When you install the Solaris OS on a system, the bootadm command creates one primary boot archive and one failsafe archive.
A primary boot archive is a subset of a root (/) file system. This boot archive contains all of the kernel modules, driver.conf files, in addition to a few configuration files. These files are located in the /etc directory. The files in the boot archive are read by the kernel before the root (/) file system is mounted. After the root (/) file system is mounted, the boot archive is discarded by the kernel from memory. Then, file I/O is performed against the root device.
If you are running a Solaris Express release on an x86 based system, two primary boot archives (one 32-bit archive and one 64-bit archive) are created at installation time. The 32-bit archive is located in /platform/i86pc/boot_archive. The 64-bit archive is located in /platform/i86pc/amd64/boot_archive.
The files that make up the SPARC boot archives are located in the /platform directory.
The contents of this directory are divided into three groups of files:
Files that are required for a sun4u boot archive
Files that are required for a sun4v boot archive
Files that are required for a sun4us boot archive
The files that make up the x86 boot archives are located in the /platform/i86pc directory.
If you are running the Solaris Express release, the contents of this directory are divided into two groups of files:
32-bit boot archive files, which are located in /platform/i86pc/boot_archive
64-bit boot archive files, which are located in /platform/i86pc/amd64/boot_archive
To list the files and directories that are included in the boot archives, use the bootadm list-archive command.
If any files in the archive are updated, the boot archive must be rebuilt. For modifications to take effect, the rebuild of the archive must take place before the next system reboot
The failsafe boot archive is the second type of archive that is created when you install the Solaris OS.
A failsafe boot archive has the following benefits and characteristics:
Can boot on its own
Is created by default during installation of the OS
Requires no maintenance
For more information about booting a system in failsafe mode, see Booting the Failsafe Archive on a SPARC Based System and Booting the Failsafe Archive on an x86 Based System.