Comment 23 for bug 21175

happened to me on 9.10. It was alright until IT update program in windows installed safeboot.

then after the next kernel update in ubuntu, the grub script simply removed the windows entry.

os-prober returns nothing.

I strongly suggest to add a simple backup of the generated grub.conf since important information may be lost on those cases.

an easy patch:
--- grub-mkconfig
@@ -266,6 +266,8 @@
fi

if test "x${grub_cfg}" != "x" ; then
+ # backup previous one
+ cp ${grub_cfg} ${grub_cfg}.backup_`date +%Y%m%d_%s`
  # none of the children aborted with error, install the new grub.cfg
  mv -f ${grub_cfg}.new ${grub_cfg}
fi