"ioctl DIOCSMBR: Operation not permitted" from "boot0cfg -s 1"

Doug White dwhite at gumbysoft.com
Wed Mar 2 03:20:04 GMT 2005

On Tue, 1 Mar 2005, David Wolfskill wrote:

> On a couple of machines here (my laptop and an SMP "build machine"), I
> track each of RELENG_4 and RELENG_5 on a daily basis.  I do this by
> using separate bootable slices.
> As a consequence of doing things this way, I have become accustomed to
> using boot0cfg to switch the default boot slice when I need to do this
> (which is usually twice daily per machine).
> I know of no problems doing this with RELENG_4 in the past, nor with
> RELENG_5 (since that tag was laid down, of course -- there had been an
> issue with 5.x when it was -CURRENT back in the earlier days of GEOM,
> but that was un-broken withiin a few days -- up through Sunday (27 Feb).
> This morning, I got through building & booting 5.4-PRERELEASE OK, so I
> tried switching back to slice 1 (where I have RELENG_4 living).  This is
> what I saw:
> freebeast(5.4-P)[1] sudo boot0cfg -s 1 -v ad0
> Password:
> boot0cfg: /dev/ad0: ioctl DIOCSMBR: Operation not permitted
> freebeast(5.4-P)[2]

This is a GEOM safety feature.  Set sysctl kern.geom.debugflags=16 to
disable the safety, but you can very easily spam any mounted volumes this
way. Use at your own risk :)

Doug White                    |  FreeBSD: The Power to Serve
dwhite at gumbysoft.com          |  www.FreeBSD.org

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