8.0-RELEASE / gpart / GPT / marking a partition as "active"

Dan Naumov dan.naumov at gmail.com
Tue Jan 19 17:11:28 UTC 2010

It seems that quite a few BIOSes have serious issues booting off disks
using GPT partitioning when no partition present is marked as
"active". See http://www.freebsd.org/cgi/query-pr.cgi?pr=115406&cat=bin
for a prime example.

In 8.0-RELEASE, using gpart, setting a slice as "active" in MBR
partitioning mode is trivial, ie:

gpart set -a active -i 1 DISKNAME

However, trying to do the same thing with GPT partitioning yields no results:

gpart set -a active -i 1 DISKNAME
gpart: attrib 'active': Device not configured

As a result of this issue, I can configure and make a succesfull
install using GPT in 8.0, but I cannot boot off it using my Intel
D945GCLF2 board.

I have found this discussion from about a month ago:
where Robert mentions that "gpart set -a active -i 1" is no longer
needed in 8-STABLE, because the pmbr will be marked as active during
the installation of the bootcode. Is there anything I can do to
archieve the same result in 8.0-RELEASE or is installing from a
snapshop of 8-STABLE my only option?


- Sincerely,
Dan Naumov

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