Solve OS X Prohibited Sign Boot Issue

Recently, I used my MacBook Pro to the end of its battery life and closed it shortly before the battery died. Something must have gone wrong there because when charging and awaking it, the touchpad ceased to work and logon didn’t work. Thus I cold rebooted it and was greeted by a nasty prohibited sign.

OS X Prohibited Sign

Unfortunately, Apple’s own recommendations did not solve the issue, so here is my solution:

Boot into the recovery partition by holding cmd+R at startup and open the terminal.
then

For me this looked like:

start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 409606
409640 916361264 1 GPT part - FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF
916770904 1269536 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
918040440 136
918040576 59064320 3 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
977104896 131
977105027 32 Sec GPT table
977105059 1 Sec GPT header

Apparently the GUID partition table got corrupted at index 1.

To fix this, first unmount the disk:

Remove the corrupt entry:

unmount the disk again:

If the partition was a normal HFS+ partition:

or for an encrypted partition as mine:

Now your partition table should be fixed. In disk utility, unlock your drive if its encrypted. Then repair the volumes and access rights as usual. For me disk utility still complains about a missing EFI Partition, but this is likely due to my refind boot loader.

Update:

After this procedure my recovery partition showed up on my desktop, you can hide it again with:

12 thoughts on “Solve OS X Prohibited Sign Boot Issue

  1. Hey Julian!

    Thanks for your tutorial.

    Unfortunately it is not working for me. Whenever I try to add the new GPT entry for the encrypted partition, it gives me:

    gpt add: disk2: error: no space available on device

    When I look at the GPT it shows me that, right after removing the corrupted entry, it automatically adds this entry:

    409640 1098170328 2 MBR part 218

    Is there any way I can remove the corrupted entry and prevent it from adding the „MBR part 218“ one in order to be able to add the correct entry?

    Thanks a lot in advance and best regards
    Armin

          • Yes I did.

            My GPT looks like this (gpt show disk2):

            gpt show: disk2: Suspicious MBR at sector 0
            start size index contents
            0 1 MBR
            1 1 Pri GPT header
            2 32 Pri GPT table
            34 6
            40 409600 1 GPT part – C12A7328-F81F-11D2-BA4B-00A0C93EC93B
            409640 1098170328 2 MBR part 218

            At first I entered:
            sudo gpt remove -b 409640 -s 1098170328 disk2

            and after unmounting the disk again I tried to:
            sudo gpt add -b 409640 -s 1098170328 -t 53746F72-6167-11AA-AA11-00306543ECAC disk2

            which gave me:
            gpt add: disk2: error: no space available on device

          • Thanks for the advice.
            Unfortunately I could not find any way of converting the MBR entry to PMBR. Do you have an idea?

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