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I have installed XFCE on an "Ubuntu Server" (in a Virtual Machine) so I have a small and fast environment. But when I want to log out, I usually (not always) see a gray shutdown and reboot button, but I like to be able to shutdown via that menu (I know of shutdown -h now, but the users of my machine don't necessarily know).

I use the display manager 'slim'.

reboot and halt are gray/not clickable

Question: how can I enable these buttons permanently?

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What Display Manager? xdm, wdm and slim do have problems with ConsoleKit, which disables those buttons, removable storages and some other stuff. I've been just investigating this myself. Known 'workaround' is to use dgm, kdm, lxdm or lightdm. –  Bobby Jun 13 '12 at 21:16
    
@Bobby I use slim. Do you have a suggestion for a small (in terms of disk usage - including dependencies) display manager? –  topskip Jun 13 '12 at 21:20
    
Not really...I verified that it works with lxdm an hour ago and it's rather light if ti comes to dependencies...but not exactly what I want as dm. lightdm might also be an option, but is a little bit heavier. –  Bobby Jun 13 '12 at 21:21
    
Works so far with lxdm and lxde, but the file manager thunar does not display icons anymore, but that's another question. I'd still like to see if it is possible to make XFCE/slim have the buttons enabled. –  topskip Jun 13 '12 at 21:39
    
I've been investigating this for the last hours. Seems like there are at least ideas for slim and patches for xdm floating around. Unfortunately nothing really useful what I found so far...though, it's the first time I have to deal with Consolekit. –  Bobby Jun 13 '12 at 21:41
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1 Answer

Short solution: Make sure that xfce4-session and upower are installed, and that the affected user is in the "power" group. If this doesn't help, here comes the scary part:

System shutdowns must always be issued from a root context. Different desktop environments use different approaches to achieve this. Mostly the shutdown is requested via a dbus call from the login manager, which in turn runs as root.

XFCE however, in an approach to make things less bloated and employ simpler technologies, uses its own helper programs. (Hey, I think that's cool!)

The shutdown helper should be contained in the package xfce4-session.

If this package isn't installed in your system, there could be the solution to your problem already.

Furthermore your user should be able to run the shutdown helper with root permissions. The xfce wiki has a paragraph on this: http://wiki.xfce.org/faq#session_manager

Different distributions prefer different solutions described in this wiki. I cannot check right now what applies to you, since I'm neither using XFCE nor Ubuntu. I would start by making sure your user belongs to the "power" group. You might need to install upower to set up this group and its infrastructure in the first place. Apart from configuring sudo or polkit as described in the wiki, issuing "chmod +s /usr/bin/xfce4-shutdown-helper" is a less secure but more convenient way to make sure the helper runs as root.

Well or has xfce4-shutdown helper become xfsm-shutdonw-helper? And is it placed in /usr/bin or /usr/sbin or /usr/lib/xfce4/ ..? I've lost track, it differs from distro to distro and from version to version. But maybe you don't need to get this deep into it.

Hope I could help ;-)

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