id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
76	Installer writes outside selected partition	Kafpauzo	kris	"This error appears if, before installing installing PC-BSD, you use a partition manager to arrange a slice for PC-BSD, and this slice does not start at the beginning of the disk, and then you arrange the MBR in such a way that the slice is the first entry in the MBR.

In other words, you have a slice /dev/---s1 (in my case /dev/ad1s1) that does not start at the beginning of the disk.

When you have this arrangement, the installer (or some part of it) apparently assumes that the slice starts at the beginning of the disk. Judging from the symptoms, it seems to create a partition that starts at the beginning of the disk, and install there, destroying any slice you have there.

(The MBR is not altered to reflect this, at least it wasn't in my case.) (I told the installer that I already had a boot manager and it should leave the MBR unaltered.)

Some people may find it odd to have the first item in the MBR point to a slice somewhere in the middle of the disk. But it's very useful if you have a boot manager that re-writes the MBR with a separate set of slices for each operating system. I have this arrangement, I have lots of different operating systems (for experimenting) and every one of them has its own set of primary partitions. This has lots of advantages!

Thus, to the installer it looks like the space before /dev/ad1s1 is unused, but it contains important data used by other operating systems.

There is a simple workaround. The error disappeared when I moved the MBR entry so that it became the second MBR entry, or /dev/ad1s2. In spite of this I think this ticket should have a very high priority, since the bug is extremely destructive.
"	System Defect	closed	blocker		Installer	1.4	fixed	slice, partition