Prohibitory sign on start up.

When starting up my MacBook, it boots to a white screen with a prohibitory sign (circle with a cross through it). I looked up some suggestions, but have not had luck yet. They were also older support posts (2010, etc).
My computer is a MacBook Pro from about 2009. It has the most recent Yosemite OS X.

Good Morning Mere-Glim,
If you are seeing a prohibitory sign and a gray screen when you start your MacBook Pro, follow the instructions in the resource below to resolve the issue:
Mac OS X: Gray screen appears during startup - Apple Support
https://support.apple.com/en-us/HT204325
Regards,
- Judy

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Power Mac G5 Showing Prohibitory Sign on Start Up?

Earlier this week my Power Mac G5 1.8 ghz dual started to show a prohibitory sign on start up. The hard drive was original to the machine (from 2004) and I wanted to upgrade it to a larger size anyhow, so I put in a new hard drive thinking that might solve the problem and give me an upgrade at the same time.
After I installed the new hard drive, I formatted it and did a restore from Time Machine of my system. When I restarted, I got the prohibitory sign again. I restarted holding down the option key to see if it found the new drive and it did. So I selected the new drive and it started up from the new drive with my restored system on it with no problem. Then I went to system preferences and made sure the new hard drive was selected as my start up disk. On restart, I got the prohibitory sign again.
Then the weirdness started. On subsequent restarts, I get the prohibitory sign intermitently whether I'm starting from the hard drive, my Leopard installation DVD, my Disk Warrior boot disk, or my old Panther installation disk. It seems to boot without any problem from the Apple Hardware test CD. I've run the extended apple hardware test and it didn't find any problems. Most of the time, I get a prohibitory sign no matter how I'm trying to boot up, but sometimes it will boot from the Leopard installation disk or the hard drive, but when it does, it freezes after running for a few minutes. I've tried swapping out the memory sticks and it's made no difference.
Is it possible this is a software problem and not a problem with the motherboard or other hardware? I sure hope so, because I love this machine. Anyone have any suggestions about what I might try next? I've read about the "hair dryer" solution, but if Apple Hardware Test didn't find any probemms with the memory or motherboard, could that still be a solution?
Thanks for any help or suggestions.

Thanks, japamac. Yep, I should have said I replaced the old hard drive with the new one. So, it now only has the one, new fresh hard drive. The new drive is a WD Caviar Blue 320gb.
I set the jumpers on the new drive for 5-6 to slow the new drive down to 1.5. I've also tried resetting the PRAM several times, and tried restarting in safe mode. Every few tries I can get it to boot from the hard drive or a boot DVD/CD (maybe once every 10 tries), but it freezes up after running for about 10 minutes. The only instance this doesn't happen is if I boot with the Apple Hardware Test CD. It didn't freeze up during the 2 hours it took to run the extended test.
Thanks for trying to help me.

Why does my MacBook Pro show a prohibitory sign when I start it up?

On the white screen it starts up as an apple and then turns into a prohibitory sign. It has the spinning thing on the bottom so it looks like its trying to start up but it isn't doing anything and I keep having to shut it off! Help please!!

Start with this:
http://support.apple.com/kb/ts2570
Ciao.

HT4790 My Mac OS Lion 10.7 FileVaulted HD does not boot, prohibitory sign, stop sign appears some minutes after boot starts. Disk Utility repair shows four error messages: Unable to bootstrap transaction group 2517: inconsistent crosscheck (the same with

My Mac OS Lion 10.7 FileVaulted HD does not boot, prohibitory sign, stop sign appears some minutes after boot starts. Disk Utility repair shows four error messages:
Unable to bootstrap transaction group 2517: inconsistent crosscheck
No valid commit checkpoint found
The volume xxxxxxxxxxxxxx(here it shows physical volume number) was found corrupt and can not be repaired.
Problems were encountered during repair of the partition map
Error: Storage system verify or repair failed.
(the same with 2518, 2519 and 2520 transaction group)
I suppose it is serious bug in Mac OS Lion managing FileVault and wonder what the help could be?

Most likely culprit is your Lacie drives which are notorious for flaky power supplies which cause just the sort of erratic behaviour that you describe. Have had similar issues myself. Lacie has been good about replacing my power converter-- twice. If you have seven of them, good luck finding the bad one or more. Like I said, the behaviour is erratic. Sometimes it'll work sometimes not. I can't comment on Samsung drives because I've never used them and have never heard anything about them. Same with Softraid. Why not just use Disk Utility. Sounds like you're ready for an external hardware raid. This will be much faster, much more reliable, and may even be cheaper than seven firewire drives. Check out G Tech, and Maxx Digital for starters.
Best of luck
Terry

IMAC starts up w/ tone, then white screen , then 1 min later grey apple - nothing else. When I boot up holding shift, no tone, white screen, grey apple, then 1 min later prohibitory sign and pinwheel ...

IMAC starts up w/ tone, then white screen, then 1 min later grey apple - nothing else.
When I boot up holding shift, no tone, white screen, grey apple, then 1 min later prohibitory sign and pinwheel ... nothing else ?

Tried disabling everything USB and FireWire and the Likes

White Prohibitory Sign When Trying To Move Files Off External Hard Drive

Why am I getting the white prohibitory sign when trying to add a new file to an external hard drive? I have run Disk Utility and permissions repair.

See Mac OS X: "Broken folder" icon, prohibitory sign, or kernel panic when computer starts
http://docs.info.apple.com/article.html?artnum=106805
 Cheers, Tom

Macbook 2010 won't boot - flashing question mark, prohibitory sign then Apple icon

Okay so some of this is my fault. We'll get to that later.
A few months back this Macbook my uncle gave me (without the Mac OS X Installer DVDs it came with) failed to boot - displaying the spinning gear/Apple icon/grey screen so many others have experienced.
I've done everything that could be done without the Installer DVDs - reset the PRAM, the SMC, attempt to go into Safe Mode (failed - only displays the progress bar until it fills up then back to the grey screen)
I've also done fsck -fy and it would always return to either "FILE SYSTEM WAS MODIFIED" so I'd run it again to receive the result "The volume Impala appears to be okay", but whenever I would hit "reboot" it's like nothing ever happened.
I got a hold of a(n illegal) copy of someone else's Installer DVDs from the net - not so I could install that but so I could load DiskUtitlity from a bootable flash drive to transfer files to my external HD by the restore option in DiskUtility - worked for a bit (ran verify permissions, repair disk permissions, the whole shebang) but then failed, was only able to copy the "Applications" folder by restoring the volume to the external HD I had plugged in, and nothing else.
So when just this afternoon, I was fiddling with the prompt that displayed whenever you entered single-user mode, trying to move documents from inside the Documents folder into the Applications folder (because I thought that if I did "restore" all over again it would copy needed files into my HD like it did the last time - the /Volumes directory disappeared.
What could have caused this? I know that this is what's causing the flashing, alternating icons during attempted startup, but I swear that I didn't even think of doing anything to modify the /Volumes directory. One minute I was entering files /Volumes just to fiddle with it, then proceeded to go in deeper to cp or mv files into the /Applications directory, the next it was gone.
What should I do? I contacted the local Power Mac Center nearby to check if they're carrying the Mac OS X Snow Leopard Installer DVDs but I'm pretty sure that those things are limited now to the U.S. and the U.K.?
Please send help/advice, I'm broke and pretty much very very desperate.
Thank you for your time.

and also we have this older MacBook (2007 I think) that flashes the prohibitory sign (circle with slash going through it) whenever I try to boot it - started doing that a few days ago and I swear on both laptops that there are no peripherals that are plugged in except for the MagSafe (this older MacBook has no batteries installed since the last one shot out two years ago and we haven't had the money to replace it..)
Could the MagSafe be the problem? Because I haven't been doing anything dangerous on this older one (even cleared out some old files/videos to free up disk space) but still, it went ahead and got into a coma.
I can only access it via Safe Boot (pressing shift right after I power it up) and thankfully, its FireWire port using Target Disk Mode.
How I wish I could use Target Disk Mode on the later (2010) model, but alas, the only solution is to purchase the Installer DVD - only the Apple Reseller I contacted hasn't contacted me back yet.

Prohibitory Sign on Mac OS 10.3.9 installed onto an iMac 350MHz

Hi.
Mi name is Jose Blanco.
I have an iMac 350MHz which has the Mac OS 10.3.9.
Six mounths ago I installled a new hard drive into this computer and I installed a fresh Mac OS 10.3 onto it.
Yesterday (august, 9) this computer showed the prohibitory sign, consequently I've installed the operating system again and the computer has worked fine until today, that it showed the same issue.
Thanks for everything.
Jose Blanco

Hola Jose!
What size is the Hard Drive, and how much space is available?
How much RAM is installed, and is it original or added?
Have you run Repair Disk?
THESE ARE THE STEPS FOR USING DISK UTILITY TO REPAIR YOUR HD
1.Insert your Mac OS X CD-ROM disc or Restore DVD disc, then restart the computer while holding the C key.
2.Once started up from CD or DVD, choose Disk Utility from the Installer menu.
Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from disc to access Disk Utility.
3.Click the First Aid tab.
4.Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
5.Select your Mac OS X volume, if necessary.
6.Click Repair. If DU reports errors it has fixed, then re-run Repair Disk until no errors are reported.
7.When finished, select Quit Disk Utility from the Installer menu.
8.Select Quit Installer from the Installer menu.
9.In the resulting pop-up window, choose restart.
10.After the computer has restarted, you can eject the CD.
Have you run Repair Permissions?
TO REPAIR PERMISSIONS ON THE STARTUP DISK
1.Open Disk Utility, located in Applications/Utilities, and select the startup disk in the left column.
2.Click First Aid.
3.Click Verify Disk Permissions to test permissions or Repair Disk Permissions to test and repair permissions. (I never "Verify". Just run "Repair".)
Rerun RP until the only message it reports is:
"We are using special permissions for the file or directory ./System/Library/Filesystems/cd9660.fs/cd9660.util.
New permissions are 33261"
This is a status message and not a cause for concern. You may safely ignore it.
Or these:
"We are using a special uid for the file or directory ./private/var/at/jobs. New uid is 1"
"We are using a special uid for the file or directory ./private/var/at/spool. New uid is 1"
Again, these are status messages, which appeared after Security Update 2005-001.
There may be others that you can ignore. Complete list at link below.
Spurious Permissions Errors Using:
Panther 10.3.x
When "Repair Permissions" is complete. Quit "Disk Utility".
If neither of those corrects it, Reset The PRAM & NVRAM.
How To
1.Shut down the computer.
2.Locate the following keys on the keyboard: Command, Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3.Turn on the computer.
4.Press and hold the Command-Option-P-R keys. You must press this key combination before the gray screen appears.
5.Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6.Release the keys.
Good Luck!
ali b

ITunes causing prohibitory sign?

yesterday I was using an applescript to take music off of my friends iPod, when my computer started slowing down, songs that i was playing were pausing at different times, and the script wouldnt take all songs that I told it to. So i figured that my computer was just doing too much at once so I turned the computer off. When I turned it back on the apple logo at the begining of the start up was sitting there with the progress circle spinning, and then the apple logo changed into a prohibitory sign. After reading around on the forums, i tried to using the reset-nvram, reset-all in theopen framware but nothing happened. So i looked around some more and i found the "control-S" command, not knowing what it did, i thought i would give it a shot, so I hit it during start up and i got a black screen with white text with lots of words, and numbers that didn't mean anything to me, but one thing did jump out at me and that was "com.apple.driver.iTunesphonedrive has no kernel dependency" I was wondering if iTunes could be the cause of my problem, if so, how do i get my computer to start up? Thanks.
Power Mac G4 "Sawtooth" 400 mHz Mac OS X (10.4.5)

The flashing question mark means that Firmware has been unable to find a startup volume. It searches around and evidently finally found something. By the old OS logo, I take it that you mean OS 9. But, it sounds like it is not finding OS X.
This begins to sound like some problem related to the disk or filesystem. I suggest that you boot off your install CD and use Disk Utility to repair the disk. The are instructions at Resolving Disk, Permission, and Cache Corruption. See the section on repair disk.
EMAC G4 1.0 GHz Mac OS X (10.4.6)

Late 2012 iMac Trouble. Prohibitory Sign help!

Hi, so I've been trying to partition my drives and install Windows on my late 2012 imac. However I've screwed up. I last adjusted my partitions using disk utility and now receive the prohibitory sign on startup and cannot boot up in safe mode; pram reset; type commands in single user mode. Please help!! Running on Mavericks OS.

Hello ssnacario
Start with booting up to the Recovery HD and then use Disk Utility to verify the hard drive. Check out the first article to go through those steps to sort you out. If for some reason that it checks out and you are still having issues booting up, then you will want to reinstall OS X Mavericks.
Also if you can somehow back up before you go through the troubleshooting to ensure you have a safe copy of your data.
Resolve startup issues and perform disk maintenance with Disk Utility and fsck
http://support.apple.com/kb/ts1417
OS X Mavericks: Reinstall OS X
http://support.apple.com/kb/ph13871
Regards,
-Norm G.

Help replaced a kext file and now I get a Prohibitory Sign and cant startup

I replaced my iovideo family.kext file trying to fix my non working dvi output. I replaced it with one from my mbp 15 because that one worked fine now I cant start up my mbp17 I get the Prohibitory Sign???

If you kept a copy of the original file, you can use the terminal to copy it back.
You should be able to boot into the Leopard DVD using the "C" on boot and get into the single user mode to do this.
If you have a TM backup, you can boot into the Leopard DVD and restore the entire OS from the backup.

Prohibitory sign on startup

Hi all,
My G5 froze this evening and I had to do a hard shutdown. Ever since then I get the prohibitory sign on startup (a no entry sign on the grey Apple boot screen).
I've followed Apple's instructions to reset pram and nvram, and replace mach-kernel, but I still can't boot from either of my internal drives, nor the CD drive.
I've tried the following:
Boot from HD1 - no entry sign
Boot from HD2 - no entry sign
Boot from Tiger DVD - no entry sign
Unplug HD drives - no entry sign
Remove 2 of 4 RAM modules - no entry sign
Unplug all peripherals, including drives, remove all but two sticks of RAM - boots from DVD
Plug back in drives and peripherals but not RAM - works fine
Shut down, install RAM - no entry sign
Now, here's the odd bit. I then took the RAM back out as it should have then allowed me to boot again but it didn't and went to the no entry sign.
Took out all peripherals, unhooked internal drives - no entry sign.
Have also removed all ram and pram battery, then started up, shutdown, put it all back, then booted again and still the no entry sign.
By the way, I've reset the PMU twice during the evening, reset PRAM and NVRAM numerous times.
Target disk mode works fine so am able to recover data, and disk utility and diskwarrior report few errors, if any.
Does this point to a major hardware failure somewhere? Can anyone help pin this down?
Many thanks,
Justin

Do you have power? Do your drives spin up when you turn on the computer? If you do then,
Try the following:
Repairing the Hard Drive and Permissions
Boot from your OS X Installer disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Installer menu (Utilities menu for Tiger and Leopard.) After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the installer. Now shutdown the computer for a couple of minutes and then restart normally.
If DU reports errors it cannot fix, then you will need Disk Warrior (4.0 for Tiger, and 4.1 for Leopard) and/or TechTool Pro (4.6.1 for Leopard) to repair the drive. If you don't have either of them or if neither of them can fix the drive, then you will need to reformat the drive and reinstall OS X.
Booting From An OS X Installer Disc
1. Insert OS X Installer Disc into the optical drive.
2. Restart the computer.
3. Immediately after the chime press and hold down the "C" key.
4. Release the key when the spinning gear below the dark gray Apple logo appears.
5. Wait for installer to finish loading.
Message was edited by: Kappy

Prohibitory Sign and unable to copy items

I restarted my Mac tonight and was presented with the Prohibitory Sign. I was able to reboot using a backup drive I have and also able to see the contents of my Mac.
Before I do an Archive and Install, which unfortunately looks like the only option available I wanted to backup some stuff I've been working on since I last backed up (around 5 days ago)
The thing is when I try to copy items from my Mac to the Backup drive it tries to copy and then I get the error: The Finder cannot complete the operation because some data could not be read or written. (Error code -36)
I seem to be able to copy items from the Backup drive to my Mac though.
Any ideas and help would be much appreciated. It's getting late now and my mind is starting to go so I think I'll leave it until the morning now in case I do something stupid!

I had to take my MBP to the Apple Repair Centre who diagnosed the fault as a blown HD. They replaced it and all works well now.

Prohibitory sign on startup + wifi not working

A few days ago my 2011 MBP refused to boot and froze at a prohibitory sign on startup. I tried SMC resets, PRAM resets etc, but to no avail. Then I've managed to get it to boot a few times, usually after opening it, removing and fiddling about with the HD a little (yes, makes little sense to me too). But now it says Wifi: no hardware installed. I tried renewing the DHCP lease like someone suggested, but that just resulted in Wifi disappearing from the list of network connections...
Verify disk said the disk seems ok. Verify permissions, however, seems to freeze the system.
If I restart, it most likely boots into the prohibitory sign again.
Now I wonder, could these issues be related somehow, the prohibitory sign (points to a faulty HD, I gather) and the Wifi? Or could it be a software issue? I just want to know whether I should replace the HD and wifi or just get a new Mac.
Also, this is so rare that I have to share: these issues started on the day I was meant to hand in a project I've been working on for a couple of weeks (no backups of course, because why would my 4-yo laptop ever fail me?). But, it happened only after I delivered the project. Ha! And when it did boot again, I managed to do a full backup, including three years of unique family photos. Ha! again. A dark day at the satanic IT department, I expect.

maho76 wrote:
The HDD seems to work normally via USB, though it's rather slow. I suppose that could just be a slow USB connection in my very cheap enclosure?
Exactly, the USB2 connection is the bottle neck.
I'll see if I can find a replacement SATA cable, I hope it's just that...
Though not the cheapest alternative, but the Apple store can do this and it should not break the bank.
Ciao.

Prohibitory Sign, Can't sign in to computer after software update

I have a MacBook Pro 13" inch, mid 2012. I updated some of my software, (I believe it was Safari, maybe a security update, and maybe a startup update?) I can't really remember, but they were all relatively small and I figured they would be quick updates. Once it updated and told me to restart, my computer will not properly start up at all. I get to the user login screen, type the password, then the apple logo shows up for a few seconds then goes to the prohibatory sign on the gray screen with the spinning gear. I left my computer plugged into the power cord all night and when I woke up it was still doing the same thing. I've held down the power button to hard restart it multiple times, tried to restart in SafeMode, but nothing changes when I hold down "shift" or "shift-command-V"
I CANNOT lose my files.I have so many documents from my entire 4 years of college on there that I've spent countless hours working on and perfecting.
PLEASE Tell me this can be an easy fix?!?!
-Kearsten

Mac OS X- Gray screen or prohibitory sign appears during startup

Prohibitory sign on start up.

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