In XFCE you can change the screen DPI in the Font tab in the Appearance dialog, which will instantly take effect. If you want to script the change, e.g. when upon connection with a docking station, you can use the following command:

xfconf-query -c xsettings -p /Xft/DPI -s <NEW_DPI>

To display the current DPI, you can just omit the -s <NEW_DPI> part.

Automatically Dimming the Backlight on Battery

Since upgrading my Thinkpad to the latest Xubuntu I have noticed that after 10 seconds of inactivity the display backlight automatically dimms down, which makes reading text for more than a couple of seconds pretty annoying. The question had already been asked on askubuntu.com but the answer was gnome specific and I could not find the specified dialog on Xubuntu, nor could I find the options in gconf-editor.

Ruling Out the Causes

As changing the auto-dimming level and timeout in xfce4-power-manager-settings did not fix it, I consecutively killed the xfce4-power-manager process, xscreensaver and upowerd, all without any success

gnome-settings-manager it is

Finally I stumbled over this bug report where a gsettings command is given, that will change the timeout. A quick

gsettings set org.gnome.settings-daemon.plugins.power idle-dim-time <seconds>

will fix it.

gconf-editor - dconf-editor

After that, I also found a gui to edit the gsettings database called dconf-editor, which is found in the dconf-tools package. Inside, browse to org.gnome.settings-daemon.plugins.power and you will find more settings and even get to disable the power plugin alltogether.

The following steps are needed to use a brother scanner via network on Ubuntu 9.10:
  1. Go to the Brother driver page and download the right .deb file (32/64bit).
  2. Install the .deb file. If you just click it, gdebi will do that for you.
  3. Install gscan2pdf, a great GTK+ tool for scanning and exporting the scanned pages to various formats.
  4. Configure the scanner to be on the network. Depending on the installed printer model, the used tool will be called brsaneconfig, brscaneconfig2 or brscaneconfig3. For the MFC-7820N the command is: brsaneconfig2 -a name="Lars MFC" model="MFC-7820N" ip=192.168.1.3
    • The IP address has to be numerical, no hostname is allowed, DNS is not used.
    • The model is checked as well. If brsaneconfig complains, you better look it up on the Brother page.
    • Of course you are allowed to name your scanner whatever name you like.
There you go. ubuntuusers.de has a wiki page with detailed information on the subject (German).

Oh how I longed for that feature: Whenever I log into XFCE, I want my ssh key to be automatically added to my authentication agent. Although it took some time, I finally puzzled together all the pieces to make it work. So here it is. 3 simple steps to get auto-adding to work in Xubuntu karmic koala:
  1. Enable "start gnome environment" in XFCE settings
  2. Comment out the line "use-ssh-agent" in /etc/X11/Xsession.options. This prevents the ssh-agent from starting. Instead gnome-keyring-daemon's internal agent will be used. However ssh-agent would overwrite it's socket variable, so we disable it here.
  3. Place the following into your ~/.xprofile: if [ -n "$GNOME_KEYRING_PID" ]; then eval `gnome-keyring-daemon --start` export SSH_AUTH_SOCK fi
There you go. If it does not work after a re-login, leave a comment below. Further information regarding the GNOME startup process and the way gnome-keyring-daemon gets started (it's actually started twice, huh!) can be found in this bug report.

16. April 2010: Update for Lucid Lynx

Apparently my fix from above prevents things from working Lucid. Therefore, if you have problems, unset everything and it should work. Nice. It seems to be totally broken in lucid. After wasting already to much time for this, I filed a bug report about it, we'll see what happens: https://bugs.launchpad.net/ubuntu/+source/xfce4-session/+bug/564831.