kern/157724: [geom] gpart(8) 'add' command must preserve gap for schemes

[Eir Nym]

The following reply was made to PR kern/157724; it has been noted by GNATS.

From: Eir Nym <eirnym at gmail.com>
To: Marcel Moolenaar <marcel at xcllnt.net>
Cc: "Andrey V. Elsukov" <ae at freebsd.org>, bug-followup at freebsd.org, 
	Marcel Moolenaar <marcel at freebsd.org>
Subject: Re: kern/157724: [geom] gpart(8) 'add' command must preserve gap for schemes
Date: Tue, 28 Jun 2011 05:06:06 +0000

 On 27 June 2011 18:01, Marcel Moolenaar <marcel at xcllnt.net> wrote:
 >
 > On Jun 27, 2011, at 10:40 AM, Andrey V. Elsukov wrote:
 >
 >> On 27.06.2011 20:39, Marcel Moolenaar wrote:
 >>>> I am partially agree with you. geom_part_bsd does not protects
 >>>> metadata from overwriting. And it is bad for users which are not
 >>>> aware about this. Also it is easy to wipe metadata now, when
 >>>> first partition of BSD scheme should not always have UFS file
 >>>> system.
 >>>
 >>> There isn't a lot we can do about it. This is one of those
 >>> historical mistakes that you can't fix without breaking with
 >>> 30+ years of history. It's not worth the hassle IMO...
 >>
 >> Hi, Marcel
 >>
 >> I think we can just set gpt_first = 16 in g_part_bsd_create for new
 >> tables and for existing tables also set gpt_first = 16 if all partitions
 >> don not use this space. Something like this (untested):
 >
 > You may want to look at /etc/disktab. Are you willing to
 > change all entries and deal with the consequences? :-)
 >
 
 according [1] and bsdlabel(8), we can preserve 0 if we use ZFS (this
 filesystem have space for boot code), and 8k for UFS (this filesystem
 have no space for boot code).
 
 So if we install UFS without boot, can we preserve no gap?
 
 [1]: [http://wiki.freebsd.org/RootOnZFS/ZFSBootPartition]
 -- Eir Nym
 
 > --
 > Marcel Moolenaar
 > marcel at xcllnt.net
 >
 >