On Sun, 1 Dec 2019 13:14:16 +0300 Anatoly <anat...@kazanfieldhockey.ru> wrote:
> On Sun, 1 Dec 2019 08:28:01 +0100 > Gary Jennejohn <gljennj...@gmail.com> wrote: > > > The geom code protects certain parts of the data area on the > > drive, in particular GPT/MBR areas, unless ``sysctl > > kern.geom.debugflags=16'' is run beforehand. One can see this in > > many places in the geom code. > > > > I always set this sysctl when I know I'm going to overwrite the > > first sectors of a drive. > > > Interesting, but I've succefully overwrited MBR many times > on FreeBSD 5.x-11.x without setting this sysctl. > I've learned about this sysctl when I first time failed to overwrite bsd > label inside MBR slice under FreeBSD 7.1 with dd (but not MBR). There > was explicit write error, not just silent succeful write to nowhere. I > may be wrong, but as I remember, I newer got this trouble again > starting from 10.x. > Is there something new on 12.x? > This sysctl has been around for quite some time. I added a shellscript to my ~/bin to set it in 2015. IIRC Julian Elischer requested it because he had problems initializing disks. I just use it by default when I write to the first sectors on a disk. There is geom code which explicitly checks whether debugflags is set to 16. I have not looked at the code to see what happens when that is the case. -- Gary Jennejohn _______________________________________________ freebsd-usb@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-usb To unsubscribe, send any mail to "freebsd-usb-unsubscr...@freebsd.org"
