Ubuntu
gnu-fdisk package

Formating a Drive

Asked by Ron

I have an external hard drive with 320 GB capacity. It was originally formatted with my Apple iMac. I am now trying to use it as a backup drive for my Ubuntu/laptop. When I connect the external hd to my laptop, the capacity is seen as 298 GB (either through Disk Utility or GParted). I should add that there's really nothing on the external hd, so I don't understand why the capacity is seen as 298 GB on Ubuntu while my Apple iMac gives me the capacity as 320 GB on the same external hd. Is it because of the Mac formatting?

Another problem is that I can't reformat the drive for some reason. Neither Disk Utility nor GParted can actually reformat the external hd. Can someone help me erase and format the external hd? How can I format this drive so that I would be able to use it as an Ubuntu backup? What are the steps? And why Disk Utility and GParted are not responding when I ask them to erase the material on the hd and reformat it?

Thanks so much.

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marcus aurelius
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Hilario J. Montoliu (hjmf) (hmontoliu) said : 		#1

Hi Ron,

For the first part of your question, you should read this article in the wikipedia [1] about different units of measurement. Maybe that's the difference you see.

[1] http://en.wikipedia.org/wiki/Hard_disk_drive#Capacity_measurements

For the second part of the question, I guess we need more info. Please run and post the results of the following command:

sudo fdisk -l /var/<your external drive>
HTH

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Hilario J. Montoliu (hjmf) (hmontoliu) said : 		#2

Hi Ron,

sorry, I meant:

sudo fdisk -l /dev/<your external drive>

for example

sudo fdisk -l /dev/sdb

HTH

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Best marcus aurelius (adbiz) said : 		#3

you need to unmount the external drive before you can format it with gparted or disk utility.
if you don't have an icon on the desktop, you can go into places, then right click on the drive then select unmount

to see what the actual size of the drive is, you can do an fdisk as hilario mentioned, then see what the actual number of bytes is.

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Ron (ronald17b95) said : 		#4

I ran the command you gave in the Terminal and I have the following as a result:

Disk /dev/sdc: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0007a75e

   Device Boot Start End Blocks Id System

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Ron (ronald17b95) said : 		#5

For a backup external hard drive, I wonder what format should I choose. Any suggestions? ext3 or ext 2 or what?

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marcus aurelius (adbiz) said : 		#6

looks like they advertised the hard drive capacity using GiB. so if you think of 1 gig as 1,024 times whatever, the 298 is correct. if you thing of i gig as being 1,000 time whatever, the 320 is correct.

you can use ext4. it's supposed to provide better data integrity than ext3 and definitey better than ext2.

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Ron (ronald17b95) said : 		#7

Thanks marcus aurelius, that solved my question.

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Hilario J. Montoliu (hjmf) (hmontoliu) said : 		#8

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On 08/01/11 16:41, Ron wrote:
> Question #140617 on gnu-fdisk in ubuntu changed:
> https://answers.launchpad.net/ubuntu/+source/gnu-fdisk/+question/140617
>
> Ron gave more information on the question:
> For a backup external hard drive, I wonder what format should I choose.
> Any suggestions? ext3 or ext 2 or what?
>

If that drive is going to be used in windows too, you should format it
as fat32 except if you are going to archive big files, in which case it
should be formated with ntfs.

If the drive is only meant to be used with linux, then IMHO you should
format it as ext3 which is rock solid and has journaling which may
prevent data corruption in case of disconnections (as is an external
harddrive)

HTH
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