OK, ubuntu stabilized, steam client reinstalled (that was broken), KSP runs, I have all saves so here´s the craft file:
http://pastebin.com/MjNL5nhE
This is the subassembly that was meant to be placed under a HECS6 and a straight C7 brand adapter. The crash happened when I tried to make Ubuntu default screenshot (PrtSc) of the subassembly not connecting to the bottom of the tank. The subassembly was built in SPH, while the main craft was built in VAH. This made the whole system crash with no response whatsoever, so next step was powering down. This caused damage so next bootup manual fsck was needed, but it kept running. Tried to make a screenshot again, same happened, but also damaging the steam launcher.
Ubuntu version is 16.04 (64bit), not much stuff installed so far. Steam (with 4 games), Wine with 2 games, some browsers, and some smaller apps like Kazam, QMMP, but those should have nothing to do with this, especially that they were not running. The PC is an Acer Aspire v3-772g, with memory expanded to 16Gigs.
Re-rooting solved the basic problem, I can now fit the subassy to the tank correctly (big shoutout to Harry, thanks mate), but if you´re hunting bugs and I can help you with further information please let me know!