FSCK Problem, Superblock

Posted on 2013-10-27
Medium Priority
Last Modified: 2013-10-29
I detonated a software bomb from misuse of unix dd on 17-inch Macbook Pro

Was using unix dd for years to backup/restore Macs, but got careless.
Forgot to use unix pdisk prior to using unix dd

1) Can't boot anything from DVD drive
2) Brief error message:  "superblock bad, use fsck -b to fix"

Tried These Things
1) Used online hookup with Apple via keyboard command-D after reboot "gong" sound.

Distant Apple online server downloaded tools like "Disk Utility" to my broken Mac.

Naively thought that I could just re-partition the 3-year old Mac, no luck for fsck problem.

Now no known way for me to access broken superblock area of my internal 512GB SSD.

Even command-D after reboot no longer works.

Before my self-inflicted software bomb, I was happily running the just-released new "Maverick" OS 10.9 from Apple, everything worked just ducky.

My knowledge of unix is almost zero, aside from me using stray commands like dd and pdisk for years.

I am almost certain there is no hardware problem.

I do not have sufficient knowledge to try to fix this, or to even follow simple unix instructions from others.

My guess is that a real unix expert   _might_   be able to revive my beloved Mac, but of course he would have no motivation to do so.

Any suggestions from Mac gurus out there?

Suicide for me comes to mind, but no bridges around here to jump from.

SuperSenile -
Question by:SuperSenile
  • 2
LVL 53

Expert Comment

ID: 39604303
Do you have a second Mac handy? Can you use Target Disk Mode?

LVL 53

Accepted Solution

strung earned 1600 total points
ID: 39604308
Also, will the computer boot if you hold down command-R?
LVL 81

Expert Comment

ID: 39604671
There are multiple locations where the superblock is stored.
On Linux using mkfs.filesystemtyoe -N will rerun the creation of the filesystem without making any changes to the hard drive/partition.

Using one of the listed items you can repair/fsck the drive.
But since you ran dd the above deals with filesystem table corruption, loss access to the primary superblock.

Author Closing Comment

ID: 39609546
Thanks strung, your "command-R" led me to a great solution.

4-year old MacBook Pro (17-inch) now happily running Apple's newest
operating-system "Maverick" version 10.9

Likewise the external boot drive attached to the MacBook is fixed,
now running Maverick also.

Only nagging problem might be that I could still have a corrupted "superblock"
on the internal drive of the MacBook.

I would not know what a superblock is even if one bit me in the buttocks.

I   _think_   the superblocks are somewhere just past the boot code.

So I will create a 2nd question on Experts Exchange about hot to check
whether a superblock is corrupted or not.

Am typing this comment in the dark without a lighted keyboard on
a 7-year old Apple "Lombard" portable which is too old to "communicate"
with my newer Mac computers.

I will get around to thanking the other experts here because their information
helped me greatly to remedy this vexing problem.

SuperSenile -

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