Upgrading Windows 7 to 10 does not like dual-boot systems where Windows is not the default (likely due to automated reboots during upgrade). In order to fix this problem, we’ll need to change the boot order (or, the default entry).

 

# grep "submenu\|^\menuentry" /boot/grub2/grub.cfg | cut -d "'" -f2
Fedora (4.1.6-200.fc22.x86_64) 22 (Twenty Two)
Fedora (4.1.3-201.fc22.x86_64) 22 (Twenty Two)
Fedora (4.1.3-200.fc22.x86_64) 22 (Twenty Two)
Fedora, with Linux 0-rescue-46724b4128e8471db41e1e7efe9c8aeb
Windows 7 (loader) (on /dev/sda1)
Windows 7 (loader) (on /dev/sde1)

# grub2-editenv list
saved_entry=Fedora (4.1.6-200.fc22.x86_64) 22 (Twenty Two)

# grub2-set-default "Windows 7 (loader) (on /dev/sda1)"
# grub2-editenv list
saved_entry=Windows 7 (loader) (on /dev/sda1)