Questo documento è rivolto a chi riscontra problemi di riconoscimento o configurazione del proprio hardware (scheda grafica e monitor) con il server X.org.

Questo documento trae spunto dal Wiki Ubuntu (di cui è parzialmente la traduzione): https://wiki.ubuntu.com/FixVideoResolutionHowto

Introduzione

I sistemi [http://www.linux.org Gnu/Linux] utilizzano in genere il [http://www.x.org server X] per la grafica. I pacchetti relativi sono denominati "xserver-xorg" ed il loro avvio consente al kernel linux di avviare il server grafico su cui si basano tutti i moderni windows e desktop manager.

L'elevato numero di prodotti (monitor, schede video, mouse, tastiere) e di specifiche dei produttori, talvolta rendono complessa l'installazione del server X su sistemi Linux. Da questo punto di vista, Ubuntu ha fatto passi avanti notevoli nel facilitare la vita dell'utente, tuttavia, in caso di erroneo o impossibile riconoscimento, è utile sapere cosa succede "sotto il cofano" per riuscire a configurare manualmente il server X.

I sintomi tipici di un problema di installazione/configurazione di X.org sono: schermo nero, schermo a strisce o bande, immagine che sfarfalla, risoluzione errata, impossibilità di utilizzare una o più periferiche (mouse, tastiera etc...) ed infine un messaggio di errore che precede l'avvio del sistema in modalità terminale.

Qualunque di questi sintomi manifesta l'impossibilità per il server X di avviarsi o di configurarsi correttamente per l'hardware utilizzato.

In questa guida cercheremo di aiutare l'utente nella risoluzione dei problemi più frequenti, fermo restando l'utilizzo delle guide specifiche per drivers o schede grafiche particolari:

• [:Enable3DAtiRadeon(fglrx):Attivazione dell'accelerazione 3D su Ati Radeon] - Attivare l'accelarazione 3D su schede grafiche Ati Radeon con i driver Ati

• [:BinaryDriverHowto/Nvidia:Installazione dei driver Nvidia] - Installazione ed abilitazione corretta dei driver Nvidia

• [:InstallazioneDriverNvidiaConModuleAssistant:Installazione dei driver Nvidia con ModuleAssistant] - Installazione alternativa dei driver Nvidia

Inoltre si consiglia la copnsultazione della [http://xorg.freedesktop.org/wiki/FAQ FAQ di X.org] e dell'elenco dell'hardware supportato.

Verificare l'installazione

Prima di iniziare a configurare Xserver è sempre meglio accertarsi che i files necessari siano stati installati sul sistema, infatti, eventuali problemi di dipendenze possono impedire un corretto funzionamento. Questi problemi prescindono dalla configurazione e riguardano la corretta installazione dei pacchetti, prima di procedere verifica la corretta installazione, per farlo digita dal terminale:

dpkg -s xserver-xorg-core

Il sistema restituirà molte informazioni importanti:

Package: xserver-xorg-core
Status: install ok installed
Priority: optional
Section: x11
Installed-Size: 9944
Maintainer: Ubuntu X Maintainers <ubuntu-devel@lists.ubuntu.com>
Architecture: i386
Source: xorg
Version: 6.8.2-77
Replaces: xserver-xorg (<< 6.8.2-46)
Provides: xserver, xserver-xfree86
Depends: xserver-common (>= 6.8.2-77), libc6 (>= 2.3.4-1), libgcc1 (>= 1:4.0.1),                                            libxau6, libxdmcp6, zlib1g (>= 1:1.2.1)
Recommends: discover1, xresprobe (>= 0.4.13), laptop-detect, xkeyboard-config
Conflicts: libxfont-xtt, xserver-xfree86
Description: the X.Org X server
 The X.Org X server is an X server for several architectures and operating
 systems, which is derived from the XFree86 4.x series of X servers.
 .
 The X.Org server supports most modern graphics hardware from most vendors,
 and supersedes all XFree86 X servers.
 .
 If the discover, laptop-detect and xresprobe packages are installed,
 this package's configuration script will use them to attempt automatic
 configuration of the X server based on your information returned by your
 video card, mouse, and monitor.

In particolare la voce "Status" resituisce un valore: install ok installed che significa che i pacchetti sono correttamente installati. A questo punto si può procedere.

Configurare il Server X

Qualunque sia il metodo utilizzato, la configurazione del server X confluisce sempre nel file di configurazione xorg.conf che si trova in /etc/X11. In esso sono contenute tutte le informazioni di configurazione del server X che ci servono.

Questo file può essere modificato con l'apposita utility di configurazione, oppure a mano con un semplice editor di testo, descriveremo entrambi i metodi.

Attenzione prima di effettuare qualunque operazione è consigliabile salvare una copia del file "xorg.conf". Per fare ciò digitate al terminale questop comando:

sudo cp /etc/X11/xorg.conf  /etc/X11/xorg.backup

ora avete creato il file "xorg.backup" che è una copia esatat di "xorg.conf", potete continuare.

Metodo grafico

L'avvio del tool di configurazione richiede i privilegi di root, quindi da terminale digitate:

sudo dpkg-reconfigure xserver-xorg

1) Manage XFree86 4.x server configuration file with debconf [YES] 2) select the desired X server driver [vesa] 3) Enter an identifier for your video card [va bene il default] 4) blablablabla semplicemente OK 5) Please enter the video card's bus identifier [puoi lasciare in bianco] 6) Enter the amount of memory to be used by your video card [lascia pure in bianco] 7) Use kernel framebuffer device interface [NO] ... per evitare eventuali problemi 8) Please select the XKB rule set to use [xfree86] 9) blablablabla [OK] 10) Please select your keyboard model [pc104] 11) Please select your keyboard layout [it] 12) Please select your keyboard variant [lascia in bianco] 13) Please select your keyboard options [lascia in bianco] 14) Please choose your mouse port [/dev/psaux] 15) Please choose the entry that best describes your mouse [PS/2] per mouse 2/3 tasti normali [ExplorerPS/2] per mouse con rotellina 16) Emulate 3 button mouse [YES] 17) Enable scroll events from mouse wheel [YES] 18) Enter an identifier for your monitor [va bene il default] 19) Is your monitor an LCD device [NO] 20) Please choose a method for selecting your monitor characteristics [medium] 21) Please select your monitor's best video mode [1024x768 @ 70Hz] 22) Select the video modes you would like the X server to use [seleziona le possibili visualizzazioni alternative - tieni presente che quella predefinita è scelta al punto 21] 23) Please select your desired default color depth in bits [24] 24) blablabla [OK] 25) Select the XFree86 server modules that should be loaded by default [lascia pure i defaults] 26) Write default Files section to configuration file [YES] 27) Write the DRI section to configuration file [YES]

Metodo manuale

Introduction

This Howto is intended for those who have installed or upgraded to Hoary, and their screen resolution is very low. A possible reason for this is that your hardware (video adapter/monitor) may not have been detected properly. There are several fixes that I have seen in the forum and in the IRC support channel. One solution will work for one person and another solution will work for someone else. I hope to provide several different solutions here, ranked in decending order from what I have seen to be the most popular and successful solution to those solutions that have helped only a few. This way, hopefully it will provide an answer for everyone. Let's start with the most popular fix.

Run the Autodetect Script Again

I'm not sure that this is the solution that works for the most people actually, but it most certainly is the quickest and easiest one. All we're doing is running the same script that tried to detect your video hardware when you initially installed. Sometimes this does help. Run the following command.

sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.custom
sudo sh -c 'md5sum /etc/X11/xorg.conf > /var/lib/xfree86/xorg.conf.md5sum'
sudo dpkg-reconfigure xserver-xorg

After completion, close any open windows or programs you have running on your desktop and press CTRL-ALT-Backspace to restart X. You will be asked to log into your GNOME session again and hopefully everything will be fixed. If not, try the next solution.

Undetected Monitor Specs

Open the file /etc/X11/xorg.conf in your favourite text editor. I'll assume you are using nano for an editor as it is fairly straight forward.

sudo nano /etc/X11/xorg.conf

Now look for a section in that file called Section "Monitor". Once you find this section, look at the lines of text between Section "Monitor" and EndSection. There should be two lines in there that begin with the words HorizSync and VertRefresh. If those lines don't appear there then don't worry. There is a good chance that we've found the problem already!

You will need to gather two bits of information for your monitor now, either from your User's Manual, the command line, or from online. We need the horizontal sync frequency (usually measured in kHz) and the vertical refresh rate (usually in Hz). Finding these values usually just involves searching [http://www.google.com Google] with the model of your monitor. Both of these values are typically given in a range such as "30-98 kHZ" or "50-160 Hz". Write those values down, or otherwise keep them handy. Additionally, if your monitor supports it, you can just run the following command:

sudo ddcprobe | grep monitorrange

The first two values returned are your HorizSync rates, the second pair is your VertRefresh values.

There are two ways to enter your monitor information into the file. One way is to run the following commands which will regenerate the file and ask you for the values in the process.

sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.custom
sudo sh -c 'md5sum /etc/X11/xorg.conf > /var/lib/xfree86/xorg.conf.md5sum'
sudo dpkg-reconfigure -plow xserver-xorg

The second way is to simply add those values to our /etc/X11/xorg.conf file with a text editor. But first, lets make a backup of that file just in case an error is made.

sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.backup

Editing this file so that it works involves adding two extra lines to the Section "Monitor" section of that file. For example, mine is shown below.

NOTE: Don't change anything that is written in the file for now. Just add the two lines. The snippet from my file is just an example and may not apply to your hardware.

Section "Monitor"
     Identifier         "FLATRON 995F"
     Option             "DPMS"
     HorizSync          30-96
     VertRefresh        50-160
EndSection

Now save the file, close all open applications, and press CTRL-ALT-Backspace to restart X. Assuming all goes well, you will be prompted to log into your session again.

NOTE: - If you are using XFree86 then you needed to edit /etc/X11/XF86Config-4. Also if you have an issue where only 800x600 is available in the dropdown for screen resolution, then modifying the Modes line within the section in that file called Section "Monitor" and adding the required resolution could solve this.

        SubSection "Display"
                Depth           24
                Modes           "1024x768" "800x600" "640x480"
        EndSubSection

Resolution is not delivered by the vBios

This problem appears sometimes for laptops with "non-standard"-screen resolution in combination with certain Intel graphic-chips. Background: It seems like the Video Bios (vBios) has to deliver the right resolution for the lcd-screen to enable the autoconfiguration to set this resolution. However sometimes the right resolution is not delivered and consequently the right resolution can not be implemented. You can fix the problem by overwriting the vBios setting in the RAM by using a program called 855resolution.

Here is the description of the 855resolution-developer: "855resolution is a software to change the resolution of an available vbios mode for the 855 / 865 / 915 Intel graphic chipset" To install 855-resolution on Ubuntu 5.10 make sure that you have includet the "universe" repository and type:

sudo apt-get install 855resolution

Once the program is installed you can use the program to list all available vBios modes:

sudo 855resolution -l

The result should look similar to:

855resolution version 0.4, by Alain Poirier

Chipset: Unknown (id=0x25908086)
VBIOS type: 2
VBIOS Version: 3412

Mode 30 : 640x480, 8 bits/pixel
Mode 32 : 800x600, 8 bits/pixel
Mode 34 : 1024x768, 8 bits/pixel
Mode 38 : 1280x1024, 8 bits/pixel
Mode 3a : 1600x1200, 8 bits/pixel
Mode 3c : 1400x1050, 8 bits/pixel
Mode 41 : 640x480, 16 bits/pixel
Mode 43 : 800x600, 16 bits/pixel
Mode 45 : 1024x768, 16 bits/pixel
Mode 49 : 1280x1024, 16 bits/pixel
Mode 4b : 1600x1200, 16 bits/pixel
Mode 4d : 1400x1050, 16 bits/pixel
Mode 50 : 640x480, 32 bits/pixel
Mode 52 : 800x600, 32 bits/pixel
Mode 54 : 1024x768, 32 bits/pixel
Mode 58 : 1280x1024, 32 bits/pixel
Mode 5a : 1600x1200, 32 bits/pixel
Mode 5c : 1400x1050, 32 bits/pixel

If the resolution of your sceen is not present then you can permanently overwrite a unused mode by the value of you screen. For example if you want to overwrite the mode 41 by the resolution 2400x1600 edit the the file /etc/default/855resolution

sudo gedit /etc/default/855resolution

Your file should look similar to: {{{} # # 855resolution default # # find free modes by /usr/sbin/855resolution -l # and set it to MODE # MODE=41 # # and set resolutions for the mode. XRESO=2400 YRESO=1600 }}} This will ensure that the vBios mode 41 is overwritten in the RAM at boot-time, before initializing the X-windows. Since the resolution is now available in the vBios your system should automatically be able to set the right resolution after rebooting.

Incorrect DefaultDepth

Sometimes the automatic X configuration sets the colour depth to a value higher than some hardware can properly handle. To see if this is the case for you, first backup your /etc/X11/xorg.conf file.

sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf.backup

Now open the file in your favourite text editor. I'll assume you'll use nano for now since it is relatively simple to use, but you can use whatever text editor you like.

sudo nano /etc/X11/xorg.conf

Search for the word DefaultDepth (notice it is one word) in that file. The default colour depth set by Hoary is typically "24", but as mentioned, some hardware may not be able to use a value that high. It's pretty safe to change it to something like "16" just to test whether it solves your video problems or not. If this change does not solve anything, it is just as simple to change it back the way it was.

Once the value of DefaultDepth is changed, save the file, close all open windows on your desktop, and press CTRL-ALT-Backspace to restart X. Assuming all goes well, you will be prompted to log into GNOME again, hopefully at a higher resolution.

The End

So far, this is all of the possible solutions I've collected for this problem. If none of the above corrected your situation, consider posting your question in the [http://www.ubuntuforums.org Ubuntu Support Forum] or in the #ubuntu IRC support channel on the irc.freenode.net network.

CategoryDocumentation