boot0cfg on does not set default selection on gmirror device

[Warner Losh]

On Fri, Oct 21, 2016 at 5:39 AM, Patrick M. Hausen <hausen at punkt.de> wrote:
> Hi, all,
>
> we are repeatedly bitten by the following misbehaviour of boot0cfg:
>
> root at hd45:/usr/local # boot0cfg -s 1 mirror/m0
> root at hd45:/usr/local # boot0cfg -v mirror/m0
> #   flag     start chs   type       end chs       offset         size
> 1   0x80      1:  0: 1   0xa5   1022:254:63        16065     16418430
> 2   0x00   1023:  0: 1   0xa5   1020:254:63     16434495     16418430
> 3   0x00   1021:  0: 1   0xa5    768:254:63     32852925   1920667140
>
> version=1.0  drive=0x80  mask=0xf  ticks=182  bell=  (0x7)
> options=packet,update,nosetdrv
> default_selection=F2 (Slice 2)
>
> So, while it should have set the default to slice 1, it simply didn't.
>
> gpart on the other hand works as expected:
>
> root at hd45:/usr/local # gpart set -a active -i 1 mirror/m0
> active set on mirror/m0s1
> root at hd45:/usr/local # gpart show mirror/m0
> =>        63  1953525104  mirror/m0  MBR  (932G)
>           63       16002             - free -  (7.8M)
>        16065    16418430          1  freebsd  [active]  (7.8G)
>     16434495    16418430          2  freebsd  (7.8G)
>     32852925  1920667140          3  freebsd  (916G)
>   1953520065        5102             - free -  (2.5M)
>
> But the "active" flag alone is not enough to convince boot0 to actually boot that partition.
>
> Additional info:
>
> root at hd45:/usr/local # uname -a
> FreeBSD hd45.hosting.punkt.de 10.3-RELEASE-p10 FreeBSD 10.3-RELEASE-p10 #0 r306942: Mon Oct 10 10:29:14 UTC 2016     root@:/usr/obj/nanobsd.hosting/usr/src/sys/GENERIC  amd64
> root at hd45:/usr/local # gmirror status
>      Name    Status  Components
> mirror/m0  COMPLETE  ada0 (ACTIVE)
>                      ada1 (ACTIVE)
>
>
> The only way to actually switch the boot0 default selection is:
>
> root at hd45:/usr/local # sysctl kern.geom.debugflags=16
> kern.geom.debugflags: 0 -> 16
> root at hd45:/usr/local # boot0cfg -s 1 ada0
> root at hd45:/usr/local # boot0cfg -s 1 ada1
> root at hd45:/usr/local # boot0cfg -v mirror/m0
> #   flag     start chs   type       end chs       offset         size
> 1   0x80      1:  0: 1   0xa5   1022:254:63        16065     16418430
> 2   0x00   1023:  0: 1   0xa5   1020:254:63     16434495     16418430
> 3   0x00   1021:  0: 1   0xa5    768:254:63     32852925   1920667140
>
> version=1.0  drive=0x80  mask=0xf  ticks=182  bell=  (0x7)
> options=packet,update,nosetdrv
> default_selection=F1 (Slice 1)
>
>
> Any hints what's going on, here? Obviously it is possible to manipulate
> the MBR of a gmirror device - as gpart proves. The boot0cfg pops up
> since FreeBSD 8 when we started using a mirrored NanoBSD setup.

Any chance you can migrate to using gpart? Is boot0cfg still
referenced in NanoBSD somewhere?

Warner