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How to Fix Prohibitory sign mac OS X

Mac users encounter with no. of problems or warning signs while booting Mac OS X. “Prohibitory sign” is common one among all the warning sign which Mac users face. Prohibitory sign on startup is the indication of trouble on Macintosh system running Mac OS X. It symbolizes the same meaning as a Sad Mac icon and the Chimes of death on pre-OS X Mac. This means that there is trouble in Mac which makes difficulties in booting. The Prohibitory sign is a large, deep –gray in color circle with a diagonal line in the middle of it, alongside a lighter grey screen. Along with this sign, you might also get “broken folder”.

The Prohibitory sign mac OS X indicates that system has found a bootable installation of Mac OS X on the system but there is something wrong in it. It might be possible that either the setting between software and hardware component is not in the proper agreement or in the OSX installation there is some critical components are missing. Such situation makes unable to boot system and it might be possible that you face the loss of data.


Those Mac users who use multiple bootable installation of OSX are prone to get this error. There would be full access by you to the file system of another Mac OS X installation when booted in one installation. This may cause unintentional changes of critical system files. If you are running Boot Camp, you may not face such kind of behavior, as by default Windows cannot access HFS + file system.


Now to fix the issue of prohibitory sign mac OS X, here are some solutions---


  1. Starting system in Safe mode can solve the problem temporarily.

  2. Reset PRAM— Now to reset PRAM (Parallel Random Access Memory), hold option + Command + P + R keys just pressing power button and system reset continually and while they are held down they make the boot chimes. Continue this and complete this cycle for few minutes and then release the keys, after that hope system will boots.

  3. Repair DISK— As you system is not booting so you can try to booth through OS X installation DVD. Try to run file for system check and permission fixes on boot drive.

  4. Replace mach_kernel file— if your current affected system have FireWire capability and you have another mac machine to access then connect them. Now reboot your current affected system by holding “T” key. After this your system will put in Target Disk mode and this will appear on the second Mac's desktop. Now come to the second computer and insert DVD of OS X installation. You should choose the same version of OS X which is running on the current affected computer. Now launch the Terminal. Now copy mach_kernel file from the DVD to the attached FireWire hard drive. To do this you can follow this command.

    5. sudo cp /Volumes/"DVD_MEDIA_NAME"/mach_kernel /Volumes/"FIREWIRE_HD"

    Now copy and paste the command. After that you should change "DVD_MEDIA_NAME" to the name of the OS X installation DVD. After this change the name of "FIREWIRE_HD" to the name of the mounted FireWire drive. After completing this command now eject FireWire hard drive from system and turn off the current affected system and now again turn it on. Hopefully your system will boot normally once again.


  5. If still you are not able to fix the problem of prohibitory sign on startup. Then you should try to format hard drive and reinstall Mac OS X once again. Formatting and installation of OS once again can solve most of the problem.

But along with this you will also get the problem of data loss if you haven’t backup of your system. But you needn’t to worry as you can fix this problem with Mac file recovery software. Software is well efficient for the recovery of lost, deleted missing or corrupted data from Mac OS X. Prohibitory sign snow leopard is also a problem with the snow leopard user but after tryi ng this if you need to recover files then you can use this software to recover deleted or lost files from snow leopard also.