Recently upgraded my Ubuntu 14.04 server at 1and1 with apt-get update and apt-get upgrade to find out that the server is no longer accessible. Was still able to connect to the server via serial console supplied by 1and1 and found out that the server was having trouble setting up network interfaces during boot process.
After further investigation there seemed to appear a new network interface called p10p1 and a bit of digging through the internet I found this blog post with a description on how to fix the issue. The culprit seems to be biosdevname package which does not work well with 1and1 servers. Followed the instructions on the blog post and server is back up and running.
In case the original post disappears from the Internet, here are the steps to fix this issue.
First connect to the server using serial console supplied by 1and1. You can find the connection details on your 1and1 Control Panel.
Log in with your username and password. Then run the following commands:
sudo apt-get remove biosdevname sudo update-initramfs -u sudo reboot
You can find more details about the issue and links to StackOverflow explanations in the original blog post.