A computer with a single hard disk can support multiple operating systems, but not in the same space on that disk. When you install your system, you have the choice of using all the space on your hard disk for a single operating system or dividing the hard disk into a maximum of four segments, called ``partitions.'' Each partition holds a separate operating system. Thus, for example, you can have three UNIX system partitions and one DOS partition. When you install UnixWare on a new machine, the default partitioning scheme is one partition which uses 100% of the disk.
The UnixWare partition of a hard disk is further subdivided into ``slices.'' Slices define filesystems, swap area(s), and dump partitions. The two slices of interest to the boot procedure are the boot and stand slices.
The boot slice is not a filesystem, but a special area of the disk that contains the boot programs. On most computers, the boot process is a three-step process that results in a load of the bootable operating system (/stand/unix).
The only operation performed on the boot slice is the loading of the boot programs; no filesystem is defined on this slice.
The bootable operating system unix is found in the stand slice. This slice has the boot filesystem (bfs) defined on it and contains all the bootable programs and data files used during the boot procedure. It can be identified, using the prtvtoc(ADM) command, as the partition labeled V_STAND. The bfs defined on this partition is mounted by default as /stand.
The contents of /stand include the following:
Note that /unix is linked to /stand/unix, or whichever kernel was actually booted.
In the delivered system, the stand slice contains a filesystem of type bfs; this boot filesystem is mounted as /stand by default.
The boot filesystem is a flat filesystem with only one directory. You can copy and move regular files to and from a boot filesystem, and use filesystem commands such as mount(ADM), umount(S), and fsck(ADM), but you cannot make directories or create other special files. We recommend you use this filesystem only for boot-related and configuration-related files.
If you want, you can use mkfs to create bfs-type filesystems on other disk partitions. (See ``Managing filesystem types'' and mkfs(ADM) for more information.) Having multiple boot filesystems on one or more partitions is particularly useful in an operating system development environment.
The maximum size of a bfs filesystem is 128MB.
Although any disk can be made bootable, only one disk can be booted on powerup, and that is the default boot disk defined in non-volatile random-access memory (NVRAM). If you define multiple stand slices on the default boot disk, the one used during a reboot or powerup will be from the active partition.
The file /etc/vfstab contains the pathname of the stand slice to be mounted in single-user and multi-user states; it is used during configuration of a new operating system on powerup or reboot. This should always be the one defined on the lowest numbered partition on your default boot disk. The device name has the form /dev/dsk/c0b0t0d0sS, where S is the slice ID. (See intro(HW) for details on device name notation.)