1)
Проверяем размер диска (/dev/sda)
[root@localhost
~]# lsblk
NAME
MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda
8:0 0 20G 0 disk
├─sda1
8:1 0 1G 0 part /boot
└─sda2
8:2 0 19G 0 part
├─centos-root
253:0 0 17G 0 lvm /
└─centos-swap
253:1 0 2G 0 lvm [SWAP]