[TAG] Virtual Hard Disks

[Thomas Adam]

2009/1/14 Michael SanAngelo <msanangelo at gmail.com>:
> Hi, I was wondering what are the possibilities of creating and using virtual
> disks for. I understand I can use dd to create it then mkfs.ext3 or
> something like it to format the disk. What purpose could they be used for
> besides serving as a foundation for creating a live cd?
>
> I want to do this from the cli so no gui.

The term "virtual disk" is misleading here -- what you're referring to
are essentially loopback files, a la:

```
dd if=/dev/zero of=/somefile bs=1024 count=300000
'''

That will create a 30GiB zero-filled file called "somefile".

Then what you want to do with that is attach a loopback device to the file:

```
losetup /dev/loop0 /somefile
'''

(It may well be that /dev/loop0 is in use -- there are up to 8 loopback devices:

```
/dev/loop{1,2,3,4}
'''

Use whichever is available.)

Then create a filesystem on it:

```
mkfs -t ext3 -m 1 -v /dev/loop0
'''

(Replacing "/dev/loop0 if applicable with the above.)

Then you can mount it somewhere:

```
mount -t ext3 /dev/loop0 /mnt
'''

(Replacing "/dev/loop0 if applicable with the above.)

Do stuff under /mnt as you would with a normal directory then when you're done:

```
umount /mnt
losetup -d /dev/loop0
'''

(Replacing /dev/loop0 if applicable.)

-- Thomas Adam