CentOS 7, grub, добавление Windows

Поставил CentOS 7.
Нужно было добавить Windows в grub
решил вспомнить куда установлена винда

# fdisk -l
 
Disk /dev/sda: 320.1 GB, 320072933376 bytes, 625142448 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: dos
Disk identifier: 0x54bbe123
 
Устр-во Загр     Начало       Конец       Блоки   Id  Система
/dev/sda1            2048    12427263     6212608   27  Hidden NTFS WinRE
/dev/sda2   *    12427264    12632063      102400   27  Hidden NTFS WinRE
/dev/sda3        12632064   380137471   183752704    7  HPFS/NTFS/exFAT
/dev/sda4       380139518   625141759   122501121    5  Extended
Partition 4 does not start on physical sector boundary.
/dev/sda5       380139520   542246911    81053696    b  W95 FAT32
/dev/sda6       542248960   546349055     2050048   82  Linux swap / Solaris
/dev/sda7       546351104   625141759    39395328   83  Linux

угу, походу дела /dev/sda3
правлю /etc/grub.d/40_custom таким образом

# cat /etc/grub.d/40_custom 
#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
 
#  Windows 7
menuentry "Windows 7" {
  set root=(hd0,3)
  chainloader +1
}

и обновляю конфиг

# grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.10.0-693.5.2.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-693.5.2.el7.x86_64.img
Found linux image: /boot/vmlinuz-3.10.0-693.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-693.el7.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-4602e55ab5ae48b996288b235f8af891
Found initrd image: /boot/initramfs-0-rescue-4602e55ab5ae48b996288b235f8af891.img
Found Windows Recovery Environment (loader) on /dev/sda1
Found Windows 7 (loader) on /dev/sda2
Found Windows 7 (loader) on /dev/sda3