Como recuperar o windows 7 para o grub2?

Question

Eu tinha um HDD com o windows 7. Depois, adicionei o 2ed HDD para instalar o centos7. Durante o processo de instalação, escolhi o particionamento cent OS Auto, mas redimensionei-o bastante. Depois de instalar o Cent OS 7, ele não detectou minhas janelas. adicionando o pacote ntfs eu vejo todos os dados do meu disco antigo, então os dados ainda estão lá.

Eu tentei adicionar manualmente, mas não tive progresso.

aqui está o meu comando fdisk

[root@localhost ~]# fdisk -l

Disk /dev/sda: 500.1 GB, 500107862016 bytes, 976773168 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: 0x10e2c68d

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048      206847      102400    7  HPFS/NTFS/exFAT
/dev/sda2          206848   276482047   138137600    7  HPFS/NTFS/exFAT
/dev/sda3       276482048   604162047   163840000    7  HPFS/NTFS/exFAT
/dev/sda4       604162048   976771071   186304512    7  HPFS/NTFS/exFAT
WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.

Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes, 1953525168 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: gpt
Disk identifier: 2141811A-B878-4910-9CE8-D3B24515F231


#         Start          End    Size  Type            Name
 1         2048       411647    200M  EFI System      EFI System Partition
 2       411648      2508799      1G  Microsoft basic 
 3      2508800   1086736383    517G  Linux LVM       

Disk /dev/mapper/centos-root: 214.7 GB, 214748364800 bytes, 419430400 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 /dev/mapper/centos-swap: 18.2 GB, 18249416704 bytes, 35643392 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 /dev/mapper/centos-home: 322.1 GB, 322122547200 bytes, 629145600 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

e depois meu grub2-mkconfig:

[root@localhost ~]# grub2-mkconfig > /dev/null
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.10.0-862.11.6.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-862.11.6.el7.x86_64.img
Found linux image: /boot/vmlinuz-3.10.0-862.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-862.el7.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-ff50ccad6fff414e8bebeeb436a02b3d
Found initrd image: /boot/initramfs-0-rescue-ff50ccad6fff414e8bebeeb436a02b3d.img
done

enquanto eu configuro 40_custom assim:

#!/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.
menuentry "Windows 7" {
        insmod ntfs
        set root='(hd0,2)'
        chainloader +1
}

Eu sei que pode ser fácil, mas eu não sei nada sobre gerenciamento de disco no sistema operacional e não encontrei nenhum documento sobre menuentry.

Obrigado!