From Sunsolve:
This is an example of how to install three Solaris releases on one disk;
you may want to change the order and Solaris versions.

1. First (Solaris 9) install:

Partition the slices as follow for a 18gb (for example) disk:

c0t0d0s0 4gb / (we will use this one for solaris 9)
c0t0d0s1 1gb swap
c0t0d0s2 overlap
c0t0d0s3 4gb sol8
c0t0d0s4 4gb sol7
c0t0d0s5 -
c0t0d0s6 -
c0t0d0s7 5gb /sharedspace


- You can use the installation CD or the software 1/2 CD.

NOTE: The installation cd will erase all data on the disk, so it is better
to use
the software 1/2 CD if data on the disk is to be preserved.


- During the installation you will reach the window with "auto" or "manual
layout" choose "manual layout", then "edit".

- To save some time later, you can name the partitions after what you want
to install on them later (/sol8 if you intend to use a partition for
Solaris 8, for instance).


2. Second Solaris 8 install:

- Boot from the software CD 1/2 of the Solaris release to be installed.

- when you reach "select disk", choose the same hard disk again.

- the next window is "Preserve Data?", choose "preserve".

- rename the / slice of c0t0d0s0 to /s9 and select "preserve" (so that
the solaris 9 install on slice 0 will not be overwritten).

- continue and select manual layout, then customize

- In the solaris 9 install (see step 1), you partitioned on slice 3
c0t0d0s3, solaris 8 (sol8)

- specify swap again with same size as you used in step 1.

- now in the customize window specify on slice 3 "/" with the same size
as you specified in step 1.

- define /sharedspace on slice 7 (c0t0d0s7) (again with same size).
This way you will be able to boot solaris 8, write a file in /sharedspace
reboot to solaris 9 and verify that the file is still there.


3. Third (Solaris 7) install:

- same as in 2, but now you have to preserve slice 0 (solaris9)
and slice 3 (solaris 8), so rename slice 3 to /sol8 and continue

- specify swap with the same size as used earlier.

- specify "/" in slice 4 (c0t0d0s4) with size

- define on slice 7 /sharedspace again with same size



4. Create bootaliases for each Solaris version

- ok>show-disks
- you will get a alphabetical list of devices
- select the bootdisk (letter "a" for example)

create aliases:

- ok>nvalias 9 ^Y (devicepath/disk)

("^Y" is "control-Y")

Use the corrsponding letter to determine the path to the slice ("a" equals
slice 0, "b", equals slice 1 and so on), then add @0,0:<slice> to the end
of the disk name.

@0,0:a <--- Solaris 9, which was installed on slice 0.

- for solaris 8, which we installed on slice 3, we use:
ok>nvalias 8 ^Y (devicepath/disk)@0,0:d

- and finally, for solaris 7, which is slice 4, we use:
ok>nvalias 7 ^Y (devicepath/disk)@0,0:e


finally setup the boot-device + diag-device variables correctly for 9,8 and 7.

ok>setenv boot-device 9 8 7 net

ok>setenv diag-device 9 8 7 net


you can now choose which os you want to boot from, all installed on one disk:

ok>boot 9
ok>boot 8
ok>boot 7


NOTE:Each os will mount /sharedspace and be able to read/ write into it.