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When I switched from su+bash to su+tmux+zsh I noticed that I get $XAUTHORITY variable defined as /root/.xauthXXXXXX where XXXXXX are 6 random alphanumeric characters. With previous configuration X worked with root flowlessly but now I need to copy ~username/.Xauthority to $XAUTHORITY.

Variable is nowhere defined (I checked .zshrc, /etc/profile*, /etc/profile.d/* etc.).

# env
TERM=screen
SHELL=/usr/bin/tmux
USER=toor
TMUX=/tmp//tmux-0/default,6495,3
PATH=/sbin:/bin:/usr/sbin:/usr/bin
PWD=/root
SHLVL=2
HOME=/root
LOGNAME=toor
DISPLAY=:0.0
XAUTHORITY=/root/.xauthUSzLl4
COLORTERM=gnome-terminal
_=/bin/env
OLDPWD=/root
EDITOR=vim
vcs_info_msg_0_=
vcs_info_msg_1_=

Edit:

% echo $XAUTHORITY 
/home/mpiechotka/.Xauthority
% su 
password:
# echo $XAUTHORITY 
/root/.xauthUSzLl4
# ls $XAUTHORITY
ls: cannot access /root/.xauthUSzLl4: No such file or directory
# cat .tmux.conf 
set -g default-command /bin/zsh
set -g default-shell /bin/zsh

su is aliased to su - toor and it opens tmux as shell. toor is an alias of root with different shell.

PS. I just discovered that it appears on normal su as well. It did not some time ago...

Edit 2 set-enviroment didn't help either

Edit 3 xhost +localhost did not helped but xhost + (disabling all control) DID helped.

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Could you be more specific about when you are executing what? –  gvkv Sep 20 '10 at 20:42
    
It's too bad my theory didn't pan out but if you fix it, please post your solution. –  gvkv Sep 22 '10 at 2:50
    
@Gilles: No. I didn't. –  Maciej Piechotka Jan 18 '11 at 19:55

3 Answers 3

Here's what I think is happening.

When you're using su and bash, the su-session inherits the environment with the exception of USER, HOME and SHELL, thus XAUTHORITY still points to ~username/.Xauthority and everything is fine. However (from the man page), when the tmux server is started:

... tmux copies the environment into the global environment; in addition, each session has a session environment. When a window is created, the session and global environments are merged with the session environment overriding any variable present in both.

and I suspect (without knowing invocation details) that when you switch credentials, su tries to find .Xauthority in /root and since it can't find one when you need to run an X app, it creates one. I can think of a couple ways you can try to fix this:

  1. Invoke su by using su -. This will copy over the real user's evironment
  2. Add set-environment <name> <value> to your tmux config.

Unfortunately, I can't test this since I recently switched over to i3 (which is awesome) and I don't have a spare machine.

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Except that I'm invoking su by su -. Also echo "$XAUTHORITY" shows there is no ~. I'll try set-enviroment. –  Maciej Piechotka Sep 20 '10 at 21:47
    
Actually I meant ~ as a shorthand to (what I presumed) was your home directory. I've edited. –  gvkv Sep 20 '10 at 23:26
1  
no, i3 is i3, awesome is awesome =P . –  Kent Fredric Feb 15 '11 at 9:40

This could be due to a misconfigured pam_xauth PAM module. It is supposed to copy your keys to a temporary file when you run su. The behavior you describe is consistent with pam_xauth creating the temporary file but somehow not copying the keys (perhaps because you have a ~/.xauth/export or a /root/.xauth/import).

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I don't have neither of those but xauth is loaded in su session (i.e. it is in /etc/pam.d/su). –  Maciej Piechotka Nov 18 '10 at 0:19

It happened to me but this time with $COLORTERM variable.

If you start tmux on a terminal emulator that has, for instance, COLORTERM=terminus and after that you start another tmux session even on another terminal client that normally would have COLORTERM=gnome-terminal, this new session will crossover and inherit COLORTERM=terminus.

These assertions are enough to conclude that, unfortunately, tmux sessions are not isolated from each other, even if you're using different terminal emulators.

Your su sub shell is probably inheriting $XAUTHORITY from another tmux session, more specifically the very first tmux session created.

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