Have you looked at
https://sparkylinux.org/wiki/doku.php/sparky_rescue
man fsck is not the easiest to read, but will have solid info.
search engines
https://duckduckgo.com/?q=repair+fsck+%2Froot&t=ffnt&ia=web
old but quote below is wise http://bitsofmymind.com/2014/03/14/how-to-fix-fsck-your-root-file-system-that-you-have-to-boot-into-on-linux/
QuoteWhich makes sense as common knowledge tells us that running fsck on a mounted file system will most likely do more damage to it.
The best option
Your best option is simply to boot into another Linux, be it on a different partition, a USB drive or a CD and run fsck manually on the faulty partition, which can easily be unmounted if necessary because no OS is using it
So, on another machine download a rescue iso, Sparky's or any other one. Put it onto a usb. Read up and see if anyone else replies.
And think over whether the probable cause is in the hard drive or something that you did.
"smartctl" can give you info as to the overall health of you hard drives. "man smartctl" would give you the proper flags.
root@raunes:~# smartctl /dev/sda -H
smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.14.0-0.bpo.3-amd64] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org
=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED
smartctl has to be run as root (or in sudo) . It might not work for you in grub rescue mode, as it is your /root that is affected. It is a gentle test to see if you might need a new drive.
peace out, Mark