[CentOS] System Start-Up Issue

> 
> Having very little experience with such start-up issues, we are at a loss
> to determine how to salvage the CentOS 6.9 virtual machine.  Is there a
> standard way to start up a system without any extras like gnome to see if
> we can get a running system?  Would it be wise to attempt using yum update
> after we get a running system to see if issues are corrected?  Thanks.
> 

Interrupt the boot process in the same way as you do when booting into
a previous kernel and then edit the grub boot line to add a run level
at the end - so '3' to boot multiuser without a gui or '1' to boot into
single user mode. The line you want to edit is the one that has 'rhgb
quiet' in it - you might want to remove those as well so that you can
see what's happening (although you will get ALOT of output).

P.