# parted /dev/sda
GNU Parted 3.2
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) rm 3
(parted) p
Model: VMware Virtual disk (scsi)
Disk /dev/sda: 32.2GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name                  Flags
 1      1049kB  538MB   537MB   fat32        EFI System Partition  boot, esp
 2      538MB   12.9GB  12.3GB  ext4

(parted) resizepart
Partition number? 2
Warning: Partition /dev/sda2 is being used. Are you sure you want to continue?
Yes/No? yes
End?  [12.9GB]? 28GB
(parted) p
Model: VMware Virtual disk (scsi)
Disk /dev/sda: 32.2GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name                  Flags
 1      1049kB  538MB   537MB   fat32        EFI System Partition  boot, esp
 2      538MB   28.0GB  27.5GB  ext4

(parted) quit
Information: You may need to update /etc/fstab.

root@unifi:~# resize2fs /dev/sda2
resize2fs 1.44.1 (24-Mar-2018)
Filesystem at /dev/sda2 is mounted on /; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/sda2 is now 6704609 (4k) blocks long.