xauth not creating .Xauthority file

Just to report, I did have a similar problem. But in my case I just follow those steps:

Follow these steps to create a $HOME/.Xauthority file.

Log in as user and confirm that you are in the user's home directory.

# Rename the existing .Xauthority file by running the following command
mv .Xauthority old.Xauthority 

# xauth with complain unless ~/.Xauthority exists
touch ~/.Xauthority

# only this one key is needed for X11 over SSH 
xauth generate :0 . trusted 

# generate our own key, xauth requires 128 bit hex encoding
xauth add ${HOST}:0 . $(xxd -l 16 -p /dev/urandom)

# To view a listing of the .Xauthority file, enter the following 
xauth list 

After that there are no more problems with .Xauthority file since then.

Thanks and credits to srinivasan.

Just to complement the excellent ton's answer.

I have once had exactly the same problem because my home directory had become 100% full. Upon connection, ssh created an empty ~/.Xauthority and was unable to write any single entry to it (so that xauth list had always produced an empty output).

So I suggest one always checks the free space (e. g.: df -h) and verifies that xauth generate and xauth add have indeed had any effect (xauth list).

Under root privileges open /etc/ssh/sshd_config and uncomment the following lines if they are commented:

X11Forwarding yes

X11DisplayOffset 10

X11UseLocalhost yes

Then logout and login again with -X flag in ssh. You do not have to set or unset DISPLAY environment variable.