You may have encountered this problem. You have recently updated your Ubuntu. One of the updates was a kernel upgrade, say from version 2.6.28-11 to 2.6.28-15, for example. Following this upgrade, you rebooted your machine for the changes to take effect. Only Ubuntu does not come up. You see a message like this on your screen: Gave up waiting for root device. Common problems: -Boot args (cat /proc