A few weeks ago I had a severe issue with my laptop, and posted a question here detailing my issue: Prohibition Sign and Can't Reinstall OS XProhibition Sign and Can't Reinstall OS X
Today, a friend of mine was having very similar issues which prompted me to run First Aid using Disk Utility. The message I received was "First Aid found corruption that needs to be repaired" with instructions on how to do so. I then restarted my laptop, and lo and behold, it would load up partway and then just shut off. Restarting several times yielded the same results.
Booting into Recovery Mode once again didn't work -- no option to re-install & verify/repair disk on there was useless. Used Internet Recovery mode which proved just as useless. Booted into single user mode and ran "fsck -fy" like last time, except this time I kept receiving "The volume Macintosh HD could not be verified completely." along with Disk I/O errors.
Tried running several variations of fsck_hfs -r /dev/diskxsy to no avail -- kept getting Disk I/O errors & the messages "corruption was found and needs to be repaired."
By absolute dumb luck, I came across an obscure fix that worked: https://discussions.apple.com/message/23205771#23205771?ac_cid=tw123456%2323205771
I followed the instructions there and it finally worked. I immediately ran First Aid again, and received the exact same original error message. Obviously, I am terrified to restart my computer or try anything, so I'm at a loss at what to do, other than make a backup. My SMART status is Verified. Any help appreciated!
