Since acquiring a small fleet of HP Chromebooks for use in network testing, I’ve discovered that once in a blue moon, one of them that’s lost power while running will have trashed its Linux boot configuration – in which case it hangs at the SeaBIOS “Booting from Hard Disk…” black screen indefinitely.
The fix is obscure but doesn’t take long. What you need to do is boot into ChromeOS, but don’t log in. Instead, press ctrl-alt-F2 (probably ctrl-alt-right-arrow on most Chromebook keyboards) to get a bash login. Log in as chronos, no password. Sudo -s to become root. Now run the “mount” command, with no arguments – you should see a few partitions from your system disk mounted; what the device name is can vary from Chromebook to Chromebook. Mine is /dev/mmcblk0, so partitions look like /dev/mmcblk0p7.
Standard chrx disk layouts that preserve ChromeOS should have the Linux partition as p7 on the system disk; so you’ll be looking at something like /dev/sda7 or /dev/mmcblk0p7. You’re going to make a temp directory, mount that Linux partition on the temp directory, then chroot inside it so that you can update the bootloader. Adjust that first mount command as necessary for your system, and you’re off to the races:
mkdir /tmp/a mount /dev/mmcblk0p7 /tmp/a mount -o bind /proc /tmp/a/proc mount -o bind /dev /tmp/a/dev mount -o bind /dev/pts /tmp/a/dev/pts mount -o bind /sys /tmp/a/sys mount -o bind /run /tmp/a/run chroot /tmp/a /bin/bash dpkg-reconfigure grub-pc
That’s it. dpkg-reconfigure will ask you a few questions, including one about the boot command line – which will come up blank, and which you can leave blank. Aside from that, enter your way through; you’re done in a few seconds, after which exit exit exit your way out, reboot, and your Linux installation will boot again!