Filed under: Troubleshooting, Mac 101
Mac 101: Building a bootable diagnostic and repair flash drive
More Mac 101, our tips and tricks for novice Mac users. Update: You cannot install Snow Leopard on an 8 GB flash drive. I was incorrect in writing that an install of Essential System Software would take 3.81 GB. As a few of our commenters pointed out, and as is the case, in testing I erroneously tried to install Snow Leopard on a flash drive that already had a version of OSX on it, making the installation much smaller than installing on an empty flash drive. According to readers, installing Snow Leopard on an empty flash drive will take 8.01 GB requiring a 16 GB flash drive. I'm very sorry for any inconvenience this has caused.
It's a good idea to have a strategy in place in case of emergencies. If your hard drive tosses you errors, behaves badly or doesn't even appear, what to do? If programs crash at random, you need to be ready. You can prepare for this by creating a bootable flash drive containing some diagnostic and repair utilities.
This is not meant to replace or in any way affect backing up your hard drive. Time Machine makes it so easy that not having a backup plan is just silly... but so much for the disclaimer.
To make a diagnostic and repair flash drive, I'd suggest buying an
I inadvertently omitted a step! Click the icon for the drive (not the disk partition -- the one that includes the size) and click the Partition tab. Choose "1 Partition" from the pop-up menu, Mac OS Extended on the right, then click Options at the bottom of the screen and make sure "GUID" is the selected partition type. Thanks to everyone who pointed this out.
At this point do the Erase as mentioned above which should look like the following screen shot.
In this example I'm using Snow Leopard, but the idea is the same using Leopard as long as your Mac is running an Intel processor.
Insert your Snow Leopard disc and click on Install Mac OS X. Choose your new flash drive as the destination, but when you get a screen or two in, click on Customize.
When you do you'll see this screen:
You can see that it'll take3.81 GB 8.01 GB (see the update note at the top of the story) to do the simplest installation. Consider what you'll need on your flash drive and select or deselect whatever you'd like, but I suggest choosing nothing at all. As a diagnostic and repair-only bootable device, you don't need anything but possibly print drivers and you probably don't need those. You may want to install Rosetta since it's only 2 MB, but if you need it later, Snow Leopard will let you know and ask if you want it installed.
Run the installation and busy yourself elsewhere for awhile.
When its done, reboot holding down the option key and you'll be presented with a list of bootable devices. Choose the flash drive. The welcome movie will play and you'll need to apply settings as is usual when first running a new Mac or installing a new operating system.
Next run Software Update repeatedly until you get a message telling you that your software is up to date. Now it's time to install utility software. Disk Utility, already be installed on your flash drive, is often all you need, but along with that I can personally recommend Diskwarrior from Alsoft and TechTool Pro from Micromat. I've been using both of those for years and although a lot of functionality is duplicated between these programs, I've often had problems that Diskwarrior can fix but Techtools Pro can't and vice versa. Having both of these in my tool belt along with Disk Utility has gotten me out of serious trouble more times than I'd like to remember.
If you are concerned about running out of space on the flash drive, remember that this is a diagnostic and repair device; you can delete just about all the programs in the application folder. The only ones I have remaining are the three utilities mentioned and Safari. It's your call.
That's it, and putting it together sounds much worse than it is. You'll be set for whatever comes along. Sure you can boot your system disc to run Disk Utility but I've found in many cases, I needed a lot more. You can also boot from your utility program discs, but that's time consuming and it's possible to run into a problem with the OS on the utility disc not playing nicely with your Mac.
You should know that booting the flash drive will take a long time, so don't be surprised. The one I have takes longer than booting from a system disc, but when it does come up, I've got a really good variety of tools that has served me well.
I have one of these in my computer bag and I've used it often at friends houses to get various Macs out of various jams along with using it on the three Macs at home.
Do you use this method already? If you've been at it awhile, what do you use when disaster strikes? The comment section is waiting for your horror stories.
Note: A few have found that rather than the 3.81 GB I found as the size of essential software, on their machine 8.01GB was required. I was testing on a Macbook Pro 17" 2.93 GHz Intel Core 2 Duo, and 3.81 GB was what came up for me. I'm interested in what machines were found to need 8.01GB.
Insert your Snow Leopard disc and click on Install Mac OS X. Choose your new flash drive as the destination, but when you get a screen or two in, click on Customize.
When you do you'll see this screen:
You can see that it'll take
Run the installation and busy yourself elsewhere for awhile.
When its done, reboot holding down the option key and you'll be presented with a list of bootable devices. Choose the flash drive. The welcome movie will play and you'll need to apply settings as is usual when first running a new Mac or installing a new operating system.
Next run Software Update repeatedly until you get a message telling you that your software is up to date. Now it's time to install utility software. Disk Utility, already be installed on your flash drive, is often all you need, but along with that I can personally recommend Diskwarrior from Alsoft and TechTool Pro from Micromat. I've been using both of those for years and although a lot of functionality is duplicated between these programs, I've often had problems that Diskwarrior can fix but Techtools Pro can't and vice versa. Having both of these in my tool belt along with Disk Utility has gotten me out of serious trouble more times than I'd like to remember.
If you are concerned about running out of space on the flash drive, remember that this is a diagnostic and repair device; you can delete just about all the programs in the application folder. The only ones I have remaining are the three utilities mentioned and Safari. It's your call.
That's it, and putting it together sounds much worse than it is. You'll be set for whatever comes along. Sure you can boot your system disc to run Disk Utility but I've found in many cases, I needed a lot more. You can also boot from your utility program discs, but that's time consuming and it's possible to run into a problem with the OS on the utility disc not playing nicely with your Mac.
You should know that booting the flash drive will take a long time, so don't be surprised. The one I have takes longer than booting from a system disc, but when it does come up, I've got a really good variety of tools that has served me well.
I have one of these in my computer bag and I've used it often at friends houses to get various Macs out of various jams along with using it on the three Macs at home.
Do you use this method already? If you've been at it awhile, what do you use when disaster strikes? The comment section is waiting for your horror stories.
Note: A few have found that rather than the 3.81 GB I found as the size of essential software, on their machine 8.01GB was required. I was testing on a Macbook Pro 17" 2.93 GHz Intel Core 2 Duo, and 3.81 GB was what came up for me. I'm interested in what machines were found to need 8.01GB.
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Reader Comments (Page 1 of 3)
KM said 3:31PM on 12-02-2009
Merely reformatting probably won't be enough. Most drives are factory-partitioned as Master Boot Record for use on Windows. You'll have to repartition the drive as GUID Partition Table to make it bootable with Intel Macs (on PPC Macs, you have to use Apple Partition Map).
In Disk Utility, select the USB drive (not the volume within it), then select the Partition tab. Choose Scheme: 1 Partition from the pop-up list, click the Options button and choose the partition format, and finally click the Apply button.
Reply
accolon said 3:57PM on 12-02-2009
I never had problems booting from an MBR partitioned drive on my Santa Rosa MacBook Pro. I tried with my USB stick as well as with my Carbon Copy Cloner backup drive.
Brian Allen said 4:29PM on 12-02-2009
The GUID partition is key to the process.
Also, $13 for a SanDisk Cruzer Micro 8 GB is best deal going that I have found without it being a no name brand.
QuarterSwede said 5:42PM on 12-02-2009
I believe GUID is the default in SL. It was the default when I was making my Windows 7 boot drive.
David Winograd said 6:12PM on 12-02-2009
Yes, you are quite right.
First partition to GUID.
As I was going through the steps, I didn't have one that I could erase so I missed that step.
Thanks for catching it.
KM said 6:15PM on 12-02-2009
@accolon: I'm surprised that an Intel Mac can boot from a MBR-partitioned drive, especially since it can't boot from APM-partitioned drive (IIRC).
@Brian Allen: Makes sense for the default to be GPT on SL, since SL is Intel-only.
Jeremy said 5:08PM on 1-07-2010
Which step do you do you do first? Do you do the "erase" step then got to the "Partition" menu and hit apply or is it the other way around?
KM said 6:26PM on 1-07-2010
@jeremy Partition first; that'll also erase the drive. However, if you want belt *and* suspenders, erase again.
Russell said 3:27PM on 12-02-2009
are you able to you say a Wester Digital 500 GB external HD instead?
Reply
Chris said 3:12AM on 12-03-2009
Yes. For Intel Macs, it can be FireWire or USB, but PowerPC Macs can only boot from FireWire.
Chris said 3:38PM on 12-02-2009
Absolutely, just partition your external drive in Disk
Utility first. Create an 8GB partition, and then Install OS X on that
particular drive partition. This way, you still have the ability to
utilize the primary HDD partition for storage, backups, etc, and yet
retain the ability to boot from the other partition. I do this very
thing myself, on my MyBook 500GB externa
David Winograd said 6:18PM on 12-02-2009
Yes I can, but a flash drive isn't as big, doesn't need power or cables and can fit in your shirt pocket.
I use a 1 TB drive with a few partitions as well for diagnostics.
There's a virtue to having something you can just throw in your pocket.
NerdyLibery said 6:58PM on 12-02-2009
Is there a reason you can't just carry the original Snow Leopard DVD installation disk with you? Unless you have a MacAir, that is ...
Reply
Chris said 3:17AM on 12-03-2009
From the installation DVD you can run basic utilities like Disk Utility and Password Reset, as well as start an install. This will make a bootable drive in the sense that it will look and function like your regular Mac desktop, and have all the capabilities that the full featured OS (as opposed to the installer) has.
Muwin said 6:40AM on 2-04-2010
There's nothing to stop you from "just" carrying your original OS X installation disk around, but your repair & diagnostic options are severely restricted when you boot-up from it; all of the utilities mentioned by this author require that they be launched from a startup volume. Since Apple's Disk Utility is the only one of those present on the OS X DVD, you'll be limited to just that. Also, many repair activities involve interacting with a drive's contents at the file or folder level (restoring files to proper locations, removing corrupted cache files or incompatible/damaged items, etc.). Since there's no functioning "Finder" app on the OS X Installation DVD, you'll be unable to perform any of these sorts repair tasks which require access to specific files or folders (UNIX geeks excepted).
Bobby said 4:01PM on 12-02-2009
This sounds like sound advice that I'd like to follow but with being a novice OSX user, I'm curious as to what would require you to use this. If my Macbook suddenly doesn't bootup and I pop in this thumb drive and boot to it, will I be able to see my Macbook HD? What would I do then, just "Repair Disk"? What do these other programs allow you to do to fix a non-bootable drive?
Reply
Johnny said 4:48PM on 12-02-2009
To start with, yes. Run Repair Disk in Disk Utility, or other, and if it can't be fixed and you can't find any help on the internet with a specific problem, then you can at least start transferring data from there (if you don't have a good backup and the drive is still readable).
If you have a current backup and the drive cannot be repaired, forget it and just repartition or replace the drive and restore from backup after installing your new system.
Dave said 8:12PM on 12-02-2009
Having this also gives you the option of being able to use your computer even if the hard drives fails. Even if the internal drive cannot be easily fixed (perhaps one needs a larger, external drive to copy recovered files to before restoring the whole thing), at least you'll be able to check e-mail, surf the web, etc. while on the road by booting off the USB key.
When I travelled to Germany for a month I brought along a copy of my OS X install DVD. Just in case something happened. During shorter trips, I often keep a bootable USB key with me. Just in case.
Gary said 4:11PM on 12-02-2009
Tried this on a 8gb joy stick and still not enough room to put SL basic on there, even if I follow K's advice.
Your graphic shows 3.81 gb for essential software. My install disk comes back at 8.01 SL OS10.0.0
Reply
James said 5:15PM on 12-02-2009
Wrong OS Snow Leopard is 10.6, I'm not sure what they called 10.0 but it is probably a bit larger in file size.