gksu not in sudo mode when installed via ubuntu-desktop / lubuntu-desktop onto existing system

Binary package hint: gksu

I performed a fresh install of an Ubuntu 11.04 Natty Narwhal Alpha 1 i386 command-line system, using the Alternate Install CD. Then, I installed the ubuntu-desktop package. I found that gksu would always report that the password was incorrect. I suspected that it was set to use su rather than sudo (which it should be using on Ubuntu), and I confirmed this as follows:

ek@Zim:~$ gconftool -R /apps/gksu
 save-to-keyring = false
 display-no-pass-info = false
 sudo-mode = false
 prompt = false
 save-keyring = session
 force-grab = false
 disable-grab = false

This also happens when lubuntu-desktop (which provides LXDE rather than GNOME) is installed on a fresh command-line system. I tested that (also from a clean install) on the same i386 machine. I presume this bug occurs for xubuntu-desktop and kubuntu-desktop installed on top of an existing command-line system too, but I have not tested those.

This bug does not occur with an Ubuntu Natty system installed on the same machine in the usual way (with the Desktop Install CD); it only occurs when ubuntu-desktop (or a similar package providing a desktop environment) is installed on top of a command-line system. It might also occur if such a package is installed on top of a fresh Ubuntu Server system--I have not tested that.

While users may decide to install desktop environments onto command-line systems during the course of normal use, this bug is additionally problematic because there are some desktop environments that can only be installed after Ubuntu is already installed, on some systems. For example, there is currently no Lubuntu Natty Alpha 1 Install CD, nor any Lubuntu install CD's for the amd64 architecture. The best way to install those systems is to install a command-line system, and then install lubuntu-desktop via apt-get or aptitude. This bug breaks that functionality.

I think this bug is specific to Natty, but I am not sure. I haven't found a bug report for it, suggesting (but not proving) that it doesn't affect Maverick. Many months ago, I installed lubuntu-desktop on a Lucid amd64 system, and this problem did not occur.

While this bug resembles Bug 27636, it is not a duplicate of that bug, since (a) that bug was fixed over four years ago, and (b) that bug was not specific to systems where a -desktop package is installed on top of a command-line system. This bug might be related to Bug 624095, but there are a few differences; my understanding is that that bug affected some systems upgraded from Lucid to Maverick, whereas I am seeing this bug on fresh installs of Natty where the desktop environment packages are added after the installation.

I am reporting this bug on the system that has ubuntu-desktop (not lubuntu-desktop) installed, since that's the more popular package. I have the following possibly relevant package versions:

gconf2 2.32.1-0ubuntu1
gksu 2.0.2-5ubuntu1
login 1:4.1.4.2-1ubuntu3 (provides /bin/su)
sudo 1.7.2p7-1ubuntu3
ubuntu-desktop 1.209

And the output of "uname -a" is:
Linux Zim 2.6.37-7-generic #19-Ubuntu SMP Tue Nov 30 23:46:45 UTC 2010 i686 GNU/Linux

The version of lubuntu-desktop with which I reproduced this bug is 0.19.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: gksu 2.0.2-5ubuntu1
ProcVersionSignature: Ubuntu 2.6.37-7.19-generic 2.6.37-rc3
Uname: Linux 2.6.37-7-generic i686
Architecture: i386
Date: Sat Dec 4 18:56:23 2010
ExecutablePath: /usr/bin/gksu
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha i386 (20101202)
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: gksu