Public bug reported: I did this test run with Lubuntu 13.10 amd64 and Xubuntu 13.10 amd64 in separate VMs.
Steps to reproduce: - Install fresh Lubuntu/Xubuntu - Open the XFCE terminal. - Type "sudo -i", enter password, and do the following: # create a secondary useraccount adduser testuser # use nano or your favorite editor: nano /etc/sudoers.d/testuser # allow your main useraccount to execute ANY commands as the "testuser" user using sudo. password will NOT be required your_main_username ALL=(testuser) NOPASSWD: ALL # save the file. # set permissions of sudoers.d correctly chmod 440 /etc/sudoers.d/* - now open a shell as your main user, NOT as root. do: gksudo -u testuser xfce4-terminal This should open a terminal logged in as "testuser". But it does nothing. Add the debug option and pipe to less to view what happens: "gksudo -du testuser xfce4-terminal 2>&1 | less" Output: No ask_pass set, using default! xauth: /tmp/libgksu-wPttP0/.Xauthority STARTUP_ID: gksudo/xfce4-terminal/2799-0-xubuntu1_TIME2139054 cmd[0]: /usr/bin/sudo cmd[1]: -H cmd[2]: -S cmd[3]: -p cmd[4]: GNOME_SUDO_PASS cmd[5]: -u cmd[6]: testuser cmd[7]: -- cmd[8]: xfce4-terminal buffer: -No protocol specified- buffer: -- buffer: -(xfce4-terminal:2802): Gtk-WARNING **: cannot open display: :0.0- buffer: -- buffer: -- buffer: -- buffer: -- buffer: -- buffer: -- (a lot more of the previous messages) brute force GNOME_SUDO_PASS ended... No password prompt found; we'll assume we don't need a password. xauth: /tmp/libgksu-wPttP0/.Xauthority xauth_env: /home/xor/.Xauthority dir: /tmp/libgksu-wPttP0 The fact that there is output of xfce4-terminal BEFORE gksudo talks about password, .Xauthority, etc. might indicate that it tries to run the child application too early? I haven't read the source code though, please validate this claim by reading it. ** Affects: gksu (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1242975 Title: "gksu -u other_user .." is broken To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gksu/+bug/1242975/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs