Raspberry PI - EXT4

To mount a USB drive:
sudo mkdir /mnt/usbdrive
sudo mount /dev/sda1 /mnt/usbdrive
ls /mnt/usbdrive

To list your file systems:
sudo fdisk -l
sudo mount -l
df -h

Before disconnecting a USB drive:
sudo umount /dev/sda1

Format a drive to Linux EXT4
sudo mkfs.ext4 /dev/sda1 -L untitled

Add Apple OS X HFS+ read/write support
sudo apt-get install hfsutils hfsprogs hfsutils

Format a drive to HFS+
sudo mkfs.hfsplus /dev/sda1 -v untitled

Add Windows NTFS read/write support
sudo apt-get install ntfs-3g

Format a drive to NTFS
sudo mkfs.ntfs /dev/sda1 -f -v -I -L untitled

Add Windows/DOS FAT32 read/write support
sudo apt-get install dosfstools

Format a drive to FAT32
sudo mkfs.vfat /dev/sda1 -n untitled