UNEXPECTED INCONSISTENCY - run fsck manually

[oygle]

Today I booted up Kubuntu 16.04.2 LTS and it just hung. So, booted to 4.4.0.89 recovery mode; quite a few message about the hard drive.

dev/sda1/ UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY
fsck excited with status code 4
Failure: File system check of the root filesystem failed
The root filesystem on /dev/sda1 requires a manual fsck

I was able to use a USB .iso and can boot to that okay. Can browse the hard drives. I do have smartmon installed; not sure if that helps.

What fsck command do I use please ?

Edit: extra info - I got the computer in 2008, so the main HDD is at least that old (plus ram and other hardware), and the 2nd HDD is way beyond that. Possibly 12 years or more.