Yesterday when I got home, my laptop was acting crazy, programs were not working properly. First time I have seen that. I thought 'reboot and everything will be ok'.

When I did, I ended up in initramfs. It said 'you need to run fsck manually' I guessed and entered fsck /dev/sda9 (which is the partition for Ubuntu 16.04) fsck found various orphaned inodes, whatever that is, and afterwards I could boot again.

Does this mean my HD is going home? Time to buy a new laptop? This one is 3 years old. What causes the system to drop to initramfs?

During the day I often just shut the lid on the laptop at the end of a class. That, combined with connecting to overhead projectors might get the system confused I suppose.

https://serverfault.com/a/280728

ohdoho's answer was good, but I don't believe it provided a technically complete answer to this question. It dropped to initramfs because the root filesystem had errors that could not be automatically corrected. Thus it could not be mounted, which left you with only the filesystem and tools contained within the initramfs to work with. "Acting crazy" before rebooting could very well mean the HD is "going home", which is more likely than the whole laptop going bad.

This is the likely cause if you run out of battery after closing the lid.
Make sure you have you power events set correctly - I haven't used Ubuntu in years, so I can't advise.

Thanks for the answers. I make sure the battery is charged at all times. Actually I just bought a new battery.

What diagnostics can I run?