$ xauth list
<hostname>/unix:0 MIT-MAGIC-COOKIE-1 1fb2c048e3a32a3fe013c565b8422727
<hostname>/unix:12 MIT-MAGIC-COOKIE-1 29b9ba4a72136095e43540119c8da384
<hostname>/unix:11 MIT-MAGIC-COOKIE-1 99b08ccb7e8a76e75c70d7c75723505d
<hostname>/unix:10 MIT-MAGIC-COOKIE-1 b2ea07f58365b8672bea7497ffacee4f
<hostname>/unix:0 MIT-MAGIC-COOKIE-1 1fb2c048e3a32a3fe013c565b8422727
<hostname>/unix:12 MIT-MAGIC-COOKIE-1 29b9ba4a72136095e43540119c8da384
<hostname>/unix:11 MIT-MAGIC-COOKIE-1 99b08ccb7e8a76e75c70d7c75723505d
<hostname>/unix:10 MIT-MAGIC-COOKIE-1 b2ea07f58365b8672bea7497ffacee4f
Then execute, change user as root with sudo -i
and execute xauth add
followed by one entry from above output that having the highest number.
$ sudo -i
# xauth add <hostname>/unix:12 MIT-MAGIC-COOKIE-1 29b9ba4a72136095e43540119c8da384
# xauth add <hostname>/unix:12 MIT-MAGIC-COOKIE-1 29b9ba4a72136095e43540119c8da384
Explanation
xauth list
being executed before sudoing to root to output the xauth authorization hex key- after sudo as root,
xauth add
to add the authorization hex key from non-root into root