as the title says... The automatic kernel update by ubuntu 15.04. broke the wifi driver after the reboot. I can still use the 3.19.0-16 kernel with working wifi, but I thought I'd mention this issue here.
Can you connect your machine to the internet and do an apt-get update/upgrade? My wifi is working and here is my uname -a:
Linux ronin 3.19.0-18-generic #18~14.04.1-Ubuntu SMP Wed May 20 09:38:33 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
So I am on kernel 3.19.0-18 on 14.04 and have not had issues. On initial upgrade, wifi dropped out but doing an apt-get update/upgrade installed updated dependencies for the new kernel and wifi functionality returned to normal.
Some suggestions for how to get connected: USB -> Ethernet adapter or use your phone as a Mobile hotspot. I used my iPhone 6+ as a mobile hotpsot and connected it to my machine via USB cable.
I thought I tried it afterwards and it did not work, but today I tried it again, some more packages got upgraded, but I think the apt-get dist-upgrade did the trick. so now I'm running 15.04 with the 3.19.0-18 kernel and wifi works fine. thank you for your help!
No problem, I am glad it resolved your issues!
I think we are very close to having a repeatable upgrade process for getting the new XPS 13's to a stable Ubuntu experience.
I got this same issue in my Dell XPS 13 (9343) after installing the Ubuntu 15.04 updates. And it was also solved after a 'dist-upgrade' and a restart, as you say. So wifi is back with the 3.19.0-18 kernel.
Glad to see Ubuntu running so smooth in this laptop.
Thank you very much.