Simply use the following command:

cat /etc/fstab

And have a look at the line with your root filesystem.

From there we have 3 possibilities:

  • If the line starts with UUID=xyz, then it means it is a physical partition.
  • If the line starts with /dev/sdaX, it is a physical partition.
  • The indicator for LVM would be something with /dev/mapper/xyz.

You can also check in the mounts and fstab using this command:

if  grep -Pq '/dev/(mapper/|disk/by-id/dm)' /etc/fstab  ||  mount | grep -q /dev/mapper/
then
    echo "LVM in use"
fi