Create an ext4 file system and disk quotas.
 

Hello everybody!
I am having some problems in linux that are disorienting me...
I have a project for linux storage management.
I installed on my virtual machine ubuntu.
I started performing the tasks i was intrested and...confusion came up.
First i tried to create an ext4 file system with the command:
# mkfs.ext4 /dev/sda1
but it says me that this device is in use by the system and will not create a file system here.
I tried the same command with all other devices i have: /dev/sda2 ,/dev/sda4 , /dev/sda5 but it reports me the same thing.
The problem is that i only have one disk :
/dev/sda and i don't know how to create another one.
I'mm totally disoriented becouse i am new in linux,but i have to finnish this project until monday...
Anybady can help me please???
I also want to configure disk quotas and i can't.
When i open the vim text editor to edit /etc/fstab i don't know where to put usrquota and/or grpquota options becouse it doesn't shows me the /home partition that i need....
I thought all this problems came from ubuntu and tried fedora...but the same things are hapenning
HELP ME PLEASE
PS: I also can't resize my partitions and don't know why ...

If you want to create another virtual disk, that's easy, do it by your virtualization software to add the disk in the fly!

What sort of virtualization platform are you using? VMware or Xen or KVM?

virtual box

could you please be more specific?
How to create the new virtual disk?