This documentation will introduce how to use the configuration file of the Ubuntu system.

env.txt is located in the /boot directory and is an environment configuration file used to configure the functions of the Ubuntu system.The system will read this file when it starts to set HDMI, fan, CPU frequency, etc.

The default setting is yes, it will automatically detect HDMI and set the best resolution, if it is closed, it will be set manually:

# HDMI resolution auto detection
# yes - auto detection
# no  - set HDMI resolution via 'hdmi' node
hdmi_autodetect=yes

Disable auto detect:

hdmi_autodetect=no

In some situations HDMI resolution auto detect will not work, and you can try to setup the HDMI resolution manually.

Only when hdmi_autodetect=no, the changed configuration will take effect, the default is 720p.

# HDMI mode
# Resolution Configuration
#    Symbol             | Resolution
# ----------------------+-------------
#    "480x272p60hz"     | 480x272 Progressive 60Hz
#    "480x320p60hz"     | 480x320 Progressive 60Hz
#    "480p60hz"         | 720x480 Progressive 60Hz
#    "576p50hz"         | 720x576 Progressive 50Hz
#    "720p60hz"         | 1280x720 Progressive 60Hz
#    "720p50hz"         | 1280x720 Progressive 50Hz
#    "1080p60hz"        | 1920x1080 Progressive 60Hz
#    "1080p50hz"        | 1920x1080 Progressive 50Hz
#    "1080p30hz"        | 1920x1080 Progressive 30Hz
#    "1080p24hz"        | 1920x1080 Progressive 24Hz
#    "1080i60hz"        | 1920x1080 Interlaced 60Hz
#    "1080i50hz"        | 1920x1080 Interlaced 50Hz
#    "2160p60hz"        | 3840x2160 Progressive 60Hz
#    "2160p50hz"        | 3840x2160 Progressive 50Hz
#    "2160p30hz"        | 3840x2160 Progressive 30Hz
#    "2160p25hz"        | 3840x2160 Progressive 25Hz
#    "2160p24hz"        | 3840x2160 Progressive 24Hz
#    "smpte24hz"        | 3840x2160 Progressive 24Hz SMPTE
#    "2160p60hz420"     | 3840x2160 Progressive 60Hz YCbCr 4:2:0
#    "2160p50hz420"     | 3840x2160 Progressive 50Hz YCbCr 4:2:0
#    "640x480p60hz"     | 640x480 Progressive 60Hz
#    "800x480p60hz"     | 800x480 Progressive 60Hz
#    "800x600p60hz"     | 800x600 Progressive 60Hz
#    "1024x600p60hz"    | 1024x600 Progressive 60Hz
#    "1024x768p60hz"    | 1024x768 Progressive 60Hz
#    "1280x800p60hz"    | 1280x800 Progressive 60Hz
#    "1280x1024p60hz"   | 1280x1024 Progressive 60Hz
#    "1360x768p60hz"    | 1360x768 Progressive 60Hz
#    "1440x900p60hz"    | 1440x900 Progressive 60Hz
#    "1600x900p60hz"    | 1600x900 Progressive 60Hz
#    "1600x1200p60hz"   | 1600x1200 Progressive 60Hz
#    "1680x1050p60hz"   | 1680x1050 Progressive 60Hz
#    "1920x1200p60hz"   | 1920x1200 Progressive 60Hz
#    "2560x1080p60hz"   | 2560x1080 Progressive 60Hz
#    "2560x1440p60hz"   | 2560x1440 Progressive 60Hz
#    "2560x1600p60hz"   | 2560x1600 Progressive 60Hz
#    "3440x1440p60hz"   | 3440x1440 Progressive 60Hz
hdmi=720p60hz

Set to 1080p:

hdmi=1080p60hz

Restart the system to take effect.

• off : Cooling fan is disabled.
• low : Cooling fan is working at low speed mode.
• mid : Coolinn fan is working at middle speed mode.
• high : Cooling fan is working at high speed mode.
• auto : Cooling fan is working at auto speed mode. By default, the fan speed is determined by CPU temperature.

• Set cooling fan to low speed mode:
  • Edit file /boot/env.txt and set fan_mode=low.

• Set cooling fan to mid speed mode:
  • Edit file /boot/env.txt and set fan_mode=mid.

• Set cooling fan to high speed mode:
  • Edit file /boot/env.txt and set fan_mode=high.

• Set cooling fan to auto speed mode:
  • Edit file /boot/env.txt and set fan_mode=auto.

• Disable cooling fan:
  • Edit file /boot/env.txt and set fan_mode=off.

After edit the file, you need to save the file and reboot the board.

khadas@Khadas:~$ sync
khadas@Khadas:~$ sudo reboot

khadas@Khadas:~$ cat /boot/env.txt | grep "fb_rotate"
fb_rotate=0

Rotate 90 degrees:

khadas@Khadas:~$ sudo vim /boot/env.txt
[sudo] password for khadas:

fb_rotate=0 change to fb_rotate=1.

After edit the file, you need to save the file and reboot the board.

khadas@Khadas:~$ sync
khadas@Khadas:~$ sudo reboot

After restarting, you will see the framebuffer console rotated 90 degrees.