What is file system check exit code 8?

Bitbucket63 wrote:

It would have been nice to know right from the start if exit code 8 indicates an unrecoverable file system error or not.

Mentioned above fsck_hfs indicates "some" status by exit value. 8 indicates a corrupt filesystem was found during a check, or repairs did not succeed. That's it. All you can do is run First Aid multiple times for some resolve. You can boot into single user mode and try from there.

Of course this will only fix logical damages and keep failing if the disk itself is damaged. There is no way to know if your system is recoverable or not.

Bitbucket63 wrote:

Again, the question is: What does exit code 8 indicate?

BobTheFisherman has it right.

Exit code 8 is a generic failure where a special character cannot be read, or a character is unexpectedly in the wrong place. Given that code is a series literally 10,000,000x strings of 1 and 0's things do go astray.

My only suggestion would be if re formatting did not fix the disk from DiskUtility's point of view, Format it in to some other partition table—when that is complete—reformat it again back to GPT extended journaled and see if it sorts itself.

All data of course will be lost on a reformatted Disk. How to create a boot clone

It is documented in many places. See https://www.google.com/search?q=file+system+check+ecit+code+8&ie=utf-8&oe=utf-8

It appears to be a corrupted disk which could have many potential causes.

Disk Utility from local SSD and Recovery Partition disagree

http://forums.macrumors.com/threads/file-system-check-exit-code-8-disk-wont-repa ir.1819660/

It means you have a corrupted disk. What else do you want? Disks can become corrupted in many ways. Reformatting your disk apparently did not fix the corruption. Follow the instructions already provided or try a new disk.