You're right, fbdev managed the graphic interface...

I correct the boot options, Now, Nouveau works !

Cf the new Xorg.log

xrandr give this output :

Screen 0: minimum 320 x 200, current 1440 x 900, maximum 4096 x 4096
DVI-I-1 connected 1440x900+0+0 (normal left inverted right x axis y 
axis) 408mm x 255mm
    1440x900       59.9*+   75.0
    1280x1024      75.0     60.0
    1280x960       60.0
    1280x800       74.9     59.8
    1152x864       75.0
    1024x768       75.1     70.1     60.0
    832x624        74.6
    800x600        72.2     75.0     60.3     56.2
    640x480        75.0     72.8     66.7     60.0
    720x400        70.1

Thank you a lot.

I have only a little problem now. In all applications, the displayed 
color for the text is not correct. It's green khaki instead of black. 
(cf the screenshoot)

Can it come from Nouveau?

Le 28/10/2014 22:24, Ilia Mirkin a écrit :
> There is no sign of the nouveau kernel module being loaded. Make sure
> it's loaded, otherwise it won't work. Some distributions blacklist it
> in modprobe.conf or a related file. I believe the nvidia blob
> installer might as well.
>
> Actually, looks like you've explicitly disabled it --
>
> Oct 28 21:57:22 victorlefevre-MS-7235 kernel: [    0.000000] Kernel
> command line: BOOT_IMAGE=/boot/vmlinuz-3.13.0-38-generic
> root=UUID=7b0559d9-fbbe-4635-b244-bda94aa0a640 ro quiet splash
> nomodeset vt.handoff=7
>
> "nomodeset" turns off all modesetting, which disables nouveau from
> being loaded. Remove that, and you'll get further.
>
> On Tue, Oct 28, 2014 at 5:15 PM, Victor Lefèvre<victorlefevre@free.fr>  wrote:
>> Yes. I attached the logs.
>>
>> (There is several error messages.)
>>
>> Le 28/10/2014 21:43, Ilia Mirkin a écrit :
>>
>>> Output name 'default' is not the name of an output nouveau can produce
>>> (or nvidia for that matter, afaik). This is the vesa driver or...
>>> something. Can you supply xorg log + dmesg?
>>>
>>> On Tue, Oct 28, 2014 at 4:40 PM, Victor Lefèvre<victorlefevre@free.fr>
>>> wrote:
>>>> Hi Illia,
>>>>
>>>>
>>>> With Nouveau :
>>>> xrandr: Failed to get size of gamma for output default
>>>> Screen 0: minimum 1024 x 768, current 1024 x 768, maximum 1024 x 768
>>>> default connected 1024x768+0+0 0mm x 0mm
>>>>      1024x768       76.0*
>>>>
>>>>
>>>> With the Nvidia Driver :
>>>>
>>>> xrandr: Failed to get size of gamma for output default
>>>> Screen 0: minimum 640 x 480, current 1280 x 1024, maximum 1280 x 1024
>>>> default connected 1280x1024+0+0 0mm x 0mm
>>>>      1280x1024       0.0*
>>>>      1024x768        0.0
>>>>      800x600         0.0
>>>>      640x480         0.0
>>>>
>>>>
>>>> Le 27/10/2014 05:19, Ilia Mirkin a écrit :
>>>>
>>>>> What does 'xrandr' output?
>>>>>
>>>>> On Sun, Oct 26, 2014 at 10:51 AM, Victor Lefèvre<victorlefevre@free.fr>
>>>>> wrote:
>>>>>> Hi everybody,
>>>>>>
>>>>>> I'm using Lubuntu 14.04 on an old desktop PC with a NVIDIA GeForce 7600
>>>>>> GS
>>>>>> and a screen of 19 inches.
>>>>>>
>>>>>> The maximal resolution of my screen with Nvidia drivers is 1280x1024.
>>>>>> (In
>>>>>> particular, I use the Nvidia 331.89 driver)
>>>>>>
>>>>>> With Nouveau driver, the maximal resolution falls to 1024x768.
>>>>>>
>>>>>> Is there a solution for increasing the maximum resolution with Nouveau
>>>>>> ?
>>>>>>
>>>>>> Best regards,
>>>>>>
>>>>>> Victor Lefèvre
>>>>>> _______________________________________________
>>>>>> Nouveau mailing list
>>>>>> Nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org
>>>>>> http://lists.freedesktop.org/mailman/listinfo/nouveau