CentOS 7.2 "X сервер"/bin/X "не может быть выполнен"

Question

Я откатил драйвер wacom и переустановил драйверы Nvidia, и теперь kdm не запускается.

> systemctl status kdm
  kdm[3954]: plymouth is running
  kdm[3954]: plymouth is active on VT 1, reusing for :0
  kdm[3954]: plymouth should quit after server startup
  kdm[3967]: X server "/bin/X" cannot be executed
  kdm[3954]: X server for display :0 cannot be started, session disabled
  kdm[3954]: Quitting Plymouth without transition
  kdm[3954]: plymouth is NOT running

Проверка nvidia-smi:

> nvidia-smi

  +-----------------------------------------------------------------------------+
  | NVIDIA-SMI 390.25                 Driver Version: 390.25                    |
  |-------------------------------+----------------------+----------------------+
  | GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
  | Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
  |===============================+======================+======================|
  |   0  TITAN Xp COLLEC...  Off  | 00000000:17:00.0 Off |                  N/A |
  | 23%   38C    P0    61W / 250W |      0MiB / 12196MiB |      0%      Default |
  +-------------------------------+----------------------+----------------------+
  |   1  TITAN Xp            Off  | 00000000:65:00.0 Off |                  N/A |
  | 26%   45C    P0    60W / 250W |      0MiB / 12192MiB |      0%      Default |
  +-------------------------------+----------------------+----------------------+

  +-----------------------------------------------------------------------------+
  | Processes:                                                       GPU Memory |
  |  GPU       PID   Type   Process name                             Usage      |
  |=============================================================================|
  |  No running processes found                                                 |
  +-----------------------------------------------------------------------------+

Проверка grub

> cat /etc/default/grub
  GRUB_TIMEOUT=5
  GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
  GRUB_DEFAULT=saved
  GRUB_DISABLE_SUBMENU=true
  GRUB_TERMINAL_OUTPUT="console"
  GRUB_CMDLINE_LINUX="powernow-k8.disable=1 intel_pstate=disable selinux=0 crashkernel=auto rd.lvm.lv=centos_vxfhost/root rd.lvm.lv=centos_vxfhost/swap nomodeset net.ifnames=0 rhgb quiet"
  GRUB_DISABLE_RECOVERY="true"

Каков наилучший способ диагностики и повторного запуска?