xhost: unable to open display "desktop:0"

UPDATE 1: I am not using SSH. I am using a local machine. UPDATE 2: I restarted the X and notice that the Xauthority file that I am exporting to is actually being updated: $ sudo systemctl restart display-manager $ ls /run/user/1000/gdm/Xauthority* -rwx------ 1 mona mona 96 Jan 25 16:07 /run/user/1000/gdm/Xauthority Also, after I restarted the X, the other two Xauthority files, namely /run/user/1000/gdm/Xauthority-c and /run/user/1000/gdm/Xauthority-l, are gone as can be seen below: $ fd Xauthority / /run/user/1000/gdm/Xauthority and I can call xauth after reboot: $ xauth Using authority file /run/user/1000/gdm/Xauthority xauth> Following https://unix.stackexchange.com/questions/199891/invalid-mit-magic-cookie-1-key-when-trying-to-run-program-remotely I tried: [9080:9072 0:2035] 02:14:50 Mon Jan 25 [mona@goku:pts/0 +1] ~/research/code/vision/integration $ export DISPLAY=desktop:0 18838/31772MB(vision) and then: $ xhost +local: xhost: unable to open display "desktop:0" how could I fix this problem? $ lsb_release -a LSB Version: core-11.1.0ubuntu2-noarch:security-11.1.0ubuntu2-noarch Distributor ID: Ubuntu Description: Ubuntu 20.04.1 LTS Release: 20.04 Codename: focal Another similar example: $ xclock Error: Can't open display: desktop:0 More details: $ xclock Error: Can't open display: desktop:0 27296/31772MB [3266:3258 3:2008] 02:54:16 Mon Jan 25 [mona@goku:pts/0 +1] ~ $ export DISPLAY=":0.0" 26016/31772MB [3266:3258 3:2009] 02:57:24 Mon Jan 25 [mona@goku:pts/0 +1] ~ $ xclock Invalid MIT-MAGIC-COOKIE-1 keyError: Can't open display: :0.0 $ export DISPLAY=":0" 26238/31772MB [3266:3258 3:2011] 02:57:40 Mon Jan 25 [mona@goku:pts/0 +1] ~ $ xclock Invalid MIT-MAGIC-COOKIE-1 keyError: Can't open display: :0 $ xhost +mona Invalid MIT-MAGIC-COOKIE-1 keyxhost: unable to open display ":0" $ firefox Invalid MIT-MAGIC-COOKIE-1 keyUnable to init server: Could not connect: Connection refused Error: cannot open display: :0 $ xclock Invalid MIT-MAGIC-COOKIE-1 keyError: Can't open display: :0 25694/31772MB [3266:3258 3:2026] 03:04:35 Mon Jan 25 [mona@goku:pts/0 +1] ~ $ export DISPLAY=desktop:0 25694/31772MB [3266:3258 3:2027] 03:04:49 Mon Jan 25 [mona@goku:pts/0 +1] ~ $ xclock Error: Can't open display: desktop:0 Also, I am having weird characters in Xauthority file: $ xrandr | nc termbin.com 9999 Invalid MIT-MAGIC-COOKIE-1 keyCan't open display :0 21618/31772MB [9136:3258 0:2002] 03:49:16 Mon Jan 25 [mona@goku:pts/2 +1] ~ $ fd Xauthority / /run/user/1000/gdm/Xauthority /run/user/1000/gdm/Xauthority-c /run/user/1000/gdm/Xauthority-l 22048/31772MB [9136:3258 0:2003] 03:51:26 Mon Jan 25 [mona@goku:pts/2 +1] ~ $ cat /run/user/1000/gdm/Xauthority-c 22048/31772MB [9136:3258 0:2004] 03:51:49 Mon Jan 25 [mona@goku:pts/2 +1] ~ $ cat /run/user/1000/gdm/Xauthority-l 22081/31772MB [9136:3258 0:2005] 03:51:58 Mon Jan 25 [mona@goku:pts/2 +1] ~ $ cat /run/user/1000/gdm/Xauthority gokuMIT-MAGIC-COOKIE-1R��9��s{�H��H�l��gokuMIT-MAGIC-COOKIE-1R��9��s{�H��H�l22081/31772MB [9136:3258 0:2006] 03:52:03 Mon Jan 25 [mona@goku:pts/2 +1] ~ Also, setting it to the found Xauthority file didn't solve the problem: $ export XAUTHORITY=/run/user/1000/gdm/Xauthority 22022/31772MB [9136:3258 0:2010] 03:54:31 Mon Jan 25 [mona@goku:pts/2 +1] ~ $ xclock Invalid MIT-MAGIC-COOKIE-1 keyError: Can't open display: :0 I am uid 1000: uid=1000(mona) gid=1000(mona) groups=1000(mona),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),120(lpadmin),131(lxd),132(sambashare) I also have these about xauth: $ xauth info Authority file: /run/user/1000/gdm/Xauthority File new: no File locked: no Number of entries: 2 Changes honored: yes Changes made: no Current input: (argv):1 21740/31772MB [11979:11971 0:2016] 05:26:34 Mon Jan 25 [mona@goku:pts/0 +1] ~ $ xauth list goku/unix: MIT-MAGIC-COOKIE-1 SECRET_KEY #ffff#676f6b75#: MIT-MAGIC-COOKIE-1 SECRET_KEY