How to increase the size of / in Ubuntu 16 server?

Question

linux

Already tormented just pipets! help me please.
There is a virtual machine on Hyper-V where the Ubuntu 16.04.2 server
ran out of space, I increased the hard disk in Hyper-V from 12 to 18 gigs.
Then I booted into live cd ubuntu 16 desctop and there gparted increased the size of the hard drive. but nothing worked, in the end this is the picture

[email protected]:~# df -h
Filesystem                   Size  Used Avail Use% Mounted on
udev                         468M     0  468M   0% /dev
tmpfs                         98M  5.5M   93M   6% /run
/dev/mapper/ubuntu--vg-root   12G  4.8G  5.9G  45% /
tmpfs                        488M     0  488M   0% /dev/shm
tmpfs                        5.0M     0  5.0M   0% /run/lock
tmpfs                        488M     0  488M   0% /sys/fs/cgroup
/dev/sda1                    472M  154M  294M  35% /boot
tmpfs                         98M     0   98M   0% /run/user/0

[email protected]:~# fdisk /dev/sda

Welcome to fdisk (util-linux 2.27.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): p
Disk /dev/sda: 18 GiB, 19327352832 bytes, 37748736 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0xf8490f13

Device     Boot   Start      End  Sectors  Size Id Type
/dev/sda1  *       2048   999423   997376  487M 83 Linux
/dev/sda2       1001470 37748735 36747266 17.5G  5 Extended
/dev/sda5       1001472 37748735 36747264 17.5G 8e Linux LVM

Partition 2 does not start on physical sector boundary.

Command (m for help):

I've looked all over the internet and can't figure out what to do!
here is this /dev/mapper/ubuntu--vg-root (I don’t even know what it’s called)
for some reason it’s 12 G and I need 17
there’s some kind of /dev/sda5 there 17.5 giga, so I need them !!

[email protected]:~# resize2fs /dev/mapper/ubuntu--vg-root
resize2fs 1.42.13 (17-May-2015)
The filesystem is already 3008512 (4k) blocks long.  Nothing to do!

Answer 1

Judging by the characteristic name of the block device, your system is on LVM.
Accordingly, in addition to increasing the block device and expanding the FS, it is necessary to tell LVM that the block device has become larger and say to increase the logical volume.

pvresize /dev/sda5
lvextend -l +100%FREE /dev/mapper/ubuntu--vg-root

Then already resize2fs