Forward user x sessions

When logging into a remote host as root, you lose the ability to forward x sessions after an su to another user.

To allow x-forwarding after you perform an su, you need to request the cookie for the current server:

ssh root@somehost

xauth list

returns:

 somehost.somedomain/unix:10  MIT-MAGIC-COOKIE-1  d9fc3512df83a70ea8054dff21f58e28

Now, su to the user:
 

su - someuser

xauth add somehost.somedomain/unix:10  MIT-MAGIC-COOKIE-1  d9fc3512df83a70ea8054dff21f58e28

now x apps will forward correctly - test with xterm.