Boot scenarios

There are several circumstances under which a boot can occur after the system is up and running:

• You explicitly request a reboot following the installation of new hardware or software, or to correct a problem. This is done by executing the init 6 command or the shutdown -i6 command, or by pressing the <Ctrl>, <Alt>, and <Del> keys simultaneously). In these cases, all system activity is stopped (all processes are killed, and so on). The system checks to see whether a new unix needs to be configured, and, if so, configures one. Then, the system unmounts all filesystems and boots unix. The system comes up in the state defined by the initdefault entry in /etc/inittab.

• The computer crashes and automatically reboots. In this case, the sequence of events is the same as described for the first scenario.

See ``Starting (rebooting) your system'' for more details on rebooting.

Prior to UNIX^® System V Release 4, the programs and data files needed during booting resided in the root filesystem, and it was assumed that a System V (s5) filesystem was defined on the root slice.

With UNIX System V Release 4 and later releases, a file-system-independent boot procedure is implemented through the use of the boot filesystem (bfs), and the boot procedure no longer depends on the filesystem type of the root filesystem.