Adding new disk

Start with check 

fdisk -l

you should see it. 

parted /dev/DISK
 mklabel GPT
 mkpart primary 0% 100%

Create ext4 and reduce root space

mkfs.ext4 /dev/DISKpart
tune2fs -m 0 /dev/DISKpart

disk information and format

It is quote common that you need information about disk. There are many commands (sometimes distribution depended) that can do that. Try following:

lshw -class disk
smartctl -i /dev/sda
hdparm -i /dev/sda
hwinfo --disk
ls /dev/disk/by-id
cat /proc/partitions

cat /proc/mdstat




To add new disk you just need

fdisk -l

parted /dev/sdb

(parted) mklabel GPT                                                      

(parted) mkpart primary 0% 100%                                           

(parted) quit

mkfs.ext4 /dev/sdb1

tune2fs -m 0 /dev/sdb1

Add line to /etc/fstab

disk space

Free space on disk:

df -H

Size of directory:

du -hs directory