b0 error when installing Mac OS X

So you’ve installed Mac OS X, the computer has restarted, and you’re left with the following when the computer tries to boot from the hard drive:

b0 error

What does this mean? Simply that the partition isn’t active. Why the MacOS installer doesn’t automatically set the partition as active (especially when it’s the only partition) puzzles me. Maybe it has something to do with me installing OS X on a PC. Regardless, here is a fix I came across here.

There are a lot of people who experience a b0 error on their first boot up after installation. Or the bootloader immediately takes them back to the Windows installation (on dual boot).

These people probably forgot to set the MacOSX partition “Active”

A common mantra provided here to newbies for setting up for installation is:

  • Make the partition Primary
  • Make the partition ID=AF (signifies an HFS partition)
  • Make the partition Active

There is a built-in Unix utility in MacOSX that can be used to set your partition “Active”. It is called Fdisk

Setting Your Partition “Active” Using Fdisk

Words in bold below are things you must type (followed by Enter).

1. Boot your Mac OS X install dvd
2. Once the installer is running, go to the Utilities menu and open Terminal

3. Determine which disk your MacOSX partition is on

Type diskutil list

Verify which disk number holds your partition (disk0, disk1, etc.)


4. Start using Fdisk

Assuming the MacOSX disk is the first disk (“disk0”), then
type fdisk -e /dev/rdisk0 <== use “rdisk” with your disk number here !!

Ignore the error “fdisk: could not open MBR file …”


5. Determine which partition for MacOSX needs to be set “Active”

Type p

Verify which partition is for MacOSX (1, 2, 3, etc.)


6. Set the partition “Active”

Assuming it is partition 1, then
type f 1 <== use your partition number here !!


7. Save and exit

Type write

Type y (yes you are sure)

Type exit (to quit)


8. Remove the install DVD and reboot


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  1. I encountered a number of failed attempts—when I booted into Mac OS X, it prompted me to restart my machine. But after several attempts, it worked. Every time it is happening so..
    Also the device drivers are not working properly… The OS seems to be very slow.

  2. I am installing 10.4.6 via VMWare. It gets installed but when I restarted, it gave me a “b0 error.” So I went into the terminal and set the partition active using fdisk. When I rebooted again, it will get to the grey screen and then will give the power logo and tells to restart my computer. It looks like a kernel panic. Please help me!

  3. I haven’t tried installing through VMWare, so I’m not sure if there’s anything in specific you can set up or change from within VMWare that will help. Trial and error’s probably going to help you the most. Try unplugging any extras you have (USB sound cards, etc), install with different options, and swap around some hardware if you can. It *could* be BIOS settings, although in the past when BIOS settings have caused panics for me, they happened while the install CD was booting. Since you’re past that part, I’m inclined to think it’s something else.

  4. in regards to that power sreen it is because you dont have sse2/sse3 patches installed.

    but I have my own problems… it installs and it runs but when it restarts it gives me a kernel panic saying:
    panic(cpu 0 caller 0x00399ca3): unable to find driver for this platform: “ACPI”


  5. Computerpanic

    you should have a back up, i install mac os X leopard but before that i have windows 7, if u have error in installing mac os x and u dont know how to fix it just remember what u change and turn it back into its old, and install windows maybe it is in ur motherboard or video card or something that cant support your os

  6. Computerpanic

    1 more thing dont ever change anything in BIOS that may lead you to by a new computer

  7. I installed mac os X x86 on vmware but after this b0 error i can’t boot from dvd anymore.
    so looks like i’m trapped

  8. i have done this but now it is saying that

    system config file ‘/Library/Preference/SystemConfiguration/’ not found

    i am using vmware version 7

    please guide

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