How to flash factory default?

Please provide the following info (check/uncheck the boxes after creating this topic):
Software Version
DRIVE OS Linux 5.2.6
DRIVE OS Linux 5.2.6 and DriveWorks 4.0
DRIVE OS Linux 5.2.0
DRIVE OS Linux 5.2.0 and DriveWorks 3.5
NVIDIA DRIVE™ Software 10.0 (Linux)
NVIDIA DRIVE™ Software 9.0 (Linux)
other DRIVE OS version

Target Operating System

Hardware Platform
NVIDIA DRIVE™ AGX Xavier DevKit (E3550)
NVIDIA DRIVE™ AGX Pegasus DevKit (E3550)

SDK Manager Version

Host Machine Version
native Ubuntu 18.04

Hello, I am completely newbee to this forum.
I want to flash factory-default image to xavier.
Flashing drive-os 5.2.6 sdk with sdk-manager works
but I can get nothing from HDMI ports. (console works)
" Manually Starting X Server" from installation guide not works.
If factory image is available I would prefer this.
Thank you.

Dear @hirofumi_momose,
sdkmanager installs factory image. By default, The DRIVE OS 5.2.6 does not include GUI. Could you please check the discussion on Error trying to connect monitor

Hi SivaRamaKrishnaNV,
Thank you quick reply.
I will read document you told me, and choose another os version.

Dear @hirofumi_momose,
ok. Please file a new topic incase you hit any issues to avoid cluttering of topics.