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April 06, 2008

Sharing external HD between Linux and Mac OS X

So I have an external HD that I'm using for backup purposes. I use Ubuntu Linux on my machines at home while I use Mac OS X on my work laptop. I've been backing up to DVD for a few years now, but I finally have hit the point where backing my data up to a DVD, or even a Blu-Ray disc, just doesn't fit my needs anymore. Hence the need for the HD.

So I started to research what kind of file system would be necessary to be able to share data between these two operating systems. I figured it wouldn't be terribly complicated, as Mac OS X and Linux are both based off UNIX. Come to find out that this wasn't necessarily true.

It seems that Mac OS X only uses HFS and HFS+ for it's file systems. While it can support FAT and FAT32, these file systems wouldn't fit my needs as they have a 4GB limitation. The other file system supported by Mac OS X is ufs, which isn't supported well in Linux. So, it seems that my best option was to use HFS+.

I formatted the HD using HFS+, using the non-journalled version of the file system to ensure compatability. After the drive was formatted and I verified that it was mounting and read/writing properly on the Mac, I unmounted the drive and plugged it into my Linux laptop. I received an error that the system couldn't automatically mount the file system properly. I could mount the file system with no problems manually using mount -t hfsplus /dev/sdb3 /mnt ... but I wanted the ability to have the system automatically see the drive and mount it to my desktop for ease of use.

I discovered after doing some research on the Web that it is possible to get Ubuntu to do this. It requires the installation of the following applications:

- usbmount
- pmount

After installing these two apps, I unplugged the drive, waited a second and plugged it back in. Sure enough, Ubuntu was able to successfully detect the HD and it showed up on my desktop as I was expecting. I tested the drive to ensure that it was read/write, which it was.

I ejected the HD from Linux and plugged it back into my Mac OS X laptop and verified that I could read/write to the files written to the HD by my Linux machine. I confirmed that everything worked as expected.

Now I just need to update the rest of my desktops here at the house and I will be good to go for backing up all of my data.

EXTRA NOTE: For good measure, I made sure that Linux auto loaded the HFS and HFS+ file systems on boot by edited the /etc/modules file and adding a line for hfs and hfsplus, respectively.

ADDITIONAL NOTE: You can also use FAT32 to share the data as well. Both Linux and Mac OS X have built in support for formatting large hard drives (120+ GB) with FAT32. Windows 2K, XP, etc limits the size to 32GB, so attempting to use Windows for formatting the external HD really isn't an option.

~out...

Posted by ed at April 6, 2008 12:23 AM

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