The system is a laptop with nvidia optimus. After an update (many packages including kernel and virtualbox 5), ubuntu 14.04 does not start no more.
Symptoms:
- boots into grub, Enter key on 14.04, screen turns black, the backlight led turns off, then on, then nothing happens except the fan going on high revs, nothing on the screen (black screen with backlight on)
- ubuntu 15.10 on another partition starts fine (no virtualbox there)
- no /var/log/syslog info
- to restart I need to turn it off
- purged everything nvdia - no luck
- forced reinstall virtualbox, no error messages - no go
- update, upgrade, install -f, autoremove - no difference
- tried older kernel versions - same thing
- it starts in recovery mode and I can continue normal boot (this is how I wrote this question).
Any ideas what to try next?