Encountered quite a few problems while install the RHEL7, with the Windows system already installed.

Problem 1:/dev/root does not exist

Downloaded the Redhat 7 ISO file and generate the bootable USB drive by using software ‘rufus-1.4.9.exe‘. 

in the installation menu, press tab key, and enter to modify the install command, change the “hd:……“ to "hd:/dev/sdb#", and then press enter, problem solved.

Problem 2: cannot boot both system

modified the /boot/grub/grub.conf (for RHEL6), changed the (hd1,0) to (hd0,0), it is starting from 0, the value 1 comes from the USB drive bootable drive.

Problem 3, how to change the sequence on the in Grub of RHEL6

change the default from 0 to 1 in /boot/grub/grub.conf, 0 will be the linux at defalt, 1 will be windows be default.

Problem 4: only boot into RHEL7, cannot see the dual boot interface in Grub2.

Create the file and add the following

    /etc/grub.d/10_windows7

     #! /bin/bash
     echo "Adding Windows7 entry to grub"
     cat << EOF
     menuentry "Windows" {
     set root=hd0(0,1)
     chainloader +1
      }
     EOF

Adjust hd0(0,1) accordingly. You can use hd0(0,1) if windows is installed on /dev/sda1

2. chmod +x /etc/grub.d/10_windows7

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

change the name of /etc/grub.d/10_windows7 to 09_windows7, 09 has lower number as linux file (in my Linux system it‘s 10_linux, change to 09 is smaller than 10), has higher priority.

then execute ‘grub2-mkconfig -o /boot/grub2/grub.cfg‘, reboot, the system will default as Windows to boot.