Running an strace on the remote system where xauth is failing will show you what's tripping up xauth.
$ strace xauth list stat("/home/sam/.Xauthority-c", {st_mode=S_IFREG|0600, st_size=0, ...}) = 0 open("/home/sam/.Xauthority-c", O_WRONLY|O_CREAT|O_EXCL, 0600) = -1 EEXIST (File exists) rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0 rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 nanosleep({2, 0}, 0x7fff6c4430e0) = 0 open("/home/sam/.Xauthority-c", O_WRONLY|O_CREAT|O_EXCL, 0600) = -1 EEXIST (File exists) rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0 rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 nanosleep({2, 0}, 0x7fff6c4430e0) = 0 open("/home/sam/.Xauthority-c", O_WRONLY|O_CREAT|O_EXCL, 0600) = -1 EEXIST (File exists) rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0 rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0 So xauth is attempting to open a file and it already exists. The culprit file is /home/sam/.Xauthority-c. We can confirm the presence of this file on the remote system:
$ ls -l .Xauthority* -rw------- 1 sam sam 55 Jul 12 22:04 .Xauthority -rw------- 1 sam sam 0 Jul 12 22:36 .Xauthority-c -rw------- 1 sam sam 0 Jul 12 22:36 .Xauthority-l As it turns out. Those files are lock files for .Xauthority, so simply removing them resolves the issue.
$ rm -fr .Xauthority-* With the files deleted, exit from the SSH connection and then reconnect. This will allow xauth to re-run successfully.
$ ssh -t skinner ssh sam@blackbird Welcome to Ubuntu 14.04.1 LTS (GNU/Linux 3.13.0-44-generic x86_64) * Documentation: https://help.ubuntu.com/ Last login: Sun Jul 12 22:37:54 2015 from skinner.bubba.net $ Now we're able to run xauth list and X11 applications without issue.
$ xauth list blackbird/unix:10 MIT-MAGIC-COOKIE-1 cf01f793d2a5ece0ea58196ab5a7977a The GUI
$ xeyes 