Windows OS not visible on dual boot |

We had attempted a dual boot vps on KVM based vps

The os were installed using ISO

First to start with windows and then linux

However after installing linux the windows OS went missing

ON googling around found a solution

The issue was due to missing modules where we had to install module ntfs-3g

[root@ohours ~]# yum install ntfs-3g
Loaded plugins: fastestmirror
base                                                                                                                                                                                 | 3.6 kB 00:00:00
extras                                                                                                                                                                               | 3.4 kB 00:00:00
updates                                                                                                                                                                              | 3.4 kB 00:00:00
(1/4): base/7/x86_64/group_gz                                                                                                                                                        | 156 kB 00:00:00
(2/4): extras/7/x86_64/primary_db                                                                                                                                                    | 167 kB 00:00:00
(3/4): updates/7/x86_64/primary_db                                                                                                                                                   | 6.0 MB 00:00:00
(4/4): base/7/x86_64/primary_db                                                                                                                                                      | 5.7 MB 00:00:01
Determining fastest mirrors
* base: centos.mirror.lstn.net
* extras: centos.mirror.lstn.net
* updates: centos.mirror.lstn.net
No package ntfs-3g available.
Error: Nothing to do

we had to use epel repository to install ntfs-3g as its not available with normal repository

#Command to enable epel repository

[root@ohours ~]# yum install epel-release
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: centos.mirror.lstn.net
* extras: centos.mirror.lstn.net
* updates: centos.mirror.lstn.net
Resolving Dependencies
–> Running transaction check
—> Package epel-release.noarch 0:7-9 will be installed
–> Finished Dependency Resolution

Dependencies Resolved

============================================================================================================================================================================================================
Package Arch Version Repository Size
============================================================================================================================================================================================================
Installing:
epel-release noarch 7-9 extras 14 k

Transaction Summary
============================================================================================================================================================================================================
Install 1 Package

Total download size: 14 k
Installed size: 24 k
Is this ok [y/d/N]: y
Downloading packages:
warning: /var/cache/yum/x86_64/7/extras/packages/epel-release-7-9.noarch.rpm: Header V3 RSA/SHA256 Signature, key ID f4a80eb5: NOKEY
Public key for epel-release-7-9.noarch.rpm is not installed
epel-release-7-9.noarch.rpm                                                                                                                                                          | 14 kB 00:00:00
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
Importing GPG key 0xF4A80EB5:
Userid     : “CentOS-7 Key (CentOS 7 Official Signing Key) <security@centos.org>”
Fingerprint: 6341 ab27 53d7 8a78 a7c2 7bb1 24c6 a8a7 f4a8 0eb5
Package    : centos-release-7-4.1708.el7.centos.x86_64 (@anaconda)
From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-7
Is this ok [y/N]: y
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : epel-release-7-9.noarch                                                                                                                                                                  1/1
Verifying : epel-release-7-9.noarch                                                                                                                                                                  1/1

Installed:
epel-release.noarch 0:7-9

Complete!

[root@ohours ~]# yum install ntfs-3g
Loaded plugins: fastestmirror
epel/x86_64/metalink                                                                                                                                                                 | 16 kB 00:00:00
epel                                                                                                                                                                                 | 4.7 kB 00:00:00
(1/3): epel/x86_64/group_gz                                                                                                                                                          | 266 kB 00:00:00
(2/3): epel/x86_64/updateinfo                                                                                                                                                        | 899 kB 00:00:00
(3/3): epel/x86_64/primary_db                                                                                                                                                        | 6.3 MB 00:00:00
Loading mirror speeds from cached hostfile
* base: centos.mirror.lstn.net
* epel: mirror.oss.ou.edu
* extras: centos.mirror.lstn.net
* updates: centos.mirror.lstn.net
Resolving Dependencies
–> Running transaction check
—> Package ntfs-3g.x86_64 2:2017.3.23-1.el7 will be installed
–> Finished Dependency Resolution

Dependencies Resolved

Total download size: 263 k
Installed size: 612 k
Is this ok [y/d/N]: y
Downloading packages:
warning: /var/cache/yum/x86_64/7/epel/packages/ntfs-3g-2017.3.23-1.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID 352c64e5: NOKEY
Public key for ntfs-3g-2017.3.23-1.el7.x86_64.rpm is not installed
ntfs-3g-2017.3.23-1.el7.x86_64.rpm                                                                                                                                                   | 263 kB 00:00:00
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Importing GPG key 0x352C64E5:
Userid     : “Fedora EPEL (7) <epel@fedoraproject.org>”
Fingerprint: 91e9 7d7c 4a5e 96f1 7f3e 888f 6a2f aea2 352c 64e5
Package    : epel-release-7-9.noarch (@extras)
From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
Is this ok [y/N]: y
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
Installing : 2:ntfs-3g-2017.3.23-1.el7.x86_64                                                                                                                                                         1/1
Verifying : 2:ntfs-3g-2017.3.23-1.el7.x86_64                                                                                                                                                         1/1

Installed:
ntfs-3g.x86_64 2:2017.3.23-1.el7

Complete!

#Using below command find the OS loaded in system

[root@ohours ~]# grub2-mkconfig > /dev/null
Generating grub configuration file …
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-4754405db1084b4e8d440c2aef41bef8
Found initrd image: /boot/initramfs-0-rescue-4754405db1084b4e8d440c2aef41bef8.img
Found Windows Recovery Environment (loader) on /dev/sda1
done

if windows is not found the OS may have got formatted while installing other OS

However our windows os was intact as the results show

#make backup copy of grub.conf

sudo cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg.old

#Recreate the grub.conf to load windows and linux os using below command

sudo grub2-mkconfig -o /boot/grub2/grub.cfg

and now reboot and see both OS load