When booting on a default installation of CentOS 7, after the grub boot loading menu displays the screen refreshes into a progress bar during the boot process. I’m used to seeing the detailed kernel output during the boot process to diagnose boot problems. So these are the steps to disable to progress bar and give detailed boot kernel messages.
Edit grub file
Remove rhgb quiet from this entry, should look like this right now
GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet"
after making those changes you’ll need to rebuild the grub2 configuration file with
grub2-mkconfig -o /etc/grub2.cfg
Now reboot your server and you’re able to see the detailed kernel message output during the boot process.