I have a recent installation of Ubuntu 14.04.4 that is freezing at the "Loading initial ramdisk" stage of booting. What is the best way to troubleshoot this?
The hardware is a Lenovo Thinkpad e410, with an Intel i3 processor, Intel graphics, and a hardware-encrypted Samsung SSD. Ubuntu is installed under UEFI, and the kernel version is 4.2.0-35.
Everything was fine until a few days ago, except that graphics hardware acceleration was (sometimes? always?) not working correctly (images cutting into other windows, flashing blue, etc.). I eventually traced this to this bug and applied the fix suggested at #9, running "sudo update-initramfs -u -k all" afterwards. After the fix, the i915 driver did appear to load correctly, but it still did not appear to be working correctly. I then did two things: (1) updated the system, and (2) installed Flash for Firefox. Everything still appeared to be fine, with the exception of the graphics.
This morning, when I started my computer, the cursor was gone in Unity. I could still access the terminal, and decided to try undoing the above bug fix, running update-initramfs again afterwards. Rebooting, it froze at the urple screen. Rebooting via grub2's advanced menu, normal boot mode freezes at "Loading initial ramdisk." Recovery mode loads the ramdisk, then generates a few screens worth of errors including:
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ...[5 lines + call traces omitted]... ---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ...[more lines + call traces omitted]... ---[ end trace ... ]---
And that's it. Results are the same if I try booting into 4.2.0-27, in both normal (freezes at "Loading initial ramdisk") and recovery (lots of kernel panic output, then freeze) modes.
I can try modifying grub boot options, but I'm not sure how to do this in grub2 or which options to try. Or I can try booting the live disk, mounting the hard drive, and poking around from there, but I don't really know where to begin.
Any suggestions very much appreciated.