For some reason, while I did create a 20 GB disk, I quickly got a warning that my disk space was nearly full. Having used Ubuntu for a while, I was surprised to see my 20 GB would already be full on this fresh install.

So I verified using the commands below. As you can see, it did detect that my physical volume was slightly short of 20 GB.

root@ubuntu01:/opt# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda3
  VG Name               ubuntu-vg
  PV Size               <18.23 GiB / not usable 3.00 MiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              4665
  Free PE               2105
  Allocated PE          2560
  PV UUID               bsAlMw-TKc1-hMOx-8tdy-fjKR-NwW6-uMG5fg

But my volume group was a different story. The volume group size (VG Size) was close to what the output of the physical volume told us. However, only 10 GB was allocated; and 8.22 GiB was for some reason not allocated. Probably an oversight on my side.

   
root@ubuntu01:/opt# vgdisplay
  --- Volume group ---
  VG Name               ubuntu-vg
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               18.22 GiB
  PE Size               4.00 MiB
  Total PE              4665
  Alloc PE / Size       2560 / 10.00 GiB
  Free  PE / Size       2105 / 8.22 GiB
  VG UUID               sYknqJ-0ZCm-9Cqc-qXp2-yU80-IC7N-eM75Jb

lvdisplay confirms this:

root@ubuntu01:/opt# lvdisplay
  --- Logical volume ---
  LV Path                /dev/ubuntu-vg/ubuntu-lv
  LV Name                ubuntu-lv
  VG Name                ubuntu-vg
  LV UUID                YAs7Vb-5luh-TBOs-IVOH-cxiT-s4zX-OhFinf
  LV Write Access        read/write
  LV Creation host, time ubuntu-server, 2024-01-28 08:44:17 +0000
  LV Status              available
  # open                 1
  LV Size                10.00 GiB
  Current LE             2560
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

Now, let’s make sure this logical volume group uses all the available space.
Above, we see the LV Path, which is what we need to run our next command.

root@ubuntu01:/opt# lvextend -l +100%FREE /dev/ubuntu-vg/ubuntu-lv 
  Size of logical volume ubuntu-vg/ubuntu-lv changed from 10.00 GiB (2560 extents) to 18.22 GiB (4665 extents).
  Logical volume ubuntu-vg/ubuntu-lv successfully resized.

If like me you forgot to add “-r” in the command above, check the type of file system.

# Check sizes
root@ubuntu01:~# df -h
Filesystem                         Size  Used Avail Use% Mounted on
tmpfs                              388M  1.9M  386M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv   18G  9.3G  7.8G  55% /
tmpfs                              1.9G     0  1.9G   0% /dev/shm
tmpfs                              5.0M  4.0K  5.0M   1% /run/lock
/dev/sda2                          1.8G  136M  1.5G   9% /boot
tmpfs                              388M  132K  388M   1% /run/user/1000

# Check file system
root@ubuntu01:~# df -T 
Filesystem                        Type  1K-blocks    Used Available Use% Mounted on
tmpfs                             tmpfs    397092    1984    395108   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv ext4   18696940 9680488   8109936  55% /
tmpfs                             tmpfs   1985444       0   1985444   0% /dev/shm
tmpfs                             tmpfs      5120       4      5116   1% /run/lock
/dev/sda2                         ext4    1790136  138800   1542076   9% /boot
tmpfs                             tmpfs    397088     140    396948   1% /run/user/1000

In my case, I needed /dev/mapper/ubuntu–vg-ubuntu–lv which is an ext4 file system. My final step:

root@ubuntu01:~# resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv