booting from wrong disk

Polytropon freebsd at
Thu Oct 15 19:08:58 UTC 2009

On Thu, 15 Oct 2009 14:42:24 -0400, PJ <af.gourmet at> wrote:
> But sysinstall will overwrite all the info on the disk and that defeats
> the whole purpose of the exercise.

If you only change a slice's state and add an MBR, it won't
do anything to the data inside the slice.

> What complicates matters is the use of GAG as boot manager.

Hmmm... I'm not familar with that, nor have I ever heared of

> If I select
> to boot from ad4 and the boot is from ad12, then there is something
> wrong.

Check /etc/fstab as suggested. Furthermore, check what GAG
actually does - just to be sure it boots the correct device.
I always assumed that you use the standard MBR which does,
as I explained, simply boot the first "active" slice on the
first disk it finds. Maybe GAG acts differently.

> It indicates to me that the mbr is loading the wrong disk.

In this case, it's good to read how booting works. MBR, and
bootN, the FreeBSD loader and the kernel own specified points
in this race. :-)

> I noticed this when trying to boot a disk on my other computer... it was
> looking for ad12 when there was no ad12 installed.

"Who" was looking for ad12? Was it at the "boot>" or the "Ok"

> I found that strange,
> but then I recalled thatManolis Klagias had warned about something of
> the sort. Now, I'll have to sort that out.

You have to be entirely sure that the booting process works as
intended. The easiest way to ensure this is to first use only
one disk at once in the system. There are different stages where
things can get messed up, such as the loader or /etc/fstab.
They have to match the situation.

As a sidenote, GEOM supports labelling partitions so it does not
matter anymore if, for example, a / partition is ad4s1a or ad12s1a.
There's a section in the handbook that illustrates how to get rid
of device names in /etc/fstab.

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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