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How to format a drive to Ext2/Ext3 from a Mac (or Windows)

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Why am I doing this?

With the prices of exter­nal dri­ves falling faster than the stock mar­ket, I decided to invest in a Sea­gate FreeAgent Desk USB hard drive. I wanted to use my old, trusted 160GB hard drive as a shared stor­age resource that I can access any­where from within my home net­work. In net­work lingo, it is called a NAS (Net­work Attached Storage).

A com­mer­cial grade NAS is pretty expen­sive, but the Asus 520gu router comes with a USB port (most routers only have eth­er­net ports), which opens it up to a num­ber of devices. Con­vert­ing a USB printer to a shared printer, con­vert­ing your USB exter­nal hard drive to a net­work drive or both. (BTW, never, ever buy a Belkin hub).

So I bought the Asus 520gu, installed Tomato and every­thing was hunky-dory!  But, the spare 160GB hard drive was for­mat­ted for tak­ing back­ups from my Mac­Book (HFS+) and Tomato runs Linux.  Linux can rec­og­nize dri­ves for­mat­ted either using FAT or its native for­mat Ext2/Ext3, not Mac filesys­tem, HFS+.

I wanted to par­ti­tion my hard drive to use both FAT32 and Ext3. FAT32 isn’t a very effi­cient filesys­tem. It has a file size lim­i­ta­tion of 4GB and more impor­tantly it is from Microsoft.  Linux’s choice, Ext2/Ext3 has no such lim­i­ta­tion.  The only dif­fer­ence between Ext2 and Ext3 is Ext3 is a jour­nal­ing filesys­tem.  What this means is it has addi­tional safe­guards to pro­tect against data cor­rup­tion, like if you pull out your exter­nal drive with­out unmount­ing first.

So how do you for­mat a drive to Ext2 or Ext3? Mac (or Win­dows for that mat­ter) does not have any native tools like Disk Util­ity, to for­mat a drive to the Linux for­mat.  Enter gparted.

GParted “Live” CD

GParted is a cool free util­ity to par­ti­tion and for­mat dri­ves to a vari­ety of filesys­tem. GParted is a ‘live’ CD. What that means is, you boot into gparted from either a PC or a Mac and gparted would run entirely off your cdrom drive with­out touch­ing your hard drive. Noth­ing changes once you boot back to Win­dows or OS X. Best of all, gparted is Mac­book friendly.

What you’ll need:

1. Mac or Win­dows PC that can burn CDs
2. Blank CD
3. Patience!

Get­ting started:

1. Down­load lat­est ver­sion of gparted
2. Using Disk Util­ity on a Mac burn gparted iso into a blank CD
3. With the CD inside, reboot your Mac
4. While reboot­ing keep the option key on the Mac pressed, this will prompt you to choose where to boot from
5. Choose gparted. Don’t worry noth­ing is touched on your Mac

My exter­nal drive (/dev/sdc)was for­mat­ted for HFS and had two par­ti­tions — Mir­ror and Backup. (There is an addi­tional par­ti­tion cre­ated by Sea­gate with some Sea­gate spe­cific firmware — /dev/sdc1)

I’m delet­ing /dev/sdc1, which con­tained some Sea­gate spe­cific firmware.

I’m delet­ing the old par­ti­tions and  cre­at­ing two new par­ti­tions — one Ext2  and one Fat32

All done! Now remove the cd and boot your mac. When boot­ing press the option key to select OS X.

Your exter­nal hard drive is now has two par­ti­tions. One for­mat­ted to Ext2 and one to Fat32.  If you directly con­nect your hard drive to win­dows or Mac, you’ll be able to see the Fat32 par­ti­tion, but not the Ext par­ti­tion as Macs and Win­dows can’t rec­og­nize Linux filesystems.

A word of cau­tion: In gparted, when you pick a device to for­mat, be very care­ful.  You don’t want to pick your PC or Mac’s inter­nal hard drive to par­ti­tion, pick the exter­nal drive.  I don’t have to tell you this, but once for­mat­ted, all your exist­ing data is gone for­ever, so make sure you take ade­quate back­ups.

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Tags: ext2, ext3, format, formatting for tomato nas, gparted, linux