installation: definition_demarrage

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Change the definition of the screen at startup

After you have installed Dapper, it may be necessary to change the screen resolution used at system startup (sequence during which the Ubuntu logo appears). This definition is chosen in the home screen of the CD-ROM (CD Desktop) via the [F4] and then used at every boot.

For newer versions of Ubuntu, you can get higher resolutions using framebuffer .

Technical details

When a screen resolution has been selected by pressing [F4] on the home screen of the Desktop CD (before installation), the parameter "vga" is saved in the file "/ boot / grub / menu.lst "and then passed to the kernel at startup. This parameter accepts different types of codes to indicate the chosen definition.
Further, a non-exhaustive table summarizing the codes found on various websites ...

Code table for the parameter "vga"

There are two types of codes - decimal or hexadecimal - one that can be passed as the other via the kernel parameter "vga".
Use 'hwinfo' to identify the modes supported by your graphics card:

  $ Sudo aptitude install hwinfo
 $ Sudo hwinfo - framebuffer

Or use the following table (note that some values in the table seem to vary according to the graphics card):

Definition			8-bit display		16-bit display		24-bit display
Size	Name	Ratio	decimal	hex.	decimal	hex.	decimal	hex.
640 × 480	VGA	1.33	769	0x301	785	0x311	786	0x312
800 × 600	SVGA	1.33	771	0x303	788	0x314	789	0x315
1024 × 768	XGA	1.33	773	0x305	791	0x317	792	0x318
1152 × 864	XGA +	1.33	353?	0x161	355?	0x163	356?	0x164
1400 × 1050	SXGA +	1.33	839?	0x347?	834	0x342	835	0x343
1600 × 1200	UXGA	1.33	796	0x31C	798	0x31E	799	0x31f
2048 × 1536	QXGA	1.33	?	?	?	?	850?	0x352?
3200 × 2400	QUXGA	1.33	?	?	?	?	?	?

640 × 400	?	1.60	?	?	829	0x33D	830	0x33E
1280 × 800	WXGA	1.60	867	0x363	868	0x364	869	0x365
1440 × 900	WXGA +	1.60	864	0x360	866	0x362	867	0x363
1680 × 1050	WSXGA +	1.60	872?	0x368?	?	?	873	0x369
1920 × 1200	WUXGA	1.60	892?	0x37c?	?	?	893?	0x37d?

1280 × 1024	SXGA	1.25	775	0x307	794	0x31A	795	0x31B
2560 × 2048	QSXGA	1.25	?	?	?	?	?	?

1280 × 720	WXGA	1.77	?	?	?	?	?	0x037b
1600 × 1024	WSXGA	1.56	?	?	?	?	?	?

Code 836 (0x344) seems to be used for 32-bit.
A page full of codes VESA is available here (in English).

Change the code

To change the code currently in use on your system, open the file "/ boot / grub / menu.lst" with your favorite editor.

  gksudo gedit / boot / grub / menu.lst

Then in the bottom of the file, locate the line that begins with one of the following ways:

  # # Eg DefOptions = vga =???  resume = / dev/hda5
   = Quiet splash # DefOptions

Where "??? "Represents the current definition of the startup screen. Examples: vga = 792 or vga = 0x318
If no mention of the parameter "vga" is made in the second line, you can always add, for example like this:

  # DefOptions = quiet splash vga =???

When the file "/ boot / grub / menu.lst" has been changed, use the command "update-grub" to apply the changes. This command is not required under Edgy Eft and later.
Home (Ubuntu 8.04), this command is necessary.