After update, system will not boot, stops with 'kernel panic' message

Issue

• After updating, we try to reboot, but it stops at a kernel panic

Kernel panic - not syncing: Attempted to kill init!
Pid: 1, comm: init Not tainted 2.6.32-573.8.1.el6.x86_64 #1
Call Trace:
[<ffffffff81537e51>] ? panic+0xa7/0x16f
[<ffffffff8107cce7>] ? do_exit+0x867/0x870
[<ffffffff81193585>] ? fput+0x25/0x30
[<ffffffff8107cd48>] ? do_group_exit+0x58/0xd0
[<ffffffff8107cdd7>] ? sys_exit_group+0x17/0x20
[<ffffffff8100b0d2>] ? system_call_fastpath+0x16/0x1b