Ubuntu LiveCD screen resolution workaround

[carpie]

After much searching the web without success, I finally found my own solution to the 800x600 video resolution limitation with Ubuntu guests running in VirtualBox from a live cd.

First the issue: When running a live cd version of ubuntu (at least for 7.10 and 8.04) under virtualbox the only video resolutions available to you are 800x600 and 640x480. The solution in the FAQ (and the other half million posts on this issue ) is to "install the Linux Guest Additions and set up the vboxvideo driver." That's fine and dandy for an installed ubuntu, but hard to impossible on a live cd. (Yes, I did get them installed but kinda scratched my head when it told me I had to reboot to use it )

The underlying issue: After much research without resolution (pun intended), I started poking around myself. I loaded up my xubuntu livecd image and took a look at /var/log/Xorg.0.log. I noticed lines like the following output in the log:

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...
(II) VESA(0): Not using built-in mode "1024x768" (hsync out of range)
...

This lead me to...
The work around: Edit /etc/X11/xorg.conf

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sudo vi /etc/X11/xorg.conf

and add the following line under the "Monitor" section directly under Identifier "Configured Monitor" and before EndSection:

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        HorizSync         31.0 - 67.0

Now in virtualbox's Machine menu, select "Insert Ctrl+Alt+Backspace" to restart the VM's X server. It should then come up in a higher resolution! At that point you can use whatever display resolution setting application comes with your brand of ubuntu to set the resolution you want...

Unfortunately, with this being a live cd, you'll have to do this everytime you boot it, but if you want to try out unbuntu live cds in virtualbox, it seems to be the easiest way...

Hope this helps...

[Sasquatch]

Now in virtualbox's Machine menu, select "Insert Ctrl+Alt+Backspace" to restart the VM's X server. It should then come up in a higher resolution! At that point you can use whatever display resolution setting application comes with your brand of ubuntu to set the resolution you want...

Hitting that combination is not advised. If you run a Linux Host, that X will restart, not the VM's. Best to hit Host key + Backspace. The manual states that the Host key should be used for combinations like these, as the Host often grabs them even though the VM has the keyboard.

[carpie]

Hitting that combination is not advised. If you run a Linux Host, that X will restart, not the VM's. Best to hit Host key + Backspace. The manual states that the Host key should be used for combinations like these, as the Host often grabs them even though the VM has the keyboard.

Sorry if I wasn't clear. There is an option on the Machine menu that says "Insert Ctrl+Alt+Backspace" that sends an X reset to the VM. That's what I was suggesting you do as opposed to hitting "Ctrl+Alt+Backspace" on your keyboard. Using the menu is the same as hitting Host key + Backspace.

[slickvguy]

carpie,

I registered just to say THANK YOU! I was googling for a few hours trying to find a solution to this specific problem, and you have nailed it my friend. When using the virtual cd-rom w/ a LiveCD iso image you cannot mount the guest additions! One virtual cd drive only.

Note: On my Ubuntu livecd when I use this fix it changes the desktop icons, colors, etc., automatically for some reason. Strange, but not a problem.

Anyways...I'm now looking at a beautiful fullscreen 1280x1024 virtual machine. Perfect.

Thank you.

[carpie]

Glad it helped you! I've found the answers to countless problems by searching the 'net, so posting my own answer was the least I could do...

[AbtZ]

Exactly the solution i was looking for, but... How do we do now that Ctrl+Alt+Backspace is disabled by default in X?

[Sasquatch]

Exactly the solution i was looking for, but... How do we do now that Ctrl+Alt+Backspace is disabled by default in X?

You switch to a virtual terminal, called TTY, by hitting Host+F2, log in, then issue a sudo /etc/init.d/gdm restart. You can also just log off, which should restart X too.