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Travis, Mac-Trained Product Designer
Category: Mac
Satisfied Customers: 759
Experience:  19+ Years of Mac Experience, BSA in Design and 6 Years of Mac Training from University of Cincinnati
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invalid B-tree node size error when running first aid

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invalid B-tree node size error when running first aid
If the following suggestions work, please let me know and you can Accept the answer (and if possible, leave positive feedback). If not, please DO NOT Accept the answer. Instead, let me know and we'll try some more things or I can refer you to another Expert who may be able to help you further.

This is a definite sign of a failing hard drive. Why did you run First Aid in the first place?

The most important thing at this point would be to get a backup of your data if you don't already have one. If you restart the machine from the install disk, can you see the hard drive and it's contents? Or is it not mounting at all? If it is mounting, but you are unable to boot because of an error with the Mac OS X, then, I suggest first you attempt the following first (make sure the Install Disk is not in the computer):

1) Start the mac and hold down the apple key (Command) and the S.
2) After the Apple logo (and if the hard drive can mount), it will have a black screen with white text. When it finally stops loading and you are given a prompt, type this command EXACTLY (there is only a space between "k" and "-") and then press return:

/sbin/fsck -fy

fsck will go through five "phases" and then display info about your hard disk's state. Once it finishes, it'll display this message if no issue were found:

** The volume (name_of_volume) appears to be OK

If fsck found issues and has done anything, it will display this message:


If the above message appears, repeat the fsck command until fsck tells you that your volume "appears to be OK"
The first-pass repairs may uncover additional issues, so it's normal to have to do it more than once.

3) When fsck reports that your volume is OK, type the following EXACTLY and press return:


Does the machine boot up now? Or are you still stuck?

Next, do you have access to another mac that you can try to connect this mac to and pull your info off in Firewire Transfer mode?

Have you attempted to repair the hard drive with a program like Disk Warrior? This may be able to repair the drive.
Customer: replied 7 years ago.
I get the "?" instead of the apple log on start
The "?" means it can't find a valid startup folder. Were you able to run the fsck in Single User mode? Hold the Apple-S immediately after pressing power, and dont let it go until it boots into the Single User Mode or it flashes the ? folder for about 30 seconds.
Customer: replied 7 years ago.

Holding the Apple-S does not seem work, still getting the flashing "?"

Ok, can you try the following? We need to get the computer to at least boot up so tha t we can try to get your files backed up. Do you have another mac readily available or an external hard drive?

Hold the "X" key during startup immediately after pressing the power button (Don't let go until it starts from the disk or locks up on the ? mark). This may force the computer to start up to Mac OS X. If it does, open System Preferences and be sure that your Mac OS X System Folder is selected. If this works, STOP HERE and we'll see about getting your data backed up. If not, go on to the next step...

1) Restart while holding down the Option key immediately after pressing the power button (Don't let go until it starts from the disk or locks up). This should bring up the Startup Manager and would allow you to select the startup volume. May work, if the computer is stuck and can't find the correct startup volume. If this works, STOP HERE and we'll see about getting your data backed up. If not, let me know and we'll try a couple of other things.
Customer: replied 7 years ago.
Urgh that did not work
Try doing all of the following. If you get hung up at any part, stop and let me know where you are and we'll see if we can work past that point.

1) Shut down your computer completely.
2) While the computer is shut down, locate these keys: command (has an apple on it), option (sometimes called alt), P, and R.
3) Turn the computer on, then press and hold Command-Option-P-R before the gray screen appears.
4) Hold these keys down until you hear the startup sound a total of 3 times.
5) Release the keys. Regardless of what happens, shut down the computer here.
6) Start up the computer and immediately after the startup chime, press and hold the Shift key
7) Once the gray Apple and progress indicator appear, release the Shift key. Note: Startup will likely take substantially longer than normal. If you can't get the apple to appear (even after 15 - 30 seconds of the ? folder), then skip to step 13
8) In Mac OS 10.4 or later, you will have to login to your account, even if it normally does so automatically.
9) Go to Hard Drive / Library / Startup Items / Drag anything in here to the desktop.
10) Shut down the computer.
11) Restart normally. If you get the question mark, then go on to Step 13
12) STOP HERE. Let's try to backup your data now, before we go any farther. Do you have an external USB Hard Drive or another mac you can connect to this machine to get off any important documents?
13) Insert the Mac OS X Install Disk and shut down the computer.
14) Restart the computer while holding down the C button until the machine boots up from the Mac OS X Install Disks.
15) Once you are running off of the Install Disk, quit the installer. Go to Disk Utilities (top menu under Applications or Disk Utilities depending on the version of OS X).
16) Is your Hard Drive visible? Did it mount? If not, skip to step 21
17) Run Disk Repair on your Hard Drive. Are you still encountering errors? If yes, skip to step 21
18) Open the Install Disk back up and run the Install program again. When asked what kind of install, choose "Archive and Install". VERY IMPORTANT. You may have to click on a "Customize" button in order for this to appear.
19) Restart normally after installation. If the ?mark folder appears again, then skip to step 21
20) Eject the Install Disk and you should be a-ok from here on out. STOP HERE
21) Do you have access to Disk Warrior? If so you may be able to mount the drive and repair, although this is a big "May Be". Otherwise, it appears that the problem is a hardware issue and I am unable to help diagnose the problem without running diagnostics on the computer itself to determine whether the problem is with the hard drive or the Logic Board. I would suggest you take the machine to the Genius Bar at your locat Apple Store or another authorized Apple Repair Center. Sorry I wasn't able to help further.
Customer: replied 7 years ago.

That did not work - I don't have Disk Warrior but I do have Tech Tool Deluxe CD does it have anything that would hep?

Possibly. Try booting up from Tech Tool Deluxe. Can you mount the Hard drive with it? This disk is given with Apple Care, I do not have the disk personally. Do you still have AppleCare on this product?

Also, you still haven't answered why you were running Disk Utilities to begin with? Did the computer freeze and if so, why and how did it freeze?
Customer: replied 7 years ago.

I did have Apple Care (just expired)

To answer your qeustion - the laptop froze and when and after waiting for over an hour I used the power button to turn it off and when I restarted I got the flashing ?. I restarted using the Leopard OSX disk which got me to the Disk Uility.

Try to start off of Tech Tool Deluxe. It may be able to diagnose and at least mount the hard drive.

You never answered my previous question. If you go to Disk Utilities on the Install Disk, can you see the Hard Drive? Or is it still not mounting at all?
Customer: replied 7 years ago.
I can see the Hard Drive but it is not mounting
Ok, I am confused. If you can see the hard drive, it should already be mounted. It would have to mount to be able to be seen. If you go to Disk Utilities and it can see the hard drive, what happens if you attempt to repair it now?

Are you able to startup from the Mac OS X Install Disk and run an "Archive and Install" or are receiving errors when attempting it? If it can see the hard drive, then I may have gotten confused at the beginning of the problem when you said you can't mount the hard drive.

Were you able to see the Hard Drive after running Tech Tools, if so was it able to repair anything on the hard drive?
Customer: replied 7 years ago.

When I run the Disk Utility this is what I see


111.8 GB ST9120821AS.....



disk0s2 is not mounted and I get the invalid B-tree when I try to Verify or Repair Disk. I don't see the drive as an option when I run an "Archive and Install"


What are the commands I need to boot from the Tech Tool CD, I tried using the C on start up but it did not work





When you do try to run "Archive and Install" do you see any drives at all?

As far as Tech Tools goes, you should be able to start by holding the C down if the disk is in. What are you getting on screen when you try to do this? You may not be holding the C down long enough. If you can't get it to start up that way, try booting into the Startup Manager (hold down Option during the startup sequence and not letting go until the manager appears) with the Install Disk loaded and choosing the Install Disk. It may take a minute or two before it pops up as a choosable startup disk.
Travis and 3 other Mac Specialists are ready to help you
I am about to head home from the office for the evening (lovelyXXXXXahead of me). I will be back online this evening though so please post any questions or comments here and I'll get back as soon as I can (about 3 hours from now). Thanks!
Customer: replied 7 years ago.

So far nothing has worked

Were you able to boot up from the Tech Tools Disk?
Customer: replied 7 years ago.
No I was not. Trying to reinstall from Leopard CD
Archive and Install or a clean install?

What happened when attempting to start the computer from the Tech Tools Disk and the Startup Manager?
Customer: replied 7 years ago.

Didn't work

The Startup Manager didn't work? Were you able to load into the startup manager and it didn't show the Tech Tools Disc or was it unable to start at all? When it gets to the startup manager (if it did get that far), it may take a minute for the disk to spool up.

Or the install from Leopard Disks didn't work?
Customer: replied 7 years ago.

Was able to reinstall and back up, I did lose the data I was trying not to loose. Thank you for your assistance.



Thanks for the Accept and the Bonus! Glad you were able to get it up and running. Sorry about the lost documents though.

Please feel free to contact me in the future with any other questions you might have. I'd be honored to help again.