I know a BSD needs one of the primary partition to reside in but I didn't know it probably counts as an extended partition, thus preventing another one to be made in the same disk.

Anyway I found my DestopBSD in trouble when I installed a PCBSD into the same drive, even though the two were separated by 2 primary paritions.

Also I discovered my Solaris 10 partition having geometry problem whenever I put a FreeBSD into the disk.

Anyone have been successfully to put two BSDs together in the same disk? or have them co-exist with a few Linux in an extended partition?

On one hard drive, you can have a max of 4 primary partitions or 3 primary partitons and 1 extended partition. If you install FreeBSD on a primary partition then NetBSD, Solaris or OpenBSD should install and work fine from the other primary partitions. At one time I had FReeBSD, NetBSD and Solaris on the same hard drive and everything worked fine.

I also had a disk with a DOS, FreeBSD, Solaris and PCBSD and they seem to work fine. However there are reports of geometry errors of the disk, claiming overlapping areas of the partition boundaries plus suddenly unused small empty space appear. The 4 systems still boot but I am unsure of its future.

Another example is I installed DesktopBSD in another disk and it worked alright in the 4th primary partition, which is the only system there. The next installation of PCBSD trashed the partition table causing it unreadable in some partitioning program with overlappped boundaries again. Now I can only boot to the PCBSD and lost the first system the the 4th partition.

My finger was first burn when I install a FreeBSD and Solaris in the two primaries of another disk with quite a number of Linux in the extended partition. The geometry problem appeared again. For some reason empty spaces appear in front and after the Solaris partition and this had a grave effect on the extended partition, necessitating me to rebuild it as it had over 40 logical partitions inside.

Now I could not install any of the BSD if I have any disk with a large number of logical partitions. I believe the BSD system counts the number of logical partitions and refuses to install if the number exceeds the total number of alphbets. This is purely my speculation but my hda, hdc sda and sdb have 60, 54, 15 and 15 partitions respectively. As soon as I remove the hda and hdc and put in another spare disk the BSD can be installed in it. BSD system do not want to know the empty primaries in my hda and hdc.

NetBSD is an odd one out as it can be installed in a logical partition and its internal subdivisions can "blend in" as part of the extended partition.

I am aware of a PC can only have one extended partition and that can only come out from one of the 4 primaries. I have read about the sub-slices of the Unix system counts as part of the logical partitions and user may be in trouble if they want install Linux in logical partitions after having a BSD system first in the same hard disk.