OS - Dual boot Oracle Linux / Windows 10

Versão Portuguesa

Sometimes is useful to have two operative systems in the laptop, is possible to get that creating two partitions in th disk, and to install the OS in the respective partition.
But this post is not about that - this post is about .. after have the installation is done.
After install Linux, is expectable to have a menu to select the operative system.
That didn't happened in my latptop, it's loading directly the Linux .. upss Windows 10 "has gone" !!!
This post is about that .. feature

Quick check

From the bellow commands we can get some usefull info - about the Operative Systems .. and about the disk partitioning . We can see a partition for/with Windows.
Nice, I didnt installed in the wrong partition :)

[root@mylaptop ~]# cat /etc/oracle-release
Oracle Linux Server release 7.3

[root@mylaptop ~]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 7.3 (Maipo)

[root@mylaptop ~]# uname -a
Linux mylaptop.rogerioantonio.com 4.1.12-61.1.18.el7uek.x86_64 #2 SMP Fri Nov 4 15:48:30 PDT 2016 x86_64 x86_64 x86_64 GNU/Linux

[root@mylaptop ~]# fdisk -l

Disk /dev/sda: 180.0 GB, 180045766656 bytes, 351651888 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xc0ff46d8

Device Boot Start End Blocks Id System
/dev/sda1 * 2048 139920590 69959271+ 7 HPFS/NTFS/exFAT/dev/sda2 139921408 140914687 496640 27 Hidden NTFS WinRE
/dev/sda3 140914688 142866431 975872 83 Linux
/dev/sda4 142866432 351651839 104392704 5 Extended
/dev/sda5 142868480 146784255 1957888 8e Linux LVM
/dev/sda6 146786304 351467519 102340608 83 Linux

Disk /dev/mapper/ol-swap: 2000 MB, 2000683008 bytes, 3907584 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

Setup dual boot Oracle Linux / Windows 10

To get the menu it looks is need to make some manual configurations, to make that happen I will do two steps :

1 - To add the below entries into the /etc/grub.d/40_custom file

menuentry "Windows 10" {
insmod part_msdos
insmod ntfs
set root='(hd0,msdos1)' chainloader +1
}

2 - recompile the grub : grub2-mkconfig -o "$(readlink -e /etc/grub2.cfg)"

[root@mylaptop ~]# cat /etc/grub.d/40_custom
#!/bin/sh
exec tail -n +5 $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 10" {
insmod part_msdos
insmod ntfs
set root='(hd0,msdos1)'
chainloader +1
}

[root@mylaptop ~]# grub2-mkconfig -o "$(readlink -e /etc/grub2.cfg)"

Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.1.12-61.1.18.el7uek.x86_64
Found initrd image: /boot/initramfs-4.1.12-61.1.18.el7uek.x86_64.img
Found linux image: /boot/vmlinuz-3.10.0-514.el7.x86_64
Found initrd image: /boot/initramfs-3.10.0-514.el7.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-cde31ac14a2b4b86b98701797bbb530f
Found initrd image: /boot/initramfs-0-rescue-cde31ac14a2b4b86b98701797bbb530f.img
done

[root@mylaptop ~]# reboot

At this point - after the reboot you will have the menu for dual boot

Futher Reading : https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/sec-customizing_the_grub_2_configuration_file

Thank you for reading, hope this post was helpful.
Rogerio