A colleague of mine has built a kernel module that is part of our system. He wrote it for Linux 4.4 but in the meantime our servers got updated to 4.15. The kernel API changed from 4.4 to 4.15 so the module does not build anymore. He said he will update it, but in the mean time I figured it would be easiest to just use 4.4 in the meantime. I downloaded the kernel deb package and installed it. Now, after reboot I can't ssh into the machine any more. I just started this project and I'm already tired of it. Every time I fix something a new issue appears. And I did not even start what I am supposed to do