In recent releases of Ubuntu (at least 10.x) by default the non-graphical console attempts to use the max possible resolution supported by the connected monitor. Other than being hard on the eyes, this can cause issues with some KVM units and even more issues for headless machines that need to be troubleshooted with a crash cart. The worst result is ‘unsupported video mode’ displayed on the monitor or KVM which only a full reboot can fix.
The solution is to edit /etc/default/grub. Change the GRUB_CMDLINE_LINUX_DEFAULT line (9th line or so) to be the following:
GRUB_CMDLINE_LINUX_DEFAULT="nomodeset vga=768"Then issue the following command and reboot:
update-grub
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