mkimg used to create gpt image, problem booting

John-Mark Gurney jmg at
Mon Aug 25 17:38:43 UTC 2014

Andrey V. Elsukov wrote this message on Mon, Aug 25, 2014 at 19:02 +0400:
> On 25.08.2014 18:40, Marcel Moolenaar wrote:
> >> Also, now FreeBSD 11.0 uses different first usable LBA. By default it is
> >> 4k aligned. And this creates some incompatibility with older versions.
> >> You can't do `gpart restore` and get the same table, as you had on older
> >> system.
> > 
> > It sounds restore is broken then. The restore command
> > cannot ever assume anything about the GPT. Including
> > the tool that created the GPT. In order to restore a
> > GPT, it must be properly backed-up. The backup header
> > and table should suffice most of the time for that
> > purpose as it's a replica, but as soon as meta-data is
> > missing and the restore command has to guess, things
> > will go wrong.
> `gpart restore` just uses a number of commands to geom_part(4) to create
> partition table similar to what was backed up. If your partition table
> on the old system had a partition that starts from LBA 34, now `gpart
> create` isn't able to create such partition table. Because by default
> the first usable LBA is 40.

Luckily, gpart restore won't work:
# gpart backup /dev/md0
1 freebsd-ufs      8 262144  
# gpart restore md1 < /tmp/foob.gpt.back 
gpart: entries '4': Invalid argument

So, we're somewhat safe, guess gpart restore needs to learn how to
handle entries properly....

We should fix this, since other OS's might not use 128 for entries..

  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."

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