I've found the culprit. This bugs still occurs for me, and its not grub's fault.
On powerpc machines, the bootloader (grub2 along with yaboot) are put on a separate partition, which is HFS formatted.
I mount this partition as /boot/grub.
The problem is with hfsutils: even if they report (e.g. via the output of "mount") that this filesystem is mounted read-write, after an abrupt halting of the machine it's mounted read-only. The only real fix is to manually unmount /boot/grub, run fsck on it which clears the dirty flag, and then remounting it and running grub2 installation again.
So I believe that fixing the output of mount, or forcing a fsck when mounting a hfs volume, is the only real solution to this.
Or whenever the filesystem gets dirty, and update-grub is called, you'll get errors, potentially leaving your system unusable.
This is not a duplicate of bug #401663.
I've found the culprit. This bugs still occurs for me, and its not grub's fault.
On powerpc machines, the bootloader (grub2 along with yaboot) are put on a separate partition, which is HFS formatted.
I mount this partition as /boot/grub.
The problem is with hfsutils: even if they report (e.g. via the output of "mount") that this filesystem is mounted read-write, after an abrupt halting of the machine it's mounted read-only. The only real fix is to manually unmount /boot/grub, run fsck on it which clears the dirty flag, and then remounting it and running grub2 installation again.
So I believe that fixing the output of mount, or forcing a fsck when mounting a hfs volume, is the only real solution to this.
Or whenever the filesystem gets dirty, and update-grub is called, you'll get errors, potentially leaving your system unusable.