partition black magic but no data lost phew!

[Chris Whitehouse]

Hi,

This is from memory (brain not ram) and I can't recreate the steps for 
reasons which will be obvious, so may not be entirely accurate.

I have a sata hard disk which is divided into 2 slices. Slice 1 (ad4s1) 
is about half the disk and had the remains of a standard install with 
swap, / , /var, /tmp, /usr. Slice 2 (ad4s2) is the remainder and has a 
single partition for data, ad4s2d. It was all created with sysinstall 
and doesn't have anything special like dangerously dedicated.

The operating system on this machine is on a second hard disk which is 
what I booted from.

I moved all the data from ad4s1f onto ad4s2d so that I could delete 
partitions from slice 1 and make a single large partition.

I then unmounted all ad4* partitions. I may even have rebooted.

sysinstall - Configure - Label allowed me to delete ad4s1a but when I 
tried to delete the other ad4s1* partitions sysinstall told me I had to 
set kern.geom.debugflags=16 before I could make changes on a running 
system . I set kern.geom.debugflags but changes I made in sysinstall did 
not take effect, the partitions persisted, both as /dev/ad4s1* and as 
entries in sysinstall

At some stage sysinstall core dumped and somewhere else ad4s2d got 
deleted. I managed to recreate it and didn't lose any data.

Next I booted from a pen drive and successfully deleted the partitions 
from slice 1, being very careful not to delete the partition on slice 2, 
however when I exited from sysinstall ad4s2d was gone. Again I managed 
to recreate it and didn't lose any data.

The bit that puzzles me is that ad4s2d disappeared twice and the second 
time I am sure I didn't do any explicit steps to delete it.

Did I hit a bug in sysinstall or did I do something wrong? I didn't lose 
any data in the end but I could easily have done (I know - back up - I'm 
going to go and buy a nice big external hard disk very soon ;)

FreeBSD muji 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #0: Mon Nov 24 
20:22:16 EST 2008 
root at pcbsdx32-7:/usr/obj/pcbsd-build/cvs/7.0.2-src/sys/PCBSD  i386

Everything is sorted now so I am really asking this out of curiousity.

Thanks

Chris