Installer: no option to set geometry/corrupts partition table

walt wa1ter at
Sun Mar 4 12:38:33 PST 2007

randux at wrote:
> Matthew Dillon wrote:
>> :Hi guys,
>> :
>> :I installed the 1.8.0 release from the liveCD and it screwed up my
>> :partition table. How can I set the drive geometry so that the
>> installer :will use my c/h/s values instead of the (possibly
>> incorrect) values said :to be obtained from BIOS?
>> :
>> :I noticed this problem in FreeBSD but it seems to have been mitigated
>> by :the installer offering a "G" option to set drive geometry around
>> 6.1/6.2 :release, not sure exactly when.
>> :
>> :I posted a question on the users list on Feb. 26 but hearing nothing
>> :(and wanting to install Dfly 1.8.0 release) I am posting here on
>> bugs. :Someone with a multiboot setup who doesn't track changes to his
>> :partition table can suffer loss of data because of this error. It
>> could :be a relatively serious problem, especially for newbies to
>> multibooting :as symptoms probably won't appear immediately, it will
>> be difficult to :diagnose.
>> :
>> :Thanks,
>> :Rand
>>     Hmm. usually that sort of problem is due to the disk mode in the
>>     BIOS setup not being set to Large or logical block mode.  Nobody
>>     has used CHS in a long time, and BIOSes still get confused by faked
>>     CHS numbers.
>>                     -Matt
>>                     Matthew Dillon                    
>> <dillon at>
> Hi Matt,
> There needs to be an option such as FreeBSD (and NetBSD and iirc
> OpenBSD) are providing, to set c/h/s for use by the DFly installer. I
> don't understand the comment that nobody is using it- all the *BSD show
> their view of it and if it doesn't match the partition table (which is
> laid out to this day in terms of c/h/s whether it's actual or virtual)
> it causes problems...

I'm curious how old your machine is, and how your partition table was
created in the first place.

This is a good explanation of why modern machines 'don't use' CHS:

I don't doubt that your partition table got screwed up, but based on
many years of installing/multibooting OS's of many flavors,  I'm a
bit skeptical about the CHS thing being responsible for it.  Perhaps
there is a different problem which needs attention.

How did you recover from this problem, BTW?  Did you edit the bad
partition table by hand, or restore a backup copy, or.....?

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