// grep -E --color "multiboot|module" /boot/grub2/i386-pc/command.lst
[root@localhost ~]# grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2
Fedora (4.6.4-301.fc24.x86_64) 24 (Workstation Edition)
Fedora (4.5.5-300.fc24.x86_64) 24 (Workstation Edition)
Fedora (0-rescue-5a7811782f504e58b061fcc2863b9246) 24 (Workstation Edition)
Fedora, with Xen hypervisor
[root@localhost ~]# grub2-set-default 'Fedora, with Xen hypervisor'
[root@localhost ~]# grub2-editenv list
saved_entry=Fedora, with Xen hypervisor
[root@localhost ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
Now reboot.