How to make Ubuntu recognize an unknown external display (so I can adjust its resolution)?

Question

I have a Dell laptop with an external monitor attached (a Samsumg SyncMaster 931c).

My laptop display was recognized, and I can adjust its optimum resolution.
My external display is still unknown, thus I'm stuck at a lower resolution (1024x768):

enter image description here

I tried the "Detect Displays" button, but it didn't work, nothing happens.

I recently upgraded from Ubuntu 12.04 to 12.10.
Things were working before.
I don't know if I can actually change this configuration, or if this is a bug.

I searched for an answer here and also in Launchpad's website, but found none.

I even tried to install Nvidia drivers, and just messed things up.
It seems I wasn't even using nvidia before, as I guessed by looking at my additional drivers configuration:

enter image description here

My laptop has an Intel chipset, I guess:

$ dpkg --get-selections | grep -i -e nvidia -e intel
intel-gpu-tools                 install
libdrm-intel1:amd64             install
libdrm-intel1:i386              install
nvidia-common                   install
xserver-xorg-video-intel            install

I don't have an xorg.conf file (I think this is nvidia related, am I right?):

$ cat /etc/X11/xorg.conf
cat: /etc/X11/xorg.conf: No such file or directory

$ ls -l /etc/X11/
total 76
drwxr-xr-x 2 root root  4096 Out 19 23:41 app-defaults
drwxr-xr-x 2 root root  4096 Abr 25  2012 cursors
-rw-r--r-- 1 root root    18 Abr 25  2012 default-display-manager
drwxr-xr-x 4 root root  4096 Abr 25  2012 fonts
-rw-r--r-- 1 root root 17394 Dez  3  2009 rgb.txt
lrwxrwxrwx 1 root root    13 Mai  1 03:33 X -> /usr/bin/Xorg
drwxr-xr-x 3 root root  4096 Out 19 23:41 xinit
drwxr-xr-x 2 root root  4096 Jan 23  2012 xkb
-rw-r--r-- 1 root root     0 Out 24 08:55 xorg.conf.nvidia-xconfig-original
-rwxr-xr-x 1 root root   709 Abr  1  2010 Xreset
drwxr-xr-x 2 root root  4096 Out 19 10:08 Xreset.d
drwxr-xr-x 2 root root  4096 Out 19 10:08 Xresources
-rwxr-xr-x 1 root root  3730 Jan 20  2012 Xsession
drwxr-xr-x 2 root root  4096 Out 20 00:11 Xsession.d
-rw-r--r-- 1 root root   265 Jul  1  2008 Xsession.options
-rw-r--r-- 1 root root    13 Ago 15 06:43 XvMCConfig
-rw-r--r-- 1 root root   601 Abr 25  2012 Xwrapper.config

Here is some information I gathered by looking at other related posts:

$ sudo lshw -C display; lsb_release -a; uname -a
  *-display:0             
       description: VGA compatible controller
       product: Mobile 4 Series Chipset Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:48 memory:f6800000-f6bfffff memory:d0000000-dfffffff ioport:1800(size=8)
  *-display:1 UNCLAIMED
       description: Display controller
       product: Mobile 4 Series Chipset Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2.1
       bus info: pci@0000:00:02.1
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: pm bus_master cap_list
       configuration: latency=0
       resources: memory:f6100000-f61fffff
LSB Version:    core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:cxx-3.0-amd64:cxx-3.0-noarch:cxx-3.1-amd64:cxx-3.1-noarch:cxx-3.2-amd64:cxx-3.2-noarch:cxx-4.0-amd64:cxx-4.0-noarch:desktop-3.1-amd64:desktop-3.1-noarch:desktop-3.2-amd64:desktop-3.2-noarch:desktop-4.0-amd64:desktop-4.0-noarch:graphics-2.0-amd64:graphics-2.0-noarch:graphics-3.0-amd64:graphics-3.0-noarch:graphics-3.1-amd64:graphics-3.1-noarch:graphics-3.2-amd64:graphics-3.2-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-3.2-amd64:printing-3.2-noarch:printing-4.0-amd64:printing-4.0-noarch:qt4-3.1-amd64:qt4-3.1-noarch
Distributor ID: Ubuntu
Description:    Ubuntu 12.10
Release:    12.10
Codename:   quantal
Linux Batcave 3.5.0-17-generic #28-Ubuntu SMP Tue Oct 9 19:31:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

$ xrandr -q
Screen 0: minimum 320 x 200, current 2304 x 800, maximum 32767 x 32767
LVDS1 connected 1280x800+0+0 (normal left inverted right x axis y axis) 286mm x 1790mm
   1280x800       59.9*+
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA1 connected 1024x768+1280+32 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0* 
   800x600        60.3     56.2  
   848x480        60.0  
   640x480        59.9  
DP1 disconnected (normal left inverted right x axis y axis)

If there's anything else I can do, any other information I can post here, to help me configure this external display, please let me know.
If this is actually a bug, I apologize (I know bugs are not allowed here), but I really wasn't sure. And I will promptly file a bug report in Launchpad if that's the case.

Thanks a lot in advance. ;)

I did not see it in your post but I assume hitting the "detect display" did nothing? My 2nd monitor was detected when I hit that button ;) — Rinzwind, Oct 25 '12 at 14:57
Hi @Rinzwind, you're right, I tried the "Detect Displays", but it didn't work. I've edited the question with this information. Thanks. :) — andreoliwa, Oct 26 '12 at 13:16
If you want to be sure about your CPU, you can use this command; cat /proc/cpuinfo — jeremiah, Jul 10 '13 at 08:38
The issue I found was a bent ping on the vga cable, changed the cable and it worked like a charm..... — , Mar 18 '16 at 12:43

andreoliwa · Accepted Answer · 2014-08-22T20:05:09.387

21

The monitor cable was loose.
When I removed the cable and firmly plugged it in again, everything suddenly worked.
The monitor was recognized, and now I am using my previously desired resolution:

I feel kind of silly, because I never thought merely touching a loose cable would be of any help.

edited Aug 22 '14 at 20:05

answered Oct 27 '12 at 03:13

andreoliwa

441

So, it's fine now. Right? – TomKat Oct 27 '12 at 08:06
2

In my case, I had a VGA-DVI adapter plugged into my laptop, but the VGA end wasn't plugged securely into the adapter. – lreeder Jun 18 '16 at 02:54
2

I can't believe that this was actually my case too. – Lazar Ljubenović Mar 21 '17 at 16:55
Man, this worked like a charm! – DarkteK Aug 28 '17 at 14:25
It's not working for me, I tried another VGA cable and it changes nothing :( and it worked before, and I think it's a software causing this, as it started doing this after a restart – Amine M Mar 08 '19 at 09:50
I changed my cable and it fixed the problem. It would be interesting to know why it would happen when I opened Pycharm. Sometimes I could open and close the laptop lid to get it working again. – absynce Jul 01 '19 at 15:10

score 1 · Answer 2 · answered Jan 21 '16 at 08:03

1

I reconnected HDMI cable to a second HDMI port on my monitor and it fixed the problem of "unknown display"

answered Jan 21 '16 at 08:03

Marcin Radecki

11

Praveen Ravipati · Answer 3 · 2017-09-18T07:07:48.740

Just check your monitor specified VGA cable.There are different types of VGA cable.

Same problem I too faced,And Im using Dell s2216h(manufactured on July 2016).I tested with 2 - 3 cables,but no luck.

And finally i tried with "Dell Hotron VGA Cable 20276 VW-1 30V E246588 AWM Male to Male" it detected.

I dont know it may solves your problem,But this will helps you think in this direction too.

Thanks,

Praveen R

score 0 · Answer 4 · answered Dec 09 '22 at 09:24

0

I turned off computer, ejected monitor power plug and HDMI. After boot i attached monitor and that worked.

Just reboot or replacing cables did not work for me

answered Dec 09 '22 at 09:24

artmmslv

1
1

score 0 · Answer 5 · answered Oct 25 '12 at 14:47

1] There are some tools to automate the switching between monitors. you can use this tools, to automate it RandR, disper, displex or this one http://gnomefiles.org/content/show.php/Laptop+external+display+hotplugging?content=138742

2] Else, you may use the command xrandr to check if external monitor is connected. Then, create a script file that automatically uses your favourite resolution when the monitor is connected.

DO NOT connect it to the monitor now. Reboot, choose your favourite resolution and run

$ sudo cp /etc/X11/xorg.conf /etc/X11/xorg.undock

Connect monitor now, and reboot. Choose your new favourite resolution and run

$ sudo cp /etc/X11/xorg.conf /etc/X11/xorg.dock

Make a script file and add it to autorun:

# Check if system is docked or undocked and use correct xorg.conf file.
# <lm_name> is name of laptop monitor
DOCKED="`hwinfo --monitor | grep "<lm_name>" | wc -l`" 
# Next line is for debugging
# echo $DOCKED > /root/docked-state.txt 
if [[ $DOCKED = "0" ]] 
then 
cp /etc/X11/xorg.dock /etc/X11/xorg.conf 
else 
cp /etc/X11/xorg.undock /etc/X11/xorg.conf 
fi 
# End of dock-undock script

If the script doesn't work, replace DOCKED="hwinfo --monitor | grep "<lm_name>" | wc -l" # Next line is for debugging # echo $DOCKED > /root/docked-state.txt if [[ $DOCKED = "0" ]] then with if xrandr -q |grep -q "VGA-0 connected" ; then and run.

Hi TomKat. I don't have an xorg.conf file, so I didn't even try the rest of your solution. I've already edited the question with this information. Thanks anyway. ;) — andreoliwa, Oct 26 '12 at 13:18
I see this line in your result: -rw-r--r-- 1 root root 0 Out 24 08:55 xorg.conf.nvidia-xconfig-original Change the code accordingly. Will work. :-) — TomKat, Oct 26 '12 at 14:07
Hi! I've tried to install your 1) option software. It doesn't have a Quantal package, I had to change the PPA to a Oneiric package. And it didn't work, Ubuntu complains with an automated bug report on every launch. :/ — andreoliwa, Oct 27 '12 at 03:07
Try the script; it has worked on a few 12.10 systems I know, and also on another AU user's. — TomKat, Oct 27 '12 at 08:05

How to make Ubuntu recognize an unknown external display (so I can adjust its resolution)?

5 Answers5

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