MacBook Pro won't boot.. showing prohibitory sign.. Plz help!!!

Try to reinstall it again, and possibly again.


Sounds like something major was corrupted, so you might have to reformat/reinstall.


Check the installer log during installation.

(I think its under the 'window' menu during installation)

It should tell you what kind of error it's running into.

If it still fails after a reformat/reinstall, the hard drive might have problems.

Worst case scenario, just take it into Apple.

In Disk Utility, with your hard drive selected.
What does it say beside "S.M.A.R.T. Status :" (near the bottom right of the window)?

Sounds like a hard drive breaking down. (Assuming you have a mechanical drive, and not a retina MBP).

How old is the Macbook?

It _could_ be a hard drive "failure", although it's interesting that SMART status still shows "verified".

My suggestion is that you consider replacing the hard drive anyway. If the MB isn't too old, you might consider using an SSD, which will give a VERY nice speed boost (if your current drive is HDD). it will feel like "a new machine".

You ask, "What should I do?"
If it was me, I would do this:

1. Get a new SSD or HDD
2. Also get a USB3/SATA "docking station" (they're only about $25)
3. Put the NEW drive into the dock, connect it to the MB (or to your other Mac, if you have one available. Use whatever works.)
4. Install a fresh version of the system capable of booting and running the MB
5. When the installation was finished, boot up and create a "temporary account" (name it "administrator" or something like that). The purpose of the temp account is to get the drive "live and running" BEFORE you start migrating stuff onto it
HOW TO BOOT FROM THE DOCK:
Power down. Press the power-on button. As soon as you hear the startup sound, hold down the option key and KEEP HOLDING IT DOWN. The startup manager should appear. Select the docked drive with the pointer, tab, or arrow keys, then hit return. MB should boot from the docked drive.
6. Run any software updates to get the OS "up to current"
7. Now, use Migration Assistant to manually migrate over your account, apps, data, etc. (this assumes you can get some off the old internal drive. Or, you could try to re-construct from your backups)
8. Once all this is done, DO A TEST BOOT to make sure it will boot and run BEFORE you install it into the MB. Repeat the booting process described above.

When you get this far, NOW you are ready to open up the MB and "do the drive swap".
BE SURE TO USE THE RIGHT SIZE SCREWDRIVER TO REMOVE THE SCREWS (shouting very intentional). You can find guides for disassembly/reassembly on macfixit.com. Also note that some screws may be longer than others. Keep notes!

Once the new drive is in and the old one is in your hand, put the old drive into the USB/SATA dock. See if it mounts first, you never know. If it does mount, get what you want off of it and copy those files to the new drive.

When this is done, I suggest you try to re-initialize it using Disk Utility.
If it initializes ok, run the DU "Repair disk" feature on it about 5 times.
If it shows ok by that point, you can use it as a "scratch drive" -- that is, storage of stuff you might want to have around, but CAN "afford to lose".

You could also use CarbonCopyCloner (free to use for 30 days after downloading) to create a bootable clone of the new internal onto the old drive. Then keep it around as an "emergency booter".

I just had this happen to me literally about 30 minutes ago.

Just after I installed Parallels, well yesterday but first cold boot from yesterday.

How did I solve the problem? This is the weird part, after about 5 minutes of seeing the prohibitory sign I stepped out for about 10 minutes, when I came back my iMac was in the desktop and everything seemed normal.

I ran disk util verify disk and checked my console logs. I did see one disk i/o error in the vast error log on startup. But when I ran verify disk everything looked OK.

Just a random glitch? Anyway may be a sign my drive is on its way out?

CarreraGuy said:

I just had this happen to me literally about 30 minutes ago.

Just after I installed Parallels, well yesterday but first cold boot from yesterday.

How did I solve the problem? This is the weird part, after about 5 minutes of seeing the prohibitory sign I stepped out for about 10 minutes, when I came back my iMac was in the desktop and everything seemed normal.

I ran disk util verify disk and checked my console logs. I did see one disk i/o error in the vast error log on startup. But when I ran verify disk everything looked OK.

Just a random glitch? Anyway may be a sign my drive is on its way out?

Click to expand...

The boot into Single-User-Mode and run /sbin/fsck -fy on it. Then really consider getting an SSD into the Mac Book Pro.