Solved. Re: Dualboot and ZFS

Victor Sudakov vas at
Thu Mar 22 01:26:31 UTC 2018

Warren Block wrote:
> On Mon, 19 Mar 2018, Victor Sudakov wrote:
> >
> > sysctl kern.geom.debugflags=0x10
> Please reconsider doing this without it being required.  It means "allow 
> destroying mounted partitions" and is usually not necessary.

It is recommended, or even required ("must") by the zfsboot(8) man page:

     zfsboot is typically installed using dd(1).  To install zfsboot on the
     ada0 drive:

           dd if=/boot/zfsboot of=/dev/ada0 count=1
           dd if=/boot/zfsboot of=/dev/ada0 iseek=1 oseek=1024

     If the drive is currently in use, the GEOM safety will prevent writes and
     must be disabled before running the above commands:

           sysctl kern.geom.debugflags=0x10

     zfsboot can also be installed in an MBR slice:

           gpart create -s mbr ada0
           gpart add -t freebsd ada0
           gpart create -s BSD ada0s1
           gpart bootcode -b /boot/boot0 ada0
           gpart set -a active -i 1 ada0
           dd if=/boot/zfsboot of=/dev/ada0s1 count=1
           dd if=/boot/zfsboot of=/dev/ada0s1 iseek=1 oseek=1024

Victor Sudakov,  VAS4-RIPE, VAS47-RIPN

More information about the freebsd-questions mailing list