When you automount a drive in /etc/fstab even if it's not important like an external drive that you only use sometimes and is not required for booting, it will prevent a successfuly boot.
If you disable quiet mode for booting you will see something like below "A start job is running for dev-disk ...."
How do we fix an fstab entry from preventing our boot?
The drive in question is mounted to /mnt/vdb1
All we have to do is add ",nofail" after defaults on that line entry and it will continue to boot normally if the drive is not found or cannot be mounted.