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I am running Ubuntu 12.04 (beta) with a triple head setup and GNOME 3 desktop (ie "GNOME" selected not "Ubuntu" at login screen). It seems that it handles multiple monitors by blessing one monitor to receive the Activities bar, Clock, Login Menu, etc. Let's call this the "primary" monitor. How do I change it (permanently) ?

Update: Ok so:

$ xrandr --output DFP4 --primary

Does the trick temporarily. How do I make it permanent? I'm using latest fglrx ATI Catalyst driver

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up vote 36 down vote accepted

By opening System Settings > Displays you can change your "primary" screen by dragging the black little bar to the display you want and hit the Apply button. Restarted my PC and i didn't have to use xrandr anymore ^_^

Better explanation than mine you can find here:

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Found a solution here: Apparently, there's no longer such a thing as "Primary Monitor" (at least with my setup). With the Displays config window open, I had to hold down the alt key and drag each of the panels to the window that you want to see them on. – Lawrence I. Siden Dec 21 '12 at 23:29
Would it kill them to have a tick box rather than assume people will see that little black bar and then try moving it? I was scratching my head for ages until I read your post... thanks. – Steve Apr 15 '13 at 3:48
Your suggestion didn't work (I was not able to drag the little bar on Ubuntu 12.10 Gnome). Yet, disabling the secondary screen and enabling it again moved the little bar ;) – Sosi Aug 11 '13 at 19:54
Apparently this is not the case for ubuntu 14.04. – Alessandro Cuttin May 2 '14 at 7:24
Coming from OSX, this is what I tried. However, the bar does not seem draggable on Gnome 3.14.4 (Debian Jessie). – Joost Nov 23 '15 at 17:47

What I did:

places>home folder. Under view, check show hidden files. find monitors.xml and open it with text editor. make a copy just to be safe.

identify the monitor you want to be primary (vendor brand, resolution etc) and look for the command line < primary>no< /primary>. change it to < primary>yes< /primary>

Save the doc and reboot to see if it took.

hope that helps someone out there.

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echo -e "xrandr --output DFP2 --primary" >> ~/.bashrc

Or add xrandr --output DFP2 --primary at the end of .bashrc

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I have a Three monitor Layout in Ubuntu 14 LTS. One monitor is positioned Vertical. I plugged the monitors in a way that the log on screen is in one of the horizontial monitors!

I used arandr (apt-get install arandr) to adjust the monitors layout and saved the layout file, for example /home/username/

I had only to add --primary to the desired monitor and put the file to the Startup Applications of Ubuntu! (At the command field of 'Add Startup Program' just point and klick your edited layout file!

xrandr --output VGA-0 --mode 1920x1080 --pos 3000x532 \
  --rotate normal --output DVI-D-0 --mode 1920x1080 \
  --pos 1080x532 --rotate normal --primary \
  --output DVI-D-1 --mode 1920x1080 --pos 0x0 \
  --rotate left --output HDMI-0 --off
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