A 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.
The bootadm command manages the boot archive on both SPARC and x86 platforms, including the details of boot archive update and verification. During the process of a normal system shutdown, the shutdown process compares the boot archive's contents with the root file system. If there have been updates to the system, such as drivers or configuration files, the boot archive is rebuilt to include these changes so that upon reboot, the boot archive and root file system are synchronized.
The files that are part of the x86 boot archive are located in the /platform/i86pc/amd64/archive_cache directory. The files in the SPARC boot archive are located in the /platform/`uname ‐m`/archive_cache directory. To list the contents of the boot archive on both the SPARC and x86 platforms, use the bootadm list-archive command:
$ bootadm list-archive
If any files in the boot archive are updated, the archive must be rebuilt. The bootadm update-archive command enables you to manually rebuild the boot archive. The command can be used either as a preventative measure or as part of a recovery process.
# bootadm update-archive
For modifications to take effect, the rebuild of the archive must take place before the next system reboot. For more information, see Managing the Oracle Solaris Boot Archives.