Date: Fri, 14 Sep 2012 17:19:45 -0700 From: Yuri <yuri@rawbw.com> To: freebsd-hackers@FreeBSD.org Subject: Why fdisk can't open root disk with MBR for writing? Message-ID: <5053C9A1.3030605@rawbw.com>
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I am trying to change the active partition in MBR.
This should be a matter of changing only two bits (clearing one in one
byte and setting another one in another byte).
However, fdisk complains:
fdisk: Failed to write MBR. Try to use gpart(8).
truss reveals that fdisk failed to open the root disk for writing:
open("/dev/ad4",O_RDWR,00) ERR#1 'Operation not
permitted'
open("/dev/ad4",O_RDONLY,00) = 3 (0x3)
...
...
pwrite(0x3,0x34048200,0x200,0x0,0x0,0x0) ERR#9 'Bad file descriptor'
Failed to write MBR. Try to use gpart(8)
The question is: why the disk can't be open RW under root?
The secondary issue is the bug in fdisk: once -a option is supplied and
it can't open it RW it should just say so, and not suggest using gpart
because gpart will probably have the same issue.
Yuri
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