[Bug 225564] Re: fdisk doesn't write MBR if only Windows NT ID is changed.

[Alberto Salvia Novella]

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** Changed in: util-linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/225564

Title:
  fdisk doesn't write MBR if only Windows NT ID is changed.

Status in “util-linux” package in Ubuntu:
  Incomplete

Bug description:
  Binary package hint: util-linux

  Ubuntu 7.10, util-linux 2.13-8ubuntu1.

  If the only change to a disc's MBR in fdisk is to use the `expert'
  menu's `i' option to set the MBR's Window NT's ID, now used by Linux
  for EDD, then the altered partition isn't written back to disc so the
  change isn't done.  This seems to be because write_table() doesn't
  call write_sector() which calls write(2) unless one of the four
  primary partition entries has been altered, which is the case of `i',
  they haven't.

  fdisk misleadingly goes onto say

      Expert command (m for help): w
      The partition table has been altered!

      Calling ioctl() to re-read partition table.

      WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
      The kernel still uses the old table.
      The new table will be used at the next reboot.
      Syncing disks.

  but this isn't true and on the next reboot the old ID will still be
  present.  This can also be seen with a hexdump before reboot, "hexdump
  -C -s 440 -n 4 /dev/sda".

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