Ygtjki

How can I change my screen resolution to 1368x768 on Xubuntu 18.04? I tried

jaakko@jaakko-GL553VW:~$ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected 1920x1080+0+0 0mm x 0mm
 1920x1080 77.00* 
 Modeline (0x2db) 1368.000MHz
 h: width 85 start 1368 end 1440 total 1576 skew 0 clock 868.02KHz
 v: height 1784 start 768 end 771 total 781 clock 1111.42Hz
jaakko@jaakko-GL553VW:~$ xrandr --newmode Modeline "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798
xrandr: Failed to get size of gamma for output default
X Error of failed request: BadName (named color or font does not exist)
 Major opcode of failed request: 140 (RANDR)
 Minor opcode of failed request: 16 (RRCreateMode)
 Serial number of failed request: 19
 Current serial number in output stream: 19
jaakko@jaakko-GL553VW:~$ 

Then I type less /etc/default/grub the output is

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
# info -f grub -n 'Simple configuration'

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=0
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="nomodeset"
GRUB_CMDLINE_LINUX=""

# Uncomment to enable BadRAM filtering, modify to suit your needs
# This works with Linux (no patch required) and with any kernel that obtains
# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"

# Uncomment to disable graphical terminal (grub-pc only)
#GRUB_TERMINAL=console

# The resolution used on graphical terminal
# note that you can use only modes which your graphic card supports via VBE
# you can see them in real GRUB with the command `vbeinfo'
#GRUB_GFXMODE=640x480

# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
#GRUB_DISABLE_LINUX_UUID=true

# Uncomment to disable generation of recovery mode menu entries
#GRUB_DISABLE_RECOVERY="true"

# Uncomment to get a beep at grub start
#GRUB_INIT_TUNE="480 440 1"

Try the following steps as root:

1. 
   

   Edit /etc/default/grub and replace

   
   
   

   GRUB_CMDLINE_LINUX_DEFAULT="nomodeset"
   

   
   
   

   with

   
   
   

   GRUB_CMDLINE_LINUX_DEFAULT="quiet"
   

   
   


2. 
   

   Update grub and reboot

   
   
   

   sudo update-grub
   reboot
   

   
   


3. 
   

   In XFCE you should be able to change your resolution with xfce4-display-settings.

   
   
   

   You can run it from commandline or select it from the your "Settings" menu (I don't know the exact name in Xubuntu) as the "Display" setting.

   
   

If you encounter video card problems, you can manually edit your kernel options in the grub boot screen with e, then replace "quiet" back to "nomodeset" and boot with Ctrl+x or F10.