86 boot loader that is used to transfer the boot archive from disk is GRUB. See x86: Boot Processes.
In the case of a software installation, the ramdisk image is the root file system that is used for the entire installation process. Using the ramdisk image for this purpose eliminates the need to boot the system from removable media. The ramdisk file system type can be either a High Sierra File System (HSFS) or UFS.