Creating an LVM snapshot in RHEL7 can render the system unbootable

Issue

• After creating a new LVM snapshot in the root volume group, boot fails with errors like the following:

  [  183.741859] dracut-initqueue[259]: Warning: dracut-initqueue timeout - starting timeout scripts
  [  183.742024] dracut-initqueue[259]: Warning: Could not boot.
  [  183.811432] dracut-initqueue[259]: Warning: /dev/mapper/rhel_unused-root does not exist
  [  183.812162] dracut-initqueue[259]: Warning: /dev/rhel_unused/root does not exist
           Starting Dracut Emergency Shell...
  Warning: /dev/mapper/rhel_unused-root does not exist
  Warning: /dev/rhel_unused/root does not exist
  
  Generating "/run/initramfs/rdsosreport.txt"
  
  Entering emergency mode. Exit the shell to continue.
  Type "journalctl" to view system logs.
  You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or /boot
  after mounting them and attach it to a bug report.
  
  dracut:/#
  

• After updating a RHEL 7 kernel or manually executing dracut, the initramfs no longer contains the dm-snapshot.ko module