[SOLVED] laptop doesn't recognise external monitor

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[SOLVED] laptop doesn't recognise external monitor

Postby angela_p » 2018-02-12 09:25

I currently have Wheezy running on a Lenovo Thinkpad T540p, and about to do a fresh install of Stretch (as I want to start clean). I thought it best to try to get my external monitor running on Wheezy first, to ensure it works etc, before installing Stretch (especially given the problems I have had previously with NVIDIA). The external monitor I am trying to get working is an ACER X213w LCT widescreen. When I plug it into my laptop's VGA port, then reboot, a message appears on the monitor saying “no signal”. So it looks like the monitor recognises it's been plugged into the laptop, but the laptop does not recognise it.

I have Optimus technology and when I originally installed Wheezy, I had trouble getting it all working: I first had a blank screen and trouble getting GNOME to load (for memory I think removing /etc/X11/xorg.conf fixed the blank screen and allowed me to boot). I tried installing bumblebee but still had problems. So I installed xfce as I don't need to use advanced graphics, and this worked (so I didn't need to use optirun). Now (ie the past week since troubleshooting this) when I try “optirun firefox” it seems to work for some reason (although I'm not using this).

I tried to install intel-virtual-output as per the multi monitor set up instructions in bumblebee, but am having trouble installing it (I found a version of xf86-video-intel-2.99.911 older than Dec 2014 which needed compiling, I ran the configure script first and it gave errors, the main one being about package libdrm not found. I then stopped as I'm unsure whether I'm heading in the right direction and hence my post here).

I don't need advanced graphics or good battery life, so I'm now wondering, whether I actually need bumblebee at all to get my external monitor working? Could it be more simple in terms of just using Intel, and if so how do I do this? Or are there other options?

Other things I've discovered which may (or may not) be important:

I cannot find an option in the BIOS to disable Optimus etc, and I found a posting on a Lenovo forum that the T540p does not have this capability.

I don't know whether my VGA port is wired to Intel or NVIDIA, I'm having trouble working that out.

$ xrandr -q (only lists my laptop screen and doesn't recognise the external monitor, it's output is as follows:)

xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected 1920x1080+0+0 0mm x 0mm
1920x1080 0.0*


/var/log/Xorg.0.log: in this log it says it's using /usr/share/X11/xorg.conf.d, and that there's no Screen section available so using defaults (maybe this explains the xrandr output?)

/var/log/Xorg.8.log: this looks like it is coming from bumblebee and has references to config files in /etc/bumblebee as well as /use/share/X11/xorg.conf.d, and it also says there's no Screen section available so using defaults.

I'm wondering whether recognising/setting up the monitor requires Screen/Device/Monitor sections in a config file?

Should I be installing Stretch first, does it handle things differently/easier?

Also, if I need to I can buy a new monitor (as mine is not that recent) and I'm not attached to xfce, although I don't think these are the issue here.

I'm really confused (as is probably obvious by my post), I've looked at so many different things, if anyone can help point me in the right direction would be appreciated. Thank you.
Last edited by angela_p on 2018-02-20 07:54, edited 1 time in total.
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Re: laptop doesn't recognise external monitor

Postby bw123 » 2018-02-12 14:35

Should I be installing Stretch first, does it handle things differently/easier?


Yeah, I would not spend time on wheezy. The other questions are harder to answer, especially without access to the hardware. You have access, but you don't include any real info like lspci output or actually what drivers are being used for the outputs.

The way I approach things is more like a checklist.

ID the hardware
Research the hardware
Tweak it to best performance

It's kind of a circular pattern. I'm always finding out things about hardware on my machines, even old ones that I've had for years.

This is a good start for figuring out the hardware.
https://wiki.debian.org/HowToIdentifyADevice

Once you do that, a few searches for the specific hardware and the word linux will take you places.
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Re: laptop doesn't recognise external monitor

Postby angela_p » 2018-02-12 22:00

Thank you. Maybe I'll just install Stretch - however I still don't understand whether I actually need to be heading down the bumblebee/nvidia direction.

I did have that information, I just hadn't posted it:

$ lspci -nn|egrep -i "3d|display|vga"
00:02.0 VGA compatible controller [0300]: Intel Corporation Haswell Integrated Graphics Controller [8086:0416] (rev 06)
00:16.3 Serial controller [0700]: Intel Corporation Lynx Point KT Controller [8086:8c3d] (rev 04)
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation Device [10de:1290] (rev ff)

$ optirun glxinfo|grep OpenGL
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: GeForce GT 730M/PCIe/SSE2
OpenGL version string: 4.3.0 NVIDIA 319.82
OpenGL shading language version string: 4.30 NVIDIA via Cg compiler
OpenGL extensions:

$ glxinfo|grep OpenGL
OpenGL vendor string: VMware, Inc.
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 0x209)
OpenGL version string: 2.1 Mesa 8.0.5
OpenGL shading language version string: 1.20
OpenGL extensions:
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Re: laptop doesn't recognise external monitor

Postby angela_p » 2018-02-20 07:52

I installed Stretch with xfce, did not install any extra graphics drivers or bumblebee, and xfce was able to recognise the screen. So it's all working now, thank you.
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