Tanguy Ortolo

Major desktop environments such as Xfce or KDE have a built-in computer suspend feature, but when you use a lighter alternative, things are a bit more complicated, because basically: only root can suspend the computer. There used to be a standard solution to that, using a D-Bus call to a running daemon upowerd. With recent updates, that solution first stopped working for obscure reasons, but it could still be configured back to be usable. With newer updates, it stopped working again, but this time it seems it is gone for good:

$ dbus-send --system --print-reply \
            --dest='org.freedesktop.UPower' \
            /org/freedesktop/UPower org.freedesktop.UPower.Suspend
Error org.freedesktop.DBus.Error.UnknownMethod: Method "Suspend" with
signature "" on interface "org.freedesktop.UPower" doesn't exist

Read more GNU/Linux graphic sessions: suspending your computer

Allowing computer suspend

Major desktop environments such as Xfce or KDE have a built-in computer suspend feature, but when you use a lighter alternative, things are a bit more complicated, because basically: only root can suspend the computer. Possible solutions include:

• using sudo to allow members of a given group to run a suspend command, e.g. pm-suspend as root;
• using a D-Bus UPower thingy, which communicates with a running daemon upowerd:

  $ dbus-send --system --print-reply \
              --dest='org.freedesktop.UPower' \
              /org/freedesktop/UPower org.freedesktop.UPower.Suspend
          

With recent updates of the related Debian packages — no idea of which one exactly — the latter solution may not work any more, in which case it will only return the following error:

Error org.freedesktop.UPower.GeneralError: not authorized

It appears that this error is linked to ConsoleKit, a part of all this modern *Kit gizmo pile. If you are in this case, try prefixing your session launcher with the undocumented dark magic call ck-launch-session. For instance, this is what I have in my .xsession to launch my window manager i3:

exec ck-launch-session i3

Note: I do not know what ck-launch-session does exactly, why it is needed, and I do not want to know. To me, all that WhatsitKit pile is just some opaque, under-documented — as in: no man page — crap, that no one but their author really understand, designed to solve theoretical problems no one really cares about — like: how to allow locally connected users to use the sound card while forbidding it to remote users — while creating new issues such as this one. This stuff is too complex and under-documented for me to dive into it, so if it does not work out of the box, it is just some crap that gets in my way to using my computer as I wish.

Disabling a monitor

In some configurations, you have two monitors and want to disable one. For instance, in addition to my LCD monitor, I have a projector which I only use for movies. According to xorg.conf's man page, it can be disabled this way:

Section "Device"
    Identifier  "Internal graphic card"
    Option      "Monitor-DVI"   "LCD Monitor"
    Option      "Monitor-VGA"   "Projector"
EndSection

Section "Monitor"
    Identifier  "LCD Monitor"
EndSection

Section "Monitor"
    Identifier  "Projector"
    Option      "Enable"    "false"
EndSection

Except that does not work, because contrary to what the man page says the real option to use is not Enable but Disable! So here is the correct configuration to disable that monitor at start-up:

Section "Device"
    Identifier  "Internal graphic card"
    Option      "Monitor-DVI"   "LCD Monitor"
    Option      "Monitor-VGA"   "Projector"
EndSection

Section "Monitor"
    Identifier  "LCD Monitor"
EndSection

Section "Monitor"
    Identifier  "Projector"
    Option      "Disable"   "true"
EndSection

Note: yes, I will send a bug report with a patch against xorg.conf's man page.

UPower for regular users

Major desktop environments usually provide a user-friendly menu to suspend your computer. Internally, if seems to use something called UPower, which uses something called PolicyKit, which in turn may or may not use another piece called ConsoleKit (do not ask me what all these pieces are and how they relate to each other, I do not know and I do not want to know). For the regular user, the result is the following: when they click on that button, it suspends their computer.

Read more Suspend your computer from a non-mainstream desktop environment